3rd World Conference on Phorovolioic Enera Conversion May 11-18. 2003 Osaka, Japan S30-A2-02 PROPOSAL OF UNIQUE PV SYSTEM FOR LARGE-SCALE PHOTOVOLTAIC POWER GENERATION SYSTEM Kimitoshi Fukae, Akiharu Takabayashi, Shigenori Itoyama, Ichiro Kataoka, Hidehisa Makita, Masaaki Matsushita, Takaaki Mukai, Nobuyoshi Takehara E Development Center 2, Canon Inc., 1-1 Kizugawadai 4-chome, Kizu-cho, Souraku-gun, Kyoto 619-0281, Japan Masaki Konishi E Business Promotion Headquarters, Canon Inc., 3-30-2 Shimomamko, Ohta-ku, Tokyo 146-8501, Japan ABSTRACT In order to make a PV power generation system survive as an economically viable option against other renewable energy sources, drastic reduction of energy cost is inevitable. The authors have been working on the development of a unique PV system to reduce total system cost including solar panel, power conversion unit and installation work [I]. In the proposed concept, AC photovoltaic device and adhesive mounting method were introduced for the dedicated use in power station. By introducing this concept, it is feasible that the system cost will be reduced to 113 compared to the conventional system. The authors believe that the concept is suitable for very large-scale PV systems in desert areas. 1. INTRODUCTION Market penetration of PV power generation system has been accelerated in recent years. Especially in Japan, roof-top PV power generation system has shown a steep growth in sales volume. But, when we take a serious look at the global energy and environmental issues, the realization of a very large scale photovoltaic power generation system is expected. IEA PVPS Task VI11 has been promoting the feasibility study on very-large scale photovoltaic power generation (VLS-PV) system in desert areas. The study reports the global necessity of VLS-PV and its feasibility [23. The study also shows that energy cost of 16 to 17 centslkwh will be achieved in Gobi Desert with total system cost of 3 US$lW. New Energy and Industrial Technology Development Organization (NEDO) in Japan has the goal to develop 300 WW roof-top system by the end of fiscal year 2010, which CoKesponds to 25 WkWh in Japan. By limiting the usage of the proposed system within a power station which is always kept under controlled as a restricted area, specifications required to the system components might be simpler than ordinary PV system and module. The authors have been investigating the substantial requirements for use in restricted area. “Photovoltaic device” is designed just to satisfy substantial requirements for use in a restricted area. AC photovoltaic device has one large area unit cell with built-in DCIDC converters and a three-phase inverter, The advantage of this configuration is to reduce the PV device cost, power conversion units cost, and installation work cost. The idea to use a large area unit cell incorporated with DC1DC converter has been proposed and studied by European researchers [3],[4],[5]. They have developed the concept of single cell module integrated converter system (SCMIC). Two types of prototype converters were fabricated. The conversion efficiency recorded more than 95% at partial load and 91% at full load of 1.4V, 130A to 350V conversion. The advantages of the concept were indicatcd that the elimination of series connection cost in the production process, the decrease of power loss caused by the partial shade on the array or by the mismatch of output power among cells, and the realization of simple insulation and safety due to low voltage of a unit cell. The authors have proposed the set of unique PV system, actually fabricated the prototype device, conducted some reliability tests, and carried out experimental installation test to verify the adhesion mounting method. Although the development work is still underway, this paper reports the latest progress of AC photovoltaic device and its installation method. 2. AC PHOTOVOLTAIC DEVICE 2-1. Goal Image Fig.1 is the goal image of the AC photovoltaic device. Thin film microcrystalline silicon solar cell is formed on the stainless steel substrate to form a large area unit cell. Step-up DCiDC converters and a three-phase power conditioner are incorporated with the cell. Step-up DC1DC converters boost 1.4 V output from the cell to 420 V and then DC output is inverted to three-phase AC by a power conditioner. The device is encapsulated with a simple lamination to assure required weather resistance. Electrical connection is done by the water-proof connecters. Power conditioner 1- Step-up DClDC convener Fig. 1 Goal Image ofAC Photovoltaic Device Weather rcsistml encapsulation Oral 28153rd World Conference on Photovoltaic Energv Conversion May 11-18,2003 Osaka, Jo~on 2.2 Prototype ofAC Photovoltaic Device Although the DCiDC converter and the power conditioner have not been fully developed yet, the prototype device was fabricated in advance in order to establish the weather resistant mounting technique of DCDC converters and evaluate outdoor power generation performance of the device. Fig. 2 shows the photograph of the prototype device. Since a large area unit cell has not fabricated yet, eight standard sized cells were electrically connected in parallel to form an electrically equivalent large unit cell. Four prototype DCiDC converten which can he seen on left side of the cell array were attached to the cells in the manner to withstand outdoor weather conditions. Fig. 2 Photograph of Prototype Device 3. ENCAPSULATION STRUCTURE 3.1 Structure and Materials Design policy is to simplify the lamination structure as much as possible within the extent to satisfy substantial reliability for the limited use in a restricted area. The selection of weather resistant material is essential. The authors have confirmed the excellent weather resistance of fluorocarbon resin film and EVA sheet as a light receiving surface cover. UV light with the wavelcngth from 300 to 400 nm was irradiated to the ETFEiEVAiglass laminated sample. No substantial degradation was observed in light transmittance over the wavelength of 400 nm afler the UV irradiation corresponding to 27.5 year outdoor exposure in Tokyo as shown in
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