Hardware Home Energy Management System for Monitoring the Quality of Energy Service at Small

Consumers

Ciprian Ionut PAUNESCU, Tudor ZABAVA, Lucian TOMA, Constantin BULAC, Mircea EREMIA Department of Electrical Power Systems University POLITEHNICA of Bucharest

Bucharest, Romania Email: ciprian@nssweb.ro

Abstract This paper presents a laboratory hardware system, developed in the Department of Electrical Power Systems of University Politehnica of Bucharest, that simulate an energy management system to be applied in a smart home. The core of the system is a controller that is capable of switching on/off various domestic appliances as a response to price signals. The system may be capable of communicating with all loads and with the main meter, and may provide information about the power quality. Also, the system may be capable of responding to suppliers signals in order to provide a demand response service.

Index Terms-- home energy management system (HEM), smart home, smart grids

I. INTRODUCTION According to Siemens [1], the buildings are responsible

for 40% of the world energy consumption and for 21% of the total greenhouse emissions. For these reasons, buildings are key elements in the targets to reduce the energy consumption and to implement sustainable development programs. Implementation of advanced technologies and transforming the buildings into manageable entities may help reducing the greenhouse emissions by up to 40%.

The smart home concept, together with the energy management systems for small applications, are normal evolutions in the implementation process of the smart grids concept towards transforming the traditional consumers in more active ones, becoming in some cases prosumers. Various solutions have been proposed in the literature, and innovative projects have been implemented in pilot projects, many of them focusing on metering and data management.

A connected home platform and development framework for design, development and deployment of smart home services is presented in [2], whereas a lightweight key establishment protocol for smart home energy management systems and the implementation details of the protocol are proposed in [3]. One challenging technical issues is the

compatibility between equipments. The Zigbee technology for application in the smart home is presented in [4], where a new routing protocol DMPR (Disjoint Multi Path based Routing) to improve the performance of the ZigBee sensor networks is proposed. The interaction between the user and the home energy management system is decisive in helping the customer to easily adopt the new technology. A user interaction interface for energy management in smart homes is proposed in [5].

Various control and optimization algorithms have been proposed. An optimal and automatic residential energy consumption scheduling framework which attempts to achieve a desired trade-off between minimizing the electricity payment and minimizing the waiting time for the operation of each appliance in household in the presence of a real-time pricing tariff combined with inclining block rates is proposed in [6]. Authors of [7] and [8] propose optimization algorithms to be implemented in the home energy management systems to determine the optimal operation of residential appliances within 5-minute time slots while considering uncertainties in real-time electricity prices.

II. THE CONCEPT OF HOME ENERGY MANAGEMENT SYSTEM

A home energy management (HEM) system includes any hardware and software elements by means of which various energy management objectives can be achieved. HEM includes metering systems, sensors and communication infrastructure and thus it can be easily identified by a smart metering system. A HEM is customized in terms of customers needs and the type of energy services provided by the suppliers.

A home energy management may be configured mainly into three areas (Fig. 1): the main metering area, the home appliances area and the external communication area. The home controller is the brain which hosts the applications for

978-1-4673-6487-4/14/$31.00 2014 IEEE

control and optimization. The communication with the home appliances is performed via sensors.

The software implemented in the HEM system, through the home controller, allows the customer to get informed about a large range of economical and technical characteristics, among which:

Power/energy quality supplied from the public distribution grid; the most important parameters are the voltage level, voltage dips, overvoltages, flicker and harmonics;

Energy cost, for both the already consumed energy and for the next period consumption based on forecasts; furthermore the energy price for the next hours may also be provided; it is expected that hourly or 15 minutes tariffs will be regular at small consumers in the near future;

Operation scheduling and energy consumption may be performed in terms of energy price and availability of local generation;

Figure 1. HEM Architecture [9].

A display may be used as the interface between the owner and the HEM system. The owner may set the operation schedule, may start up or shut down load appliances, or may change the status of various load appliances for volunteer disconnection when requested by the energy supplier.

A HEM may be designed so that to manage not only information about electrical energy but also information about other services, including water, natural gas, heating, etc.

The three zones of the HEM system are presented as follows.

A. The Home Appliances area This area consists of all load appliances, generation units

(wind turbine, PV panel, diesel genset, battery, etc.), sensors, switches, and communication infrastructure with the home controller.

In order to apply some control functions, the load appliances may be divided into two categories:

vital loads, which cannot be controlled, e.g. life systems, refrigerator, desktop computer, etc.

controllable loads, which may be optimally scheduled for operation or can be switched on/off at any time, e.g. heating system, iron, air conditioner, washing machine, electric vehicle, etc.

The home controller can get information from each load appliance regarding the on/off state and the instantaneous consumption. On the other hand, the home controller can receive information from the generation units regarding instantaneous generation, state of charge, atmospheric conditions, etc. and may schedule charging/discharging of the battery (or the electric vehicle), operation of controllable loads (e.g. washing machine).

Based on the information about the load appliances and the local generation, the home controller may forecast the load for the next hours, may calculate the amount of power available for disconnection if required by the energy supplier.

B. The Metering Area It consists of all meters authorized by the service supplier

and the distribution company (for electricity, water and natural gas) and the communication infrastructure with the home controller.

Until now, no clear general characteristics of the meters have been defined in no country. The European Commission has issued a directive by which the EU member states, if feasible [10], are required to implement the smart metering for electrical energy at all levels, while at least 80% of the meters to comply with the smart metering requirements until year 2020.

Since these meters are the only equipments authorized as judicial interface between the customer and the service supplier and the distribution company, besides the energy quantity, they should be designed so that to provide at least energy quality parameters and compatible communication protocol. Other functions (e.g. operation scheduling) are more appropriate to be implemented in the home controller as they may be customized according to the customers needs. Examples of meters, for electrical energy, water and natural gas are shown in Figure 2.

a. b. c.

Figure 2. Meters: a) electrical energy; b) water; c) natural gas.

New administrative service can be provided after smart metering implementation. The electrical energy supplier may become a service provider and may include in its services contract other services like water and natural gas, representing, from judicial point of view, the customer in relation with the distribution companies.

C. The External Communication Area It represents communication infrastructure and protocol

between the smart home and the supplier, via the home controller, although the supplier may get information about the customer load directly from the authorized meter. Information from a certain number of meters are gathered into a data concentrator then sent to the central system of the supplier. The most efficient communication is by Ethernet type infrastructure, although radio communication is more secure.

Example of information exchanged between the customer and the energy supplier is shown in Table I.

TABLE I. INFORMATION EXCHANGED BETWEEN THE SMART HOME AND THE ENERGY SUPPLIER

from smart home to energy supplier

from energy supplier to smart home

instantaneous load load forecast availability to disconnect loads

energy price monthly invoice scheduled service interruptions daily information in the energy

field

III. THE SMART HOME ENERGY MANAGEMENT SIMULATOR

A. HEM architecture The HEM system was designed so that to fulfill the

requirements for home-comfort of a smart home, which means that a friendly interface should be attached for remote control, by smart phone, pad, computer, etc. The GUI software was implemented under PHP, thereby facilitating communication with the database, sensors, smart meter, as well as with the user terminals using a single platform. The GUI can be accessed from any terminal that incorporates a web browser, and thus installing a software on all user devices is not necessary. Another advantage of the web platform is that, with the internet router installed, it can be accessed from any corner of the world.

Figure 3 shows the main HEM architecture.

The decision module is a Raspberry PI simulator, which is a programmable board that hosts the simulation and control software under the Linux platform. This type of device is the best choice considering the performance/price ratio, and its price is about $35 only.

The command module is a programmable logic controller (PLC), called MicroDev D4-USB, which is a device that communicates with the decision module (home controller) via an USB 2.0 protocol. Its role is to implement the decisions taken by the control software. This PLC has been designed in the Department of Electrical Power Systems of University Politehnica of Bucharest, and its front and back views are shown in Figure 4.

The MicroDev PLC device was manufactured for the purpose of performing simulations in a student laboratory and not for commercial purposes, thereby its architecture allows easy configuration and implementation of various functions so that the home area management concept is much easy to teach.

Decisionmodule

Interface with thecommand module

Interface to theintelligent meterWeb interface

Interface withthe database

PHP

Database Commandmodule

USBMySQL

TCP/IPHTTP

Meter(simulated)

Browser(client)

Figure 3. HEM Arhitecture.

a)

b)

Figure 4. Front (a) and back (b) views of the MicroDev D4-USB device: 1 microcontroller; 2 - USB port; 3 digital inputs; 4 relays; 5 - relays exists; 6 - LCD port; 7 LCD; 8 - RF module; 9 - RF module antenna.

The PLC unit have one LCD with 4 lines and 40 characters per line, which displays information from the home controller via USB, such as energy price or real power consumptions, 7 relay outputs for auxiliary circuits and SSR control for high power consumption, digital and analog inputs for sensors and other data acquisition. It consists also of an 433MHz radio frequency (RF) module for wireless communication with the RF controlled plugs.

MicroDev can be used as a meter as it is capable of metering electrical parameters, and thus for this stage no other meter was used. However, in terms of future developments of the installation, a smart meter will be installed mainly to test characteristics and functionality of the future metering equipment.

MicroDev receives decisional signal from the Raspberry PI simulator and commands switching on/off of the electrical appliances via solid state relays.

The Pinguino IDE (Integrated Development Environment) was used to program the MicroDev device thanks to its important advantages: it is open source and open hardware and there are open source compilers available for all platforms (Windows, GNU/Linux and Mac OS X)

The database was created under MySQL because it can run on a large number of software platforms. Furthermore it is easy to use also due to the free application phpMyAdmin written under PHP.

The database stores various types of information, from admin information to energy information. The information stored in the database is accessed and processed by the decision module.

B. The hardware simulator A laboratory hardware smart home simulator (Fig. 5) was

developed within the Laboratory of Smart Grids from the Department of Electrical Power System, University Politehnica of Bucharest, according to the home energy management system concept presented above. It is an open system and it can be easily used for teaching.

Figure 5. Laboratory hardware smart home simulator.

The components of the HEM laboratory platform are:

1. Smart meter; 2. Bipolar fuses, from left to right: S1, S2, S3 and S4; 3. MicroDev command module; 4-5. Solid State Relays (SSR) 40 A; 6-7. Regular plugs, connected to S2 and S3 through

SSR1 and SSR2;

8-10. Controllable plugs, connected to fuses S4, with control on the addresses 11111A, 11111B, and 11111C;

11. Load, 100W, connected to plug 6; 12-14. Loads, 60W, connected to plugs 7, 9 and 10; 15. Plug to supply the router and the microcontroller to

fuse S1; 16. Home controller - Raspberry PI simulator; 17. Wireless router TP-LINK - TL-WR740N.

The loads are simulated through electric lamps. The loads are supplied either through controlled or uncontrolled plugs. Loads 11 and 12 are controlled via SSP, whereas loads 13 and 14 are controlled via controlled plugs. A large number of loads can be also simulated.

A controllable plug is shown in Figure 6.

Figure 6. Controllable plug.

An ID is associated to each plug. The user may choose from what plug to supply a certain load. The plugs communicate on the 433 MHz frequency and they continuously analyze any signal to check if the controlled ID signal match with their ID. This type of plugs allows remote control of the loads from the used terminal. All other loads, controlled via SSRs are controlled by the home controlled only based on a predefined algorithm.

C. Functions of the simulation and control software The algorithm implemented in the home controller aims

mainly to minimize the total energy costs by optimally switching on/off controllable loads in terms of energy price. The energy price is assumed to vary at predefined time intervals. The interval length was set to one hour. It is assumed that the energy price for all interval of the next day is known in advance, thus allowing the software to perform minimization of the total cost. The software may also generate random price profile within a minimum and a maximum limit so that the price may be known in advance also in a predefined time.

The user interface with the HEM system is done via a dedicated software developed under Android OS. The user can have access to the loads characteristics and also can remotely switch on/off a load appliance.

Figures 7 and 8 show print screens of a few pages as seen from a smart phone. The GUI is similar for a pad or a PC. Using the WiFi user terminal, loads can be added or deleted from the list, loads can be remotely switched on/off according to the customer decision, loads can be edited and so on.

Figure 7. HEM GUI.

Figure 8. HEM GUI.

D. Simulations Figure 9 shows the load response to energy price for a

boiler and an air conditioner. The loads are switched on when the price is low, while during high price periods the loads are switched off.

a.

b.

Figure 9. Load response in terms of energy price: a) boiler; b) air conditioner.

The simulations were performed using some hypothetic energy consumptions or price profile.

E. Future developments This technology and architecture for the home energy

management concept will be implemented in a laboratory passive house built in the yard of University Politehnica of Bucharest. The house is provided with advanced construction technology and heating/cooling technology. Real electrical appliances will be added to the house and then additional functions will be added to the already tested HEM system.

IV. CONCLUSIONS The laboratory home energy management simulator

developed in UPB follows the actual trends of the smart grid concept. The architecture and the algorithms implemented are based on authors experience and not on existing legislation since no regulation is in force regarding smart metering. The controller is flexible for implementation of various functions and algorithms. It is expected that smart metering to small consumers will be available for the market in the near future.

The HEMS system may be able to record currents, voltages, power, but also can communicate with a certified electrical meter to record and process information related to the power quality, including voltage dips, flicker, harmonics, etc. All the information can be shown to the user through a friendly interface via a smart phone of tablet.

REFERENCES [1]. ***, Siemens The company: Infrastructure & Cities Sector Online:

http://www.siemens.com/about/pool/business/infrastructure_cities/ic_2013_q1_update_en.pdf

[2]. N. Papadopoulos, A. Meliones, D. Economou, I. Karras, I. Liverezas, A Connected Home Platform and Development Framework for Smart Home Control Applications, Proceedings of 7th IEEE International Conference on Industrial Informatics, INDIN 2009, Cardiff, Wales, UK, 23-26 June 2009.

[3]. Y. Li, Design of A Key Establishment Protocol for Smart Home Energy Management System, Proceedings of 2013 5th International Conference on Computational Intelligence, Communication Systems and Networks (CICSyN), Madrid, Spain, 5-7 June 2013.

[4]. D.-M. Han and J.-H. Lim, Design and Implementation of Smart Home Energy Management Systems based on ZigBee, IEEE Trans. Consumer Electronics, vol. 56, issue 3, pp. 1417-1425, August 2010.

[5]. B. Becker, A. Kellerer, H. Schmeck, User Interaction Interface for Energy Management in Smart Homes, Proceedings of 2012 IEEE PES Innovative Smart Grid Technologies (ISGT), Washington DC, 16-20 January 2012.

[6]. A.-H. Mohsenian-Rad, A. Leon-Garcia, Optimal Residential Load Control With Price Prediction in Real-Time Electricity Pricing Environments, IEEE Trans. Smart Grid, vol. 1, no. 2, September 2010.

[7]. Z. Chen, L. Wu, Y. Fu, Real-Time Price-Based Demand Response Management for Residential Appliances via Stochastic Optimization and Robust Optimization, IEEE Trans. Smart Grid, vol. 3, no. 4, December 2012.

[8]. Z. Chen, and L. Wu, Residential Appliance DR Energy Management With Electric Privacy Protection by Online Stochastic Optimization, IEEE Trans. Smart Grid, in press.

[9]. M. Eremia, L. Toma, Towards the intelligent cities of the future Smart cities (in Romanian), The 7th edition of International Conference on the Academic Days of the Academy of Technical Sciences of Romania, Bucharest, Romania, Agir Publisher, ISSN 2066-6585, 11-12 October 2012.

[10]. ***, Intelligent metering in Romania (in Romanian), study prepared by A.T. Kearney, Romanian National Energy Regulatory Authority, 3 September 2012.

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