The oil crisis of the mid-1970s fueled the search for alternative sources of energy. Among the options, solar appeared to be the most promising. Since the initial hoopla, solar power has continued to quietly develop as a viable home-energy source.

What Is Solar Energy?

The sun radiates more energy in one second than people have used since time began. Like most stars, the sun is a huge gas ball made up mostly of hydrogen and helium gas. The sun makes energy in its inner core in a process called nuclear fusion.

It takes the sun's energy just a little over eight minutes to travel the 93 million miles to earth at a speed of 186,000 miles per second, the speed of light.

Today's homeowners have the option of utilizing solar technologies that harness the sun's energy to heat the home, produce hot water, and generate electricity.

Passive Solar

Passive solar heating operates on the principle that when certain materials are properly positioned, they will capture and store the sun's heat. For example, on a sunny day a closed car is an effective solar collector. Light rays pass through the glass, are absorbed, and changed into heat. The heat then gets trapped inside.

The use of concrete and masonry is common in passive solar homes because these materials are most effective in storing heat. When the indoor air-cools in winter, this heat is distributed, albeit at an uncontrolled rate. Depending on the amount of solar heat gain desired, concrete or masonry can be used as the primary structural material, or simply in the foundation slab, fireplace, the exterior finish (brick or stucco) or even a tile floor.

Passive solar, in fact, is part of every home at some level, even if it is unplanned. The most common materials used in a home - namely wood for framing and exterior finishes, asphalt-composition roofing, and windows - serve in some capacity to transfer, collect and distribute that heat throughout the house. Wood has natural insulating qualities, while windows allow both solar heat gain and ventilation.

Active Solar

Active solar requires special equipment to collect the sun's heat and transform it into energy. An active solar house may use special collectors that look like boxes covered with glass. These collectors are mounted on the rooftop, facing south to take advantage of the winter sun. Dark-colored metal plates inside the boxes absorb sunlight and change it into heat (black absorbs sunlight more than any other color). Air or water flows through the collector and is warmed by the heat. The warmed air or water is then distributed to the rest of the house just as it would be with an ordinary furnace system.

Solar Hot Water Heating

Using solar energy to heat domestic hot water is cost-effective anywhere and can be expected to provide 50-75% of domestic hot water needs. This active system uses collectors to gather the sun's energy, which is then used to preheat water entering a domestic hot water heater. The gas burner or electric elements in the water heater provide a back-up heat source - primarily during the cooler months and on cloudy days. The hot water is piped to faucets throughout a house just as it would be with an ordinary water heater. Today over 1.5 million homes in the United States use solar water heaters.

Active systems can also use the sun's energy to preheat water for radiant under-floor heating. These systems can use a domestic hot water heater for hot water storage. A back-up heater can provide heat and hot water during extended absence of the sun.

Hybrid System

Hybrid systems incorporate active technology (solar collectors), and passive technology (a radiant panel concrete slab with compacted earth beneath) to achieve high levels of performance and efficiency.

Solar Electricity

Besides using solar energy to heat homes or water, solar energy also can be used to produce electricity. Two ways to make electricity from solar energy are photovoltaics and solar thermal systems.

Photovoltaic Electricity

Photovoltaic comes from the words photo meaning "light" and volt, a measurement of electricity. Sometimes photovoltaic cells are called PV cells or solar cells for short. You are probably already familiar with photovoltaic cells. Solar-powered toys, calculators, and roadside telephone call boxes all use solar cells to convert sunlight into electricity.

Solar cells are made up of silicon, the same substance that makes up sand. Silicon is the second most common substance on earth. Solar cells can supply energy to anything that is powered by batteries or electrical power.

Electricity is produced when sunlight strikes the solar cell, causing the electrons to move around. The action of the electrons starts an electric current. The conversion of sunlight into electricity takes place silently and instantly. There are no mechanical parts to wear out.

Solar Thermal Electricity

Like solar cells, solar thermal systems use solar energy to produce electricity. But instead of sunlight, solar thermal systems use the sun's heat to do it.

Most solar thermal systems use a solar collector with a mirrored surface to concentrate sunlight onto a receiver that heats a liquid. The super-heated liquid is used to make steam that drives a turbine generator to produce electricity in the same way that coal, oil, or nuclear power plants do.

Benefits of Solar Power: