Top Five Cool Features of Thin Film, Flexible, and Foldable Solar Cells
A lot of attention lately has been give to thin film, also called flexible and foldable, solar cells. Tremendous advancement has occurred in this technology over the past 5 years. Traditional solar cells, the ones that you are used to seeing on roofs over the years, may someday be replaced by thin film as the go-to technology for renewable energy users. Here are five big reasons why this is happening:
1. Cost. The biggest problem with current solar cell technology is expense. These cells are built in a similar fashion as computer chips. There are a lot of delicate parts to assemble and solder. With thin film, the process is closer to a printing process, where layers are applied to flexible plastic or metal one at a time. The materials involved are also cheaper. All this means that the product is cheaper therefore more affordable to more people. And don't forget: money is green too.
2. Application. The fact that thin-film cells are flexible means they can be applied to more surfaces than traditional panels. In this new era of solar we are seeing solar films directly applied to roof tiles, siding, windows, boats, cars, bags, and clothing. And more and more the solar is IN the products, not just on them. You could be a walking energy generator!
3. Durability & Reliability. Foldable panels are much more durable because of their flexible nature. The silicon used in traditional crystalline panels is brittle and therefore must be protected with glass and aluminum. The silicon used in film type solar is much more durable. And since the manufacturing process is simpler they more reliable and less prone to warranty issues. Many thin film panels also experience less voltage drop under hot conditions. This is important since these panels have less air circulation around them than traditional cells that are usually offset from the roof or wall.
4. Efficiency Improvements. In years past we have seen the efficiency of all sun-based technologies greatly increase. But no technology has advanced farther than flexible photovoltaics. What used to be 5%-10% efficiency (meaning that 5% of the sun's energy that strikes the panel is converted into electricity), is now 15% and approaching 20%. In 2005, the National Renewable Energy Lab in Golden Colorado achieved a world record 19.9% efficiency for a CIGS (explained below) cell. This is the area where we expect to see the biggest improvement in the coming years.
5. Portability. Obviously lighter is better. With these cells you can take them camping, boating, and move them around your house to capture the most sunlight. They can even be stored, by rolling or folding, for use on those not-so rainy days. Ever wanted to have your boom-box blasting out in the woods? With flexible solar you can do that.
There are basically three different technologies that are widely available today. Below we will summarize each technology and discuss its features.
Amorphous or Thin Film Silicon. This technology uses the same process that is used in a traditional hard-case solar array. However, instead of using rigid silicon wafers, the silicon is layered on a piece of flexible metal or plastic and then topped with a protective layer. This technology is not as efficient as the old method. But, as we talked about above, it is much cheaper to make. To produce the same amount of energy as a traditional solar panel, you would need 30-50% more surface area of thin film.
Cadmium Telluride. This technology is less popular than amorphous silicon for several reasons. While it is cheaper to manufacture cadmium telluride (CdTe), it is less efficient than silicon. The materials in these cells can be toxic, leading some to question the long term environmental effects. The National Renewable Energy Lab has asked the government to investigate the long term effects of CdTe since the economics of the technology are very attractive. The efficiencies for these cells are usually around 15%.
CIGS. CIGS is an acronym for 'copper indium gallium (di)selenide'. CIGS cells hold the most promise for lowering the cost of solar since the economics AND efficiencies are very encouraging. As stated above, CIGS efficiencies are approaching 20%. Manufacturers anticipate the cost of mass-produced thin film cells to be around $1.00/watt, compared to crystalline silicon panels at $5.00/watt. Companies such as Shell, Nanosolar, and Honda are investing heavily in this technology. Nanosolar is particularly interesting in that is has the backing of hundreds of millions of dollars in venture capital money.
So which one is right for you? Well for now it doesn't matter too much which technology your product uses. Check out our product options and decide what the best fit is for you.