Equipment and products that enable us to use renewable energy instead of fossil fuels and conventional electricity are highly beneficial. Examples include solar thermal systems, solar electric (photovoltaic) systems, and wind turbines. Other power generation equipment, such as fuel cells and some energy storage systems (like batteries) are included here because they help us accommodate varied energy sources so that we may eventually move beyond fossil-fuel dependence.
SolFocus makes concentrating photovoltaic systems for commercial power generation. The company’s SF-1100S consists of a primary mirror that captures sunlight and a secondary mirror that concentrates it at 500 suns onto high-efficiency III-V gallium-arsenide (GaAs) solar cells made with a germanium substrate. According to the company, these cells operate at 38% efficiency or greater, compared to 13%–19% for standard silicon PV, and are not affected by degradation at high temperatures. The arrays are mounted on a two-axis tracking system that uses monitoring software to ensure accuracy and allow offsite, remote management. High-wind and nighttime stow positions protect the unit. The SF-1100S is scalable for use in systems generating hundreds of kilowatts to those generating 50 megawatt or more. This module obtained the California Energy Commission listing, making it eligible for the state’s solar power rebates.
Choose a photovoltaic (PV) system to fit your energy needs, budget, and the space you have for installing the modules.
Crystalline modules are proven, efficient, and reliable, and produce the most power per square foot, especially during peak hours. You can get these as mono- or polycrystalline products and the lesser-known ribbon technology. They don’t work well on cloudy days or in high heat, however.
Monocrystalline modules are the most efficient rooftop mounted systems, with some modules reaching 20% efficiency. So if you don’t have much space for a PV installation or want maximum power production, these are a good choice. Polycrystalline modules are almost as efficient as monocrystalline, and they are less expensive, so these are a good option for those on a tighter budget or with a little more space for the modules. Thin-film PV is less efficient than crystalline, and less expensive, too.
Thin-film works well in low-light conditions and in high temperatures so over the course of a year can create more power than crystalline PV per rated capacity, but because the rating capacity is lower for the same area, you’ll need a lot more room on the rooftop to have that much capacity. Amorphous silicon (a-Si), cadmium telluride (CdTe), and copper indium selenide (CIS)/copper indium gallium selenide (CIGS) are the major technologies.
GreenSpec lists PV modules that have high warranted minimum power ratings—the amount of power the company guarantees the module will produce—and high PTC (PVUsa test conditions) efficiency ratings, which are considered more of a “real world” representation of performance. PTC ratings are used by the California Energy Commission to determine rebates and are usually several points lower than the STC (standard test conditions) ratings.
Ratings and Commentary