Solar Energy

Background

One of the most common renewable energy sources, solar power technologies capture radiative energy from sunlight and convert it into electricity or thermal heat.

Solar is part of an emerging class of renewable energy that can diversify a region’s or nation’s power generation portfolio while reducing the use of fossil fuels. 

In 2023, renewables accounted for 23% of generated electricity in the US, with 5.1% coming from solar (see data). Solar power is the country’s fastest-growing source of electricity. 

History

Societies have long harnessed the sun’s power—Neolithic Chinese villagers began using solar architecture 6,000 years ago, orienting their homes to face south to heat them in the winter. Ancient Greeks and Romans added the invention of clear glass to help heat bathhouses and homes (see timeline). 

It would be several millennia before solar power would be used to create electricity. Albert Einstein's 1905 paper on the photoelectric effect—for which he won the Nobel Prize—introduced a new theory of light scientists used to develop modern solar technology. 

Charles Fritts invented the first solar cell in 1883 with selenium, however, it had less than 1% efficiency. In 1953, scientists at Bell Labs invented the first solar cell using silicon, increasing the efficiency to 6%.  

Silicon solar cells didn’t immediately catch on commercially, but were widely adopted by NASA during the Space Race to power satellites and spacecraft. Solar technology is still used in space flight today.

Technology has continued to improve, with the average efficiency at 21%, and the world record at 47.6% (see timeline). Costs have also substantially decreased from roughly $1,500/watt in the 1950s to now less than $1/watt. 

How It Works

Solar power uses radiation from the sun to generate electricity, typically via devices known as photovoltaics—more commonly known as solar panels. 

Smaller panels, made of dozens of solar cells, can be found on neighborhood rooftops to generate residential solar power for the homes they are attached to. Larger solar farms consisting of hundreds of panels generate utility-scale power, creating electricity for the entire grid. 

Regardless of size, the panels act the same: When light falls on photovoltaic materials, energy from individual photons of light is absorbed by electrons in the material, which become conductive (like electrons flowing through a metal wire). This electricity is then used as a power source (watch process).

Just like the ancients, we still use passive solar design to heat and cool buildings. There are no mechanical parts, and no electricity is created. But the design uses strategically placed windows, walls, and floors to collect, store, and distribute solar energy. 

Future

Since its development, solar cells have gotten faster, cheaper, and more efficient, leading to wider adoption. In 2023, the US saw record-breaking solar installations and total electric generation from solar continues to increase every year (see charts). 

The US solar industry is expected to grow at a rate of 14% until 2028, where analysts project it could decline due to potential legislative influences, longer wait for transmission lines, and labor shortages.