What are the Different Generations of Solar Cells?
There are three basic generations of solar cells, though one of them doesn't quite exist yet, and research is ongoing. They are designated as first, second, and third, and differ according to their cost and efficiency.
The first generation are high-cost, high-efficiency. These solar cells are manufactured in a fashion similar to computers, involving extremely pure silicon, use a single junction for extracting energy from photons, and are very efficient, approaching their theoretical efficiency maximum of 33%. In 2007, first generation products accounted for 89.6% of commercial production, though the market share has declined since. The manufacturing processes that are used to produce them are inherently expensive, meaning that these cells may take years to pay for their purchasing costs. It is not thought that first generation cells will be able to provide energy more cost effective than fossil fuel sources.
The second generation, which has been under intense development during the 1990s and early 2000s, are low-cost, low-efficiency cells. These are most frequently thin film solar cells, designs that use minimal materials and cheap manufacturing processes. The most popular materials used for this type are copper indium gallium selenide, cadmium telluride (CdTe), amorphous silicon, and micromorphous silicon.
A standard example of second generation cells would be those made by Nanosolar, which uses a special machine to print the cells at an extremely fast rate. Though these cells have only 10-15% conversion efficiency, the decreased cost more than makes up for this deficit. Second generation cells have the potential to be more cost effective than fossil fuel.
Third generation solar cells are just a research target and do not really exist yet. The goal of solar energy research is to produce low-cost, high efficiency cells. This is likely to be thin-film cells that use novel approaches to obtain efficiencies in the range of 30-60%. Some analysts predict that third generation cells could start to be commercialized sometime around 2020, but this is just a guess. Technologies associated with third generation products include multijunction photovoltaic cells, tandem cells, nanostructured cells to better pick up incident light, and using excess thermal generation to enhance voltages or carrier collection.
@Georgesplane- I study renewable energy and have read up on these systems so I can answer your questions. These new solar cells are not going to be s cheap as the solar cells the CPV manufacturers were using before, but they are more than double their efficiency.
CPV systems can also concentrate solar radiation up to 1000 times, which is double what they were capable of two or three years ago. This allows the systems to use fewer cells (about half of current and about a quarter of what would have been necessary a few years ago) for a collector while not sacrificing output.
As for residential use, these systems will be strictly grid tied commercial generation plants. They will be used for plants rated at about 50MW, give or take. They will not necessarily make the cost of generated electricity more as long as the increase in cost does not surpass the percentage increase in efficiency. This technology improvement will help the industry mature and eventually drive down costs.
@Amphibious54- What are the costs of this third generation solar cell technology compared to the costs of the cells the CPV manufacturers were using before? Has the company manufacturing these cells delivered a cheaper product with increased efficiency as many in the industry have touted this technology before? Will these CPV systems be available for residential use, and if so, how much will they cost per installed kW? Does the technology compete with electricity from centralized generation plants?
I would just like to add that a company announced earlier this year that they will start full-scale, commercial production of third generation cells by the beginning of next year. The company has produced a cell that is rated at a record holding 41.4% efficiency.
The cell is basically a number of layers of semi conductive material that each absorb a certain wavelength of light. The wavelengths that each the first layer does not absorb is passed through to the next layer and so on. Each layer is then organized in series to convert the solar radiation into electricity.
The cells are meant to work with Concentrating Photovoltaic (CPV) systems. This means they will not be sold directly to the public, but to other companies that produce CPV systems. The company plans to produce 250,000 cells per year if it receives the grant from the Department of Energy for production expansion.
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