Solar Farms

A “solar farm” is a commercial solar facility (that is, a solar power plant) using solar cells, i.e. the photovoltaic effect, to generate electricity from sunlight. This distinguishes a solar farm from the other main type of solar power plant, the thermal solar facility, which uses mirrors to focus sunlight for high temperatures to drive a generator. A solar farm is basically a rooftop home solar array writ large, using a very large number of solar power panels capturing sunlight over a large area. It is the currently-preferred method of generating solar power on a large scale, thanks to recent technological improvements.

How Solar Farms Work

A solar farm will usually have enough capacity to produce megawatts of electricity –– normally five megawatts or more. Solar farms increase efficiency over most home solar systems by using computer-controlled machinery to move groups of solar panels, keeping them aligned with the sun to increase energy production throughout the day. Other than these motors, solar farms have no moving parts, and usually require less maintenance than other type of power plants, including solar thermal plants, fossil-fuel power plants, nuclear power plants, and hydroelectric plants. They do require some maintenance, however, to keep the solar panels clean and to replace them when they become damaged or when they eventually lose productive efficiency with age.

The Photovoltaic Effect

The principle behind solar farms is the photovoltaic effect. This is a function of quantum mechanics. Within an atom, each electron has an energy state which can be visualized as similar to an orbit around the nucleus of the atom, with higher energy states corresponding to higher orbits. (This isn’t literally accurate, but it’s a decent metaphor and allows for visualization.) When energy is added to an electron, it rises into a higher energy state, like a moon that speeds up in its orbit rising into a higher orbit. Quantum theory holds that there is a maximum energy state that an electron can occupy before it becomes free of the atom.

Certain materials, such as silicon, have an atomic structure such that sunlight is absorbed by the electrons of their atoms, increasing their energy state, and eventually causing the electrons to be knocked free of the atoms so that they become an electric current. That’s how a solar panel, which is made of silicon crystal or another photoelectric material, generates electricity. The same principle applies whether we are talking about a rooftop solar system or a solar farm.

Advantages Of Solar Power

The advantages of solar power are considerable, in terms of both economics and environmental concerns. The “fuel” for solar power is inexhaustible and free. Enough sunlight falls on the Earth to power all of the world’s energy needs more than eighty times over. Solar power has an initial capital cost that’s fairly high for building a solar facility, but thereafter ongoing costs are very low. With advances in the technology of solar cells and solar panels over the past twenty years plus the rising cost of fossil fuels, solar power is very close to parity in cost per watt-hour to fossil fuels and has already become considerably cheaper than nuclear power. It is arguably the most environmentally-friendly form of energy production possible at this time. There is of course no such thing as energy production that has literally zero environmental impact, but solar power has less impact than energy from fossil fuels or nuclear reactions by far, and marginally less than wind energy.

Even better is the fact that solar power will never run out. It is a renewable energy source and the cost of it to produce will only go down, not up, which is another advantage over fossil fuel energy.

World’s Largest Solar Farms

As of the end of 2011, the world’s largest solar farm (actually a linked collection of farms) was the Gujarat Solar Park in India, which has a combined output of more than 600 megawatts.

Other very large solar farms include the;

Golmud Solar Park (China) with a capacity of 200 megawatts;

Perovo Solar Park (Ukraine) running at 100 megawatts;

Sania Photoelectric Power Plant (Canada) at just under 100 megawatts;

Monalty di Castro Photovoltaic Power Station (Italy) which produces 84 megawatts.

Several other solar farms produce in the 80-megawatt range. These are peak production capacities, i.e., the solar farm produces that amount of power under the best conditions. Average production is somewhat lower throughout the day, and of course no solar  plant produces energy at night.

Even bigger solar farms are being built and expected to go on line in the next few years. The United States has plants under construction in California that will generate a peak production of over 1,500 megawatts, and other facilities are being built in other parts of the country as well as elsewhere in the world.