Cheap, plentiful ways to tame intermittent renewables. So what’s the catch?

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By Doug Peeples

SGN News Editor

Wind farms and solar arrays are being built so fast that transmission networks can't keep up with them. But the other nagging issue is how to efficiently integrate those power sources into a smart grid when they're so undependable. The wind doesn't blow on demand and solar arrays don't contribute when the sun sets or the weather doesn't cooperate.

But two very different technologies may be at least part of the answer: natural gas is becoming more popular as a choice for filling in the gaps when renewables aren't contributing, and researchers at Case Western Reserve University are working on a flow battery based on plain old (and really cheap) iron.

GE's natural gas turbines as partners to renewables

GE is betting that the industry is ready for natural gas as a backup power source when wind and solar are offline, and has put a lot of effort into perfecting its gas turbine technology. Over the years, GE has been increasing its turbines' energy output – its latest incarnation, the 7FA gas turbine, can produce 211 megawatts of power. And unlike traditional coal plants, natural gas turbines can fire up fast – they can hit 75% or more of peak output in 10 minutes, and shut down quickly too.

The catch?

While a recent National Energy Technology Laboratory study found that natural gas burns cleaner than coal, the study also admitted some uncertainty with its data. And others contend that shale gas wouldn't be an improvement over coal as far as emissions are concerned. While natural gas is certainly plentiful, is it clean enough?

Cheap energy storage, really?

Researchers at Case Western are working on a promising flow battery technology that mixes cheap, readily available iron in benign solutions. It's worth mentioning that most flow batteries are based on vanadium, primarily mined in China, Russia and South Africa - with a price tag of between $8-$20 per pound, while iron sells now for a little less than 25 cents per pound and is relatively easy to find. The Case Western researchers are working on a flow battery that can be built to supply power to a home or a community. Their intent, however, is to develop an efficient system that could store power from wind farms and solar arrays, and that could be connected to the smart grid, storing power when demand is low and discharging it as needed. DOE took the concept seriously enough to fund the research with a $500,000 grant.

The downside?

The flow battery research is a three-year project to fine tune and develop the most efficient system possible and a working model to validate the technology, so it's not hitting a wind farm near you anytime real soon. Also, there's another issue: size. A grid-scale energy storage plant that could work with a wind farm and store up to 20 megawatt-hours of power would require two roughly 250,000-gallon storage tanks for the iron solution, or as the researchers noted, the equivalent of eight railroad tank cars each.

What do you think? Do either of these show real promise? Use the Talk Back form below to weigh in.     

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