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SOLAR POWER is a tantalizing concept. Sunlight is there half the time in many places, free for the asking.
Well, not exactly free, with some recent developments very promising and others that are disappointing. Here’s an overview.
There are two primary means of transforming sunlight into electricity, either concentrated solar power (CSP) or photovoltaics (PV).
CSP uses an array of mirrors and lenses that focus sunbeams to concentrate their heat. From this point on, concentrated solar power operates like a conventional power plant: A working fluid, typically water, is heated by the focused beams and drives a turbine that generates electricity. CSP is akin to a hydroelectric dam’s water pressure or a nuclear plant’s heat of fission.
By contrast, photovoltaics technology performs a direct conversion of sunlight into electricity through semiconducting materials embedded in solar cells. These are the familiar arrays of shiny panels seen on roofs and also employed on space craft. PV solar arrays can be vast as well, these facilities producing outputs comparable to those of CSP plants.
Spain leads the world in CSP, with 11 power stations in operation.
One of Spain’s larger facilities is the Solnova Solar Power Station outside Seville, in the south of the country. Its three units were completed in 2010 and produce a total of 150 Megawatts capable of supporting more than 25,000 homes. (As a rule of thumb, depending upon locale, 1 MW of electricity is sufficient for perhaps 150 to 200 homes.)
The Ivanpah Solar Power Facility, in the Mojave Desert of California, was designed to be the world’s largest CSP plant producing 377 MW.
Ivanpah has not been without controversy (see http://goo.gl/VgS6cC). Scorched birds angered environmentalists. What’s more, Ivanpah’s average output since it went on-line commercially in December 2013 has been only about one-quarter of the anticipated amount.
One problem is an inherent aspect of solar power: Some days are sunnier than others. However, even Ivanpah’s production in sunny May through August was 40 percent below target. Operators requested and were granted an allowance to use 60 percent more natural gas in auxiliary boilers, this fossil-fuel addition hardly enhancing the facility’s image.
Photovoltaic technology has been one of incremental enhancements of efficiency and reductions in cost. Today, a typical production solar cell has a PV conversion of between 12 to 18 percent. Advanced technology (cells spelled with $$$) have improved on this, some with efficiencies as high as 40 percent.
The latest PV news is from Australian researchers at the University of New South Wales. They report efficiency of more than 40 percent with conventional solar cells, a result that’s been independently confirmed by the U.S. National Renewable Energy Laboratory. (For background on NREL, see http://wp.me/p2ETap-n3).
The Australian achievement makes use of optical bypass filters that are said to fine-tune solar energy otherwise wasted. These filters permit the focusing of particular wavelengths while reflecting others.
That is, akin to CSP, the idea is to direct concentrated beams of sunlight. Here, though, the beams are filtered and focused onto solar panels, not used merely as heat sources.
With either approach, the intermittency of sunlight requires storage and transmission of electricity, each a significant challenge of efficiency and cost.
Proponents predict an equality—without subsidies—of solar power versus that of the conventional U.S. grid by 2015. Hedges on this grid parity involve costs of conventional energy, environmental aspects affecting these costs—and predictable sunshine.
Thus far, my interests in solar power have been confined to the technical, not the financial. ds
© Dennis Simanaitis, SimanaitisSays.com, 2014