Most people associate solar power with photovoltaic cells used to generate electricity, or perhaps solar water heaters, or even large solar power plants, where the heat of the sun is used to produce steam which runs turbines to produce electricity. It’s easy to forget that most other energy sources also trace back to the sun.

The simplest of fuels, wood, is produced when trees capture the sun’s energy to build the hydrocarbons necessary for growth. Fossil fuels come from buried organic matter produced ages ago from ancient plants that also depended upon the sun. Wind energy comes from the sun heating up the atmosphere creating convection currents. Hydropower comes from the sun’s energy evaporation of sea water, carrying it into the sky where it later falls as rain, generating power as it falls back to the sea. In fact, with the exception of nuclear power and geothermic power, all our energy comes from the sun. (Nuclear and geothermic power both come from the heat generated by disintegrating atoms.)

When people talk about solar power, they are usually focused on systems that directly convert the sun’s rays into energy, usually electricity. The modern solar power industry is built upon the attempts of scientists and engineers around the world to come up with ways to perform this conversion so efficiently that it can compete with fossil fuels, nature’s stored solar energy.

Today, the solar power industry, though still struggling to find the optimum combination of technologies, is represented by more money and larger installations than ever before. In California, one solar plant uses the most popular approach. Giant parabolic mirrors heat oil to over 700 degrees Fahrenheit. The oil is then used to vaporize water into steam that runs turbines, generating over 300 megawatts of electricity. Two other large plants, using the parabolic mirror approach, are currently being planned for Arizona, and a number of smaller plants are already running in the U.S., Spain, and a handful of other countries. A newer approach involves the use of large Fresnel lenses to focus the sun’s rays, heating water directly. The system is more durable and puts out more power per acre than oil based systems. A small plant using the technology has already opened in central California to power 3,500 homes. And, of course, photovoltaic modules are used in every part of the country to provide instant localized electricity.

The number of full size solar power plants is still relatively small, but every experimental step reduces the per unit energy cost, making the solar option increasingly competitive. The price per watt-peak (the standard unit of measure for the solar industry to measure the cost of installation relative to the power produced) has dropped dramatically in the last 25 years, from $27 in 1982 to only $4 today. However, solar electricity prices are still higher than standard grid electricity, depending upon the details of the installation. Government subsidy programs are available, but the goal has always been to make the industry free standing.

One of the major challenges is energy storage, since the sun doesn’t shine 24 hours a day. A worldwide grid isn’t currently feasible, and without a cost effective storage system, solar power can only do so much. There are a number of proposals, but the subject is still strongly debated. Only if that problem is solved can solar power be expected to someday provide a major share of the nation’s energy.

Nevertheless, solar power is seen as continually improving, with technical and cost issues gradually being resolved. That’s why it is now seen as an inevitable part of America’s energy future. In fact, it is estimated that, using certain proposed technologies for solar energy capture and storage, a combined area about the size of Vermont could fill all of America’s energy needs (including transportation using electric cars). The location of such generators would be in the desert Southwest, in places like Arizona and Nevada where cloudless skies allow the sun to blast tremendous amounts of energy to the surface, and would require high-energy transmission lines for distribution. However, it’s still well in the future.

But, if the number of existing solar power plants is small, the number of solar stocks is not. Below are just a few of the many publicly traded stocks directly involved with solar power.

• Akeena Solar, Inc. (Nasdaq CM: AKNS)
• Ascent Solar (Nasdaq: ASTI)
• DayStar Technologies, Inc. (Nasdaq CM: DSTI)
• Energy Conversion Devices, Inc. (Nasdaq: ENER)
• Evergreen Solar, Inc. (Nasdaq GM: ESLR)
• First Solar, Inc. (Nasdaq GS: FSLR)
• Solar Enertech Corp. (SOEN.OB)