Solar-Electric Panel Technologies

Currently, two types of thin-film PV products are on the market—amorphous silicon (abbreviated a-Si) and Copper Indium Gallium diSelenide (CIGS), which uses no silicon at all.

The advantage to CIGS technology is higher absorptivity than amorphous silicon, with 99% of the light shining on the panel being used for energy production. The addition of gallium to the copper indium diselenide semiconductor material widens the spectrum of solar radiation that can be absorbed, improving overall efficiency of the panels. In addition to being more efficient than a-Si, these panels are more environmentally friendly in their manufacturing process. They also do not suffer degradation in cell efficiency associated with other thin-film PV products.

The Choice Is Yours

So, how do you go about choosing which modules to buy? Price isn’t the only factor to consider. A lot depends on where you live and the environment where the modules will be placed in service.

Almost all solar modules are designed and built for outdoor use, so the durability factor is often covered. Most modules are framed in metal and covered in tempered glass. Hail impact ratings for up to 1" stones at 50 MPH are common. Some of the amorphous panels (like those from Unisolar) use a UV-resistant polycarbonate covering, which avoids the possibility of shattered glass while still offering excellent weather-proofing.

How large an array do you want to put in and how much room do you have on your roof or other location? If space is at a premium, then consider mono- or poly-crystalline modules. Modules are not uniformly shaped, so the dimensions of one model over another may make better use of your available space. Carefully measure the proposed installation space (avoid rooftop vent stacks or chimneys—even small shadows can dramatically drop your solar array output!) and then see what configurations work best. However, if you simply need to get the most energy for your buck and space is not an issue, then you might consider amorphous panels.

Aesthetics is often a major factor in homeowners’ purchase decisions, especially for solar modules that will be placed in plain view, on the ground, or on a visible roof pitch. Monocrystalline and amorphous panels tend to have darker colors while multi-crystalline panels often have an iridescent blue color. But technology is the not the only determinant of color; one amorphous type has a deep maroon color! Not only color but module shape contributes to appearance. Some module manufacturers are coming up with solutions to fit more modules onto rooftops and with more aesthetically pleasing profiles—from solar shingles to triangular shapes to fit in corners so that the entire area of a roof can be used.

Another major consideration is availability. Module manufacturers change their product lines to keep up with market demands and technology refinements, so what’s available today may not be available two years, one year, or even six months hence. If you’re planning to expand your solar array in the future, you run the risk that the modules you install today will not be available when you’re ready to expand. Further factors to consider: What sorts of environmental safeguards and improvements are being made to the manufacturer’s process? How much embodied energy is represented in a given module and therefore how long must the module operate to “pay for itself” in terms of the energy used to make it? Don’t forget to consider the length of the warranty, the weight of the modules to be lifted onto the roof, where the modules are manufactured, and shipping costs.

Clearly, there are many subtle, as well as not-so-subtle, differences among solar panel technologies. Understanding the differences—at least in the broad strokes offered here—can assist you in selecting the best panel type for your situation. Factors affecting your selection include price and availability, electrical characteristics, installation location dimensions and temperatures, and aesthetics. While it may seem a daunting task to make a selection among the many types and models available, it often happens that one or more of the factors above, as it will tend to lead you toward a likely candidate. And, of course, we're here to assist you with our expertise as you move toward installation of your own solar electric system.