webinar 6 of 6 english
TRANSCRIPT
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PhotovoltaicSystemsTraining
Session6 Off
grid
installations
http://www.leonardo-energy.org/training-pv-systems-design-
construction-operation-and-maintenance
JavierRelancio&LuisRecuero
GeneraliaGroup
October6th 2010
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PHOTOVOLTAICSYSTEM
Design,Execution,Operation&Maintenance
STANDALONEFACILITIES
JavierRelancio.GeneraliaGroup. 06/10/2010
www.generalia.es2
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
4http://www.leonardo-energy.org/training-pv-systems-design-construction-operation-and-maintenance
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5
B a s ic t o p o l o g y
PV modules
PV regulator
Inverter
DC Consumption
AC Consumption
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Differences with a grid connected system
Designed for self-consumption
An electricity storage is required
Regulator / charger
Batteries
Inverters with capacity " to create a grid"
For facilities with consumptions in DC and output power below 2 kW, we may require modules
with particular characteristics:
If the consumptions are in DC 12 V, modules of 18 V
If they are in DC 24 V, modules of 30-32 V
NOTE: The modules of 12 V are more expensive, but it is possible to avoid their use by using
regulators with power maximizers. Only for powers over 2 kW
6
I n t r o d u c t i o n
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Criterion of winter production maximization VS annual production maximization
In the grid connected facilities, the objective is to obtain the maximum annual profitability of
the installation
In stand-alone facilities, the objective is to feed the demand for any day of the year. For it:
We have to design the installation for the " worse day of the year "
We will choose the modules tilt that maximizes the production in the above mentioned
month
7
I n t r o d u c t i o n
Sofia,Bulgaria Madrid,Spain
Ed(32) Ed (61) Ed(34) Ed (60)
Jan 1,65 1,79 2,66 2,96
Feb 2,25 2,34 3,05 3,19
Mar 2,75 2,63 4,32 4,23
Apr 3,42 3,01 4,1 3,63
May 3,61 2,95 4,63 3,75
Jun
3,79 2,97 4,78 3,69
Jul 4,06 3,23 4,91 3,85
Aug 3,95 3,37 4,79 4,08
Sep 3,48 3,28 4,38 4,14
Oct 2,68 2,74 3,54 3,63
Nov 1,71 1,84 2,66 2,9
Dec 1,3 1,41 2,15 2,39
Totalyear 1050 960 1400 1290
0
1
2
3
4
5
6
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Sofia,Bulgaria(32) Sofia,Bulgaria(61)
Madrid,Espaa
(34) Madrid,
Espaa
(60)
N o t e : we can use backup system for the worst production months
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
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Inverter
Lower range of powers than for grid connected facilities
Possibility of connection in parallel or series
Prepared for auxiliary inputs in parallel, in case of hybrid systems:
diesel, grid, modules
Manufacturers:
9
El e m e n t s
Manufacturer Power (per unit) System Power Observations
Xantrex 6 kW 36 kW
It integrates a battery charger It allows to inject surplus to the grid It allows different configuration modes for themanagement of the generation and the consumption
Victron 10 kVA100 kVA(90 kW)
It integrates a battery charger It allows different configuration modes for themanagement of the generation and the consumption
Ingeteam 15 kVA 120 kVA It integrates a battery charger It allows different configuration modes for themanagement of the generation and the consumption
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Regulator / Charger
It is used to:
... protect the batteries against overcharging
To avoid excessive discharges within a cycle
It is recommended to work with a oversizing of 125 %
Differences between regulator and charger
Charger: it is only used to charge the batteries
Regulator: it is used both for charging the batteries and
managing the loads in DC
10
El e m e n t s
NOTE : The chargers are not simple devices:
The battery charge stage depends on many factors and is difficult to determine
Multiple algorithms exist to optimize the battery charging and to increase its
lifetime
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Introduction
Batteries are used for storing the energy that is produced by the
modules during the day, for being consumed in the periods that
there is no solar irradiation
This storage takes place due to chemical reversible reactions
11
B a t t e r i e s
A battery is composed by the connection of several "cells in series
Between the electrodes there is a certain potential difference (Generally: 2V)
In photovoltaic applications we can generally find batteries of 12, 24 or 48 volts
Normally, the system is designed to store energy for several days of consumption
In case of several days of low irradiation: clouds, rain, etc
Three days can be a good recommendation, depending on each case
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Real capacity
12
B a t t e r i e s
Capacity
Electricity that can be obtained during a full discharge of a completely charged battery
The capacity, in Amperes - hours (A - h), is the current that the battery can supply,
multiplied by the number of hours in which the above mentioned current is delivered
Theoretically, a battery of 200 A - h might supply: 200A during an hour, 100A for two hours,1A for 200 hours and so on.
However, in the reality, the capacity of the battery will change according to the regime of
charge and discharge. (Generally, lower speed of discharge implies a bigger capacity)
For example: a battery which specifies a capacity of 100 A - h during 8 hours (C-8):
It might supply 12,5 A during 8 hours. C = 12.5 x 8 = 100 A - h
But it might provide 5.8 A during 20 hours. C ' = 5.8 x 20 = 116 A - h
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Depth of discharge
B a t t e r i e s
Percentage of the total capacity of the battery that can be used without need of rechargeand without damaging the battery.
As a general rule, the less depth of discharge is reached in every cycle, the longerthe battery lifetime will be
Classification:
Several manufacturers
Isofoton, Hoppecke, BAE, TABB, Tudor, etc
Lightcycle Deep
cycle
Designedforhighcurrentintheinitial
discharges
Constantchargesanddischarges
Depthsofdischargelowerthan20%
Designedforlongperiodsofutilizationwithout
beingrecharged
Theyaremorerobustandhavehigherenergetic
density
Depth
of
discharge
around
of
80
%'
Note: This classification is generally used for Lead-Acid batteries
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Type of batteries
B a t t e r i e s
For photovoltaic applications the most suitable batteries are the stationary ones, designed tohave a fixed emplacement and for the cases in which the consumption is more or lessirregular. The stationary batteries do not need to supply high currents during brief periods of
time, but they need to reach deep discharges
Lead Acid(deep cycle)
Lead Acid(light cycle)
Gel-Cell NiCad
Observations High commercialavailability
Sudden death couldhappen
They aremanufactured withlead antimony
High commercialavailability
Sudden death couldhappen
They are manufacturedwith lead - calcium
The acid is in gelstate
They need lessmaintenance
They can operate inany position
They are moreexpensive than leadbatteries
Better performancewith high temperature
They cost the doublethan Lead Acidbatteries
Discharge depth 40-80% 15-25% 15-25% 100%
Self discharge per month 5% 1-4% 2-3% 3-6%
Typical capacity (Ah/m3) 35,314 24,720 8,828 17,660
Capacity range (Ah/m3) 7,062 to 50,323 5,791 to 49,000 3,672 to 16,400 3,630 to 34,961
Typical capacity (Ah/Kg) 12.11 10.13 4.85 11.10
Capacity range (Ah/Kg) 4.18 to 26.65 2.42 to 20.26 2.20 to 13.87 2.64 to 20.90
Minimal temperature (oC) -6.6 -6.6 -18 -45
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The diesel generator as a backup (I)
The use of a diesel generator can allow us to avoid the oversizing of solar modules
and batteries.
The diesel generator would cover the periods of low irradiation or the situations of
extraordinary consumption
Nowadays, the energy generated by a diesel group can be more expensive than
the energy obtained from a photovoltaic solar system
It will depend on the price of the fuel in each country
NOTE : In the following slide we can find an example
15
D i e se l g e n e r a t o r
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16
N o t e s :
1. For this study we have considered that the price of the electricity from a Diesel Generator is, today, 0.35 perkWh (Including the costs that the logistics of the fuel supposes).
2. The study has considered a radiation of 1500 HSP3. In the graph we can find, in green, an estimation of the repercussion that would suppose the extra charges for
the emission of pollutant gases (Price of ton of CO2).4. The prices are in Euros
5. The word "hybrid" refers to a photovoltaic installation with a diesel generator as a backup.
0,20
0,40
0,60
0,80
1,00
1,20
1,40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
PreciokWhhibrido PreciokWh GDiesel PreciokWh GDieselCO2
Price per kWh: Diesel generator VS Solar Facility
D i e se l g e n e r a t o r
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
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18
H y b r i d Sy s t e m : D ie se l - So l a r
PV modules
PV regulator
Inverter
DC
Consumption
ACConsumption
The chosen diesel generator must have
automatic starter:
Using its own electronic starter to
automatically switch on when an auxiliary
signal is received
Using an external electronic starter
specially designed for this function
The generator is connected to the AC BUS
The diesel generator is automatically switched on if
the batteries are under a certain level
The generator can produce energy exclusively to
supply the consumption or, also, to charge the batteries
The inverter has to be specially designed with
this function (AC/DC Converter)
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19
H y b r i d Sy s t e m : W i n d - So l a r
Thewindpotentialisdeterminedby:
Speedofthewind:thekineticenergyofthewind
increasesaccordingtothecubeofitsspeed
Windresourcesbecomeexploitablewhere
averageannualwindspeedsexceed45m/s
Alsoitisinfluenced,toalesserextent,bythe
characteristicsanddensityofthewind
This type of system is currently being studied on the R&D departments of manyinstitutions and companies.
Good correlation between the wind and the solar resource
Generally, the wind & solar systems are connected to the DC BUS (of the batteries)
There is not too much information about the wind resource
The guarantees for the wind system are lower than for the PV system
Average, three years
Description
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Windgenerator
20
H y b r i d Sy s t e m : W i n d - So l a r
PVmodules
PVregulator
Inverter
DC Consumption
AC Consumption
Windregulator
Topology
DC BUS
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21
Ef f i c i e n c y i n t h e c o n s u m p t i o n ( I )
The importance of reducing the consumption
Nowadays, we can find great evolutions in the consumption reduction of many
massive devices: electrical appliances, lighting, air conditioning, PCs, etc
Considering the high initial investment per kWp for an isolated solar system
and considering the dependency between this peak power and the consumption
every stand alone solar facility should begin by the
optimization of its consumption efficiency
Ex am p l e :
Electricity price: 0,40 per kWh
Fridge consumption A+ Class: 150 kWh/year
Fridge consumption G Class: 800 kWh/year
Saving: 260 per year
* If we reduce our energy consumption, installing a more efficientdevice, we will be able to reduce the price of our solar PV Facility
Source: IDAE
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Co n s u m p t i o n e f f i c i e n c y ( I I )
Examples
ElementLow
consumption
Ordinary
consumption
FridgeClass A
150 kWh/yearClass G
800 kWh/year
WashingMachine
Class A1.42 kWh
Class G6.9 kWh
Lighting 1 Incandescent100 W
LED10 W
Lighting 2Incandescent
100 WLow Consumption
18 W
PC(Desktop)
250 W 70 W
Energy
class
Energy
consumption Evaluation
LOW
MED
HIGH
Less efficient
More efficient
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23
Sm a r t Gr i d s ( I )
Global objective
To success:
Increase the integration of renewable
energies in the Global electric grid The need of dealing with an
intermittent & distributed generation
International governments commitment (such as the EU)
Minimize the environmental impact.
Reduce the CO2 emissions
Reduce the dependency from fossil fuels
Increase the use of Renewable Energies
Reduce costs & Increase the energy efficiency
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Sm a r t Gr i d s ( I I )
Improve the control & supervision of the generation
Intermittent generation profile of the Renewable Energies
Low forecast on the production
Improve the demand management
High peakvalley ratio
Low correlation with renewable production
Mechanisms towards the smart grids
Improve the international grid connection
Improve the electricity storage
New facilities to pump water and then produce energy
R&D for new in situ storage systems: hydrogen/ batteries
The electrical vehicle
Source: REE
Demand profile for anaverage day in Spain
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
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Zones distant from the grid
Zones currently supplied by diesel generators
Exceptionally, areas with instabilities from the grid
26
A p p l ic a t i o n A r e a s
Gr e a t p o t e n t i a l i n
A f r i ca n c o u n t r i e s
Especially, areas withhigh fuel prices
Source: World energy outlook 2009
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Single family houses
Public buildings: hospitals, schools, etc
Public lighting and traffic lights
Communication Stations
Water pumping
For human consumption
For agriculture
Desalination & Water sewerage
Industrial uses
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A p p l i c a t i o n e x a m p l e s
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Great advantages to be fed with solar
energy:
There is no need for batteries
The construction of a high water tank
can be used as a energy storage
Therefore we do not need regulator
either
Neither inverters
Nowadays, we can find great quality
DC bombs
Installation with few elements:
We reduce the price of the installation
We reduce the possibilities of
breakdown
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P a r t i c u l a r c a se :
W a t e r p u m p i n g f a c i l i t i e s
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Limits on the system
Maximum power output
It is limited by the inverters: nowadays
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
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We begin by creating a table with all the consumptions we will find in the system
31
Sy s t em d e s i g n ( I )
Device Numberof
UnitsPeak
Power(W)Average
Power (W)Hours of
usage
(hperday)Consumed
energy
(Whperday)
Lamp 10 11 88* 8 880
PC 1 300 150 6 900
Fridge 1 1000 400 24 9600TV 1 90 90 8 720
TOTAL 1500W 728W 12.100 Whperday
The peak power will affect the inverter calculation
The daily energy consumption will affect:
The storage system
The solar modules
Study of consumptions
* Simultaneity ratio 80%
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According to the consumption study, we have to produce 12.100 Wh per day (average)
As we have explained previously, this production must be guaranteed even the worst
day of the year, in this case, in December
32
Sy s t e m d e s i g n ( I I )
Solar generator calculation
Madrid,Espaa
Ed*(34) Ed* (60)
Jan 2,66 2,96
Feb 3,05 3,19
Mar 4,32 4,23
Apr
4,1 3,63May 4,63 3,75
Jun 4,78 3,69
Jul 4,91 3,85
Aug 4,79 4,08
Sep 4,38 4,14
Oct 3,54 3,63
Nov 2,66 2,9
Dec
2,15 2,39Totalyear 1400 1290
We have to consider the losses in all the elements of the system:
modules, inverters, chargers, batteries and cables.
The battery losses can be estimated around 15 %
The whole system losses, can be estimated around 34 %
WLossesHSP
EnergyP demandedsolar 85,670.7
66,039,2
12100=
=
=
We could install, for example:
34 modules of 230 W = 7.820 Wp
*Ed: Average daily electricityproduction for 1kWp
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According to the consumption study, the batteries should supply 12.100 Wh/day (average)
In this example, the system will consider that the batteries have to be able to store energy
for two days without solar radiation
The batteries, then, should be able to store 24.200 Wh
For this example, we will choose Lead-Acid batteries, with a Cycle-Depth of 80%
In order to increase the battery life-time, we will consider a maximum dischargedepth around 60 %
We will consider the battery losses around 15%.
33
Sy s t em d e s i g n ( I I I )
Battery calculation
hACapacity hA =
=
=
12.19772485,06,0
212100
VoltageLossesdepthDischarge
daysnEnergydemand
Conclusion: 12 batteries of 2000 A-h (C-20)
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Now, we have to consider the peak power of the system
In this case, the maximum power would be 1500 Wp
However, usually we use a Simultaneity Ratio, because normally all the devices will
not be connected at the same time
Furthermore, the inverters are prepared to supply the double of their nominal output
power, during a certain period of time
34
Sy s t em d e s i g n ( I V )
Inverter calculation (I)
In this case, we will consider that thepeaks from the washing machine and
the fridge will not be longer than theseperiods
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We will reach a maximum output power of 1500 Wp, so the Nominal Output
Power should be higher than 750 Wp
Considering the average consumptions, and applying a Simultaneity Ratio of
80% for the lights, t h e n o m i n a l O u t p u t P o w e r o f t h e i n v e r t e r sh o u l d b e h ig h e r
t h a n 7 2 8 W p
35
Sy s t e m d e s i g n ( V )
Inverter calculation (II)
So, we will choose any inverter with a Nominal Output
Power higher than 750 Wp
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Demanded energy: 12.100 Wh
Solar modules peak power: 7.820 Wp
Batteries capacity: 2.000 A-h (C-20) x 24 V = 48.000 W-h
Inverter nominal output power: 750 1000 Wp
36
Sy s t em d e s i g n ( V I )
Conclusions
We have considered that the consumption is homogeneous during the year
If this was not the case (For example, if we had an air conditioning system) we
would have studied also the maximum demanding day
We could reduce the amount of batteries, by reducing their autonomy or increasing
their discharge depth and introducing a diesel generator as a backup for the periods
that the batteries cannot assume
Observations
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INDEX
Introduction
Elements. Storage System & Backup System
Trends: Hybrid Systems. Efficiency. Smart Grids
Applications. Examples
Design
Maintenance
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Periodical cleaning of the modules
Depending on the pollution of each area
Generally, once per year
Checking the cables and connections
Retightening the screws
Checking the structure
If it is not protected against open air (aluminum, galvanized steel, etc) it will
require a periodical antioxidant paint
Checking any shadowing effect
38
So l a r m o d u l e s m a i n t e n a n c e
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The battery is a dangerous element, due to its chemical and electrical properties
39
B a t t e r i e s m a in t e n a n c e ( I )
Main risks
The electrolyte is, generally, dilute acid: it may
produce burns if contacting the skin or the eyes
Electrocution risk
From 24 V, in wet environments
From 48 V, in dry environments
Risk of fire or explosion
The batteries produce hydrogen gas
An appropriate ventilation system is needed
Recommendations:
Use appropriate gloves and shoes
Use plastic handle tools Avoid wearing any metallic object
Avoid sparks and flames close to the
batteries
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B a t t e r i e s m a in t e n a n c e ( I I )
Main tasks
Checking that the room is well ventilated and protected against the sun light
Checking that the electrolyte level is between the manufacturer limits
Add only distilled water
Except for Gel type batteries
Protecting the connection terminals with antioxidant grease to avoid sulfurizing
Checking the tightness of the battery connections
Cleaning the battery covers and terminals
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En d o f Se s s io n 6
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En d o f Se s s io n 6
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Thank you for attending