In a two-part series, Chris Kneeland, NABCEP – Solar PV, project engineer in RTM’s Milwaukee office, shares his solar energy expertise. Part one provides an overview of photovoltaics (PV) basics and part two dives into photovoltaics panel design and structure.
Solar energy, powered by photovoltaic technology, has grown and advanced in recent years. On a global scale, installed solar capacity was 139 GW at the end of 2013, an increase from 1.3 GW in 2000. China, Japan, the United States and Germany have been leading the movement toward greater photovoltaic installation. The European Photovoltaic Industry Association estimates that by 2018, cumulative installed PV capacity will grow to between 321 to 430 GW.
As U.S. policies, such as federal tax credits and state and local incentives, are created that offset the costs for solar energy, more people invest in this renewable energy option. The increase in demand, in turn, continues to reduce solar hardware costs. In 42 of the 50 largest U.S. cities, a typical fully-financed residential PV system costs less than purchasing energy from a local utility company according to a recent report by the North Carolina Clean Energy Technology Center. The length of payback varies per location depending on certain factors, such as electricity costs, hardware warrantees, and availability of incentives, but the benefits of going solar continue to increase in numerous nationwide markets, including industrial applications.
Photovoltaics is the process of converting sunlight directly into electricity. Solar or PV cells, made of semiconductor materials, absorb photons of light and release electrons in what’s called the photoelectric effect – quite remarkable given that current efficiency of semiconductor materials only harnesses <20% of the sun’s energy. The process creates an electrical current, which can then be used to power a load.
Silicon is the most popular material for solar cells, including monocrystalline or single crystal silicon, multicrystalline silicon, polycrystalline silicon and amorphous silicon. Non-silicon semiconductor materials also are used, such as cadmium telluride.
Each PV cell consists of multiple layers:
- The top layer is an anti-reflective coating (ARC) that increases the light effect from the sun.
- Under the ARC, there are two layers of chemically treated semi-conducting material (usually silicon). The electrons in the first layer and the holes in the second layer are attracted to each other, and their movement creates an electrical field across the two layers. When sunlight hits this electrical field, the electrons and holes separate – and voltage is created.
Call 414.273.1432 to speak with Chris Kneeland to learn more about solar energy and photovoltaics basics. Stay tuned to part-two of the series to learn about PV in the industrial sector.