How does solar energy work?

You may have seen solar panels on rooftops and perhaps even a solar farm, with acres and acres of black, shiny panels hoisted on racks. Inside these panels are photovoltaic cells, and their job is to turn light into electricity. According to NASA, these cells transform photons from sunlight into electrons. When the electrons are passed through a semiconductor, a current is created that can be made into electricity. Another less common form of solar energy is solar thermal, which concentrates the sun's rays on mirrors to heat a fluid (usually water). The steam from that fluid powers a turbine that makes electricity.

The state of solar power

Solar energy is the fastest-growing energy source in the United States. As of the third quarter of 2023, the United States installed over 160 gigawatts of solar, which is enough electricity for nearly 30 million homes. And over the last decade, the solar market in the United States has grown at an average rate of 24% each year. With continued investment and innovation, solar energy is poised to play a significant role in meeting our nation's energy needs in the future.

What are the advantages of solar energy?

When you stack the upsides of solar energy next to other energy sources, it has a rather impressive list of advantages:

• While solar systems take up land space, they don't always have to. Panels can be mounted on rooftops, making them well-suited for urban areas.
• Rooftop solar also lends itself to distributed generation instead of centralized, creating a more diverse and resilient electric grid.
• Solar is silent, which makes it ideal for more populated areas.
• There are no moving parts, so it needs less maintenance than wind.
• The energy is easy to generate and transport.
• Panels work in cold climates, as air temperature doesn't matter if they catch rays.
• Home rooftop panels can reduce a homeowner's electricity costs. This would be advantageous during a heat wave when energy loads are high.
• Once you install the panels, power generation is nearly free. You don't have to pay a penny for sunshine.
• Several federal solar incentives are offered to people who choose to install solar panels. These include tax incentives and special rebates to save even more money.

What are the challenges of solar energy?

Solar isn't a cure-all for our energy needs in and of itself, however. You're only capturing energy during the daytime, and production levels can vary depending on how clear the sky is. Furthermore, while battery technology is advancing rapidly, we haven't yet attained an optimal way to store the energy needed to power large population centers when the sun isn't offering optimal production. Although various promising storage systems are under development, we still rely on other energy sources on cloudy days or after dark.

How does wind energy work?

Wind turbines generate electricity using principles similar to fossil fuel production, using a different fuel source. If you look at the wind turbine, the electricity is being made at a high altitude, right inside the cylinder shape behind the rotating blades. The wind pushes the edges into motion, which turns a shaft. This chain of movement eventually leads to a generator that makes electricity. The electricity then travels down the stem of the turbine and is taken to transmission lines to be transported and distributed to customers.

The state of wind energy

Wind is America's largest renewable energy source, providing just over 10% of the country's electricity and counting. Wind power capacity totals nearly 150 gigawatts, which equals enough wind power to serve the equivalent of 46 million American homes. Like solar energy, the costs of building wind turbines continue to fall. And thanks to better technology and engineering, taller turbines can harvest wind more reliably, boosting their capacity.

What are the advantages of wind energy?

Wind energy also has an impressive list of advantages:

• Wind energy is a clean fuel source, meaning it doesn't pollute the air like power plants that rely on the combustion of fossil fuels.
• Wind turbines can be built on farms and ranches, so leasing available land can become a source of income in rural areas while the owners can still use the land for other purposes.
• Wind power is cost-effective. Much like sunshine, wind costs nothing to produce.
• It is a domestic energy source, and the nation's wind supply is abundant. 

What are the challenges of wind energy?

The most prominent problem wind production faces is the cost of transporting the energy generated, as the windiest areas are usually remote. In addition, like solar, wind is an intermittent power source, so you can't count on turbines to supply energy around the clock. Also, wind is less ideal for residential use for two reasons. One, turbines make noise. While the models are getting quieter, your home turbine may be frowned upon by neighbors, your homeowners association or even your city. And in order to generate any significant amount of electricity, you would have to erect a taller turbine — up and away from wind-blocking buildings and trees and other urban obstacles. That, too, may not make you the most popular person on the block.

Other sources of renewable energy

Wind and solar aren't the only sources of renewable energy in play.

Hydroelectric energy

Hydroelectric power remains a big player in electricity production in the United States, particularly in Washington, Oregon and California, and accounts for about 6 percent of energy generation. It uses water to turn electricity-generating turbines and is reliable enough to supply base-load power for large areas of the country. Like wind and solar, the fuel source is free, and the production doesn't directly produce carbon emissions.

However, dams built to create hydroelectric reservoirs can be disruptive enough to river ecosystems upstream and down that some people question whether hydroelectric should genuinely be considered a green source of power at all, and decomposing biomatter in areas flooded by dams can release significant carbon and other contributors to climate change into the atmosphere. Effective capture of hydroelectric power also depends on having a large volume of flowing water in the vicinity, of course.

Geothermal energy

We can also capture and use heat for energy directly from the ground. On the household level, that can mean a pump that uses the difference in temperature between the air and the underground to heat your home. We can use naturally occurring underground heat sources to produce electricity on a larger scale. Geothermal taps into a sustainable resource - there is more heat than we could ever use within the Earth, and it is constantly being created.

On the other hand, sending infrastructure deep underground is expensive, has the potential to emit certain harmful gases into the atmosphere, and can also cause earthquakes. Efficient use of geothermal energy also depends on having a heat source close enough to the Earth's surface to exploit, which is only possible in some regions of the world.

Biomass

Humans typically produce biomass energy by converting plant matter into heat or fuel. Your fireplace is a classic example of using biomass, and we also use it to fuel vehicles in the form of ethanol and biodiesel. On a large scale, we can burn biomass to produce electricity. Biomass production can use otherwise unwanted byproducts like cornstalks. Still, it also takes away plant resources that would otherwise return nutrients to the soil, and production at any scale requires diverting land away from other uses. Burning biomass also necessarily pumps carbon into the atmosphere. However, this is considered less harmful than burning fossil fuels because it's short-term carbon already engaged in the global cycle, which would be released when the plant dies and decays anyway, as opposed to burning oil or coal that would otherwise be trapped underground for millions of years.

Other renewable energy production methods show promise, such as capturing the power of ocean waves and burning hydrogen molecules. Still, they haven't yet been used in widespread commercial use.

The future of renewable energy

Knowing the difference between wind and solar energy is important, but fortunately, we don't need to choose one over the other. All types of renewable energy can complement each other, depending on what types of production are available in a given geographic location, and overcome the weaknesses of any one method.

Although the renewable energy industry has experienced significant growth in the past decade, coal and natural gas are still generating the lion's share of electricity for the United States. Even so, the IEA predicts renewable energy will become the number one source of new power generation by 2025. This growth, however, will fall short of achieving net zero emissions by 2050. In the meantime, watch for developments that will help renewables overcome their challenges of storage and capacity.