Solar Photovoltaic Generation

Since the practical silicon solar cells emerged, photovoltaic generation was soon to be applied in the world. In the early stage of development, due to the expensive cost of solar cells, photovoltaic was limited to provide electricity for satellites in the space. Along with the improvement of solar cells technologies, decline of cost, photovoltaic was gradually applied in the ground with the increment of scale. According to the report, the worldwide production of solar cells modular reached 157.8MW in 1998, which was almost 3 times to that of 58.2MW in 1992. In recent years, the photovoltaic industry has been developed increasingly. The US scheduled to install 1000 to 3000MW solar cells until the year of 2010, while Japan planned to install 7600MW solar cells until the year of 2010.

Photovoltaic generation possesses many advantages invaluably to other method of generating electricity, which consumes no any fuels, has no region-based limitation, short construction period and can produce electricity on-grid or off-grid with no noise and no pollution, is not required to layout the distribution network, is safe and reliable, simple in maintenance, no need to safeguard¡­ It has been important technology foundation for mass utilization of solar energy.

Since the solar cell firstly utilized in the satellite launched by the US in 1958, 4000 satellites have been blastoff in the world so far, among which more than 90% were employed photovoltaic generation system for power supply. The utilized solar cells were chiefly single-crystal silicon cells. The gallium arsenide cells and the indium phosphide cells are being applied in recent years. The solar cell for photovoltaic generation in the space is required with high conversion efficiency, lightweight, good property of radiation proof and small temperature coefficient. The future development should focus on thin film solar cells.

After the photovoltaic generation was successfully applied in satellites, concept of constructing space power station was proposed as a consequence, taking advantage of high solar radiation in the space, no impact from day and night, season and climate. In this way, solar energy is converted into electric energy in the space and transmitted to the ground by microwave or laser.

In the 1970s, the US has once proposed to build one set of 5 million kW space power stations. But after being analyzed and demonstrated, agreement was reached in 1981 that it was too early to research the space power station in the short term, which will lead to incompetence in economic balance. As a consequence, the schedule was finally changed.

After the photovoltaic technology was applied in the ground, it was firstly utilized in some special field due to its expensive cost, for example, navigation, electric enclosure in pastoral region, microwave telecommunication, cathode protection for duct.

Along with the decline of price, it has been gradually applied to more fields including:

a.        In consumption products, for example calculator for non-crystal silicon solar cells, solar watches, solar lighting lamps, solar radio and TV, occupying 14% of sales capacity in worldwide photovoltaic products

b.        For residential utilities system away from grid, including decentralized power supply and alone photovoltaic power station centralized supply, occupying 35% of sales capacity in worldwide photovoltaic products.

c.        For off-grid industrial power supply system, occupying 33% of sales capacity in worldwide photovoltaic products.

d.        For on-grid photovoltaic power supply system, occupying 18% of sales capacity in worldwide photovoltaic products.

Accompanying with the scale increment of photovoltaic generation, on-grid power supply will be increased rapidly. In the 1980s, on-grid photovoltaic power stations built in some industrial countries were scaled up ranging from 100kW to 1MW. At present, 10MW on-grid photovoltaic power station was under the construction. Furthermore, the solar rooftop schedule constructed in the US, Germany and Japan was employed on-grid photovoltaic technologies.

Photovoltaic technologies are also applied in developing countries focusing on small-scale system to settle the power supply needs for the households that are not available or seriously absent of electricity.

In 1971, China launched the second satellite firstly utilizing solar cells. In 1973, photovoltaic generation started to apply in the ground. Before 1985, it was generally applied in the special fields such as navigation buoys, signal lamp for railway, black-light lamp, electric enclosure and small communicator, and a few demonstration projects were also established. Since the 1990s, applications of photovoltaic generation gradually expanded to the areas of telecommunication, communication, petroleum, meteorology, national defense and electrification in rural regions. The utilization capacity of solar cells was increased in a rate of 20% per year. Until the end of 1998, the accumulated utilization capacity of solar cells in China accounted for 13.2MW. In view of the region, photovoltaic generation was concentrated on the pastoral areas which were not available or seriously absent of electricity such as Qinghai, Xizhang, Jinxiang, Inner Mogolia and Genxu, where 40 sets of photovoltaic power station have been built with the capacity ranging from 10 to 100kW and 150,000 sets of household power supply have been promoted with the total capacity of 2.9MW.