CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2013 CENELEC

All rights of exploitation in any form and by any means reserved worldwide for CENELEC national Members.

Ref. No.:CWA 50611:2013 E

CENELEC WORKSHOP AGREEMENT

CWA 50611

April 2013

ICS 29.220.99

English version

Flow batteries - Guidance on the specification, installation and operation

This CENELEC Workshop Agreement has been drafted and approved by a Workshop of representatives of interested parties, the constitution of which is indicated in the foreword of this Workshop Agreement. The formal process followed by the Workshop in the development of this Workshop Agreement has been endorsed by the National Committees of CENELEC but neither the National Committees of CENELEC nor the CEN-CENELEC Management Centre can be held accountable for the technical content of this CENELEC Workshop Agreement or possible conflicts with standards or legislation. This CENELEC Workshop Agreement can in no way be held as being an official standard developed by CENELEC and its Members. This CENELEC Workshop Agreement is publicly available as a reference document from the CENELEC Members National Committies. CENELEC members are the national committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

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Contents Page

Foreword ............................................................................................................................................................. 4 Introduction ........................................................................................................................................................ 6

1 Scope ..................................................................................................................................................... 7

2 Normative references ........................................................................................................................... 7

3 Terms and definitions .......................................................................................................................... 7

4 Technology selection – comparison against batteries and other storage, financial implications ......................................................................................................................................... 19

4.1 Summary.............................................................................................................................................. 19 4.2 Life Cycle Cost Methodology ............................................................................................................ 19 4.3 Comparison between different types of batteries ........................................................................... 22 4.4 System costs ....................................................................................................................................... 22 4.5 Investment criteria .............................................................................................................................. 23 4.6 Influence of peak power ..................................................................................................................... 23 4.7 Influence of rated energy ................................................................................................................... 23 4.8 Battery sizing ...................................................................................................................................... 23 4.9 Maintenance ........................................................................................................................................ 23

5 Specification, performance, test methods, life cycle ...................................................................... 24 5.1 Parameters to be specified ................................................................................................................ 24 5.2 Test procedures – Flow Battery ........................................................................................................ 26 5.3 Test procedures – Flow Battery Energy Storage System .............................................................. 29

6 User Manual ........................................................................................................................................ 30 6.1 General ................................................................................................................................................. 30 6.2 Introduction ......................................................................................................................................... 30 6.3 Overview of battery product or system ............................................................................................ 30 6.4 Important contact information and other basic details .................................................................. 30 6.5 Safety Warning .................................................................................................................................... 30 6.6 Technical Specifications .................................................................................................................... 31 6.7 Product Description ........................................................................................................................... 32 6.8 Site Requirements .............................................................................................................................. 32 6.9 Operation ............................................................................................................................................. 33 6.10 Maintenance ........................................................................................................................................ 34 6.11 Fault finding ........................................................................................................................................ 34 6.12 Warning Labels ................................................................................................................................... 35 6.13 Disposal ............................................................................................................................................... 36 6.14 Appendices.......................................................................................................................................... 36

7 Installation of Flow Batteries ............................................................................................................. 36 7.1 General ................................................................................................................................................. 36 7.2 Existing Standards and Guidelines .................................................................................................. 36 7.3 Shipping ............................................................................................................................................... 40 7.4 Pre-Commissioning ............................................................................................................................ 41 7.5 Commissioning ................................................................................................................................... 41 7.6 Operation ............................................................................................................................................. 41 7.7 Decommissioning ............................................................................................................................... 42 7.8 Regulations ......................................................................................................................................... 42

Annex A (informative) Listing of Applicable Regulations, Standards and Guidelines ........................... 44 A.1 Piping and Pressure Vessels............................................................................................................. 44 A.2 Process Safety .................................................................................................................................... 44 A.3 Rotating Equipment ............................................................................................................................ 44

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A.4 Chemicals Handling ............................................................................................................................ 45 A.5 Safety Instrumented Systems (SIS) ................................................................................................... 45 A.6 Process Control ................................................................................................................................... 45 A.7 Electrical Grid ...................................................................................................................................... 46 A.8 ATEX Regulations ............................................................................................................................... 47

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Foreword

This CENELEC Workshop Agreement has been drafted and approved by a Workshop of representatives of interested parties by correspondence on 2013-03-18, the constitution of which was supported by CENELEC following the public call for participation made on 2011-09-21.

A list of the individuals and organizations which supported the technical consensus represented by the CENELEC Workshop Agreement is available to purchasers from the CEN-CENELEC Management Centre. These organizations are as follows:

Participating Companies/Participants This CEN-CENELEC Workshop Agreement was developed by:

Cellstrom Austria Adam Whitehead DICP China Huamin Zhang Enervault USA Bret Adams Fraunhofer ICT Germany Jens Noack Innovation Core USA Erica He JOFEMAR S.A. Spain Beatriz Ruiz Castello Lyenergy China Hunter Zhou MEMC USA Babu Chalamala New South Innovations Australia Chris Menictas Next Energy Germany Jan Austing PNNL USA Vilayanur Viswanathan Prudent Energy Canada Gary Lepp Redflow Australia Chris Winter REDT UK John Samuel Resenergie / Ironflow Spain Vicent Garcia i Llorens Rongke Power China Dong Wang Sandia USA Summer Ferreira Schmid Germany Mirko Frank SGL Carbon Germany Dirk Schneider Swanbarton UK Anthony Price Tecnalia Spain Alberto Garcia ZBB Australia Peter Lex With the collaboration of: Jill Cainey, Nathan Coad, Martin Dennenmoser, Juan Escudero, Peter Fischer, Mirko Frank, Eva Maria Hammer, Craig Horne, Bjorn Jonshagen, Lidiya Komsiyska, Meinert Lewerenz, Ronald Mosso, Peter Ridley, Martha Schreiber, Thorsten Seipp, Kim Soowhan, Georgios Tsotridis, Xiaoli Wang, Wolfgang Winkler, Stefan Woehner, Susan Zhang

Chairman: Anthony Price Swanbarton UK Secretary: Richard Valenta OVE AT

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The CENELEC Workshop Agreement is a technical agreement, developed by an open workshop structure within the framework of CENELEC and owned by CENELEC as a publication, which reflects the consensus of only the registered participants responsible for its contents. The Workshop Agreement therefore does not represent the level of consensus and transparency required for a European Standard (EN) and is not designed to support legislative requirements (e.g. the New Approach) or to meet market needs where significant health and safety issues are to be addressed. It is instead designed to offer market players a flexible and timely tool for achieving a technical agreement where there is no prevailing desire or support for a standard to be developed.

The formal process followed by the Workshop in the development of the CENELEC Workshop Agreement has been endorsed by the National Members of CENELEC but neither the National Members of CENELEC nor the CEN-CENELEC Management Centre can be held accountable for the technical content of the CENELEC Workshop Agreement or possible conflict with standards or legislation. This CENELEC Workshop Agreement can in no way be held as being an official standard developed by CENELEC and its members.

The final review/endorsement round for this CWA was started on 2013-02-13 and was successfully closed on 2013-03-18.The final text of this CWA was submitted to CENELEC for publication on 2013-03-18.

This CENELEC Workshop Agreement is publicly available as a reference document from the National Committees of the following countries: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Comments or suggestions from the users of the CENELEC Workshop Agreement are welcome and should be addressed to the CEN-CENELEC Management Centre.

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Introduction

Flow Battery Hierarchy

This CENELEC Workshop Agreement (CWA) covers a number of separate types of Flow Batteries and Flow Battery Energy Storage Systems

Flow Batteries used for experimental, work, research, development, design or laboratory purposes are outside the scope of this Workshop Agreement. For purposes of this CWA, systems have been grouped into a hierarchy with three broad categories, based on their physical configuration:

Packaged Systems: Self-contained units, packaged, sold and installed as a single unit containing all parts of the Flow Battery, including the power conversion system, all contacts and fittings for connection to the local AC electricity network. Packaged systems may also be supplied as detailed above but configured for use on an off-grid AC or DC system.

Such devices will tend to be at the smaller power and energy levels. The user has restricted access to the Flow Battery Energy Storage System within the packaging. Examples include small Flow Battery devices designed for use as standalone installations for remote telecom systems.

Containerised systems: Units designed and packaged in shipping (ISO) containers, or similar large scale enclosures. The system is factory assembled, the containers are transported to the operating site, and installed in their as-supplied condition, with minimal on-site installation works.

Containerised systems may be supplied with the power conversion system or without a power conversion system and this latter unit would be configured for connection to a power conversion system or other electrical connection.

Large-scale installations: Installations, which may use a generic or specific design for an individual installation. These systems may be assembled from individual components listed in 3.34 or from sub-assemblies such as skid mounted modules complete with associated pipes, pumps, valves and sensors.

Flow Battery types

There are a number of different types of Flow Batteries, using different electrochemistries and layouts. Manufacturers may supply from a standard product range, or supply customised or bespoke Systems. Users of this CWA are advised to consult up-to-date references for details of each type of Flow Battery.

NOTE The definition of a Flow Battery is given in Section 3.34 of this CWA.

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1 Scope

This CWA provides guidance on the specification, installation and operation of Flow Batteries. It facilitates the pre-commercial phase, when a potential client needs to compare technical requirements of different types of Flow Batteries, or simply needs to compare between Flow Batteries and conventional electricity storage devices. It gives potential clients confidence that the batteries are sufficiently robust to meet the requirements of the designated application. This CWA also provides guidance for conformity assessment bodies to benchmark the Flow Batteries’ conformity with existing directives and other regulations.

2 Normative references

N/A

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply1.

3.1 Area specific energy system rated energy divided by the system footprint (see 3.36)

Note 1 to entry: This metric determines the area of an energy storage system for energy intensive applications.

3.2 Area specific power system rated power divided by the system footprint (see 3.36)

Note 1 to entry: This metric determines the area of an energy storage system for power intensive applications for the rated system power.

3.3 Battery Housing including Facility Management System (i.e. heating, cooling) enclosure of Flow Battery Energy Storage device to ensure that manufacturer specific climatic operating parameters are maintained

3.4 Battery Management System (BMS) control and instrumentation system which is specific to the operating characteristics of the Flow Battery and ensures that the Flow Battery operates within its recommended design parameters

Note 1 to entry: The BMS is linked to other sub systems and components such as pumps, heat exchangers thermal/pressure/concentration sensors, within the Flow Battery.

3.5 Battery terminals electrical connection points for all external electrical equipment (loads, external measuring equipment, and sources) to the Flow Battery

3.6 Calendar Lifetime total lifetime of the Flow Battery for which the battery continues to operate within acceptable limits if the battery is in an operating condition but not subject to any cycling

1 IEC definitions are shown at http://www.electropedia.org/iev/iev.nsf/index?openform&part=482

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Note 1 to entry: Because of the characteristics of many types of Flow Batteries, calendar lifetime is a function of the degradation of materials used in the construction of the Flow Battery Energy Storage System and is expected to be measured in years.

3.7 Cell single Flow Battery cell consists of electrodes and other components within a container that can operate as an electrochemical cell, using a flowing electrolyte pass or through each electrode

Note 1 to entry: Individual Flow Battery cells can be connected in series to create a stack (see 3.69).

3.8 Cell Voltage (V) potential difference across a single cell (more generally it is an average because it is normally only possible to directly measure stack or string voltages in a battery) and may be measured with or without current flow

3.9 Charge capacity measured charge required to charge the Flow Battery, from 0 % charge level (see 3.11), until charging is terminated by reaching a limiting condition, beyond which the power cannot be applied (e.g. 100 % charge level, maximum voltage, etc.)

Note 1 to entry: the charge behaviour of a Flow Battery is dependent on its electrochemistry, and optimum charging may be at constant power, stepped or tapered. A practical measurement is to use Wh (kWh or MWh) but it is recognised that some manufacturers will specify this in Ah.

3.10 Charge energy measured energy (typically in kWh or MWh) required to charge the Flow Battery, from 0 % charge level (see 3.11) at a given constant charge power, until charging is terminated by reaching a limiting condition, beyond which the power cannot be applied (e.g. 100 % charge level, maximum voltage, etc.)

3.11 Charge level (%) measure of the charge in the Flow Battery, where limits of maximum and minimum permissible state of charge (SOC – see 3.71) are defined by the manufacturer of the Flow Battery

Note 1 to entry: The charge level is then given by (SOC – minimum SOC)/(maximum SOC – minimum SOC). Therefore, 100 % charge level corresponds to the maximum SOC and 0 % charge level corresponds to the minimum SOC. As voltage may not be constant throughout the range, the State of Charge should be provided in Wh (kWh or MWh) as this is reflective of practical operation.

3.12 Charge Rate (C Rate) charge rate – for a conventional battery – is defined as the rated coulombic capacity in Ah divided by the corresponding charge time in hours which results in an electric current

Note 1 to entry: Conventional batteries make frequent use of charge and discharge rates, which are based on a multiple of coulombic capacity or energy content of the battery. In Flow Batteries, which often have variable energy/power ratios the definition of the C rate is not a useful parameter, and its use is not recommended.

3.13 Climatic operating conditions ambient conditions under which the manufacturer suggests the battery can be operated

Note 1 to entry: These should include maximum and minimum air temperature, whether it is suitable for indoor or outdoor application and optionally maximum and minimum relative humidity and maximum and minimum altitude (air pressure).

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3.14 Commissioning commissioning is initiated at the end of pre-commissioning activities

Note 1 to entry: this stage encompasses the addition of the process fluids – e.g. electrolyte(s), nitrogen blanket gas, etc. The system is then progressed through a number of steps to full operation in a structured manner.

3.15 Constant Current Charging charging at a constant current, with the current not exceeding the maximum current for the stack

Note 1 to entry: Typically, this charge mode is accompanied by a voltage cut-off.

3.16 Constant Power Charging charging at constant power, with the power not exceeding the maximum power for the stack

Note 1 to entry: Typically, this charge mode is accompanied by a voltage or charge level cut-off.

3.17 Cost/kWh delivered during service life cost parameter that is calculated using the Life Cycle Cost methodology described in 4.2 "Life Cycle Cost Methodology", and is a term combining such aspects as component reliability and connected system demand

3.18 Cycle sequence of a discharge followed by a charge or a charge followed by a discharge under specified conditions such as rate and ambient temperature

Note 1 to entry: This sequence may include rest periods.

3.19 Cycle lifetime number of cycles (n) at a given percentage of depth of discharge (% DoD) for which the Flow Battery continues to operate within acceptable limits2 (conventionally taken as 80 %)

Note 1 to entry: There is no universal accelerated test that may be reasonable employed for rechargeable batteries or even Flow Batteries. Because cycle lifetimes, however defined, may be expected to require years of testing, to a defined point of failure, a definition or test for cycle life is considered to lie outside the scope of this CWA.

A key attribute for many types of Flow Battery is the ability to separate the rated power and rated energy by increasing the volume of electrolyte. This will therefore have a significant impact on the measurement of Cycle Lifetime. In a Flow Battery, as the ratio of energy to power is increased, discharge and charge times are increased. This is expected to decrease the cycle life of the stack, while the electrolyte cycle life is expected to remain unchanged3. Hence two separate definitions may be necessary – one for stack, and one for the electrolyte.

Cycle lifetime should therefore state the applicability of this parameter to the lifetime of the stacks and the electrolytes if these are different.

2 (Maintenance of 80 % of its initial capacity is the convention in secondary batteries). and equivalent terms are often used as guideline parameters for rechargeable batteries, but are measured by a wide variety of tests, even for a single battery chemistry 3 The electrolyte cycle life may decrease slightly, since it takes longer to be fully charged and discharged, thus introducing calendar life effects.

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3.20 Decommissioning decommissioning encompasses all activities undertaken at the end of the Operation period, where the Flow Battery Energy Storage System is withdrawn from service

Note 1 to entry: The system will be removed from site, with components and sub systems dismantled as required. The Flow Battery site is then remediated according to local, regional and national regulatory requirements. System components removed from site are sent for recycling and disposal as required by local, regional and national regulatory authorities. Recommendations for recycling are provided in Section 7.7 of this CWA.

3.21 Depth of Charge (DoC) charge energy capacity absorbed by the battery during a cycle expressed as a percentage of the maximum charge energy capacity for a Flow Battery

3.22 Depth of Discharge (DoD) discharge energy capacity delivered by the battery during a cycle expressed as a percentage of the maximum discharge energy capacity for a Flow Battery

3.23 Discharge capacity measured charge (typically in Ah) that can be drawn from the Flow Battery, from 100 % charge level at a given rate, until discharge is terminated by reaching a limiting condition, beyond which current cannot be supplied (e.g. 0 % charge level, minimum voltage, etc.)

3.24 Discharge energy measured energy (typically in kWh or MWh) that can be drawn from the Flow Battery, from 100 % charge level at a given constant discharge power, until discharge is terminated by reaching a limiting condition, beyond which the power cannot be supplied (e.g. 0 % charge level, minimum voltage, etc.)

3.25 Discharge Rate see definition of charge rate (3.12).

3.26 Duty Cycle sequence of specified charge and discharge loads which a battery is expected to supply for specified time periods while battery voltage stays within a specified range

Note 1 to entry: Duty cycles are usually application specific and defined by a repeatable pattern of power usage.

3.27 Electrolyte usually a fluid (including a gel) that carries the reactants in a Flow Battery cell

Note 1 to entry: An ion exchange membrane or electrolyte separator (if used) is not considered part of the electrolyte.

3.28 Energy Efficiency AC/AC or DC/DC ratio (as a percentage) of the electrical energy provided from the Flow Battery during discharge to the electrical energy supplied to the Flow Battery during the preceding charge

Note 1 to entry: This should include all necessary electrical energy required for operation of pumps, valves, battery management systems, electrolyte conditioning, thermal management, monitoring and other auxiliary processes, which may be included in the BMS and FMS. . Because different flow battery types may have different operating characteristics it is recommended that this term takes into account those Flow Battery Energy Storage Systems where additional electrical

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energy requirements may vary between cycles, such as caused by a special event - for example electrolyte or electrode management. A recommended test procedure is provided in section 5.2.4 of this CWA.

Note 1 to entry: See also definition of roundtrip efficiency – section 3.62

GeneratorDCAC/DC

LoadACDC

InverterDC / ACDC / DC

BatteryDC

LOSSESInternal restistanceSelf DischargeBMSPumps

LOSSESInternal ResistanceVentilationAir ConditioningFMS

Charging DischargingGeneratorDCAC/DC

LoadACDC

InverterDC / ACDC / DC

BatteryDC

LOSSESInternal restistanceSelf DischargeBMSPumps

LOSSESInternal ResistanceVentilationAir ConditioningFMS

Charging Discharging

Figure 1 - Schematic drawing of energy flow

3.29 Energy lost during service life difference between the total energy absorbed by the Flow Battery or Flow Battery Energy Storage System summed over all charging events during the operational (service) life and that delivered by the Flow Battery or Flow Battery Energy Storage System summed over all discharge events

Note 1 to entry: The lost energy reflects the energy inefficiency of the Flow Battery or Flow Battery energy storage system

3.30 Facility Management System (FMS) system that includes the regulation of the heating/cooling/air flow through the facility/building hosting the Flow Battery

3.31 Fast Charging fast charging occurs when the charging rate is greater than the rated or nominal rate defined by the manufacturer

3.32 Fast discharging fast discharging occurs when the discharging rate is greater than the rated or nominal rate defined by the manufacturer

3.33 Flow Assisted Battery battery type using pumps to circulate electrolyte in order to improve the operating performance of the battery system

Note 1 to entry: While flow assisted batteries do not necessarily have an external electrolyte tank or tanks, they will share some common features with Flow Batteries and parts of this CWA may be applicable to such systems.

3.34 Flow Battery rechargeable battery in which electrolyte flows through one or more electrochemical cells from one or more tanks

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Note 1 to entry: The electrical – chemical energy conversion takes place in the electrochemical cells. A Flow Battery is further defined as being a self-contained device that includes all necessary control and regulation elements in order to operate as a battery under the specified environmental conditions. Therefore, a Flow Battery may contain heat-exchangers in order to regulate the electrolyte temperature. A Flow Battery necessarily includes at least one tank for storage of electrolyte, fluid conduit(s), electrolyte transfer means (e.g. electric pump) for the flow of the electrolyte, electrochemical cell(s) and electrical contacts (battery terminals). Additionally a Flow Battery contains all other components necessary for operation, for example, but not limited to, fluid valves, electrolyte filters, heat-exchangers, battery management system (e.g. pump controller) and sensors (e.g. state-of-charge sensor). A Flow Battery is charged and discharged with direct current.

Figure 2 - Schematic drawing of a Flow Battery Energy Storage System

3.35 Flow Battery Energy Storage System stand-alone device, based on a Flow Battery, which can be used to store and release electricity

Note 1 to entry: The Flow Battery Energy Storage System will necessarily contain a Flow Battery and may additionally contain, for example, secondary containment, housing, Facility Management System, ventilation means, graphic interface, data transmission equipment (e.g. for wireless monitoring and control), battery control system (with or without communication means to the load(s)), environmental sensors, electrical regulation equipment (e.g. fuses) and power conversion equipment (e.g. DC/DC convertors, DC/AC inverters, bidirectional inverters, etc.). Therefore, a Flow Battery Energy Storage System may be able to provide electricity with direct and/ or alternating current (1 or more phases).

3.36 Flow Battery Energy Storage System footprint area of the smallest horizontal rectangle that when viewed from above, contains all of the floor space shadow directly under every part of the piece of equipment during its operation

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Note 1 to entry: This area includes all the area which is required in the installation guidelines including any temporary projections from the piece of equipment during servicing or operation, space around the installation required for easement and service, and safety spaces. For installations with multiple systems, the system footprint is the average area, or the total installation area divided by the number of systems.

3.37 Initial performance test performance test carried out during the commissioning of a Flow Battery

3.38 Input Power total net electrical power applied to the Flow Battery or Flow Battery Energy Storage System during a charging event

Note 1 to entry: In the event that all or part of the input is AC, the real component rather than reactive power is meant.

3.38.1 Input Power AC power measured at the AC side of the terminals of the Flow Battery Energy Storage System

3.38.2 Input Power DC power measured at the DC connection to the Flow Battery

3.39 Installation installation/construction encompasses all site preparation and system erection activities

Note 1 to entry: This includes civil works (i.e. concrete pad installation for cabinet or containerised units) and connections to external utilities.

3.40 Layout (Cell Assembly) group of modules or stacks connected in series or parallel

3.40.1 Series in a series-connected configuration, the negative of one module or stack is connected to the positive terminal of the adjacent module or stack, resulting in increase in voltage

Note 1 to entry: In the figure below, the voltage of the three series connected modules is three times that of the individual module, while the maximum current is the same as that of the individual modules.

Figure 3 - Series layout

3.40.2 Parallel in a parallel-connected configuration, the positive terminals of each module or stack are connected together, and the negative terminals of each module or stack are also connected together

Note 1 to entry: In the figure below, the voltage of the three parallel connected modules is the same as that of the individual module, while the maximum current is three times that of the individual modules.

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Figure 4: Parallel layout

3.40.3 String group of modules or stacks connected electrically in series

3.40.4 Stream group of modules connected hydraulically in series

3.41 Lifetime Energy delivered during service life total lifetime energy of the Flow Battery for which the battery continues to operate within acceptable limits expressed in terms of the total energy throughput during charge and discharge

Note 1 to entry: The energy is measured in Wh or kWh. It is the sum of energy absorbed or delivered during all cycles over the battery life.

The measurement should specify the point of measurement, for example the AC or DC terminals of the battery, inverter or power conversion equipment.

3.42 Maximum charge power maximum electrical power (typically in kW or MW) that can be applied for a fixed duration (e.g. 20 s), to charge the Flow Battery as measured at the battery terminals at a given external air temperature and is a function of charge level

3.43 Maximum discharge power maximum electrical power (typically in kW or MW) that can be drawn for a fixed duration (e.g. 20 s), on discharge of the Flow Battery as measured at the battery terminals at a given external air temperature and is a function of charge level

3.44 Maximum voltage (V) maximum potential difference that may be applied to the battery terminals on charging of the Flow Battery as specified by the manufacturer

3.45 Minimum voltage (V) minimum potential difference that may be applied to the battery terminals on discharging of the Flow Battery as specified by the manufacturer

3.46 Module module – at a minimum – is an assembly of one or more stacks that form a discrete unit4 and share electrical and electrolyte connections

4 A module is assembled on a battery base or battery crate.

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Note 1 to entry: The design of the Flow Battery will determine whether the module is configured with its own hydraulic pumps to move the electrolyte between stacks and a battery management system (BMS). The term “module” should be used with care to prevent misunderstandings.

3.47 Nominal capacity maximum discharge capacity (typically in Ah) obtained in the range from 1 % to 100 % of the nominal power

Note 1 to entry: The maximum discharge capacity is the capacity obtained when discharging the battery in accordance with the manufacturer’s published operating instructions for normal and repeatable operations

3.48 Nominal energy maximum discharge energy (typically in kWh or MWh) obtained in the range from 1 % to 100 % of the nominal power

Note 1 to entry: The maximum discharge energy is the energy obtained when discharging the battery in accordance with the manufacturer’s published operating instructions for normal and repeatable operations

3.49 Nominal energy efficiency (%) energy efficiency measured at the nominal power

3.50 Nominal power see rated power 3.60

3.51 Open circuit cell voltage cell voltage without net flow of current in the external circuit

3.52 Operation period of the project lifecycle when the Flow Battery Energy Storage System operates according to design – i.e. importing and exporting electrical energy

3.53 Output Power total net electrical power supplied by the Flow Battery or Flow Battery Energy Storage System during a discharging event

Note 1 to entry: In the event that all or part of the output is AC, the real component rather than reactive power is meant. It should be stated whether the terminals are on the AC side or DC side (see below) of the inverter

3.53.1 Output Power AC power measured at the AC terminals of the Flow Battery Energy Storage System

3.53.2 Output power DC power measured at the DC terminals of the Flow Battery Energy Storage System

3.54 Peak Power – see also maximum charge power (3.42) and maximum discharge power (3.43) peak power is the power delivered over a fixed duration of a few seconds to minutes

Note 1 to entry: The peak power rating and the maximum period for which the peak power can be sustained must be provided. It is important that this requirement is clearly defined for each application in order to allow proper selection of the

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energy storage device. Peak power may be different for charge and discharge. The peak power may change with the charge level. Hence the energy storage device must be selected such that it can meet the peak power requirement throughout the charge level range in which it is designed to operate.

3.55 Pipes, Pumps and sensors pipes and manifold systems are used to direct and distribute the flow of electrolyte(s) through the Flow Battery; Pumps are used to provide circulation of the electrolyte(s)

Note 1 to entry: It is possible to design a system where electrolyte flow is achieved without the use of pumps. The system contains sensors and other instrumentation necessary to interface with the BMS and other control equipment.

3.56 Power Electronics or Power Conversion System electronics needed to convert between the DC voltage levels at the battery terminals of the Flow Battery to the voltage and current type (e.g. DC, AC 1-phase, AC 3-phase) provided at the connectors of the Flow Battery Energy Storage System

Note 1 to entry: For example this may include charge controllers, voltage choppers and inverters.

3.57 Pre-commissioning (mechanical completion) pre-commissioning generally applies to large-scale installations

Note 1 to entry: Initiated at the end of installation, this activity encompasses the structured, thorough assessment that all Flow Battery Energy Storage System components have been installed according to the Original Equipment Manufacturer (OEM) specifications. In addition, all piping connections are leak-checked and pressure tested using a suitable inert fluid. All control loops are also checked to confirm that each loop from the field control element to the Human-Machine Interface (HMI) display screen meets the design functionality. This stage of the project lifecycle is also termed 'Mechanical Completion'.

3.58 Prospective fault current highest level of fault current that can occur at a point in a circuit

Note 1 to entry: This is the fault current that can flow at any point in the circuit in the event of a zero impedance short-circuit and if no protective devices operate.5

3.59 Pulsed Charging charging using pulses with the pulse charge rate > 1 of the nominal charge rate, with the pulse width less than or equal to the maximum time for which the pulse may be maintained

3.60 Rated Power = nominal power nominal power of the Flow Battery

Note 1 to entry: As energy storage devices are frequently specified by reference to a nominal power and energy rating, rated power is an important characteristic. The power rating can be defined as the power delivered continuously for a fixed duration. The Rated Power will be specified by the manufacturer for each product or system. Rated power is the power delivered by the battery for the average duration needed by the specific application. Hence the rated power for a particular device may differ by intended application.

Rated power should be defined for both charge and discharge where this is different or where the application requires or takes advantage of a differential between charge and discharge power.

5 Note that the short circuit current is measured specifically between the Flow Battery terminals

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3.61 Response Time (to a fluctuating load) time needed to provide the required input/output power from a given operating power

Note 1 to entry: Different response times may also be expected when there are sudden changes in load under operating conditions, or in response to a change in polarity. At zero input/output power, there are two broad categories of stand-by modes: Cold stand-by mode and Hot stand-by mode. Each category of stand-by mode will be associated with a different response time. The response time is a useful parameter for the specification of a Flow Battery, and the operating conditions or stand-by mode must be clearly stated when this parameter is used.6.

3.62 Roundtrip electrical efficiency or Energy Efficiency (%) measured energy obtained during the discharge divided by the measured energy used to charge for a given cycle where the discharge follows the charge

3.63 Sealed Flow Battery Flow Battery which is designed to be sealed against the emission of vapours, gases or liquids to the local environment

3.64 Service life time of utilization for an initially defined application and represents the period of useful life of a Flow Battery under specified conditions, including where specified, the replacement or maintenance of serviceable parts or components

Note 1 to entry: A minimum estimate of service life is given by the Number of cycles/day multiplied by the service life of the weakest (technically and economically) component. However, as many parts can be replaced during service, longer service life can be achieved.

3.65 Service power or works power where a Flow Battery draws power for running pumps, valves, battery management, power conversion systems, heating, cooling or ventilation, this power must be included in the calculation of overall efficiency and is known as service power

Note 1 to entry: If the service power is provided from an external source and not drawn from the main electrical system, this service power must be stated separately

3.66 Service test special test of the ability of a Flow Battery to satisfy the design requirements (Flow Battery duty cycle) of the DC system

3.67 Shipping encompasses the transport of all Flow Battery Energy Storage System components including electrolytes from the various manufacturing sites to the project location

Note 1 to entry: This includes systems that are shipped as complete packages – i.e. cabinet or container-type Flow Battery Energy Storage Systems.

6 Test arrrangements for response times are given in in M. Futumata, S. Higuchi, O. Nakamura, I. Ogino, Y. Takada, S. Ozakaki, S. Ashimura, S. Takahashi, Journal of Power Sources, 24 (1988) 137-155

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3.68 Short-circuit current maximum current (typically in A) that can flow in any instant when the Flow Battery is initially at 100 % charge level, following connection of a highly conductive element between the battery terminals

3.69 Stack group of connected Flow Battery cells, assembled in a contiguous form and usually connected in series electrically7

3.70 Stand-by mode non–operating state from which the Flow Battery can be brought into operation with the minimum of intervention

Note 1 to entry: For a Flow Battery, hot stand-by is considered to be the state in which electrolytes are circulating and the system is not electrically connected. Cold stand-by is the state in which electrolytes are within the cells but electrolyte circulation is not active. Cold Stand-by is usually more economical in the use of auxiliary power.

3.71 State-of-charge or SOC (%) theoretical amount of charge that may be released from the Flow Battery expressed as a proportion of the maximum theoretical amount of charge that may be released in operational mode

Note 1 to entry: In order for this to be a practical measure it includes self-discharge or parasitic electrical loads (for example for temperature regulation, battery monitoring, pumping, etc.).

3.72 State of Health (SOH) performance of the Flow Battery at a given time in use

Note 1 to entry: This will reflect power and energy decrease as a function of aging (capacity loss combined with increase in internal resistance). A simple published procedure needs to be developed in order to determine SOH. SOH is an important system characteristic relating to separate parts of the Flow Battery Energy Storage System, and may be estimated by measuring:

• The change in internal, charge transfer and mass transfer resistance at fixed SOC to indicate the SOH of the Stack

• The change in energy capacity at fixed rate to indicate the SOH of the electrolyte(s)

3.73 State of Initial Performance (SIP) performance as tested after production and prior to delivery

3.74 Vented Flow Battery Flow Battery which is designed to allow vapours or gases to vent to the local environment

3.75 Volume 3.75.1 Electrolyte Volume entire volume of electrolyte(s) contained within the Flow Battery stacks, fluid handling systems, and electrolyte storage containers

7 In theory, stacks can also be formed by connecting cells in parallel. But due to minimum voltage requirements, the cells are usually connected in series.

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Note 1 to entry: This volume, combined with specific information concerning the electrolyte composition, is relevant for compliance with local and regional hazardous materials storage and handling regulations.

3.75.2 System Layout Volume volume of the complete Flow Battery Energy Storage System determined by multiplying the total horizontal footprint of the system (including all electrolyte storage, electrochemical stacks, power containers, buildings, electronics, and balance of system) multiplied by the maximum vertical dimension of the system, the greater of the installed equipment or any enclosures

3.76 Weight 3.76.1 Total System Weight for packaged or containerised Systems total battery weight, inclusive of module weight, balance of plant weight (pumps, manifolds, valves, electrolyte, tanks) and BMS

Note 1 to entry: This will not include power electronics, or battery enclosures or housing. Note that the definition of average weight is a critical definition in the whole CWA as an understanding of this is essential for compliance with EU directive 2006/66/EC8

3.76.2 Total System Weight maximum weight of the Flow Battery or Flow Battery Energy Storage System as required to calculate floor loading

Note 1 to entry: The total system weight therefore includes all relevant containers, housing and power electronics.

4 Technology selection – comparison against batteries and other storage, financial implications

4.1 Summary

This section sets out the main guidelines and key parameters to support the choice between different available technologies for energy storage. It is based on general criteria to select the most suitable system to fulfil their needs.

4.2 Life Cycle Cost Methodology

It is recommended that the Life Cycle Cost (LCC) methodology applied to various Flow Battery Energy Storage Systems utilise the methodology described in ISO 15663-1:2000-08-01, Petroleum and Natural Gas Industries – Life Cycle Costing – Methodology9. The purpose of ISO 15663 is to provide "… project and asset management staff [with] a clear and unambiguous definition of the overall economic objectives of a project and how to apply the same business criteria when making major engineering decisions." Through defining a standardised methodology for completing LCC analyses of various technology options, ISO 15663 provides a framework for realising the following benefits:

• Reduced cost of ownership,

• Alignment of engineering decisions with the objectives of the project principles,

8 This directive places a responsibility to recycle 50 % of the average weight of a battery or accumulator 9 Although ISO 15686-5:2008-06-15, Buildings and constructed assets -- Service-life planning -- Part 5: Life-cycle costing provides a methodology that could also be applicable to small-scale Flow Battery systems designed specifically for building applications, the methodology and examples provided in ISO 15663 is more relevant to all possible scales (i.e. cabinet, containerised, and large-scale) of Flow Battery systems.

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• Definition of common criteria that can be applied by all project participants,

• Mitigation of project risk,

• Maximisation of the value of operating experience,

• Ability to compare technology options at all stages of a project,

• Identification of major cost drivers. The primary principles of ISO 15663 are derived from IEC 60300-3-3, Dependability Management – Part 3-3: Application Guide – Life Cycle Costing, which is a very general standard that identifies typical LCC analysis elements.

The scope of the LCC analysis framework detailed in ISO 15663 applies to:

• The process concept,

• Equipment location (i.e. islanded or integrated solution),

• Project execution strategies,

• Health, Safety and Environment (HSE) aspects,

• System concept and sizing,

• Equipment type,

• Equipment configuration,

• Layout,

• Maintenance and operation strategies,

• Operating crew (e.g. manning) strategies,

• Logistic support strategies,

• Facility modifications (N.B. closely related to Process Safety – Management of Change described in Section 7),

• Spares and technical support strategies,

• Decommissioning and recycling strategies. All definitions, terms and abbreviations provided in ISO 15663, Section 2 are sufficiently generic as to be applicable to Flow Battery Energy Storage Systems, and should be adopted for all Flow Battery Energy Storage System LCC analyses.

The organisation and planning process described in ISO 15663, Section 3 is also sufficiently generic as to be applicable to Flow Battery Energy Storage System projects, as this section describes roles and processes that are already in place in many organisations.

The core of ISO 15663-1 is Section 4, which describes the methodology in detail. As with the previous sections already described, the methodology described is generic in terms of its application to a technological system that it can be immediately applied to a Flow Battery Energy Storage System.

NOTE The methodology is not sufficiently detailed for component-level costing: this is stated clearly in Section 1 of the standard.

Section 5 provides a checklist of tasks that should be completed prior to finalising the LCC analysis.

After establishing the generic methodology in ISO 15663-1, a subsequent standard, ISO 15663-2, Petroleum and Natural Gas Industries – Life-cycle costing Guidance on application of methodology and calculation methods, provides additional details for applying the LCC methodology. As with ISO 15663-1, the first two

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section concerning the scope and definitions are generic and can be applied to Flow Battery Energy Storage Systems.

Section 3 entitled, "The Process of Life-Cycle Costing", uses examples specific to the petroleum and oil and gas industries. However, the examples given are simple in nature, and phrases such as, "maintenance costs across the platform", can be easily exchanged with, "maintenance costs within the enclosed Flow Battery Energy Storage System", for example. The detailed text associated with each example can be readily applied to Flow Battery Energy Storage Systems. Obviously, cost items such as, "cost per standard barrel of oil" (Section 3.2.3.2), would not be applicable to Flow Battery Energy Storage Systems and can be ignored without affecting the overall LCC analysis. In addition, 3.3.1 makes reference to the major cost elements for the offshore oil industry; however, the elements listed are readily applicable to Flow Battery Energy Storage Systems. Finally, 3.3.4.2 makes reference to the use of the OREDA® database for ascribing reliability data to the cost calculations. Unfortunately, a similar reliability database is not yet established for the Flow Battery industry. It is thus recommended that the reliability data inputs to the LCC analyses be checked by an independent party until such a time as a publicly available (and vetted) reliability database specific for Flow Battery components is established. The independent check provides the additional assurance (confidence) that the decision-making process is as objective as reasonably achievable.

The remaining sections of ISO 15663-2 detail the formulas for calculating the NPV, IRR, etc.

The formula for the "cost per standard barrel oil" described in 4.1.8 can be replaced – in the context of Flow Battery Energy Storage System – with the "cost per kWh delivered over service life", where the denominator of the formula would be the "expected total energy delivered" instead of the existing "expected total production". It is recognised that the determining the "expected total energy delivered" over the lifetime of the Flow Battery Energy Storage System would be very difficult, as it would depend on the operation of the connected electrical systems. Unfortunately at this time there is not a standardised methodology for determining this parameter, although it is expected that subsequent revisions of this CENELEC document will provide more guidance in this area. As a first approximation, it is recommended that this number be derived from:

Expected Total Energy Delivered = E x D x A

Where E = energy delivered per cycle (i.e. 80 % to 20 % SOC)

D = number of cycles per year (i.e. 80 % to 20 % SOC)

A = operating life of Flow Battery Energy Storage System

The variable 'D' would be the most difficult to describe accurately, as it is dependent on the operation of the connected electrical grid. However, assuming that a Flow Battery Energy Storage System is providing diurnal load shifting services, the value of 'D' would typically be in the range of 300 to 365 – i.e. the Flow Battery Energy Storage System provides the load shifting service approximately daily. The operating life of the Flow Battery Energy Storage System can be established, as a first approximation, using a first-principles based approach within structured Reliability, Availability, and Maintainability (RAM) analysis framework.

The final part of the ISO 15663 series, ISO 15663-3 Petroleum and Natural Gas Industries – Life-Cycle Costing – Part 3: Implementation Guidelines uses terminology that is much more specific to the industries for which the standard was written. However, looking past the specific terminology, the guidelines can be readily applied to a Flow Battery Energy Storage System, as the project lifecycle components are the same for a Flow Battery project as for an oil production platform, for example. This document provides a much more specific, structured application of the generalised methodology described in ISO 15663-1, and aligns with the asset management, process safety, and other system-wide considerations associated with the installation, commissioning, operation, and decommissioning of Flow Battery Energy Storage System described in Section 7 of this CWA document.

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4.3 Comparison between different types of batteries

There are a number of commercially available types of secondary batteries which may be used for large scale energy storage applications. A number of new battery types are also under development. The following section is to highlight the main characteristics of alternative battery systems to enable a high level comparison to be made. Detailed reference should always be made to specific specifications supplied by manufacturers.

Lead acid batteries are considered a mature technology available from a wide range of manufacturers with a relatively low cost. Recycling infrastructure is in place, hence material costs are expected to remain low. Some manufacturers lengthen battery cycle life by incorporating carbon in the negative electrode. The batteries can be designed for high power, or for high energy with deep cycling. The design can be either the flooded or valve regulated type, with the manufacturers claiming both to be maintenance free. However, water loss is common in flooded batteries, with current batteries not allowing topping off, thus leading to potential failures. In valve regulated batteries with starved electrolyte, drying out of the cell during overcharge is a major concern. These batteries have had a history of premature failures in stationary applications. Users are recommended to refer to existing standards and literature for references to cycle life, especially at high depth of discharge.

High temperature batteries using the beta alumina electrolyte are commercially available from several suppliers. There are two principal types, using either the sodium sulphur electrochemistry or the sodium nickel chloride / sodium metal halide electrochemistry. Thermal management of these batteries must be taken into account when calculating the power and energy requirements for the battery system, Extensive research and development provides a predictable cycle and calendar lifetime.

Li-Ion batteries were initially developed for small scale applications, and have been adapted for use in electric vehicles and more recently for grid scale applications. There are a significant number of Li-Ion battery manufacturers, with a very wide range of chemistry types, each of which has different operating and safety characteristics. Li-Ion batteries are characterised by a relatively small cell size, and a high power to energy ratio. This tends to make Li-Ion batteries more suitable for power applications, such as frequency response or UPS rather than energy management applications such as peak shaving.

Metal air batteries are in a much less mature stage of development. Aluminium-air batteries have been developed for defence related applications but have not gained traction for commercial use due to high resistance of the aluminium electrode. Mechanically rechargeable zinc-air batteries are being used in various European countries in government vehicles. Electrically rechargeable zinc-air batteries have issues associated with dendrite growth that are being addressed by following the zinc species past the anode. Efforts are also underway to improve the power density at the cathode, especially during reduction of oxygen. The additional difficulty for Li-Air batteries is the volume change at the cathode during charge and discharge, with associated clogging of pores. Efforts to improve cycle life are underway.

Flow batteries present a number of advantages over other battery types, with the potential for low cost, high energy to power ratios, long lifetime and capability for use in small, medium and large scale installations. There are many different chemistries and manufacturers and accordingly there is a large number of alternative products available for commercial application. Flow batteries are available as packaged units, containerised units or large scale systems, which are assembled on site.

4.4 System costs

Cost comparisons between battery types, other energy storage types, and other electrical infrastructure investment are often made on the basis of cost parameters such as:

• System cost/kW installed,

• System cost/kWh installed. The nature of a Flow Battery is such that these parameters are not sufficiently comprehensive to allow a simple and relevant cost comparison to be made. Most Flow Batteries will be installed for energy based applications, and for these systems, the most appropriate parameter is to use the whole lifetime cost of energy supplied. This parameter takes into account the following:

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• Initial capital cost,

• Operational and maintenance cost,

• Roundtrip efficiency,

• End of life costs. This methodology should also be applied to other systems, including non energy storage alternatives in order to achieve a satisfactory economic analysis.

Applications which tend towards delivery of power, rather than energy are frequently assessed by means of the system cost/kW installed parameter.

4.5 Investment criteria

The investment analysis for an energy storage system will take into account the applications of the system and hence the physical specification of the system. This should be analysed to determine whether a power system or an energy system is most appropriate.

4.6 Influence of peak power

Where a technology type can deliver a high peak power, this should be taken into account, especially when considering applications such as frequency response/primary response.

4.7 Influence of rated energy

Systems mainly devoted to energy applications should be characterised by the capability to store large amounts of energy. Typically energy will be collected during the day to be used at night or it will be collected during a few hours to be used after that. It will be important to estimate the amount of energy required during that period of time in order to correctly size the battery.

Rated energy should be the most important parameter when investing in applications where large amounts of energy will be exchanged at low rates. In such cases the cost of the exchanged energy (currency/kWh) should be minimised to maximize the rate of return.

4.8 Battery sizing

Typically Flow Batteries are heavy devices. The final location of the battery, the space needed, and the load bearing capacity of the floor should be taken into account as well as considerations for transport to site.

4.9 Maintenance

Adequate protection must be provided for all personnel, including those who may be untrained in the vicinity of Flow Batteries and Flow Battery Energy Storage Systems. Flow batteries which are to be operated in a domestic environment, or commercial (non industrial) environment without trained specialist staff will generally be the packaged system type. Containerised and large scale installation systems may be installed in industrial and larger commercial environments where satisfactory arrangements for securing the installation have been made.

The maintenance requirement for the three types of Flow Battery Energy Storage Systems will differ along the following lines:

Packaged systems are expected to have few or no user serviceable parts, and the supplier will provide a maintenance service and inspection.

Containerised systems will require inspection at specified intervals, either by qualified staff from the operator, or by specialist maintenance staff from the supplier or appointed service organisation.

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Large scale installation systems will also require inspection at specified intervals. Some plants may be scheduled to operate in an unmanned environment, usually with remote monitoring. Because these will be larger installations the operator’s staff may be trained to inspect and if necessary provide maintenance as required. Training should be carried out by specialised maintenance staff from the supplier or an appointed service organisation.

Larger installations may be designed such that part of the plant may be isolated in the event of planned or unplanned maintenance or repair. Isolating individual modules or stacks, strings or streams enables plant operation to be continued, increasing overall availability of the plant and reducing whole life costs.

5 Specification, performance, test methods, life cycle

5.1 Parameters to be specified

All information should state whether it refers to individual or type information. Testing may be on an individual basis or type testing (where many units of a standardised product are considered).

The test procedures are similar in both approaches, although for type specifications the minimum parameters obtained should be used from measurement of a representative sample, i.e. at least two Flow Batteries or Flow Battery Energy Storage Systems should be tested.

Flow Batteries have many differences in operation from other battery types and some test procedures and parameters which are in widespread use in the battery industry are not directly applicable to the use of Flow Batteries in commercial and industrial applications. Within the Flow Battery industry, different electrochemistries and physical arrangements of cells and modules will lead to substantial differences in operation and performance. This should not be seen as a disadvantage of Flow Batteries, and this CWA is intended to support manufacturers, developers and users in the selection, installation and operation of Flow Batteries. Wherever possible, specifications should be based on parameters and units of measurement that are most appropriate to the application of the Flow Battery. It is preferred that energy is measured in kWh or MWh. The conventional battery industry traditionally refers to charge in Ah and uses C rates as comparative measurements, but because of the variable energy content of many Flow Battery Energy Storage Systems these measurements are of limited value in specifying Flow Batteries or Flow Battery Energy Storage Systems. In addition to other information listed in Chapter 6 the Flow Battery manufacturer should provide the following information:

Single values

a) Nominal capacity (with an uncertainty of ± 1 %),

b) Nominal energy efficiency (with an uncertainty of ± 1 %),

c) Nominal power (with an uncertainty of ± 1 %),

d) Nominal efficiency (with an uncertainty of ± 1 %),

e) Short-circuit current (with an uncertainty of ± 1 %),

f) Minimum voltage (with an uncertainty of ± 0,5 %),

g) Maximum voltage (with an uncertainty of ± 0,5 %),

h) Physical dimensions (with an uncertainty of ± 0,1 %),

i) Climatic operating conditions (with an uncertainty of ± 2 °C and ± 3 % RH).

Tables of data or graphs

j) Maximum charge power as a function of charge level,

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k) Maximum discharge power as a function of charge level,

l) Charge capacity as a function of charge power,

m) Discharge capacity as a function of discharge power,

n) Charge energy as a function of charge power,

o) Discharge energy as a function of discharge power,

p) Energy efficiency as a function of power.

In all cases the average air temperature during the testing should be stated with an uncertainty of ± 1 °C. For applications where the air temperature is expected to be outside of 20 °C to 25 °C the manufacturer may provide additional data covering a more relevant temperature range.

The above represents a minimum data set. Additional performance information may also be supplied by the manufacturer, for example charging regimes with alternative charge profiles (not just constant power) are possible.

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5.2 Test procedures – Flow Battery

5.2.1 General

All electrical testing of the Flow Battery is performed by connection to the battery terminals.

The air temperature in the vicinity of the Flow Battery is measured prior to and during the test and should be in the range 20 °C to 25 °C on average or specified outside this range with an uncertainty of ± 1 °C.

The Flow Battery should be tested with an electrical power supply and an electrical load capable of providing and dissipating pre-set regulated power. All appliances must be used in accordance with the manufacturers’ guidelines and electrical testing in accordance with local electrical regulations.

If the Flow Battery contains a charge level sensor this will be used to determine the charge level, alternatively the charge level may be determined by analysis of the electrolyte; either continuously or intermittently and based on some physical-chemical parameter that varies reproducibly and systematically with the charge level. If the above methods are not practical the charge level may be estimated by measurement of charge passed, correcting for self-discharge losses.

Examples of possible test regimes are given in section 5.2.2 to 5.2.5. In these test regimes it is proposed that charging and discharging is carried out at constant power levels, as this reflect the most useful operation mode of a large Flow Battery in an industrial or commercial context.

The tests should be repeated as often as required to obtain characteristic data (it is suggested to repeat 3 times and use only the last measurement values).

• The charge profile should be as specified by the manufacturer,

• The discharge profile should be as specified by the manufacturer,

• Cycling characteristics should be as specified by the manufacturer,

• Short circuit current. It should be noted that as different types of Flow Batteries may have different operating characteristics, particularly based on either electrode or electrolyte management, the energy requirements may vary over a number of cycles. Accordingly, test procedures and the reporting of results should determine an average result taken over a number of cycles, as given in the sections below.

5.2.2 Example of charging characteristics measurement:

a) Discharge the Flow Battery to 0 % charge level,

b) Charge at a constant power until a limiting condition is reached, beyond which the power cannot be maintained (e.g. 100 % charge level or maximum voltage),

c) During charging the charge level should be measured (or estimated), as described above, and recorded,

d) Steps (a) to (c) should be repeated at different values of charging power. It is advised to use at least 5 different values until the final charge level at the lowest power employed is 100 % and the final charge level at the highest power level is ≤ 50 %,

e) The maximum charge power is then the maximum power used to charge in steps (a) to (d) for a given charge level,

f) The charge capacity is the charge passed at any given power between 0 % charge level and the limiting condition is reached,

g) The charge energy is the electrical energy supplied in charging at any given power between 0 % charge level and the limiting condition is reached.

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5.2.3 Example of discharging characteristics measurement:

a) Charge the Flow Battery to 100 % charge level,

b) Discharge at a constant power until a limiting condition is reached, beyond which the power cannot be maintained (e.g. 0 % charge level or minimum voltage),

c) During discharging the charge level should be measured (or estimated), as described above, and recorded,

d) Steps (a) to (c) should be repeated at different values of discharging power. It is advised to use at least 5 different values until the final charge level at the lowest power employed is 0 % and the final charge level at the highest power is ≥ 50 %,

e) The maximum discharge power is then the maximum power used to discharge in steps (a) to (d) for a given charge level,

f) The discharge capacity is the charge passed at any given power between 100 % charge level and the limiting condition is reached,

g) The discharge energy is the electrical energy supplied in charging at any given power between 100 % charge level and the limiting condition is reached.

5.2.4 Example of full cycle characteristics measurement:

a) Charge the Flow Battery to 100 % charge level,

b) Discharge at a constant power until a limiting condition is reached, beyond which the power cannot be maintained (e.g. 0 % charge level or minimum voltage),

c) Charge the Flow Battery at the same power rate until a limiting condition is reached, beyond which the power cannot be maintained (e.g. 100 % charge level or maximum voltage),

d) During charging and discharging the charge level should be measured (or estimated), as described above, and recorded.

Repeat steps (b) to (d) at least 3 times. Values from the first two cycles will be discarded and the energy efficiency calculated from the remaining cycles. For Flow Batteries where the additional electrical requirements may vary between cycles, such as caused by a special event such as electrolyte or electrode management, the energy efficiency is calculated as an average figure over at least twice the number of cycles that contain a special event. Therefore, at least 4 cycles will be needed – where the first two are discarded and the special event occurs in the third or fourth cycle. The efficiency is calculated using a weighted average. That is the efficiency during the special event should be weighted with a value of 1, and the efficiency during the normal cycle should be weighted with the number of normal cycles between special event cycles. For example, if a special event cycle occurs once every 40 cycles, the average efficiency can be calculated after discarding the first two cycles, and then weighting the normal cycle efficiency by 39, special event efficiency by 1, and taking the average. This should be repeated for at least 3 significantly varied charge rates while keeping the discharge rate constant. The efficiencies at each charge rate should then be specified separately as per the steps outlined above,

e) The energy efficiency is calculated as the average energy passed on the discharge half-cycles (not including the first two) divided by the average energy passed on the charge half-cycles (not including the first two). This is numerically equivalent to the average discharge time divided by the average charge time at constant power,

f) Steps (a) to (e) should be repeated at different values of power. It is advised to use at least 5 different values of power, including the nominal power.

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The rate and duration of charge and discharge should also be taken into account when considering efficiency. As such, different efficiencies should be specified for different applications that utilise specific charge and discharge rates and durations. This is illustrated in the two graphs below. The first graph shows the relationship between a lead-acid battery’s rate of discharge and efficiency. This is contrasted by the second graph, which shows a similar relationship for a zinc-bromide flow battery.

Figure 5 – Typical discharge and efficiency curve for a lead acid battery10

Figure 6 – Typical discharge and efficiency curve for a zinc bromide flow battery11

5.2.5 Example of short-circuit current measurement:

a) Charge the Flow Battery to 100 % charge level,

b) A Flow Battery may include measures to limit short circuit current and/or duration. These can be through control measures or a combination of passive devices (fuses, etc.). If any of these measures are employed, they should be active during the test,

c) The short-circuit current should be estimated by extrapolation from the maximum discharge currents, determined in 5.2.3, to the maximum at 100 % charge level,

10 Source: Cadirci, Y. and Y. Ozkazanc. 2004. “Microcontroller-based on-line state-of-charge estimator for sealed lead–acid batteries”. Journal of Power Sources 194: 330-342 11 Source: Rose, David M. and Summer R. Ferreira. Feb 2012. “Initial Test Results from the RedFlow 5kW, 10kWh Zinc-Bromide Module, Phase 1”. Sandia Report SAND 2012-1352

Energy Efficiency

Discharge Rate (A)

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d) The battery should be electrically short circuited with electrical components (wires, relays, current meter) specified to withstand in excess of the estimated short-circuit current12,

e) The current should be recorded every 0,1 s for at least 180 s starting immediately prior to shorting the battery terminals,

f) The measurement should be repeated at least three times (allowing the electrolyte to cool to a standard operating range between tests),

g) The maximum current arising within the total testing period is taken as the short-circuit current,

h) If it is expected that a higher current could be obtained under different conditions (e.g. at a different charge level, or if the battery is already in a discharging mode) then the Flow Battery should also be tested under these conditions (repeating steps (b) to (d)) and the highest value obtained, from either sets of measurements, taken as the short-circuit current.

The test should be conducted for operating Flow Batteries and Flow Batteries in a standby state (and/or not operating). This is because the energy available to sustain a short circuit is different for the two cases and therefore the risks of damage are different.

5.3 Test procedures – Flow Battery Energy Storage System

The Flow Battery Energy Storage System may (in principle) be specified and tested in the same method as the Flow Battery, with the proviso that the electrical contact points should be the connection points for the load/power supply and are not necessarily the battery terminals of the Flow Battery.

However, the Flow Battery Energy Storage System differs from the Flow Battery in several ways, especially as it includes many additional components, which also require electrical power. Therefore, a Flow Battery Energy Storage System is likely to have reduced performance characteristics (e.g. lower discharge energy at a given discharge power) in comparison to the Flow Battery.

The output current type (e.g. DC, AC 1-phase, AC 3-phase, etc.) and voltage range should be specified for the Flow Battery Energy Storage System. If more than one set of connectors are provided (e.g. DC and AC connectors), the performance of the Flow Battery energy system should be determined independently for each.

The Flow Battery Energy Storage System may include fuses or other electrical safety precautions to limit the short-circuit current – in which case the maximum current rating should be specified rather than the short-circuit current.

12 An example of high current short-circuit testing is given, where a knife-switch, electrical cables, shunt and hall-effect transducer is used to measure currents up to 5000 A, for lead-acid batteries in: S. D. Gerner, P. D. Korinek and T. E. Ruhlmann, Calculated vs. actual short circuit currents for VRLA batteries, in conference proceedings Battcon 2003, Marco Island, FL, USA (2003). Suitable shunts and knife-switches are available to very high current ratings and so should not limit this test procedure for Flow Batteries.

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6 User Manual

6.1 General

The user manual is an important document that is designed to provide the user with all pertinent information about the system.

The manual should contain chapters (sections) that address specifications, installation, site preparation, operating instructions, safety guidelines, fault finding and emergency procedures. The manual should be in a comprehensive format that includes illustrations, pictures and references to engineering drawings where appropriate.

The manual should be appropriate for the level of Flow Battery Energy Storage System that is supplied. Multiple manuals may exist, covering the specific tasks of installation, commissioning, service, and de-commissioning. The user manual is likely to contain selected information from these; with at least the guidelines needed by the user according to the extent of their rights and responsibilities with respect to service, site preparation, transport, installation, operation, maintenance and de-commissioning of the Flow Battery or Flow Battery energy supply system.

A complete manual should include the following sections

6.2 Introduction

This chapter should provide a general introduction and an overview to the manual. It should include the purpose and structure of the manual.

6.3 Overview of battery product or system

To provide a general and brief description of Flow Battery technology and product and to provide a description of the intended function of the manual

6.4 Important contact information and other basic details

This chapter should provide manufacturer’s contact details including the company’s name, website, hotline, service telephone number, fax and email to allow customers to receive information or request help when needed. Supplementary information, such as declaration or explanation of licences, patents and similar information can also be included in this section.

6.5 Safety Warning

6.5.1 General

In common with all battery types, there are inherent safety considerations associated with Flow Batteries. Therefore the manufacturer shall provide details of these potential safety risks for the Flow Battery Energy Storage System. Users/operators must be made aware of the importance of this section of the manual, and must have a good understanding of all safety instructions prior to operating the system. It is good practice that operators keep a copy of the manual in an accessible location.

A Flow Battery is an electrical device using flowing electrolyte(s) to store energy. The electrolyte(s) may comprise acid/alkali that is corrosive or caustic. There are three major potential hazards of operational Flow Batteries: (1) electrical shock; (2) electrolyte leakage; (3) danger of potential hydrogen release. Customers/ operators must be made aware of these hazards.

The manual must include precautionary statements that in all circumstances only trained and qualified personnel shall have access to the system, whether it is operating, idle, or drained for storage.

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6.5.2 Electric Shock Hazard

It should be stated that a Flow Battery is an electrical energy storage device, and contains dangerous DC and/or AC voltages. When the power is disconnected and the Flow Battery is shut down, many components may retain their electrical charge. The manufacturer shall advise users and operators of the potential electric shock hazard from various parts of the system and take measures to protect operators or any personnel on site from electric shock.

6.5.3 Electrolyte Handling

A typical aqueous liquid electrolyte used in Flow Batteries has a concentration of approximately 10-20 % by weight of acid/alkali in water, and these strong corrosive agents may burn skin and eyes; and cause damage to clothing and other materials.

Non aqueous electrolytes used in some types of Flow Batteries may have similar caustic or corrosive properties.

The section shall provide details on the primary emergency measures that shall be taken if there is exposure to electrolytes.

It shall also list requirements for protective equipment such as

• Safety eye wear,

• Chemical-resistant gloves,

• Synthetic clothing (gear),

• Safety boots with acid-resistant soles,

• Acid-proof aprons. and requirements for emergency equipment such as

• Eye wash station,

• Chemical shower,

• First aid kit that includes oxygen and facemask,

• Fire extinguishers. 6.5.4 Hydrogen Gas Release

The manual shall state if there is potential for the release of hydrogen from the electrochemical processes, and appropriate counter measures shall be stated such as

• Using the product in a well-ventilated area and ensuring that ventilation slots are unobstructed,

• All sources of ignition are excluded from Flow Battery Energy Storage Systems. Smoking is not permitted in the vicinity of the system.

Requirements to install sensors to detect hydrogen leakage (or other dangerous gas) shall be included if appropriate.

6.6 Technical Specifications

The manual should include details of parameters listed in 5.1 and additionally the physical dimensions, operational weight, environmental transport and operating conditions and control & monitoring features.

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6.7 Product Description

6.7.1 General

Users/operators require a description of the configuration and working principles and information for users to operate the Flow Battery Energy Storage System properly and effectively. Information on key components, advantages and most suitable applications can also be included in this chapter.

6.7.2 Overview

Introduction of the product: structure, feature, characteristics, and the applications for the Flow Battery technology.

6.7.3 Terminology

A list of terms relevant to Flow Battery technology and applications.

6.7.4 Product Structure

The configuration, working process and main components of the Flow Battery Energy Storage System. Illustrations with explanations of the electrical diagram, physical configuration and the like should be included.

6.7.5 Working Principle

The working principle of the Flow Battery technology in a clear and simple approach should be described and it should make clear the distinctive characteristics of the technology.

6.7.6 Applications (optional)

The manual should state suitable applications of the Flow Battery Energy Storage System. The manual should list any applications which are not suitable for the Flow Battery.

6.8 Site Requirements

6.8.1 General

This chapter explains the site requirements for the Flow Battery installation in detail. It should include the following information

6.8.2 Location and Load

The floor loading requirements for the battery installation shall be stated, including any additional loads that must be taken during installation, for example by the use of cranes or fork lift trucks. Any requirements for the provision of floors laid to slope, or bunding shall be provided. If necessary, adequate descriptions and layout diagrams for positioning tanks and other equipment and requirements for mounting and fixing must be stated. The conditions for fixing and installing battery modules, pumps, pipework and tanks before filling with electrolytes, if applicable, shall be stated.

6.8.3 Access and Clearance

In consideration of safety and the convenience of installation, maintenance and cleaning, specific space requirements should be suggested in this section. The operators must be work in accordance with local code requirements13 when accessing or clearing the device.

13 The provisions of the Construction, Design and Maintenance regulations (issued in the UK) provide an example of good practice in this topic

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6.8.4 Precautionary Measures for Electrolyte Containment

Given the corrosive or caustic nature of the electrolyte(s), the manual should provide instructions for precautionary measures against any potential leaks, spillage caused by system failure or external events.

The currently most used precautionary measures are

• Moulded plastic spill containment trays,

• Welded and coated metal containers,

• Formed and sealed barriers in anti-acid material. 6.8.5 Ventilation (see also section 6.5.3)

Flow Batteries may generate gases or vapours (such as hydrogen) during operation. Requirements for ventilation as a result of normal or abnormal operation shall be provided.

6.8.6 Temperature

The safety, performance and life of Flow Batteries are temperature dependent. The suitable temperature range for operation, transport and storage must be stated. It is also necessary to list potential risks that may occur during operation or standby outside the advised temperature range.

6.8.7 Electrical Connections

It is the installer of the Flow Battery’s responsibility to ensure that connection of the Flow Battery Energy Storage System is in compliance with local or national requirements for the connection of electrical equipment, unless this responsibility has been specifically passed to the manufacturer or vendor.

The manual may provide guidelines, relevant standards and the requirements for electrical connections, and comprehensive wiring specifications for each region. The manufacturer should also provide the requirements/ information for interface equipment for the Flow Battery terminals (such as the voltage, the cables size, etc.). Reference should be made to local regulations for the installation of electrical equipment, including compliance with anti-islanding or other distribution or transmission code regulations.

6.9 Operation

6.9.1 General

This chapter should provide in full detail instructions for system start up, shut down, normal operations, as well as how to deal with system alarms if applicable. It is suggested to include the following subsections in this chapter to make it comprehensive.

6.9.2 Checks before Operation

A list of visual or other checks prior to starting up the system should be provided.

6.9.3 Start up and operation

Describe the standard start up procedure clearly with corresponding pictures or diagrams if necessary. Guide the user to start up or change the battery to the desired operation mode.

6.9.4 Shutdown

Describe the standard shutdown procedure clearly with corresponding pictures or diagrams if necessary.

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6.9.5 Shutdown Trip

The procedure to turn off the system or re-start the system in the event of a system trip shall be provided.

6.9.6 Operation of BMS and FMS by Human Machine Interface

Describe the control panel to guide the specific operation.

6.9.7 Alarms

The manufacturer shall list all system alarms with their explanations and the actions/measures that should be taken.

6.10 Maintenance

6.10.1 General

A Flow Battery Energy Storage System is complex and involves many fields of engineering expertise. Improper operations and maintenance could generate safety issues. The manual shall specify user serviceable categories and refer other maintenance and repair to manufacturers or approved service agents.

Standardised maintenance processes and methods should be provided to help operators maintain and repair (if applicable) the system. It should contain at least the routine maintenance process. Any special additional maintenance processes should be mentioned if applicable.

6.10.2 Routine Maintenance

Current industrial Flow Batteries are designed and assembled to operate for up to thousands of charge/discharge cycles, depending on the application and the operating environment. If such a battery was to complete one cycle per work day, the life expectancy would be 10 to 15 years, and is dependent on the quality of the components such as valves, sensors, pipes, etc. The routine maintenance procedures carried out at the recommended service intervals will prolong the life of the battery and make it more efficient and stable. This section should provide the user with a list of maintenance items and optimal maintenance schedule.

6.11 Fault finding

6.11.1 General

This chapter should list all possible alarms (see 6.9.7), error codes and potential events and list the corrective actions for each situation. It should include emergency contact details and other relevant emergency information.

6.11.2 Safety

This section should list all safety measures to be taken prior to any fault-finding activities.

6.11.3 Fault finding guidelines

List all the possible problems and corrective actions

Table 1 - List of possible problems and corrective actions

ID Symptom Probable Cause Corrective actions

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6.12 Warning Labels

The manual should list all warning labels installed on the system and provide a more comprehensive explanation.

The following is an example of the warning label format

Label Explanation

Figure 7 - Example for labelling

Explanation

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6.13 Disposal

This chapter should make clear disposal requirements and recycling and re-use and other end of life procedures.

6.14 Appendices

Appendix A: Accessories and Spare Parts

Appendix B: Output Characteristic

Appendix C: Material Safety Data Sheet

Appendix D: Required Tools when Repairing

Appendix E: Alarms and Shutdown Trips list

7 Installation of Flow Batteries

7.1 General

This section outlines the requirements of the shipping, installation (construction), pre-commissioning, commissioning, operation, and decommissioning of Flow Batteries, where the components of the Flow Battery Energy Storage System are defined in the 'Terms and Definitions' section. For each aspect of the Flow Battery project lifecycle defined in section 3, a number of regulations, standards, guidelines and 'best practices' would apply, and are described in the following Sections.

7.2 Existing Standards and Guidelines

7.2.1 General

There are many existing standards and guidelines already published that are relevant to the installation of either cabinet-type, containerised (i.e. modular), or large-scale Flow Battery Energy Storage Systems. Generally, the standards and guidelines described in this Section would apply regardless of the Flow Battery Energy Storage System size.

7.2.2 Asset-Based

Asset Management, or Asset Integrity, is an umbrella term that incorporates all activities associated with the design, construction, pre-commissioning, commissioning, operation, and decommissioning of systems. It includes all aspects of process safety, control systems, operations and maintenance personnel competencies etc.

It is recommended that the PAS 55 standard (PAS 55 - Optimal management of physical assets, Publicly Available Specification published by the British Standards Institution) be followed regarding asset-based aspects of Flow Battery installations. PAS 55 is a comprehensive standard for managing multiple assets and locations within a portfolio, and is equally applicable to single site locations. The PAS 55 standard has been applied to process and power production facilities, and, most recently, to the management of airport terminal assets. It is based on the four-step Continuous Improvement (CI) structure of 'Plan, Do, Check, Act', which is familiar to many Quality Assurance practitioners in the product manufacturing sector. It is expected that within the next few years the existing PAS 55 standard will evolve into an ISO 55001 standard14.

14 It should be noted that the American Petroleum Institute (API) has formally severed ties with ISO. The result has been that many professionals who sit on joint committees or across committees have ceased involvement with ISO. It is unclear as whether or not the current political climate will affect the progress of PAS 55 to an ISO standard, and whether or not such an ISO standard would be recognised by US-based components suppliers.

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In the context of PAS 55, the 'Plan, Do, Check, Act' philosophy is defined by the following 22 key aspects:

Plan:

a) Asset management policy (foundation document upon which all key aspects is based),

b) Asset management strategy, objectives and plans,

1) Asset management strategy,

2) Asset management objectives,

3) Asset management plans,

4) Contingency planning.

Do:

a) Asset management enablers and controls,

5) Structure, authority and responsibilities,

6) Outsourcing of asset management activities,

7) Training, awareness and competence,

8) Consultation, participation and communication,

9) Asset management system documentation,

10) Information management,

11) Risk management,

12) Legal and other requirements,

13) Management of change.

Check:

a) Implementation of asset management plans,

14) Life cycle activities,

15) Tools, facilities and equipment,

b) Performance assessment and improvement,

16) Performance and condition monitoring,

17) Investigation of asset-related failures, incidents and non-conformities,

18) Evaluation of compliance,

19) Audit,

20) Improvement actions,

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21) Records.

Act:

22) Management review (at the completion of the review process, Corrective Actions to Plant, People, and/or Process are documented and implemented and the overall four-point cycle is restarted).

The above process for continuous improvement has been applied to a range of industries – from electricity suppliers (i.e. conventional coal-fired power plants) to, most recently, airport operations – to provide the necessary framework for assuring the integrity of a given set of assets.

7.2.3 Materials

7.2.3.1 General

The guidelines developed by the National Association for Corrosion Engineers (NACE) should be considered a key repository for technical guidance on materials selection based on many decades of experience and sound engineering principles. For example, NACE RP0391-2001 provides technical guidance regarding the selection of suitable materials (and material combinations) for highly concentrated sulphuric acid systems. In addition, standards specific to either piping or pressure vessels are also to be considered during the design stage of a Flow Battery project. Such standards are described in the following sections.

7.2.3.2 Piping

The American National Standards Institute (ANSI) has several standards regarding piping that are relevant to Flow Battery installations. The most relevant is ANSI B31.3 – Standards of Pressure Piping, as this standard specifically addresses the handling of corrosive chemicals. However, other ANSI B31.x standards may apply due to specific fluid handling requirements: it is left to the judgment of the design engineer to determine which other standards apply.

See Section A.1.

7.2.3.3 Static Equipment (Pressure Vessels)

The European Directive 97/23/EC – Pressure Equipment Directive (PED) applies to all pressure equipment installed in the European Union (EU) including safety devices, industrial piping, pressure accessories, and other auxiliaries associated with the pressure system. The “CE” mark is a sign that equipment conforms to the PED.

Outside of the EU, each nation has a pressure equipment technical authority that provides a comprehensive set of standards with which a pressure system must be designed, operated and maintained.

See Section A.1.

7.2.4 Process Safety

There are several elements of process safety applicable to Flow Battery installations. Firstly, there is a necessity for containment systems to prevent the escalation of a battery electrolyte spill. It is also imperative that the vent containment systems for pressure relief system(s) are minimise releases to the environment – i.e. "vent to safe location".

Pressure relief sub-systems should be designed, installed, operated and maintained according to several standards. These standards are listed in Section A.2.

It is also recommended that in addition to the application of prescriptive process safety standards, a risk-based process safety approach be adopted for Flow Battery installations. References for this can be found with publications by the Centre for Chemical Process Safety (CCPS) and the European Process Safety Centre (EPSC). An excellent example for the application of a risk-based process safety approach can be found in the

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CCPS’s Guidelines for Risk-Based Process Safety (2007), and is recommended as a starting point for the development of a rigorous Process Safety Management (PSM) system.

7.2.5 Rotating Equipment

Current regulations within the EU state that rotating equipment must conform to the two Atmospheres Explosives (ATEX) standards as listed in Section A.3. This is relevant to Flow Battery installations due to the potential of an explosive atmosphere within the cell stacks or storage tanks of Flow Battery installations – i.e. hydrogen or oxygen production during a process upset condition.

Outside of the EU there are pump standards available from the American Petroleum Institute (API) or ISO. Although the application of a pump standard to a Flow Battery installation may not be necessary – e.g. within smaller cabinet-type units – it is recommended that such standards be considered for larger installations where a confirmation of the rotordynamic performance of pump unit should be undertaken (typically part of the overall asset integrity programme).

International standards for pump systems are listed in Section A.3.

7.2.6 Chemicals Handling

7.2.6.1 Globally Harmonised System

The Globally Harmonised System (GHS), initiated by the United Nations Economic Commission for Europe (UNECE), is an accepted system for the classification and labelling of chemicals for the quick identification of potential associated hazards. It provides detailed guidelines and procedures for the handling, transport, storage and use of various classes of chemicals. Since the focus of the GHS is on safety, there are several physical, environmental, health and hazard aspects that are relevant to Flow Battery installations.

7.2.6.2 REACH and Seveso II/III

In addition to the GHS, there may also be national, regional, and local regulations that must be followed for the handling, transport, storage and use of the chemicals used within a Flow Battery installation.

One example is the REACH and Seveso II/III regulations applied within the EU.

The Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) regulation is enforceable across the EU. The main focus of this regulation is to ensure a consistent methodology for the evaluation and communication the hazards related to various classes and associated quantities of both 'established' (i.e. well known) and newly developed chemical compounds.

Seveso II/III are directives initiated by the EU focused on preventing and controlling major industrial accidents that involve dangerous substances (i.e. low probability, high consequence events).

These two documents are relevant for Flow Battery installations due to the nature of electrolyte, the metals dissolved in the electrolyte, and the potential for explosive and/or toxic gas evolution. Additional information on the regulations is provided in Section A.4.

7.2.7 Control Systems

7.2.7.1 Safety Instrumented System

Critical safety systems within a chemical process such as a Flow Battery installation are usually fully automated to ensure a quick and consistent reaction to a developing hazardous condition. An automated system that is designed only for safety is called the Safety Instrumented System (SIS). The integrity of SIS loops must be designed, operated and maintained within very strict procedures due to inherent criticality of its safety functions. The standards listed in Section A.5 describe design, validation, verification, commissioning, operation, maintenance of SIS loops.

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7.2.7.2 Process Control

Guidelines for process control are available but are less stringent than those applicable to SISs because the process control system does not, by definition, serve a safety function. Standards do apply to components of the process loop such as pressure transducers and transmitters, wiring and control blocks, but not to the entire process loop.

The Instrument Society of America (ISA) has good practice guidelines for process control system development. Standards are also available from the ISA and CENELEC regarding measurement devices, cabling, terminal blocks, etc.

For larger systems with more than 500 alarms (alarms associated with both the process control system and the SIS), alarm management is beneficial and should be considered. It has been shown in many industrial accidents that the condition of multiple simultaneous alarms results in an information overload (i.e. alarm flooding) to the human operator, thus causing a misinterpretation of a developing hazardous condition. There are a number of standards and guidelines for alarm management of relevance to Flow Battery installations and are listed in Section A.6.

7.2.8 Electrical Interface to Grid

7.2.8.1 General

Numerous international and national standards address electrical components, cabling, and control system communication protocols used within Flow Battery installations. The following sections highlight the primary regulations and standards specific to the electrical systems within a Flow Battery installation.

7.2.8.2 European Standards

EU Members have their own separate electrical grid codes and rules. As there currently is not harmonisation across the Member States, this introduces higher project costs for investors initiating projects across multiple member states. As such, several EU-sponsored projects are currently underway to develop the necessary technologies and regulatory policies to harmonise grid codes and enable the further integration of distributed energy supplies to the electrical grid.

In addition, there are relevant guidelines described in European White Book on Grid-Connected Storage by the European Distributed Energy Resources Laboratories (DERlab) as referenced in Section A.7. Furthermore, specific to the interconnection of distributed energy logical nodes, refer to Part 7-420: Basic Communication Structure of the IEC 61850-7-420 Ed. I: Communication Networks and Systems for Power Utility Automation standard.

7.2.8.3 IEEE Standards

The Institute of Electrical and Electronics Engineers (IEEE) is an internationally recognised standards body that develops, publishes and maintains standards for electrical and electronic components and systems.

There are several IEEE standards that are immediately applicable to Flow Battery installations and some standards that are very relevant but still at the development stage. Section A.7.1 lists the standards that can be immediately applied, whereas Section A.7.2 lists those standards that are relevant, but are not yet approved.

7.3 Shipping

Shipping in this context is defined as the period of the installation lifecycle involving the transportation of the Flow Battery Energy Storage System components from the various manufacturing sites to the project location. This includes systems that are shipped a complete package, for example, cabinet or container-type Flow Battery Energy Storage Systems, as well as bespoke units constructed on site.

Small Flow Battery Energy Storage Systems that can be contained within one standard freight container or smaller cabinet may be shipped complete with liquid electrolyte included. This is on the provision that the

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liquid containment system is sufficiently proved to conform to the requirements of the EU Member State Transportation of Dangerous Goods (TDG) regulations for transport of liquid electrolyte (see Section A.4).

Larger systems should be designed such that they are modular and can be shipped in standard freight containers and tankers (for liquid electrolyte). It is recommended that the best practices of project management and engineering design for small specialty chemical plants be adopted for large, bespoke systems.

The following standards taken from content in the EN 50272-1:2010, Safety requirements for secondary batteries and battery installations - Part 1: General safety information also applies to any transport of dangerous goods.

• European Agreement for the International Carriage of Dangerous Goods by Road (ADR),

• International Convention concerning the carriage of Foods by Rail (CIM and RID),

• International Maritime Organisation, Dangerous Goods Code; IMDG Code 8 Class 8 Corrosive,

• International Air Transport Association (IATA); Dangerous Goods Regulations. It is recommended that the components be shipped in climate-controlled packaging.

7.4 Pre-Commissioning

In addition to the tasks defined for pre-commissioning in Section 3, it is also recommended that extensive quality control checks be completed on all installed components. Pre-commissioning should also include weight-withhold and vibration tests to ensure mechanical robustness similar to those carried out according to IEC 61959, Secondary cells and batteries containing alkaline or other non-acid electrolytes - Mechanical tests for sealed portable secondary cells and batteries.

During pre-commissioning the electrical interconnection to the grid from the Flow Battery should be checked that the interconnection conforms to the applicable IEEE standard(s) before proceeding to commissioning.

7.5 Commissioning

Specific to Flow Battery installations, the following tests should be carried out to ensure compliance with OEM specifications.

• Charge currents,

• Discharge currents,

• Internal resistance,

• Stripping to 0 V (if required),

• Capacity in Ah in and out,

• Energy in Wh in and out,

• Rated output power – continuous and instantaneous,

• Response time,

• Operating temperature range. Additional commissioning activities are described within the definition provided in Section 3.

7.6 Operation

There is not a standard methodology of operation for a Flow Battery installation, as each unit operates in a unique manner according to its OEM requirements. However, since many elements of Flow Battery

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installations share common features across the different types of Flow Batteries, a robust and rigorous process safety framework should be adopted throughout the operating life of a Flow Battery (Section 7.2.4 - Process Safety). It is also recommended that a standardised asset management system (for example, that stated in PAS 55 – see Section 7.2.2) be used for the entire installation cycle.

7.7 Decommissioning

The possibility of recovering metals and liquid electrolyte before system disposal should be considered to reduce waste and encourage reuse of materials. Any material from the system that can be recycled should also be disposed of in this way. However, elements such as membranes that still contain electrolyte should be cleaned and disposed of according to national, regional and local regulations.

It is recommended that best practices from the chemical process industries be used for the cleaning requirements for the chemical process sections of Flow Battery installations e.g. IChemE (Institution of Chemical Engineers) and CCPS (Center for Chemical Process Safety) best practices for chemical cleaning of process piping). Once elements have been cleaned (e.g. flushed with detergents and fresh water), they can be removed and disposed of in accordance with EU Member State regulations applicable to the respective materials.

7.8 Regulations

7.8.1 General

There are many regulations from several bodies that are relevant to Flow Battery installations. These are outlined in the sections below.

7.8.2 EU – Battery Recycling

The EU regulated the manufacture and disposal of conventional batteries through Directive 2006/66/EC, Directive on batteries and accumulators and waste batteries and accumulators, which specifically addresses the need to reduce the uncontrolled release of mercury, cadmium, lead and other hazardous metals to the environment via mixing with normal household waste. In addition to recycling, the Directive also stipulates that the maximum quantities of certain hazardous chemicals and metals that can be contained within batteries.

However, it is difficult to align Flow Battery installations with stipulations in the Directive due to the difference in construction compared to more conventional batteries. Thus, it is recommended that Flow Battery installations be considered as specialty chemical manufacturing facilities for the purposes of decommissioning, recycling and disposal. In this context, provided that the practices described in Section 7.7 are followed, the Flow Battery components can be removed and recycled to the maximum extent possible.

7.8.3 Land Use – Zoning Laws

It is expected that Flow Battery installations will be zoned in a similar way to electrical substation installations – particularly for cabinet or container-type stand-alone systems. For larger bespoke units, it is expected that such installations would be required to be installed in those areas where the land-use is zoned 'industrial' – i.e. similar to specialty chemical manufacturing facility.

7.8.4 ATEX Regulations

For Flow Battery installations it may be necessary to define various hazard zones according to the applicable regulation. For installations within the EU, ATEX regulations apply equally to mechanical and electronic equipment, and are therefore relevant to Flow Battery installations. See Section A.8 for additional information on the ATEX Directives.

It is recommended that a structured, formal risk assessment be completed in accordance with the best practices from the chemical process industry to determine the number and extent of the hazard zones. If the risk assessment determines that the probability of an occurrence of a potentially hazardous or explosive atmosphere is below the As Low as Reasonably Practicable (ALARP) level established by the respective Regulatory Authority, it is acceptable to use non-ATEX rated equipment in that area. For larger installations

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(i.e. utility-scale), it is recommended to consider a risk-based safety framework and “safety case” approach similar to that adopted within the UK Health and Safety Executive, and is described in the Control of Major Accident Hazards (COMAH) regulations.

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Annex A (informative)

Listing of Applicable Regulations, Standards and Guidelines

A.1 Piping and Pressure Vessels

ANSI/ASME15 B31.3 – Process Piping

ASME – Boiler and Pressure Vessel Code Section VIII

EU Directive 97/23/EC – Pressure Equipment Directive (PED)

NACE16 RP0391-2001 – Materials for the Handling and Storage of Commercial Concentrated (90 % to 100 %) Sulfuric Acid at Ambient Temperatures

National Authority standards (Outside of the EU)

A.2 Process Safety

API17 Std 520 - Sizing, Selection, and Installation of Pressure-relieving Devices in Refineries

API Std 521 – Guide for Pressure-relieving and Depressuring Systems: Petroleum petrochemical and natural gas industries – Pressure-relieving and depressuring systems

API Std 526 – Flanged Steel Pressure-relief Valves

API 2000 – Venting Atmospheric and Low-Pressure Storage Tanks

ASME – Boiler and Pressure Vessel Code, Section VIII

EN 764-7 – Pressure equipment – Part 7: Safety systems for unfired pressure equipment (Additional to, and based on, the EU PED).

EN ISO 4126 – Safety devices for protection against excessive pressure

EN ISO 23251 – Petroleum, petrochemical and natural gas industries - Pressure-relieving and depressuring systems

A.3 Rotating Equipment

API 610 – Centrifugal pumps for Petroleum, Petrochemical and Natural Gas Industries

API 685 – Sealless Centrifugal Pumps for Petroleum, Petrochemical, and Gas Industry Process Service

EN ISO 13709 – Centrifugal pumps for Petroleum, Petrochemical and Natural Gas Industries

15 ASME – American Society of Mechanical Engineers 16 NACE – National Association of Corrosion Engineers 17 API – American Petroleum Institute

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EU Directive 94/9/EC – equipment and protective systems intended for use in potentially explosive atmospheres (ATEX 95) (required only in the EU, but can be applied elsewhere)

EU Directive 99/92/EC – minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (ATEX 137) (required only in the EU, but can be applied elsewhere)

A.4 Chemicals Handling

Globally Harmonized System of Classification and Labelling of Chemicals (GHS) – http://www.unece.org/trans/danger/publi/ghs/ghs_welcome_e.html

EU Directive 96/82/EC – control of major-accident hazards involving dangerous substances (Seveso II)

EU Directive 2012/18/EU – control of major-accident hazards involving dangerous substances, amending and subsequently repealing Council Directive 96/82/EC (Seveso III)

Transportation of Dangerous Goods (TDG) regulations (nation-specific):

e.g. Canada – http://www.tc.gc.ca/eng/tdg/clear-menu-497.htm

United States – http://phmsa.dot.gov/hazmat/regs

A.5 Safety Instrumented Systems (SIS)

ANSI/ISA18 S84.01 – Safety Instrumented Systems for the Process Industry

IEC 61508 – Functional safety of electrical/electronic/programmable electronic safety-related systems

IEC 61511 – Functional safety - Safety instrumented systems for the process industry sector

ISO 26262 – Road vehicles – Functional safety

A.6 Process Control

EEMUA19 191 – Alarm Systems – A Guide to Design, Management and Procurement

ISA 18.02 – Management of Alarm Systems for the Process Industries

NAMUR20 NA 102 Worksheet – Alarm Management

NPD21 YA 711 – Principles for Alarm System Design

VDI/VDE Guideline 3699 – Process Control Using Display Screens

18 ISA – International Society for Automation 19 EEMUA – Engineering Equipment and Material Users’ Association 20 NAMUR – Normenarbeitsgemeinschaft für Mess- und Regeltechnik in der Chemischen Industrie 21 NPD – Norwegian Petroleum Directorate

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A.7 Electrical Grid

DERlab22 – European White Book on Grid-Connected Storage http://www.der-lab.net/downloads/noe_003_grid_connected_storage.pdf

A.7.1 Established

IEEE 80 – IEEE Guide for Safety in AC Substation Grounding

IEEE 81 – IEEE Guide to Measurement of Impedance and Safety Characteristics of Large, Extended or Interconnected Grounding Systems

IEEE 367 – IEEE Recommended Practice for Determining the Electric Power Station Ground Potential Rise and Induced Voltage from a Power Fault

IEEE 1127 – IEEE Guide for the Design, Construction, and Operation of Electric Power Substations for Community Acceptance and Environmental Compatibility

IEEE 1159 – IEEE Recommended Practice for Monitoring Electric Power Quality

IEEE 1247 – IEEE Standard for Interrupter Switches for Alternating Current, Rated Above 1000 V

IEEE 1325 – IEEE Recommended Practice for Reporting Field Failure Data for Power Circuit Breakers

IEEE 1366 – IEEE Guide for Electric Power Distribution Reliability Indices

IEEE 1379 – IEEE Recommended Practice for Data Communications Between Remote Terminal Units and Intelligent Electronic Devices in a Substation

IEEE 1402 – IEEE Guide for Electric Power Substation Physical and Electronic Security

IEEE 1409 – IEEE Guide for the Application of Power Electronics for Power Quality Improvement on Distribution Systems Rated 1 kV Through 38 kV

IEEE 1453 – IEEE Recommended Practice for Measurement and Limits of Voltage Fluctuations and Associated Light Flicker on AC Power Systems

IEEE 1459 – IEEE Standard Definitions for the Measurement of Electric Power Quantities Under Sinusoidal, Nonsinusoidal, Balanced, or Unbalanced Conditions

IEEE 1547– IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems

IEEE 1646 – IEEE Standard Communication Delivery Time Performance Requirements for Electric Power Substation Automation

IEEE 1815 – IEEE Standard for Electric Power Systems Communications -- Distributed Network Protocol (DNP3)

IEEE 2030 – IEEE Guide for Smart Grid Interoperability of Energy Technology and Information Technology Operation with the Electric Power System (EPS), End-Use Applications, and Loads

IEEE C37.1 – IEEE Standard for SCADA and Automation Systems

IEEE C37.2 – IEEE Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations

22 DERlab – European Distributed Energy Resources Laboratories e. V.

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IEEE C37.13 – IEEE Standard for Low-Voltage AC Power Circuit Breakers Used in Enclosures

IEEE C37.100 – IEEE Standard of Common Requirements for High Voltage Power Switchgear Rated Above 1000 V

IEEE C37.106 – IEEE Guide for Abnormal Frequency Protection for Power Generating Plants

A.7.2 In Development

IEEE PC 37.240 – Standard for Cyber Security Requirements for Substation Automation, Protection and Control Systems

A.8 ATEX Regulations

EU Directive 94/9/EC – equipment and protective systems intended for use in potentially explosive atmospheres (ATEX 95) (required only in the EU, but can be applied elsewhere)

EU Directive 99/92/EC – minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (ATEX 137) (required only in the EU, but can be applied elsewhere)

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Bibliography

The following referenced documents should be read in conjunction with this document. For dated references, only the cited edition applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

BSI PAS 55, Optimal management of physical assets

EN 50272-1:2010, Safety requirements for secondary batteries and battery installations - Part 1: General safety information

EU Directive 2006/66/EC, Directive on batteries and accumulators and waste batteries and accumulators

IEC 60300-3-3, Dependability Management – Part 3-3: Application Guide – Life Cycle Costing

IEC 61959, Secondary cells and batteries containing alkaline or other non-acid electrolytes – Mechanical tests for sealed portable secondary cells and batteries.

ISO 15663-1, Petroleum and Natural Gas Industries – Life Cycle Costing – Methodology

ISO 15663-2, Petroleum and Natural Gas Industries – Life-cycle costing Guidance on application of methodology and calculation methods

ISO 15663-3, Petroleum and Natural Gas Industries – Life-cycle costing Implementation guidelines

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