| Sun-powered electric options were once limited to | | | | temperatures. Solar film units are less sensitive to |
| large dark panels, but now consumers have a choice. | | | | environmental temperature, losing perhaps 2% of their |
| In addition to panels of single or multi-crystal solar cells, | | | | power at 100F, compared to 6% power loss for a |
| solar film or thin film solar units are available in frames | | | | traditional crystalline system. The cell temperature can |
| or in building materials such as roof laminates. Each | | | | be modified by allowing for air flow around the system, |
| technology has advantages. The choice depends on | | | | but if ambient temperatures tend to be high, a thin-film |
| budget, space, climate, and aesthetics. | | | | system may be the right choice. |
| The cells that make up a crystalline photovoltaic | | | | New amorphous silicon modules produce 20% to 25% |
| module stand out as dark rectangles or octagons. A | | | | more energy production than rated. While this will |
| multi-crystalline cell often appears as a sparkly | | | | stabilize to the normal rated output within six to twelve |
| rectangle. The electrical connections in both | | | | months, any system using these modules must be able |
| technologies show as a pattern of silver lines. | | | | to handle the initial higher output. Traditional modules |
| "Thin-film" does not refer to a specific material. These | | | | stabilize immediately, which eliminates this consideration. |
| modules can be made of amorphous silicon (a-Si), | | | | Once the a-Si modules become stable, they will |
| copper indium gallium diselenide (CIGS), and cadmium | | | | degrade at approximately the same rate as other |
| telluride (CdTe). Amorphous silicon is popular for | | | | systems. |
| applications where looks matter. Since it can be put on | | | | Not all climates are sunny, so shade and low-light |
| plastic, as well as on glass, a-Si can be produce in | | | | performance may be an additional concern. Flexible |
| flexible continuous rolls. Amorphous silicon is used in | | | | sun-powered panel cells can be the same length as |
| laminates, solar shingles and roofing tiles. | | | | the module they are on. These cells are less likely to |
| Aside from appearance and versatility, efficiency is a | | | | be completely in shade than crystalline cells, which are |
| factor in PV material selection. A convention framed | | | | usually just five or six inches across. |
| crystalline system will produce more power in less | | | | One type of technology that gives good performance |
| space. The flexible photovoltaic systems, while more | | | | in shade or conditions of low light is that used by |
| aesthetically pleasing, are about half as efficient. This | | | | Uni-Solar products. These modules are flexible, and |
| means a flexible module will need twice as much | | | | have triple junction cells made of amorphous silicon. |
| space to generate the same amount of energy as a | | | | This technology allows bypass diodes to be used |
| conventional system. | | | | within the module, so that any cell that is in shade can |
| This has a big effect on system size. A three by three | | | | be bypassed. In addition, this arrangement lets each |
| foot solar laminate system can deliver 60 to 70 W, | | | | element in the multi-junction cell capture a different |
| with efficiencies as high as 8%. A three by five foot | | | | wavelength of light. This gives better energy |
| crystalline module can provide 170 to 220 W, with up | | | | production in conditions where lighting is indirect or not |
| to 17% efficiency. But power density is not the only | | | | uniform. |
| consideration. | | | | For more information on Solar Film, check out our |
| Cell temperature has an impact on PV cell power. | | | | website. |
| Crystalline modules lose efficiency at higher | | | | |