Solar Energy Efficiency
Conversion Rates
There are different ways to measure solar energy efficiency. Theoretical work in hi-tech laboratories point to very good maximum efficiency rates for just about all the technologies employed to create solar cells. In reality though, the panels that are installed on your roof have a far lower conversion rate of sunlight into electricity.
Why Is This So?In laboratories, scientists can carefully control the conditions the solar cells are exposed to. There is no dust, bird poo, clouds or anything else to detract from the cells' performances. Light can be shone onto the laboratory cells at the perfect angle for maximum absorption and there are no issues with degraded performance due to age of the cells. Temperature is also a factor. Crystalline silicon solar panels have an optimum solar energy efficiency operating temperature of about 250 degrees Celsius. If it's hotter than this on the panel surface the increased resistance caused by the temperature will make the panels perform more poorly. Different Cell TypesIn the real world these are all factors that contribute to a cell's limitations. Let's have a look at the typical "in the field" efficiency rates of the commonly available panel types. Monocrystalline Silicon These are cells that are produced from a single silicon crystal which is cut into the desired shape. These are the oldest cells and still the best for individual performance. A monocrystalline solar panel typically converts about 13% of the sunlight it receives into electricity.Polycrystalline Silicon These cells are cheaper to make than monocrystalline ones but suffer lower conversion rates due to greater internal resistance between the crystals. The conversion rate for one of these panels is typically around 12 - 12.5%.Mono- and poly- crystalline panels also have the longest lifespan of any commercially available cells produced to date. This is worth keeping in mind if you are looking for used cheap solar panels Thin Film Amorphous Silicon These are cheaper to produce and don't suffer from the negative effects of increased temperature, so they are suited to more tropical areas. Their performance is poor though, as they only convert between 6 and 8 percent of the sunlight hitting the panel into electricity.Amorphous silicon panels are also prone to suffering from reduced solar energy efficiency over time, though this is not as significant as for other thin film panels. Other Thin Film Panels There are many new production methods for thin film panels being used and the focus of the technology has been on reducing production costs. Current thin film technologies include CIGS, CIS, CdTe and more. On average these panels convert about 10-12% of sunlight into electricity. The down side to these panels is that on the while they have a lower price tag they also last for far less time. The average thin film panel has a useful lifespan of about 10 years. This is significantly lower than for crystalline panels which function indefinitely as long as the wiring is good.
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