Date: 24 November 2008
Efficiency of different solar technologies is improving rapidly. Innovation is occurring all over the world. Even German medium-sized companies are actively contributing when it comes to exploring new markets for PV production plants. The single most significant economic factor driving adoption of solar initiatives is the prospect of carbon use surcharges. As coal, gas, and oil usage are taxed to help prevent pollution and stimulate use of renewable energy sources, solar energy becomes more attractive to the utility grid electricity providers. The environmental impact of energy use choices promises to be an ongoing factor in energy grid supply. The speed with which solar system can be put in place by a utility company is a major factor in deciding what kinds of systems to put up. Solar utility systems can be put in place within six months.
The ability to create an operational system in six months instead of 20 years for nuclear systems is significant. Just the cost of capital weighs heavily in favour of solar utility installations. The advantage brought by having paying customers sooner is a major factor supporting implementation of solar systems for generation of utility grid electricity. A technique for making solar panels is to melt silicon powder on a cheap conducting substrate. In this manner companies are productionizing technologies that by-pass some of the inefficiencies of the crystal growth/casting and wafer sawing route. One route is to grow a ribbon of silicon, either as a plain two-dimensional strip or as an octagonal column, by pulling it from a silicon melt.
These processes may bring with them other issues of lower growth/pulling rates and poorer uniformity and surface roughness. Each c-Si cell generates about 0.5V, so 36 cells are usually soldered together in series to produce a module with an output to charge a 12V battery. The cells are hermetically sealed under toughened, high transmission glass to produce highly reliable, weather resistant modules that may be warrantied for up to 25 years.
Selected materials that are strong light absorbers need to be 1 micron thick. Materials costs are significantly reduced. The most common materials are amorphous silicon (a- Si, still silicon, but in a different form), or the polycrystalline materials: cadmium telluride (CdTe) and copper indium (gallium) diselenide (CIS or CIGS). Each of these three is amenable to large area deposition (on to substrates of about 1 meter dimensions) and hence high volume manufacturing. The thin film semiconductor layers are deposited on to either coated glass or stainless steel sheet.
The semiconductor junctions are formed in different ways, either as a p-i-n device in amorphous silicon, or as a hetero-junction (e.g. with a thin cadmium sulphide layer) for CdTe and CIS. A transparent conducting oxide layer (such as tin oxide) forms the front electrical contact of the cell, and a metal layer forms the rear contact. Thin film technologies are all complex. They have taken at least twenty years, supported in some cases by major corporations, to get from the stage of promising research (about 8% efficiency at 1 cm2 scale) to the first manufacturing plants producing early product. Modules are designed to meet rigorous certification tests set by international standards agencies.
According to Susan Eustis, principal author of the study, "adoption of solar energy has a simple market driving force. If people do not adopt solar energy, the planet will become unfit for human habitation. The fossil fuels are warming the planet at an exponentially increasing rate that makes life unsustainable if something does not change. Global warming drives solar markets." Solar is perceived as the best, perhaps the only widespread solution to global warming. Every large enterprise has adopted a social responsibility strategy that makes a nod toward solving the issues of global warming and embraces renewable energy. Every person in the world is aware of the problems that global warming is bringing.
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