Behind the Grid: Solar Power (Photovoltaic)

Posted: February 16, 2021, 12:00 am

Solar Power

(Published, 11/01/2020, Ruralite)

Solar power is energy from the sun that is converted into electrical (or thermal) energy. Sunlight is the most abundant energy resource on Earth and nearly every living thing already makes use of its immense power.

Solar energy can be harnessed as heat or converted into electricity using a photovoltaic generator. When people say “solar power” they’re usually referring to photovoltaics.

How does it work?

The quick answer is that photovoltaic cells absorb sunlight (photons) and release electrons (electric current). A deeper answer is that solar cells consist of a specially-treated semiconductor wafer. When struck with sunlight, electrons are knocked loose from the atoms in the upper layer generating an electric field that is positive on one side and negative on the other.

Does it work everywhere?

Electric output from solar panels depends on the total sunlight available. Sunlight is strongest near the equator and gets gradually weaker toward the north and south poles. There are resources online to help calculate solar panel output based on location. (See: pvwatts.nrel.gov) In our region, solar panels are usually angled toward the south to get more direct sunlight.

Is it a practical source of generation?

In 2019, solar generation facilities made up only 1.8% of all utility-scale power generated in the United States. Utility-scale generation must be available when needed. Solar power only works when the sun is shining, so although they work well in the daytime, they stop producing power when the sun goes down. That means another system must be ready to produce electricity at night. Some of the electricity generated in the daytime can be stored using batteries or heat storage (See: wikipedia.org/wiki/Molten-salt_battery) Solar cells vary in quality. In the 1950s, panels converted about 1% of sunlight energy to electricity. Today, that number is 15-23%. That’s pretty good, considering that the energy source (sunlight) was free to begin with! (It should be noted that all forms of electricity generation experience inefficiencies and losses.)

Off-Grid Application

Solar power works extremely well for offgrid, low-wattage applications. For example, a security light in the middle of nowhere can run on a small solar panel with no power lines or other infrastructure. LED lights require very little power so a single solar panel is often an adequate power source.

Net Metering & Community Solar

One of the unique qualities of solar power is that it can be installed at residential scale. Many people who invest in those systems will connect to the grid through their utility in an agreement called ‘net metering.’ Some utilities also offer community solar which is just a solar generation facility where people rent or buy the panels. Any electricity generated by the panels they own is credited to their power bill.