Solving the Green Energy Storage Problem

By Jessica Meyer

A variety of ways to store excess electricity produced by solar and wind power, to be used when the sun isn’t shining and the wind isn’t blowing, have been and are being developed and tested, and scientists are anxious to find new, better, cheaper ways.  Academic departments, businesses, and public energy research labs have been bursting with innovation and have seen steep increases in enrollment in electrical and environmental engineering programs.  The outlook for education and research on the excess wind and solar electricity problem looks more promising than ever: MIT, Stanford, and others have recently started to tap into the power of the web by offering engineering courses for free online; and accredited PhD online programs in a variety of engineering disciplines are currently in development.

Electricity generated by the use of conventional fossil fuels and nuclear power has not generally been stored; plants endeavor to produce the correct amount to power the grids. Widespread future use of renewable energy sources such as sun and wind seems dependent on the development of effective, affordable means to store excess electricity. Those who advocate continued primary reliance on fossil fuels, such as former U.S. Energy Secretary James Schlesinger, point to the intermittence problem with renewables, to say the future contribution of power by solar and wind will be minimal. The development of storage methods, however, is moving in a promising direction.

Another argument from critics of solar and wind power has been that it is far more expensive to produce than conventional power, such as coal or nuclear. But, according to Jon R. Luoma in “The Challenge for Green Energy: How to Store Excess Electricity,” wind power is nearly at “grid parity”—the cost of generating electricity from wind is about the same as that of generating it from coal—and solar power should reach grid parity in a few years.

It remains vital to find ways to store the massive amount of excess electricity sun and wind produce for the “down times” when it’s dark and the air is still. Some of the methods in use today are huge batteries, converting electricity to liquid air, and in-home storage.

Improving battery technology has been an approach, but a 1,300 metric ton battery larger than a football field that can generate 40 million watts of power, currently deployed in Fairbanks, Alaska to protect against blackouts, could only, in 2003-4, provide enough electricity for about 12,000 residents for seven minutes (Luoma). It would take hundreds of units the size of the Fairbanks unit to store electricity from solar and wind to equal the power generated by one coal plant.

Other types of batteries have been developed, but some have low “round-trip efficiency”—they lose energy as it is stored and comes out of storage. Lithium ion batteries have high “round-trip efficiency” but are very expensive, and a lithium metal-air battery, when it absorbs moisture from the air in addition to the oxygen it needs, can explode.

According to NewScientist, a promising type of power plant cools excess energy and stores it in the form of liquid air, or cryogen. The Highview 300-kilowatt pilot plant supplies energy to the UK National Grid. The process warms the cryogen when electricity is needed; it recovers only about 50 percent of the electricity fed into it, but cryogen plants can be located anywhere, costing far less to operate per kilowatt than batteries.

Excess energy from wind power can also be stored in the home, raising the temperature of an energy customer’s water heater or storing the heat in ceramic bricks in a nearby space heater. These devices, run by microchips and remote-controlled by the power administration, then act as a battery, giving back power when needed. The customer’s tap-water and room temperature are said not to fluctuate noticeably. The New York Times reported on a pilot program in the Pacific Northwest where energy customers do have to pay to participate.

Scientists are working on still other methods of storage, and constantly on the lookout for new ones. There certainly seems to be a serious commitment to making renewable energy sources an integral component of future electricity consumption.

[Image credit: Scamper Girl, Flickr]

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