reFOCUST h e I n t e r n a t i o n a l r e n e w a b l e e n e r g y m a g a z i n e

Electrifying ChinaOff-Grid Power Supply of Villages in China

2 reFOCUS ©2006 Elsevier Ltd. All rights reserved.

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Technical building for village electrification in Xinjiang province

Mr. Wang Zhiqiang, engineer from SMA-China PV Hybrid-System for Schweinezucht inlower saxony

System operator in front of Sunny Island Battery Inverter

Sunny Island 4500 Battery Inverter

Innovation in Systems Technology for the Success of Photovoltaics

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Due to progressive industrialization inChina over the years a long-termand reliable energy supply has

become more and more important. Despitegreat efforts by the Chinese government,around 30 million people in more than20,000 villages and 7 million families in

agriculture live without electricity. Wideareas of the Western and Southwesternprovinces as well as some islands along theEast Chinese coast are mainly affected.Many households will not be connected tothe public grid for the medium and longterm, the main reasons being the unfa-

vourable topographic conditions, low settle-ment density and a resulting low energy con-sumption. An extension of the grid system isthus not reasonable from an economic pointof view. The attractive prosper-ity in thecities has resulted in a migration to the citiesto an unexpected extent. An estimated 500million people in China could leave their set-tlement area within the next ten years. Amammoth process of urban development aswell as the complete depopulation of ruralareas that would be fatal for China's culturaldevelopment could be the result.

EElleeccttrriiffiiccaattiioonn ooff rruurraall aarreeaass In this context, the Chinese government ini-tiated a program in 1996 to provide ruralareas in the Western provinces with electric-ity by decentralized power supply systems,mainly by photovoltaic and wind powerplants, by 2010. The Reconstruction Loan

ELECTRIFYINGCHINAOff-Grid Power Supply of Villages in China

In 1996, the Chinese government initiated a program to pro-vide rural areas in its Western provinces with electricity fromphotovoltaic and wind power plants. As part of the program,more than 80 villages in the provinces of Yunnan and Xinjiangwill be supplied with electricity by means of solar power.Michael Wollny, SMA Technologie AG reports on experiencesto date in electrifying off-grid rural areas of China with solarPV systems.

Figure 1: AC-coupled power supply structure

Corporation supports the Chinese state gov-ernment by expanding the use of renewableenergy sources. As part of the program, morethan 80 villages in the provinces of Yunnanand Xinjiang will be supplied with electricityby means of solar power. Due to the highinsolation of 1700 kWh/m²/a and a sunshineduration of 2500 - 3100 h/a the potential forthe use of solar power is very high. By sup-plying power from renewable energy sourcesadditional CO2-emissions are avoided whichis an important contribution to climate andresource protection in the region. In additionto the funding of village power plants by theReconstruction Loan Corporation, theGerman Technical Cooperation Agency sup-ported the training of local technicians, thedevelopment of service and maintenancestructures as well as effective technical qual-ity assurance. Decentralized power supplybased on renewable energy sources thusallows an improvement in the living condi-tions of the population of the two provinces.

SSeelleeccttiioonn ccrriitteerriiaa In addition to the important training ofinstallers and local plant operators differentcriteria for selecting suitable villages havebeen considered. Besides the high potentialfor the use of solar power, the distance to thepublic grid is an important criterion for thechoice of location. A distance of at least 8 km for small villages and/or of 15 km for larger villages is specified. In order to reducesystem planning, installation, maintenanceand data monitoring costs a cohesive villagestructure is important. The major system components are thus located in a technicalbuilding specially constructed for this purpose and from where the households ofthe village are supplied with power via openlines. The PV-generator is installed outside of the technical building.

PPrroojjeecctt mmaannaaggeemmeenntt Shell Solar GmbH has been the system inte-grator of the scheme with the overall respon-sibility for technical planning and design aswell as project management with logistics and design of the generator stations for elec-tricity supply. Shell selected SMA Technologie AG as a supplier of the inver-ters. SMA delivered the main system compo-nents Sunny Island, Sunny Boy and SunnyBoy Control and prepared the part docu-mentations for the AC distribution and installation. Shell Solar was also responsiblefor selecting the Chinese subcontractors forproject management as well as the Chinesesuppliers for the batteries, generators andother subcomponents. The project involved

Figure 2: 1-phase AC-coupled off-grid supply structure

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Figure 3: PV-Modul installation for village electrification system in China

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the training of local people and installers.Shell Solar organized their training inChinese language by the respective sub-sup-pliers.

SSyysstteemm ccoonncceepptt More than 80 village power plants are expected to be installed in the selectedprovinces within two tender stages. 26 vil-lages in the provinces of Yunnan and Xinjianghave been provided with pure PV-plant or PVhybrid power plants in the first stage. The off-grid power supplies are designed as AC-cou-pled island grids allow-ing simple and cost-effective grid-connection of the energysources and consumers on the AC side. Dueto the modular design, other suppliers, suchas wind or hydroelectric power plants, canbe integrated in addition to the currently usedenergy sources of photovoltaics and genera-tors. The new system technology of AC cou-pling together with the parallel operation ofvoltage-controlled energy sources set newstandards. The power range of these islandgrids ranges from 3 to 100 kW. Single- andthree-phase solutions are possible. The sys-tems have a number of advantages in terms ofplant layout and design (design, installation,exten-sion capability and compatibility)reducing the specific system costs as well.From an economic point of view, small islandgrids with a battery bank in the kW powerrange are more cost-effective than plantswhere diesel sets are exclusively used. Evenlarger hybrid systems (5 - 30 kW) using dieselsets in order to avoid a long-term batterystorage can be operated at lower costs thanstations exclusively using diesel sets (Figure 1).

PPaarraalllleell ccoonnffiigguurraattiioonn A new feature of this modular system tech-nology is the possibility to connect the Sunny Islands or 3-phase Sunny Island sys-tems in parallel on the AC side in a voltage-controlled way. Due to parallel operationSunny Island systems can be freely scaled intheir power and simply upgraded in case ofincreasing consumer power. Some of themain advantages of AC-coupling and paral-lel connection of several inverter systems onthe AC side are: the structure is 100% com-patible with public grid; simple installation as standard components (consumers, instal-lation technology etc. for 230 V AC) for home installation can be used; can be freelyscaled and used for larger systems (from 3 kW to 27 kW in one system) as well; andcan be combined with supplementary grid-feeding and grid-forming energy sources(diesel sets, small hydro-electric powerplants, and wind energy plants).

Solar PV

Figure 4: 3-phase AC-coupled off-grid supply structure

Figure 4: PV-generator and technical building for AC-coupled off-grid power supply in the province of Yunnan, China

PPVV aanndd hhyybbrriidd ppoowweerr ssuuppppllyy The heart of a decentralized power supply isthe battery inverter. It can be used for sin-gle-phase island grids of 4.5 kW consisting of one single Sunny Island 4500 up to sys-tems with a 3-phase supply and virtually allpower ranges by connecting several devicesin parallel. The plants used in China includeat least two Sunny Island 4500 battery inverters, two String inverters and one com-munication unit in addition to the PV-gen-erator and the battery unit. The individual PV-generators have a power between 4.5 kWpand 16.5 kWp depending on the size andinfrastructure of the village. The Shell S75 multi-crystalline module was selected for use in off-grid areas. In thecase of applications under these conditions amodule size suitable for easy transport andsimple installation as well as optimal energyconversion is required. This is guaranteed bymodules in this power range and is achievedby using multi-crystalline technology withaccordingly optimized manufacturing stan-dards. Due to a constant product upgrade the new Shell PowerMax Plus 80 moduleswith a power of 80 Wp will be used in future.

IInntteelllliiggeenntt bbaatttteerryy The intelligent battery, load and system management integrated in the Sunny Island,has the ability to operate the diesel set in itsoptimal efficiency range, help to efficientlymanage the energy available and/or to min-imize the consumption of diesel fuel. Due to a regular equalizing charge, temperature-compensated charging voltage and monitor-ing of the charging state, exhaustive dis-charge of the battery is avoided and its serv-ice life increased. Four basic systems arebeing used for the 26 villages. The single-phase PV off-grid systems consist of at leasttwo Sunny Island 4500 (9 kW) battery inverters, two or three Sunny Boy 3000 (3 - 9 kW AC) and a Sunny Boy Control Pluscommunication unit in addition to the PV-generator (4.5 - 7.5 kWp) and the battery unit with an energy content of 72 - 108 kWh. In case of larger villages with more than 30 households an additional diesel set(10 - 15 kW AC) is used (Figure 2 and Figure 3). The 3-phase PV-plants consist of at least three Sunny Island 4500 (13.5 - 27.5 kW) battery inverters, three to six Sunny Boy 3000 (9 - 18 kW AC), one diesel set (up to

30 kW AC) and a Sunny Boy Control Pluscommunication unit in addition to the PV-generator (4.5 - 16.5 kWp) and the batteryunit with an energy content of 72 - 192 kWh. In cases of more than 2,500 hours ofsunshine per year, villages with less than 30households are provided with an energy supply without the diesel set. Around 50% of the selected villages has more than 30households. In addition to the solar powerthat is to provide the main part of power generation a diesel set is included in off-grid electricity supply. Due to the climatic differences with tem-peratures of approximately -30°C in the winter months in the province of Xinjiangwhich require that the diesel set is preheat-ed, the geographical position of the villagesof more than 3000m above sea level and high ambient temperatures in the province of Yunnan, additional measures, such as load disconnection in case of critical batterystate or energy saving mode in case of lowinsolation, have been implemented. A sys-tem manager is responsible for the total island and energy management in order toguarantee a long service life of the batteriesand system components (Figure 5).

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Figure 6: Inauguration of first PV-Hybrid village electrification system in Yunan, province of China

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SSuummmmaarryy AC coupling has proven itself in differentkinds of system during the last couple ofyears. Especially in the electrification of off-grid, remote areas, this technology ensures aflexible and sound energy supply. Projects inthe world show how important this technol-ogy already is and will become for the designof efficiently working island grid systems.This system technology will further expand its position in the coming years to appear inother international projects. The modularity of the system has made iteasy to adjust the systems without any greatdifficulty to the demands of the energy sup-plier or of the end-users. System integratorslike Shell Solar connect these new technolo-gies with their long-term experience and usethem successfully.

RReeffeerreenncceess [1] Engler, A.; Hardt, C.; Bechtel, N.; Rothert,M.; Next Generation of AC Coupled HybridSystems - 3 Phase Parallel Operation of GridForming Battery Inverters; Kassel Sept. 2003

[2] Cramer, G; Rothert, M.; Die Zukunft derländlichen Elektrifizierung - Felderfahrung

mit AC gekoppelten HybridsystemenErneuerbare Energien: Heft:10/2003

[3] Klinghammer, W; Shenghong, Ma, A NewVision for Remote Villages in Western China:Village Electrification by PV Hybrid Plants -The Solar Energy Program of MoF and KfW

in China, 2nd European PV Hybrid and MiniGrid Conference Sept. 2003, Kassel, Germanyrfsop28_33.qxd 23/01/2006 12:40 Page 31

Figure 7: Young villagers in front of village electrification system in Xinjiang, province of China

Figure 8:

Further informationContact: Michael Wollny, SMA

Technologie AG, Hannoversche Str.1-5,

D-34266 Niestetal, Germany.

Tel.: +49 561 9522-4122;

Fax: +49561 9522-304;

E-Mail: Michael.Wollny@SMA.de;

website: www.SMA.de

Whenever and wherever electric power is needed, theSunny Island battery based inverter provides perfect sinewave off-grid electricity with high efficiency, robust powerand outstanding reliability. Simple to install and use, yetloaded with powerful and advanced features, the SunnyIsland is designed to meet the needs of off-grid as well asback-up power systems applications.

To receive your free DVD about the possibilities of off-grid systems powered by Sunny Island, call or e-mail ustoday.

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