Though the claims of enthusiasts are sometimes overstated, it’s still true that solar power and alternative energy forms are viable and valuable. They’re low-pollution generating, even accounting for manufacturing effects to make the components. They are, in principle, inexhaustible sources of energy. And, those forms of energy don’t require looking to unstable countries to supply raw material.

Solar energy, in the form of light streaming in through the atmosphere from the sun, is converted to usable power by a now-well understood process. Sunlight strikes a PV (photovoltaic) module that respond by generating a current. That electricity flows into a home or business by the same components (wires, circuit breakers) as are used by the utility company.

Wind-generated electricity works by an entirely different principle, but there are some similarities. Wind turns a propeller on a shaft surrounded by a magnet wrapped by a coil of wire. As the magnet turns near the wire (or the wire turns, it doesn’t matter which), electrons in the wire experience a force. That force moves them along inside the wire and that movement creates an electrical current.

Both methods are simple in principle. The sun and wind are there and cost nothing. But converting those energy sources into usable electricity does have costs, along with some interesting physical limitations and engineering challenges.

There are the materials required to build a wind turbine or PV (photovoltaic) module, of course. Creating them is not free. They have to be transported and installed, something which is also not free. And, unfortunately, they are relatively cost-inefficient in terms of the amount of power produced compared to coal, oil and natural gas.

Though improvements have been made, they simply don’t produce the same amount of power as other sources for the same cost.

For example, roughly 1,000 watts per square meter of solar energy reaches the surface (at the equator). But, latitude, weather and other factors often reduce the amount to between 125-375 W/m2. Add in that the efficiency of a solar-powered PV (photovoltaic) module is generally 10-15% depending on how it’s made, and the available energy is relatively low.

Still, given the ability to cover an area the size of a house roof with panels, even that relatively small amount can generate about 1.35 kWh/m2/day. That’s enough to power an average home if the homeowner is careful about usage.

Wind systems have their own unique problems. They regularly kill birds. They rely on almost continual wind. Otherwise, like solar systems, they have to be connected to storage systems. And, they don’t put out the amount of power demanded by most applications.

But even with all these limitations, solar, wind and other alternative energy technologies can sensibly form part of a total power generation strategy. They’re clean, which makes them highly desirable by a society continually striving to improve the quality of the environment. They don’t require importation of oil, or mining of coal or other materials which meet with environmental and political controversy.

With continued technological improvements to increase efficiency and lower costs, they can contribute to supplying electrical demand. It will be sometime before they can reasonably promise to displace a significant percentage of the supply from other sources. But the future is always where the best ideas lie.

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