The Quintessential Alt-Energy

Very possibly the first thing people think of when they hear “alternative energy” is solar power.

www.asap-highlea.co.uk/ solar.html

Most people understand the basic concept behind solar power: panels facing the sun convert sunlight into electricity. But what is actually going on?

Most solar power technologies involve these panels made up of grids and grids of “photovoltaic cells”, which when exposed to sunlight generate an electrical current. According to SolarPanelInfo.com,

The energy generated from photons striking the surface of the solar panel allows electrons to be knocked out of their orbits and released, and electric fields in the solar cells pull these free electrons in a directional current, from which metal contacts in the solar cell can generate electricity.

The amount of electricity generated is based on the amount of solar insolation, or radiation, the panels receive; factors that effect the output include angle of the sun, time of the year, weather, and whether the panel is shaded. Often solar panels are built to adjust themselves throughout the day, so as to continuously keep at maximum exposure. Sometimes solar panels are custom-fitted to cover a rooftop.

http://www.inhabitat.com/2009/06/01/pvt-solar-panels-generate-heat-and-electricity-at-the-same-time/

The electricity generated by solar panels are then stored in batteries. When electricity is drawn from the battery, it must be converted from direct current to alternating current.

http://sun-energy.co.za/solar-power-calculator.htm

Photovoltaic cells, usually made of cystalline silicon and gallium arsenide (the latter used only in solar panels, can produce a current of about 2 amps at 2 volts. This is at direct sunlight at the equator, with a cell of 1/5m in diameter. Count any number of factors that limit insolation, and this peak capacity is only reached by satellites (which are built with higher-quality materials to boot).

The major reason that solar power hasn’t been widely implemented is the cost, partly due to silicon shortages throughout the last decade. According to a December 2008 Christian Science Monitor article by Mark Clayton,  current costs of solar-powered energy is 32 cents per kilowatt-hour, compared to conventional sources of energy which cost 5 to 18 cents per kilo-watt hour. Mark Clayton reports:

Whether using mirrors that focus desert sunlight to harvest heat and spin turbines or rooftop photovoltaic panels that turn sunshine directly into current, solar is on track to deliver electricity to residential users at a cost on par with natural gas and perhaps even coal within the next four to seven years, industry experts say.

“We’re confident that we’re not that far away from a tipping point where energy from solar will be competitive with fossil fuels,” said Ray Kurzweil, a National Academy of Engineers panel member after the panel reported on the future of solar power in February. “I personally believe that we’re within five years of that tipping point.”

The article reports on the current landscape of solar technology, and mentions one company invested in by Google, Nanosolar, which has created a “solar coating” that “[is] as thin as a layer of paint and can transfer sunlight to power at amazing efficiency.” Another company, 1366 Technologies, has the goal of

[producing] a 3 percentage point gain in cell efficiency. While boosting a solar cell’s efficiency from 15 percent to 18 percent may sound trivial, it would mean a huge cut in production costs, from $2.20 cents per watt today to $1 a watt – without federal or state subsidies, van Mierlo says.

At that $1-a-watt level, 1366 Technologies claims it could produce solar panels with cells delivering electricity to a home as cheaply as the delivered cost of coal power – about 10 cents per kwh.

Another technology that creates sun-derived energy is the solar thermal power plant, which

consists of approximately 184,000 mirrors arranged in long, parabolic arrays that focus the sun’s energy on a receiver–a metal tube filled with oil that’s encased in specialized glass–from German conglomerate Schott.

Sunlight heats the oil to 400 degrees Celsius (about 750 degrees Fahrenheit). The oil gets transferred to a heat exchanger where it makes steam, which then cranks a turbine to produce electricity. If the heat can’t be used right away, it gets transferred to vats of molten salt which retain the heat for later use.

http://news.cnet.com/2300-11392_3-6166085-3.html?tag=mncol

http://news.cnet.com/2300-11392_3-6166085-9.html?tag=mncol

Again, the resistance to such technology is cost. According to a 2007 CNET article,

Conventionally generated electricity ranges between 5 and 18 cents per kilowatt hour (the amount of money to get a kilowatt of power for an hour) but in most places it’s below 10 cents, according to the Energy Information Agency. Solar thermal costs around 15 to 17 cents a kilowatt hour…

The article refers to how solar thermal plants can be cost-effective, which require a pre-existing infrastructure for energy transportation, a large energy storage system, and be located near a significant base of users. (The above pictures are of an actual solar thermal plant that delivers electricity to Las Vegas.)

There are other inhibitors to solar power, such as location–the tech requires clear skies and frequently favorable weather. As well, solar power is more fruitful as the proximity to the equator increases, where the sun hits the earth’s surface the strongest.

But the thing about cost is, there must be some point at which solar power is more useful, even if more expensive — it might be slightly more costly in dollars and cents, but the environmental costs are incredibly low (i.e., nil) compared to coal-derived electricity. Trivia time:

A typical 500 megawatt coal power plant produces 3.5 billion kWh per year. That is enough energy for 4 million of our light bulbs to operate year round. To produce this amount of electrical energy, the plant burns 1.43 million tons of coal. It also produces:

Enjoy the cursor caught in my screenshot.

Solar energy, of course, produces no GHGs.

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