These are big times for solar power. Despite a spiraling economy — and arguably because of it — solar power will play a key role in developing clean, domestic energy sources and pulling America’s workers up out of the sinkhole we currently find ourselves in.
Very soon it will be solar energy’s turn to really step up to the plate. Still the question remains as to who will be sent to bat. For now conventional, silicon-based, wafer solar cells are swinging away, and doing a great job. But thin film technology is creeping up behind, and research has been very promising for other elite technologies such as nano and organic solar cells.
Which of the three generations of solar cells will take the reins? That will depend mainly on two factors: the cost and conversion rate for each solar cell. Scientists and researchers in all areas of the solar industry are scrambling to improve and/or reinvent the solar cells, in the hopes of developing the solar industry’s dream: a low-cost, high-efficiency solar panel.
Here we have the founding father of the solar industry, so to speak. The traditional single-junction, silicon-wafer, photovoltaic solar cell. They easily have the highest conversion efficiency, averaging from 15-20% in most cases. While developers of first generation PV cells are always working to improve efficiency, their main obstacle has been production costs. The extremely pure silicon needed to manufacture the cells is the primary driver behind the high costs. It has taken a good deal of government subsidizing to bring first generation solar systems down to a reasonable price.
Photo credit: SolSource Inc.
Second generation cells utilize thin film technology, involving amorphous or micromorphous silicon, or ignoring silicon altogether. First Solar, the largest thin film manufacturer in the nation, uses cadmium telluride based cells. Second generation solar cells are smaller and much cheaper than their first generation counterparts. Unfortunately they are also much less efficient, with conversion rates peaking at 15% but usually hovering more around 10% or less.
Because the panels/cells are so thin, they can be produced very fast and relatively cheap. This is compensating for lower efficiency, and second generation solar materials are closing in on, and will likely surpass, first generation panels in the next few years.
Third generation solar cells — many hope they will be the ace-in-the-hole for the solar industry. Unfortunately they are still in the research phase and don’t even exist on any commercial scale. The whole idea is to produce a low-cost, high-efficiency solar cell, the epitome of solar technologies. Although the third generation is still a baby, results have been very promising. Organic solar cells promise cheap, clean, and abundant production resources. Nanosolar cells promise strong yet tiny cells that could thrive in paint or embedded in a window or anywhere.
The issue, as you might expect, comes down to conversion rates. Recently, scientists broke a record by producing dye-sensitized solar cells with a 10% conversion efficiency. While this is an exciting development, it is still just a record and most third generation innovations remain well below that threshold. Still, innovations are moving relatively fast in the world of third generation solar cells, and they could begin seeing commercial adaptation within 5-10 years — not very long when facing eons of usable sunlight.
Photo credit: Goodcleantech.com
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Right now first generation cells have the highest conversion rates, while the second generation has the edge on production costs (with a decent conversion rate). The third generation was born specifically to beat out the first two, and it looks more and more like it will eventually succeed. But when?
It should be noted in closing that new or improved solar cells is not the only angle being looked at to increase system efficiency. Scientists in Australia are using large mirrors to concentrate sunlight onto solar panels; not necessarily increasing conversion rates, but certainly increasing the amount of usable sunlight and therefore output.
There are also hybrid PV/Thermal solar systems in the works that can improve overall efficiency and savings by simultaneously heating water and creating electricity.