Silicon Valley solar newcomer Ausra Inc. and the Queensland State Government have announced plans to give Australia’s biggest coal-fired plant a 23-megawatt solar boost.
The project calls for concentrating solar power (CSP) to be tacked on to the state’s 750-MW Kogan Creek coal unit. If the scheme wins the $200 million in government funding the parties are after, it will be the largest demonstration of its kind in the world.
The plans are part of a growing global push to squeeze more electricity out of conventional power plants with cleaner fuels — and get more solar power on the grid at lower cost.
Colorado’s largest utility, Xcel Energy, is getting in on the hybrid action. In September, it signed up solar giant Abengoa to build a 4-MW CSP test field that will demonstrate how much carbon ‘fat’ can be cut from its Cameo coal plant.
The technology works like this: A field of solar mirrors concentrates sunlight onto liquid-filled pipes, making superheated steam that drives existing coal turbines. The result: hybrid electricity generation, made from a little clean sunshine and a lot of dirty coal.
According to Xcel, its project will be "the first to integrate an industrial solar installation into a conventional electric power plant."
The first in the U.S., maybe — but the concept is not entirely new. The MIT Technology Review reports that over half a dozen new and existing natural-gas plants are being designed or adapted to incorporate CSP technology.
Abengoa is currently building a solar-natural gas hybrid plant in Morocco and one in Algeria. Florida Power and Light (FPL) has started construction on a 75-MW CSP addition to a natural-gas- and oil-fired power facility in that state.
The utility broke ground on the project in December, heralding it the "world’s first" hybrid solar-gas plant and the first utility-scale solar facility in Florida. When finished, 180,000 solar mirrors will spill across 500 acres of the plant’s grounds, providing enough electricity to serve 11,000 homes.
Connecting solar to coal is not there yet, but it is progressing. In February, The U.S. utility-backed Electric Power Research Institute launched a $640,000 study project to pin down the potential of the technology for a pair of plants in North Carolina and Texas.
For EPRI, adding solar-boosted coal as an electricity option could help utilities meet state renewable energy mandates, while also keeping coal in the mix.
For solar firms, the hybrid option is often presented as a kind of bridge technology to get us to utility-scale solar. In that way, these plants are not unlike the hybrid car — an attempt to reduce the emissions of pollutants from existing technologies until battery-electric cars can cover every market segment.
As Ausra founder and Chief Scientific Officer David Mills sees it, his 23-MW solar booster for Kogan Creek is just the beginning:
"It is a small amount, but it’s a relatively large solar array compared to what’s gone on in Australia before. The utility will be able to get familiar with the basic technology applications."
The biggest selling point of hybrid plants is that they’re relatively cheap and quick to deploy. Expensive steam turbines, and often the boilers and generators, come for free, cutting construction and electricity costs.
Abengoa claims that up to a 22 percent reduction could be achieved in total CSP costs when attached to existing coal facilities. Other estimates claim those savings are 30 to 50 percent. If true, that puts CSP in the range of six to 12 cents per kilowatt-hour, which is competitive with many conventional sources of power.
Of course, hybrid coal plants are not without their critics.
The megawatts produced by solar add-ons are tiny relative to solar’s enormous potential from stand-alone installations. In Australia alone, a desert area 50 kilometers on a side covered with concentrating mirrors could satisfy all of the nation’s electricity demand.
So, while bolting solar onto coal may improve the energy landscape in the short term— increasing power plant efficiency while cutting global warming emissions — it cannot transform it like big solar can.
The long-term ambition of electric utilities, detractors say, should be to get out of fossil fuels for good. Solar face lifts could end up keeping coal in the game even longer.
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