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When you think about it, all types of renewable energy are actually a form of solar power.

The most obvious way in which this is true is with the two types of primary solar power, photovoltaic cells like the black panels we can put up on our own roofs, and solar thermal farms which focus heat and light from the sun onto conduits containing fluid. The heat in the fluid is used to drive a steam turbine, producing electricity. Solar thermal power is currently a more efficient way to use the energy of the sun than photovoltaic cells, as more of the power from the sun is actually converted into electricity. However, unlike a thermal plant, photovoltaic cells can be installed virtually anywhere, their efficiency is steadily improving, and they are more and more affordable each year.

Water power, generated by damming a river and driving turbines from the flow of water as it is released to continue downstream, is a secondary form of solar power. Heat from the sun drives the entire evaporation cycle, picking up water from oceans and seas and dropping it far inland as rain to return to the sea through rivers. Hydroelectric power requires huge investment and a great deal of skill to build the necessary dams and equipment, but once the dam is in place, it is a very cost effective way to generate large amounts of power. The damming of rivers can be controversial, as there is clearly a large impact on the surrounding environment. A large area must be submerged to form the reservoir for the dam, while fish migration patterns and aquatic life can be badly disrupted. In some cases, as with the Three Gorges Dam in China, the creation of the dam may require the destruction of homes and even sites of historical and cultural significance.

Wind power, like water power, depends on the power of the sun as its energy warms our atmosphere, creating wind. Wind turbines take much less initial investment in construction, cost, and materials than hydroelectric dams, and can be sited virtually anywhere there is a strong or steady wind. However, wind power is only generated when the wind is blowing, so traditional wind power has not been reliable enough to serve as the core generator of any grid. Hospitals and schools cannot shut down just because it is a calm day. Again, technology is improving, and wind turbines can be used to store power in a variety of ways, including batteries, driving a pump to store water which can later be used to power a turbine when the wind dies, or even compressing air, which can also later be released to generate power.

The final form of renewable energy is derived from biomass. Plants like corn or trees use energy from the sun to grow. These plants can be harvested, and their energy converted to ethanol which can be burned directly by power plants or vehicles to generate power. The major advantage of ethanol is that it is a form of fuel that fits very well into the current infrastructure of millions of individual cars and thousands of gas stations which fuel them. Ethanol can be added directly to gasoline, reducing dependence on foreign oil, and requiring no expensive changes to how automobiles are produced. Unlike solar, hydroelectric, and wind power, however, biofuels are a source of greenhouse gases, contributing to global warming and making the air we breathe in our cities that much worse.

Each type of renewable solar power has advantages and disadvantages. A balance of each type is probably the best choice to create an environmentally responsible power grid which still keeps the lights on in our schools and hospitals.

Learn more about this author, David Thill.
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