Solar Energy

the source of solar energy

In a very real sense, almost all energy we use on earth is a form of solar energy.

We’ve all felt the sun’s warmth on a sunny day, perhaps even been burned by it. That’s an example of the sun’s radiant energy reaching earth after traveling 92 million miles through space.

That radiant energy transmutes into other forms of power as well. For example, the sun is the source of both wind and water energy.

Wind exists because the sun heats parts of the earth differently. as air masses warm and cool, wind results. Even in ancient times, humans harnessed this power with sails and windmills.



Hydro power also results from energy that originally came from the sun. Sunlight heats surface water on the earth and evaporates it. When that water later falls to earth as rain, it feeds the streams and rivers that produce water power.

Of course the sun powers the chemical reaction of photosynthesis in plants. That reaction provides the plants with energy for their growth. The energy from the sun passes from the plant to an animal when they eat it.

The oil and gas we burn today are the decomposed plants and animals of millennia ago. We could say that oil is ancient sunlight stored underground.

Nowadays, we want to use the sun’s energy in a more direct and cleaner way. And without having to wait a few million years.

The only common sources of energy I can think of that don’t come from the sun are tides (gravitational pull of the moon) and nuclear power (atomic reactions).

Even after the 92,000,000 mile trip, the amount of energy reaching the earth from the sun is staggering.

On a sunny day, the sunlight landing on a square meter of the earth’s surface has the potential to produce 1 - 1.4 kilowatts of power per hour.

For the continental United States, that amounts to some 9 quadrillion (9,000,000,000,000,000 – I couldn’t resist writing out all those zero’s) kilowatts/hour. It would take over 4 trillion barrels of oil to produce that much energy.

Put another way, enough energy reaches the surface of the earth in one hour to supply all the energy needs of the entire planet for a year – if we could harness it.

That’s the big if. The challenge now is capturing more of this energy in a useful form.

The fact is, almost everyone uses the sun’s energy to some extent already - whether it’s letting day light into their home or laying a beach towel out to dry. The question how can we do it “more and better”. That is, capture more of the sun’s energy efficiently and economically.

Right now, the rising economic and environmental costs of oil and gas are making the need for alternative energy sources very clear. This has inspired a resurgence of interest in solar energy.

Solar Energy Has Been Used Longer Than You Think

I say resurgence because the use of solar energy devices is older than people think. Most people I talk to tend to think that interest in solar energy grew out of hippy awareness of the 60’s and the energy crisis of the 70’s. Leaving aside things like the passive solar design of the Romans, solar hot water heaters were very common in sunnier parts of the US in the late 1800’s. One report I read estimated that by 1900 30% of the homes in Pasadena California were equipped with solar hot water heaters. They fell from favor when gas and oil became widely available and cheap. Can you imagine what a difference it would make if 30% of homes had solar water heaters today?)

On other pages on this site, I talk about passive and active solar systems, thermal solar systems, solar hot water systems, solar lighting and even solar cooking. Follow the links to find the information you’re interested in.

By the way, I tend to use the terms solar energy and solar power interchangeably. Some sticklers I know reserve the term solar power to refer to making electricity from sunlight. The difference doesn’t seem that important to me.

Solar Energy Pages

Solar Energy Facts

Fun and interesting solar energy facts.

Passive Solar Home Heating

Passive solar design adds little or nothing to the cost of a home, yet pays dividends in both comfort and energy savings for years.

Passive Solar Design Rules of Thumb

While every situation is different, these rules of thumb give you an idea of factors you need to consider when you design your house to passive collect warmth from the sun, even in the middle of a frigid winter.

Solar Hot Water

Using the sun's energy to heat water is one of the oldest forms of solar energy usage. Commercial solar hot water heating systems were widely available in the last century. Those systems were good for their time. We have even better systems available today.

Solar Pool Heating

Swimming pools are an enjoyable luxury. Using the sun to heat them is a perfect way to minimize their environmental impact.

Solar Panels

Solar panels are what many people think of when they think of energy from the sun. Rapid improvements in technology are making these panels more practical all the time.

Concentrating Solar Energy Systems

Several systems have proved able to concentrate the sun's energy for commercial production of electricity. These extremely clean systems are listed on this page with additional information available.


Linear Solar Concentrators

Linear solar concentrators use fields of trough-shaped mirrors to collect energy from the sun. Find out how these systems work and what they look like on this page.

Dish and Engine Solar Concentrators

Dish and engine solar concentrators combine technology that originated in the 19th century with the latest in solar engineering to create flexible electricity generating systems.

Solar Power Towers

Solar power towers are now a proven energy producing technology. A test tower in California has developed an efficient system using melted salt, while the first commercial solar tower power plant has already opened in Spain.

Solar Chimneys

Solar chimneys are another innovative way of capturing the sun's energy. Demonstration projects have been successful and commercial development is under consideration, especially in Australia. Solar Energy Costs On this page you'll find how solar panels are evaluated and the factors that affect the cost of installing a photovoltaic residential system. These systems are becoming increasingly cost effective.

Artificial Photosynthesis

Artificial photosynthesis is the attempt to mimic a plant in capturing the energy of the sun using stable, durable inorganic compounds. Artificial leaves my soon be a reality.


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Solar Hot Water Heating

Solar Pool Heating

Passive Solar Home Heating

Passive Solar Design Rules of Thumb

Solar Energy Facts

Solar Chimneys

Solar Power Tower

Linear Solar Concentrators

Solar Panels

Solar Energy Costs

Artificial Photosynthesis

Wind Power

Geothermal Energy

Biomass Energy


Energy Conservation