Solar photovoltaic (PV) cells convert sunlight directly into electricity. PV gets its name from the process of converting light (photons) into electricity (voltage). Each solar panel holds about 60 cells, but new technology is improving efficiency and many panels now contain XX cells. In the northern hemisphere, solar panels are typically mounted at a fixed angle facing south so they can capture the maximum amount of sunlight. When multiple solar panels are combined, the system they create is called a solar array.

Traditional PV solar cells are made from silicon. Silicon cell panels are generally the most efficient and have a life expectancy of over 30 years. Second-generation solar cells, called thin-film solar cells because they’re made from amorphous silicon or non-silicon materials such as cadmium telluride, use layers of semiconductor materials only a few micrometers thick, so they can be applied in more flexible building environments.

This picture depicts how a PV system works on a building. Solar panels on the roof capture solar energy, which is then collected and packaged through a combiner. The energy is then changed from direct current (DC) power to alternating current (AC) power via an inverter.

If the power generated by the solar array is not consumed on site, electricity is fed into the electrical grid and assigned a dollar value through the process of net metering. The power is sent through the utility grade revenue meter, which calculates the value of electricity introduced to the grid from the solar panels, to the main electrical grid. Along the way, it passes through safety switches (disconnects) and a monitoring system which tracks the accumulation of SRECs or DG Contracts for later sale back to the utility. The orange line in the picture above shows the path of energy supplied from the sun. The blue line shows electricity supplied by the utility through the grid. The green line shows the electricity being sold back to the utility grid via net metering. Read Net Metering 101