When excitement in an industry or movement grows, as we are seeing in the solar energy industry, it’s easy to lose track of the essentials, the building blocks. We get caught up in the latest round of funding, or the next promising innovation. Now, this is great stuff, with a potential to revolutionize the industry. But let’s not forget what is currently on our rooftops and, for the most, continues to be installed on our rooftops: silicon-based, p-n junction solar panels.
Despite the fact that the industry could conceivably take a massive turn in the near future, it is the understanding of current solar cells that will lead us into the next generation. That’s why today is review day. Because the question still persists: How do solar panels work?
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The Solar Cell
Solar panels are divided into cell blocks, which are made up of solar cells, the basic component of a solar panel. Each solar or photovoltaic cell creates its own electricity, which then joins the flow of electric current from the other cells and then other panels and on down the line until it passes through the inverter and into your light bulbs.
Solar cells contain a semiconductor material, typically silicon. Sunlight or, more specifically, a photon of light, is absorbed by the solar cell. This absorption creates solar heat which frees electrons in the semiconductor, creating an electric current. This current is created by way of a p-n junction. That is to say that two thin wafers of silicon–one “doped” with another element to be positively charged (p) and the other negatively charged (n) – are brought in close contact with each other. As photons react with the n-junction, extra electrons are freed and tend toward the p-junction, which has extra room or “holes.” This creates that electric current. Conductive wires, which run between the p-n junction, guide this electric flow out and along the circuit that eventually delivers electricity to the home.
The Power of the Panel
The electricity created by a single solar cell is rather miniscule, but when joined with the other cells in the panel, you begin to get some notable charge. Then combine one solar panel, which may create anywhere from just a few Watts to a few hundred Watts of electricity, with the other panels in a solar array, and you could have a solar system strong enough to power a home.
Efficiency and the Future
This is how most solar power systems work. The main problem with, and what drives change in, the solar panel is efficiency. You see, there are three things that happen when sunlight hits a solar panel. That light will either pass right through the silicon, bounce off and reflect back, or be absorbed. Absorption is what drives the process described above. However, at this time the vast majority of sunlight is reflected back or passes through without being absorbed. This problem forces larger solar arrays and higher equipment costs.
The solar cells described here are 1st generation. Thin-film, polymer and other solar cell innovations comprise the 2nd and 3rd generations and promise smaller size systems that are more building-integrated and cheaper to produce. These technologies are still searching for efficiency levels that consistently rival the present, silicon-based cells. When they do it will change the future of the solar industry. At which point I will have to write this article once again…I can’t wait.
Image Courtesy of Iowa State University