Thin-film is now offering strong competition against the more established crystalline technology.
The solar photovoltaic (PV) industry has been steadily growing within the renewable energy sector since 2009, and its technology costs are decreasing. According to the Solar Energy Industries Association (SEIA), silicon wafer and cell prices dropped 15 percent in the first quarter 2011 compared with the previous quarter, and module prices fell about 7 percent.
Within PV, there are two main semiconductor technologies: crystalline silicon (c-Si) and thin-films, mostly cadmium telluride (CdTe) but also CIGS (copper-indium-gallium-selenide) and amorphous silicon. The concentrating photovoltaic (CPV) technologies have also reached a commercial stage within the last year. Crystalline silicon is the oldest and most established of all PV technologies, while thin-film is quickly gaining ground. By the end of first quarter 2011, crystalline modules were still the dominant player in the solar market worldwide, making up approximately 70 percent of global sales.
According to Alfonso Tovar, Renewable Energy Consultant with Black & Veatch’s global energy business, the mass manufacture of c-Si modules falls into two types: mono-crystalline or multi-crystalline. The main difference between these two types of modules is in the crystalline structure of the photovoltaic material, which is obtained through different manufacturing methods.
The manufacturing process of mono-crystalline silicon cells is slightly more complex and with lower yields than multi-crystalline silicon cells, Tovar said. Therefore, mono-crystalline cells are more expensive to produce but have better temperature response and power conversion efficiency. The basic building blocks of the c-Si modules are the photovoltaic cells, which are manufactured as individual units.
The dominant technology in the thin-film market is CdTe, but CIGS modules are gaining momentum. Another important module technology is based on amorphous silicon (a-Si). Tovar said the term thin-film is derived from the manufacturing process of these modules. In contrast to the c-Si modules, in which each cell is produced individually and then several are connected to create a module, the thin-film modules are manufactured by depositing a photovoltaic material on a variety of substrates, such as glass, plastics or metals.
The major advantage of thin-films in comparison to crystalline silicon modules is price, as the manufacturing processes are significantly less energy-intensive and there is less waste of semiconductor material. Thin-film modules are, however, less efficient than c-Si modules.
Growth in Markets
In the first quarter of 2011, the United States witnessed 252 megawatts (MW) of grid-connected solar PV installations, about 66 percent more than first quarter of 2010. The industry is expecting the total U.S. solar PV market to double in 2011. U.S. grid-connected PV reached 2.3 gigawatts (GW) in the first quarter 2011, according to SEIA. John Felski, Black & Veatch Business Development Manager for Renewables & Energy Efficiency, said that Black & Veatch’s experience includes involvement in nearly half of the utility-scale PV plants currently operating in North America and a third of PV projects in advanced development.
Globally, cumulative solar PV capacity reached 40 GW by the end of 2010, up from 23 GW at the end of 2009, according to the European Photovoltaic Industry Association. This 70 percent growth was spurred by feed-in tariff programs in Germany and Italy, along with solid increases in the U.S., Japan, France, China, Spain and the Czech Republic.