More Information on Solar Panels and Energy

Crystalline Silicon

• According to the Siemens Solar website, manufacturers make 90 percent of solar cells from crystalline silicon (c-Si). The c-Si material produces solid solar cells with good efficiency from 15 percent to 17 percent, which represents two-thirds of the current theoretic maximum efficiency. Monocrystalline and multicrystalline make up the two types of c-Si cells. The monocrystalline manufacturing process slices high-purity crystal silicone into thin, miniature disks -- up to a diameter of 150 millimeter and 200 microns thick. The process includes repair to wafers damaged by the cutting technique. The disks receive a fine gloss and polish. Dopants, such as phosphorus or arsenic, applied to the disks modify the electric charge in semiconductors and photovoltaic solar cells. Manufacturers spread a final coating of metal conductors across the disk surface.

  Multicrystalline cells consist of sawing a molten block of silicon into bars and cutting the bars into plates. The solidification process causes abnormalities in the materials, which affect efficiency. However, the polycrystalline has a more cost-efficient manufacturing process.

Protecting Cells

• Manufacturers position multiple cells on a grid-like backing and solder them together. A thin layer of high-transmission glass is bonded to the top of the cell to provide a weather-resistant protective cover. The backing panel attaches to a substrate by a thermally conductive adhesive. The cement's thermal property keeps the module from overheating from excess energy that's not converted into electricity.

Thin Film Panels

• About 10 percent of the materials used to make solar panels consists of amorphous silicon (a-Si) or polycrystalline materials, such as cadmium telluride, copper indium and diselenide. The more common a-Si process entails a "roll-to-roll" procedure that applies silicone alloys, in a sequence of layers, on a stainless-steel or coated-glass substrate. Each cell has a transparent conducting oxide layer that makes up the front electrical contact. The rear layer of the cell provides the rear contact. A laminated cover makes thin-film panels weather-resistant. The cells have less efficiency compared to crystalline silicon, but thin film has less bulk and requires less expensive material to produce.

Panel Performance

• The U.S. Department of Energy's Energy Savers website list three methods for measuring the performance of panels. They include peak watt, normal operating cell temperature (NOCT) and AMPM standard. The AMPM standard measures a solar panel's performance over the course of an entire day. Peak watt computes the maximum power under control laboratory settings. NOCT measures the operating temperature of panels after the first module reaches a specified ambient temperature. The rating is usually more accurate than peak watt. AMPM gauges the performance of the solar panel in a realistic environment. It evaluates solar panels over the course of an entire day, including ambient temperature, light levels and air mass.