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What is Solar Energy?

There’s nothing new about harnessing the sun’s power for something other than catching some rays. Humans have been doing it since the dawn of civilization, using the sun to light fires and provide heat for homes and cooking. What’s different now is the sense of urgency attached to using solar power as a way to slow climate change and global warming.

Solar power is cleaner than energy sources such as coal, oil and gas for the simple reason that it doesn’t produce greenhouse gases. That’s why there is increasing effort being put into the use of solar photovoltaic (PV) panels to power homes, offices and cars.

Plenty of strides have been made in that direction in recent years. Solar power installations in the U.S. have grown 35-fold since 2008 to an estimated 62.5 gigawatts, according to the Office of Energy Efficiency & Renewable Energy. That translates into enough capacity to power the equivalent of 12 million average homes in the U.S. Meanwhile, the average cost of solar PV panels has declined by nearly 50 percentover the last half-decade or so.

Most people are familiar with solar panels, though the technology behind them might be a mystery. The panels use crystalline silicon as a semiconductor and contain multiple rows of cells that are treated chemically to create positive and negative electric charges. They work by letting particles of light, called photons, knock electrons free from atoms, a process that generates direct current (DC) electricity. The direct current is then converted to alternating current (AC) because AC currents are the kind used in most residential wall sockets. Solar panels are typically located on roofs so it’s easier for them to capture sunlight. Of course, on days when the sun isn’t shining, other means are needed to produce power.

PV technology has been around for a long time. The photovoltaic effect was first discovered in 1839 by French physicist Edmond Becquerel. Forty-four years later, American inventor Charles Fritz created the first working selenium solar cell, which was the precursor to the silicon cells used today. Solar PV panels were first developed by Bell Labs in the 1950s. The panels were mainly used to power different parts of spacecraft during the late 1950s and 1960s, including spacecraft used in the Vanguard, Explorer and Sputnik programs. It took a long time for PV panels to be used in the mass market because manufacturing PV cells was so expensive.

“It was only with a dramatic drop in the price of silicon PV cells, from $76 per watt in 1977 to a fraction of a dollar in recent years, that PV has come into widespread use,” explains environmental lawyer Philip Warburg to Yale Climate Connections.

Citing data from the National Renewable Energy Laboratory, Warburg noted that rooftop solar panels could generate enough electric power to offset 39 percent of the current electricity needs in the U.S. But that’s still a long way off. In 2018, solar energy supplied around 30 billion kilowatt-hours of electricity, which accounted for less than 1 percent of total U.S. power generation.

Though that percentage is small, Warburg said solar generation is still “bringing about a revolution” in the way Americans produce and consume electricity. “Utility companies and cooperatives have long been the dominant providers of electricity to U.S. consumers, relying primarily on central generating stations using fossil fuels, nuclear power and large-scale hydro,” Warburg wrote. “Yet today, net-metering laws in many states require utilities to compensate customers for the surplus electricity they generate at their homes and businesses (from solar power).”

While these aims may run counter to the usual priorities of utilities, many are still building their own solar installations to comply with new standards mandating that a certain percentage of retail electricity sales come from renewable energy sources. These new standards were the catalyst behind about half of all U.S. renewable electricity capacity and generation from 2000 to 2017.

In addition to the environmental benefits of solar energy, many supporters also tout the economic benefits. Homes that include solar panel systems typically enjoy lower utility bills, more tax deductions and higher home values. The solar energy industry has also had a major impact on employment. Nearly 3.3 million Americans worked in various clean energy positions as of 2018, according to the E2 Clean Jobs America report. Of those workers, nearly 335,000 were employed in solar energy compared to the 211,000 in coal mining or other fossil fuel industries.