- Email: [email protected]
Photovoltaics in China
la
Ph Otovol taics in in a Research, development and market potential
]
Solar cells The R&D results of solar cells in China are summarized in Table 1.
1) High efficiency single crystalline silicon solar cells R&D activities on high efficiency single crystalline Si solar cells include work on passivated emitter solar cells (PESC), inverted pyramids texturing & selective emitter (IPSE) solar cells, and laser and machine grooving for buried contact (LGBC& MGBC) solar ceils.
a) IPSE Solar Cells
bout 70% of 1.2 billion people live in rural areas in China. In spite of the rapid growth of C h i n a s national economy in recent decades, energy problems still have a very real impact on economic and environmental development, especially in rural areas. In order to mitigate the adverse impact of coal burning to the regional and global environment, the Chinese Government has adopted vigorous measures to develop renewable energy technologies. China has abundant solar energy resources. More than two thirds of China receives an annual total insolation that exceeds 5GJ/m 2 with more than 2,200
A
34
hours of sunshine a year. Hence, utilization of solar energy becomes a strategic decision in rational use of energy as well as environmental protection. Up to now, PV in China has been playing a significant role in improving people's living conditions and will make more contribution to sustainable development in the 21st century. Yuwen Zhao, Beijing Solar Energy Research Institute looks at PV activities to date in China.
PV R&D a c t i v i t i e s There are 30 research institutes and universities involved in solar PV R&D activities in China. The area of R&D covers solar cells, PV materials and PV systems and components. April 2001
RE
www.re-focus.net
The IPSE solar cell, is similar to the PESC developed in U N S W of Australia. The cells are made up of inverted pyramids that are textured by photolithography and etching. Passivation by thermal oxidation, selective emitter diffusion using POCI 3, application of AR coatings, back surface field and pulse plating are also carried out in the construction of the cells. Cell efficiency to date has reached 19.79% (Voc=656.1mV, Jsc=37.4 mA/cm 2, FF=0.806, Area=4.04 cm 2, AM1.5, 25°C).
(b) LGBC a n d MGBC solar cells Compared with IPSE solar cells, the manufacturing processes for LGBC and MGBC solar cells are much simplified with only one step of oxidation and without the use of evaporating grids or the need for several photolithograph-etching steps. In LGBC solar cells, FZ, CZ and solar grade (SG) silicon wafers are used respectively. The technologies used are of surface texturing,
FEATURE
- PHOTOVOLTAICS
IN
Table 1.The best conversion efficiencies of various solar cells developed in China
CHINA
inverters with high efficiency and sine waveforms, PV system controllers, PV lighting systems, television PV power systems, PV communications systems, and meteorological station PV power systems. Facilities for testing the performance of PV cells, modules and systems have also been set up.
PV Industry There are four Mono-Si solar cell and module production lines located in Qinhuangdao, Kunming, Ningpo, and Kaifeng respectively, and two a-Si solar cell module production lines located in Harbin and Shenzhen. The total production capacity is about 4.5 MWp, the actual output in 2000 was 3MWp. The efficiencies of commercial solar ceils are 11-13% for Single-Si cells (~10cm or 10xl0cm 2) and 5-6% (30x90cm 2) for a-Si cells respectively.
PV Applications and Markets Table 2. The characteristics of LGBC and MGBC solar sells with different materials [AM 1.5, 25°C}
LGBC MGBC LGBC LGBC
FZ FZ CZ SG
663,8 621.9 622,9 624,1
34.84 37.00 34.88 35.24
80.58 80.02 79,27 75.44
18.60" 18.47 17.22 16.59
25 4 25 25
*Certified by NREL,USA
laser or machine grooving, passivation by thermal oxidation, and several others. The characteristics of a variety of solar cells produced in these ways are shown in Table 2.
2) Multicrystalline Silicon (mc-Si) Solar Cells The R&D work carried out on mc-Si solar cells is based on work undertaken on IPSE, LGBC and MGBC solar cells. Bayer Solar mc-Si wafers have been used and have reached efficiencies of 14.53% and 12.5% (Voc=593.4.0mV, Jsc=27.45 mA/cm 2, FF=0.7671) for 1 cm 2 and 10xl0 cm 2 respectively. The efficiency will be much improved after optimization of the fabrication process.
3) Thin film solar cells The R&D activities of thin film solar cells including a-Si, poly-Si, CdTe and CIS cells are distributed over several institutions and universities. The characteristics of the cells are shown in Table 1. A p-type active
poly-Si layer of about 38btm was prepared by rapid thermal chemical vapour deposition (RTCVD) in a quartz reactor. The p-n junction was formed by POCI 3 diffusion in a conventional tubular diffusion furnace. SiO 2 AR coating was deposited by Electronic beam evaporation.
PV Materials mc-Si square ingots in 15kg units are produced by a casting process in the laboratory. Silver paste and aluminum paste for screenprinting, and EVA and PVF for module assembling have also been developed for reducing PV module cost. Some R&D work for improving relevant materials is also currently being carried out[14].
Terrestrial PV applications started in China around 1970 and total installed PV power capacity stood at about 18MWp by the end of 2000. The PV applications are mainly in the areas of communication, remote electrification, professional use, and commodities. PV grid-connection applications only recently began with the first demonstration commencing about two years ago. The PV market share is shown in Table 3. Communications applications include microwave relay stations, optical-fiber communications, wireless calling stations, satellite communication ground receivers, TV receivers and transmitters, and programcontrolled telephone systems in the countryside. Remote applications are mainly distributed over the west and south-west of China (stand-alone PV power stations, solar home systems, solar lighting, and solar pumps). For example, there are seven counties without grid-connection in Tibet . Since 1992, PV systems have been installed in remote locations and provide the dectricity to towns in the region for use mainly for lighting, radio, and TV. Around 420KW of installed capacity was in place by
Table 3.The PV market share in China[15]
PV Systems and Components R&D activities of PV systems and their applications include 1-5KWp PV water pumps systems, 10KWp and 15KWp April 2001
RE
www.re-focus.net
35
FEATURE
-
PHOTOVOLTAICS
IN
CHINA
Table 4: PV systems installed across seven counties of Tibet
Table 5. Future PV Market
1999, (see Table 4). The picture shows the largest PV system installed to date. It is a 100KW system in Anduo - a county town in Tibet and was installed in 1998. Professional applications include industry, agriculture and other applications (Railway and high-way signal systems, beacon and light houses, weather and earthquake stations, hydraulic observing systems, and cathodic protection systems for oil pipelines and sluice gates), commodities and others (street lights and streets clocks, solar calculators and watches, solar tour boats, and toys).
Future trends Strategy for development of RE technologies After the UN Summit Conference on Global Environment and Development held in Rio de Janeiro, 1992, China developed a quick response towards implementing a sustainable development strategy and issued a white paper of Chinas sustainable development strategy in the 21st Century "Agenda of China 21st Century" covering the topics of population, environment and development. In this document, it is stressed that renewable energy will form the basis of future energy use. It is also stated that: "priority should be given to the development of renewable energy in the state energy development strategy", and "energysaving, energy efficiency and developing renewable energy should become the fundamental state policy".
PV market potential In China, there are still 60 million people living in remote off-grid areas. At present, small PV kits, for instance, 10Wp for a portable lamp, 20Wp for home lighting, 50Wp for black and white TV set, 100 Wp for color TV set, are available in rural/remote markets and achieve good sales. Now that the GEF project, supported by The World Bank, to stimulate PV market development is being implemented 36
and with the rapid development of modern society, it is expected that there will be strong growth in the PV market in China. PV power stations and roof top systems will be commonplace in China. Table 5 gives an estimation of PV market development.
Summary Several areas need focused effort to realize the full potential of PV development in the region. Quality control systems for solar PV products are needed as is a robust PV service business for end users. Incentive policies for the PV industry and market development should be formulated under the guidance of the Government's general policy for renewable energy development. Demonstration and standardization of solar architecture with PV roof-top should be carried out and implemented early in the 21st century. International cooperation on technology transfer and market initiatives will speed up the processes of solar energy development in China as well as global society. Contact: Yuwen Zhao, Beijing Solar Energy Research Institute, 3, Hua Yuan Road, Beijing 100083, China. Tel: +86 10 62012881; Fax: +86 10 6201 2880, e-maih [email protected]
References [I] Chen Wenjun, " Eficiency Over 200/0 of Silicon Solar cells with mG PESC Structure ",Journal of Semicomductors (China),13(2), 1992, p116. [2] Zhao Yuwen, et al, "All Aluminum BSF High Efficiency Silicon Solar Cells", Proceedings of 1997 ISES Solar World Congress, Aug. 24 - 29, 1997, Taejon, Korea, pp137-140. [3] Zhao Yuwen, et al, "Buried-contact High Efficiency Silicon Solar Cell with Mechanical Grooving", Solar Energy Materials and Solar Cells, 1997 (48) pp167-172. [4] Shaoqi He, Yuting Wang, Xudong Li, Yuweo Zhao,et al., Laser Grooved April 2001 R E
www.re-focus.net
buried contact solar cells, 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, 6-10July 1998,Vienna, Austria. pp1446-1448. [5] Sang Shiyu, Wen Jianjun, Mo Chundong, Zhao Yuwen, "Study on Mass production of high efficiency solar cells "5th Solar Photovoltaic Conference in China, 15-20 Oct. 1998, Hongshan, Anhui, ppl 1-15. [6] Xiang Xianbi, Du Weihui, Chang Xiulan, The Study of MOCVD High Efficiency GaAs Solar Cells, Proceedings of 5th Solar Photovoltaic Conference in China, 15-17 Oct. 2000, Kunming,Yunan, pp76-79. [7] Yuwen Zhao, Shaoqi He, Wenjing WangX, "Solar Cells R&D Acitvities in National Engineering ewsearch center for Renewable Energy"2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion,6-10July 1998,Vienna, Austria.pp1452-1455. [8] Sang Shiyu, Wen Jianjun, Mo Chundong, Zhao Yuwen, Inside Report in Beijing Solar Energy Research Institute,Dec. 1998. [9] Wang Wenjing, Xu Ying, Zhao Yuwen, "The Silicon Thin Fihn Solar Cells Prepared by Rapid CVD", 5th Solar Photovoltaic Conference in China, 15-20 Oct. 1998, Hongshan,Anhui, ppl01-107. [10] Sun Yun, etc., to be Published in Acta Energiae Solaris Sinica,2001. [11] Feng lianghuan, Cai Wei, Zheng Jiagui, Cai Yapin, Libing, etc., The Study of CdTe Solar Cell with ZnTe Composite Back contact Layer, Proceedings of 5th Solar Photovoltaic Conference in China, 15-17 Oct. 2000, Kunming, Yunan, pp110-113. [12] Sun Yun, Wang Guangcai, Hu Jingkang, Wang Zongpan, Sun Zhonglin, "Development of Single Junction Integrated Type a-Si Solar Cell with Area of 400cm 2'' Acta Energiae Solaris Sinica, 13(2), 1992,203-206. [13] Wu Xuanzhi,Xiao Dechuan, Gao Wei, "Study and Build of 30x30cm a-Si Solar Cell Pilot Line"3rd Solar Photovoltaic conference in China, 1991,p 100. [14] Lin anzhong, Wang Sicheng, The Progress and future of Solar clells snd PV Power world and China, Acta Energiae Solaris Sinica(Special Issue),Oct. 1999, pp68-74 [15] Wang Sicheng, "PV Industry and Application in China", Proceedings of The 5th National Symposium on PV Technology, Oct. 15
Ph Otovol taics in in a Research, development and market potential
]
Solar cells The R&D results of solar cells in China are summarized in Table 1.
1) High efficiency single crystalline silicon solar cells R&D activities on high efficiency single crystalline Si solar cells include work on passivated emitter solar cells (PESC), inverted pyramids texturing & selective emitter (IPSE) solar cells, and laser and machine grooving for buried contact (LGBC& MGBC) solar ceils.
a) IPSE Solar Cells
bout 70% of 1.2 billion people live in rural areas in China. In spite of the rapid growth of C h i n a s national economy in recent decades, energy problems still have a very real impact on economic and environmental development, especially in rural areas. In order to mitigate the adverse impact of coal burning to the regional and global environment, the Chinese Government has adopted vigorous measures to develop renewable energy technologies. China has abundant solar energy resources. More than two thirds of China receives an annual total insolation that exceeds 5GJ/m 2 with more than 2,200
A
34
hours of sunshine a year. Hence, utilization of solar energy becomes a strategic decision in rational use of energy as well as environmental protection. Up to now, PV in China has been playing a significant role in improving people's living conditions and will make more contribution to sustainable development in the 21st century. Yuwen Zhao, Beijing Solar Energy Research Institute looks at PV activities to date in China.
PV R&D a c t i v i t i e s There are 30 research institutes and universities involved in solar PV R&D activities in China. The area of R&D covers solar cells, PV materials and PV systems and components. April 2001
RE
www.re-focus.net
The IPSE solar cell, is similar to the PESC developed in U N S W of Australia. The cells are made up of inverted pyramids that are textured by photolithography and etching. Passivation by thermal oxidation, selective emitter diffusion using POCI 3, application of AR coatings, back surface field and pulse plating are also carried out in the construction of the cells. Cell efficiency to date has reached 19.79% (Voc=656.1mV, Jsc=37.4 mA/cm 2, FF=0.806, Area=4.04 cm 2, AM1.5, 25°C).
(b) LGBC a n d MGBC solar cells Compared with IPSE solar cells, the manufacturing processes for LGBC and MGBC solar cells are much simplified with only one step of oxidation and without the use of evaporating grids or the need for several photolithograph-etching steps. In LGBC solar cells, FZ, CZ and solar grade (SG) silicon wafers are used respectively. The technologies used are of surface texturing,
FEATURE
- PHOTOVOLTAICS
IN
Table 1.The best conversion efficiencies of various solar cells developed in China
CHINA
inverters with high efficiency and sine waveforms, PV system controllers, PV lighting systems, television PV power systems, PV communications systems, and meteorological station PV power systems. Facilities for testing the performance of PV cells, modules and systems have also been set up.
PV Industry There are four Mono-Si solar cell and module production lines located in Qinhuangdao, Kunming, Ningpo, and Kaifeng respectively, and two a-Si solar cell module production lines located in Harbin and Shenzhen. The total production capacity is about 4.5 MWp, the actual output in 2000 was 3MWp. The efficiencies of commercial solar ceils are 11-13% for Single-Si cells (~10cm or 10xl0cm 2) and 5-6% (30x90cm 2) for a-Si cells respectively.
PV Applications and Markets Table 2. The characteristics of LGBC and MGBC solar sells with different materials [AM 1.5, 25°C}
LGBC MGBC LGBC LGBC
FZ FZ CZ SG
663,8 621.9 622,9 624,1
34.84 37.00 34.88 35.24
80.58 80.02 79,27 75.44
18.60" 18.47 17.22 16.59
25 4 25 25
*Certified by NREL,USA
laser or machine grooving, passivation by thermal oxidation, and several others. The characteristics of a variety of solar cells produced in these ways are shown in Table 2.
2) Multicrystalline Silicon (mc-Si) Solar Cells The R&D work carried out on mc-Si solar cells is based on work undertaken on IPSE, LGBC and MGBC solar cells. Bayer Solar mc-Si wafers have been used and have reached efficiencies of 14.53% and 12.5% (Voc=593.4.0mV, Jsc=27.45 mA/cm 2, FF=0.7671) for 1 cm 2 and 10xl0 cm 2 respectively. The efficiency will be much improved after optimization of the fabrication process.
3) Thin film solar cells The R&D activities of thin film solar cells including a-Si, poly-Si, CdTe and CIS cells are distributed over several institutions and universities. The characteristics of the cells are shown in Table 1. A p-type active
poly-Si layer of about 38btm was prepared by rapid thermal chemical vapour deposition (RTCVD) in a quartz reactor. The p-n junction was formed by POCI 3 diffusion in a conventional tubular diffusion furnace. SiO 2 AR coating was deposited by Electronic beam evaporation.
PV Materials mc-Si square ingots in 15kg units are produced by a casting process in the laboratory. Silver paste and aluminum paste for screenprinting, and EVA and PVF for module assembling have also been developed for reducing PV module cost. Some R&D work for improving relevant materials is also currently being carried out[14].
Terrestrial PV applications started in China around 1970 and total installed PV power capacity stood at about 18MWp by the end of 2000. The PV applications are mainly in the areas of communication, remote electrification, professional use, and commodities. PV grid-connection applications only recently began with the first demonstration commencing about two years ago. The PV market share is shown in Table 3. Communications applications include microwave relay stations, optical-fiber communications, wireless calling stations, satellite communication ground receivers, TV receivers and transmitters, and programcontrolled telephone systems in the countryside. Remote applications are mainly distributed over the west and south-west of China (stand-alone PV power stations, solar home systems, solar lighting, and solar pumps). For example, there are seven counties without grid-connection in Tibet . Since 1992, PV systems have been installed in remote locations and provide the dectricity to towns in the region for use mainly for lighting, radio, and TV. Around 420KW of installed capacity was in place by
Table 3.The PV market share in China[15]
PV Systems and Components R&D activities of PV systems and their applications include 1-5KWp PV water pumps systems, 10KWp and 15KWp April 2001
RE
www.re-focus.net
35
FEATURE
-
PHOTOVOLTAICS
IN
CHINA
Table 4: PV systems installed across seven counties of Tibet
Table 5. Future PV Market
1999, (see Table 4). The picture shows the largest PV system installed to date. It is a 100KW system in Anduo - a county town in Tibet and was installed in 1998. Professional applications include industry, agriculture and other applications (Railway and high-way signal systems, beacon and light houses, weather and earthquake stations, hydraulic observing systems, and cathodic protection systems for oil pipelines and sluice gates), commodities and others (street lights and streets clocks, solar calculators and watches, solar tour boats, and toys).
Future trends Strategy for development of RE technologies After the UN Summit Conference on Global Environment and Development held in Rio de Janeiro, 1992, China developed a quick response towards implementing a sustainable development strategy and issued a white paper of Chinas sustainable development strategy in the 21st Century "Agenda of China 21st Century" covering the topics of population, environment and development. In this document, it is stressed that renewable energy will form the basis of future energy use. It is also stated that: "priority should be given to the development of renewable energy in the state energy development strategy", and "energysaving, energy efficiency and developing renewable energy should become the fundamental state policy".
PV market potential In China, there are still 60 million people living in remote off-grid areas. At present, small PV kits, for instance, 10Wp for a portable lamp, 20Wp for home lighting, 50Wp for black and white TV set, 100 Wp for color TV set, are available in rural/remote markets and achieve good sales. Now that the GEF project, supported by The World Bank, to stimulate PV market development is being implemented 36
and with the rapid development of modern society, it is expected that there will be strong growth in the PV market in China. PV power stations and roof top systems will be commonplace in China. Table 5 gives an estimation of PV market development.
Summary Several areas need focused effort to realize the full potential of PV development in the region. Quality control systems for solar PV products are needed as is a robust PV service business for end users. Incentive policies for the PV industry and market development should be formulated under the guidance of the Government's general policy for renewable energy development. Demonstration and standardization of solar architecture with PV roof-top should be carried out and implemented early in the 21st century. International cooperation on technology transfer and market initiatives will speed up the processes of solar energy development in China as well as global society. Contact: Yuwen Zhao, Beijing Solar Energy Research Institute, 3, Hua Yuan Road, Beijing 100083, China. Tel: +86 10 62012881; Fax: +86 10 6201 2880, e-maih [email protected]
References [I] Chen Wenjun, " Eficiency Over 200/0 of Silicon Solar cells with mG PESC Structure ",Journal of Semicomductors (China),13(2), 1992, p116. [2] Zhao Yuwen, et al, "All Aluminum BSF High Efficiency Silicon Solar Cells", Proceedings of 1997 ISES Solar World Congress, Aug. 24 - 29, 1997, Taejon, Korea, pp137-140. [3] Zhao Yuwen, et al, "Buried-contact High Efficiency Silicon Solar Cell with Mechanical Grooving", Solar Energy Materials and Solar Cells, 1997 (48) pp167-172. [4] Shaoqi He, Yuting Wang, Xudong Li, Yuweo Zhao,et al., Laser Grooved April 2001 R E
www.re-focus.net
buried contact solar cells, 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, 6-10July 1998,Vienna, Austria. pp1446-1448. [5] Sang Shiyu, Wen Jianjun, Mo Chundong, Zhao Yuwen, "Study on Mass production of high efficiency solar cells "5th Solar Photovoltaic Conference in China, 15-20 Oct. 1998, Hongshan, Anhui, ppl 1-15. [6] Xiang Xianbi, Du Weihui, Chang Xiulan, The Study of MOCVD High Efficiency GaAs Solar Cells, Proceedings of 5th Solar Photovoltaic Conference in China, 15-17 Oct. 2000, Kunming,Yunan, pp76-79. [7] Yuwen Zhao, Shaoqi He, Wenjing WangX, "Solar Cells R&D Acitvities in National Engineering ewsearch center for Renewable Energy"2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion,6-10July 1998,Vienna, Austria.pp1452-1455. [8] Sang Shiyu, Wen Jianjun, Mo Chundong, Zhao Yuwen, Inside Report in Beijing Solar Energy Research Institute,Dec. 1998. [9] Wang Wenjing, Xu Ying, Zhao Yuwen, "The Silicon Thin Fihn Solar Cells Prepared by Rapid CVD", 5th Solar Photovoltaic Conference in China, 15-20 Oct. 1998, Hongshan,Anhui, ppl01-107. [10] Sun Yun, etc., to be Published in Acta Energiae Solaris Sinica,2001. [11] Feng lianghuan, Cai Wei, Zheng Jiagui, Cai Yapin, Libing, etc., The Study of CdTe Solar Cell with ZnTe Composite Back contact Layer, Proceedings of 5th Solar Photovoltaic Conference in China, 15-17 Oct. 2000, Kunming, Yunan, pp110-113. [12] Sun Yun, Wang Guangcai, Hu Jingkang, Wang Zongpan, Sun Zhonglin, "Development of Single Junction Integrated Type a-Si Solar Cell with Area of 400cm 2'' Acta Energiae Solaris Sinica, 13(2), 1992,203-206. [13] Wu Xuanzhi,Xiao Dechuan, Gao Wei, "Study and Build of 30x30cm a-Si Solar Cell Pilot Line"3rd Solar Photovoltaic conference in China, 1991,p 100. [14] Lin anzhong, Wang Sicheng, The Progress and future of Solar clells snd PV Power world and China, Acta Energiae Solaris Sinica(Special Issue),Oct. 1999, pp68-74 [15] Wang Sicheng, "PV Industry and Application in China", Proceedings of The 5th National Symposium on PV Technology, Oct. 15