What Is Solar Energy?

Solar energy definition

Solar energy is the radiation from the sun that can be used to produce heat, cause chemical reactions or generate electricity. In simple terms, it’s the light and heat we receive from the sun every day.

But “solar energy” isn’t the same thing as “solar power.”

Solar power vs. solar energy

Solar power refers specifically to electricity generated from sunlight. For example, when solar panels (PV systems) convert sunlight into electricity for your home, that electricity is solar power.

Solar energy is the source. Solar power is the electricity you generate from it.

Solar energy can also be used directly without converting it to electricity. For instance, sunlight can naturally light and warm your home, or it can be used in solar thermal systems to heat water.

According to Encyclopaedia Britannica, solar energy is “radiation from the sun capable of producing heat, causing chemical reactions, or generating electricity.”

Solar power, by contrast, refers to electricity produced by converting sunlight into usable electrical energy.

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How does solar energy work?

The three main types of solar energy systems are photovoltaics (PV), concentrating solar-thermal power (CSP) and solar thermal systems.

• Photovoltaics (PV) systems: Solar panels that convert sunlight directly into electricity for your home.
• Concentrating solar-thermal power (CSP): Large-scale systems that use mirrors to create heat, produce steam and generate electricity (usually for power plants).
• Solar thermal systems: These systems use the sun’s heat to warm water (e.g., solar water heaters). They are rare in the United States.

How PV panels work

Solar panels work by turning sunlight into electricity that your home can use. When sunlight hits a panel, it activates small cells inside. These cells create an electric current (basically, flowing electricity).

Solar energy works by capturing sunlight and turning it into usable electricity.

However, they produce a type called direct current (DC) power. Your home runs on alternating current (AC) power.

That’s where the inverter comes in. The inverter converts the DC electricity from the panels into usable AC electricity. From there, the power flows into your home to run your lights, appliances and electronics. Maybe even your electric vehicle or heated pool.

How CSP works

Instead of using solar panels, CSP uses mirrors, heat and steam to make power.

1. Large mirrors capture sunlight and reflect it onto a central point.
2. That central point is a reservoir of liquid (water or another heat-transfer fluid), and it gets very hot.
3. When the water is hot enough to boil, steam spins a big wheel.
4. That spinning wheel generates electricity.
5. The electricity is sent to the grid, like other power plants. Utility-scale projects (such as industrial water desalination or mineral processing) use that electricity.

Did you know?

CSP technologies are best equipped to provide electricity on a massive scale, powering whole cities, towns and communities, according to the National Renewable Energy Laboratory.

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How is solar energy stored?

Solar panels make electricity when the sun is shining. But your home still needs power at night. In fact, energy use often peaks on hot summer evenings, when panels aren’t producing much.

Residential solar storage batteries typically cost $7,000 to $18,000.

On sunny days, your system may generate more electricity than you need. A storage battery stores that extra power so you can use it later. Then at night, during bad weather or even in a blackout, you can keep your lights on.

Storage also helps when production dips. Bad weather, shade and dirt can reduce output (panels still work on cloudy days, just less efficiently). A battery gives you reliable backup when production dips.

Large CSP solar power plants commonly use thermal storage. These systems store the sun’s heat (often in materials like molten salt) and use it later to generate electricity.

Pros and cons of solar energy

There are several advantages and disadvantages of solar energy.

FAQ

Bottom line

The sun emits solar radiation that powers everything from photosynthesis to digestion and breathing. While the sun acts as the generator for almost all everyday functions, the Earth only intercepts an incredibly small percentage of the sun’s total energy.

Out of this small percentage, even less is absorbed by the Earth and its atmosphere. That being said, the U.S. Department of Energy estimates that the amount of solar energy absorbed by the Earth in just an hour and a half is enough to power the entire planet for a year.

Using solar panels, you can harness this energy to power simple tasks such as air conditioning, turning on your lights and keeping your food refrigerated — often for cheaper than other electricity alternatives — while also helping the environment.