Monday, September 01, 2008

Store it and they will come

Finding ways to store electricity that are both reliable and economical remains a major challenge facing the energy industry in general, but renewable energy developers in particular. The variable nature of solar and wind energy means that electricity generated by photovoltaic facilities and wind turbines cannot dispatched like energy from plants that rely on the combustion fossil fuels or biomass for example.

However, if the energy from renewables could be stored and be called upon when needed (as opposed to when the sun shines and the wind circulate) they're value would increase immensely. Now that solar panels and wind turbines are becoming more widespread (thanks to both engineering advances and progressive policies) new attention is being focused on storage strategies. (GW)

FLORIDA, Mass. - Deep within a mountain here, the state's eighth-largest power plant kicks into action with a thunderous clatter. A reservoir at the summit drains through a pipe in the mountain, loosing a torrent of water that spins two massive turbines, and then flows into the Deerfield River.

At night, the plant flips into reverse and pumps river water back to the top of the mountain, using more energy than it makes.

This hydropower system may seem more like a failed attempt at a perpetual motion machine than a power plant. But the Jack Cockwell Pumped Storage facility is state-of-the-art bulk energy storage, an underappreciated technology that will be essential if renewable energy generation is to increase dramatically.

While most of the attention to alternative energy focuses on wind turbines and solar panels, actually turning them into mainstream sources of power will require cheap and efficient ways to store large amounts of energy. That is creating a push for new and better technologies everywhere from MIT to local startups that are now maturing. Earlier this year, the US Department of Energy established an Electricity Advisory Committee and directed it to focus in part on research and development of storage technologies.

"Storage is a critical component. As a technology area ripe for innovation and investment, it's huge - it's a holy grail," said Nick d'Arbeloff, executive director of the New England Clean Energy Council, an organization that promotes the renewable energy sector.

Windmills and solar panels, icons of the clean energy movement, come with an Achilles' heel: breezes start up or die down unexpectedly, and the sun may be swallowed by a cloud when energy demand is highest. That vulnerability matters far more when renewable energy makes up a significant amount of the power flowing onto the electricity grid - a scenario now mandated by a state law requiring that a quarter of energy come from renewable sources by 2030.

Sporadic energy production is a challenge for the grid, because it depends on a delicate balance between supply and demand. As more renewable energy comes online, grid managers need to figure out a way to smooth out the bumps - to take advantage of gusty days, or compensate for cloudy, windless ones.

In March, for example, when wind generation hit a high in Spain, the national grid had to cut the output from wind farms because the grid didn't have enough energy from other sources to ensure that its supply would stay balanced if the wind suddenly died down.

"Most people think this is wonderful - we're going to make all these windmills and save the planet," but that oversimplifies the problem, said Bradford Roberts, chairman of the Electricity Storage Association, a trade group. Even with more turbines, fossil fuel plants can't just shut down.

"Because the wind may go away, you have to keep controllable energy sources running," he said.

Energy storage can buffer those fluctuations. For example, the Jack Cockwell plant, owned by Brookfield Renewable Power, is effectively a mountain-sized, 600 megawatt battery that makes on an average day enough energy to power 200 New England homes for an entire year. It "charges" at night when energy is cheap and fewer people are using it; then it discharges during the day when energy prices and demand are higher. It also acts as a reserve, kicking into action to meet a sudden surge in demand.

Although Jack Cockwell and other similar plants were built more than three decades ago, "there have not been any other solutions that have emerged that look better, and people have been trying for a long time," said Philip Giudice, the state's commissioner of the division of energy resources. "I think we're ripe for all kinds of new solutions."

Even the new solutions seem a tad antique.

One cutting-edge technology is basically a flywheel, a disc that spins at high speeds using electricity, then generates electricity as it slows back down.

"People say, 'How do they work?' and I say 'The concept goes back to biblical times," said Gene Hunt, director of corporate communications for Beacon Power Corp. in Tyngsborough.

Others, like General Compression Inc. in Newton, plan to make wind more reliable by using windmills to compress air in an underground space; then let the air out to generate electricity whenever it is needed. That's taking a page from a storage method even a child could understand - blow air into a balloon and later, let it whiz out.

"The electric power industry takes a long time to change because you don't want the lights to go off," said Richard Baxter, senior vice president of Ardour Capital Investments LLC.

"We are at a point now where a lot of new energy storage technologies are becoming commercial, and they are being rolled out and tested."

Storage, some believe, is a key factor that will turn renewables into a mainstream source of energy generation.

For example, Daniel Nocera, an MIT chemistry professor, reported recently in the journal Science that his laboratory had devised a new way to store solar energy, by using the sun's rays to split water into hydrogen and oxygen, creating a fuel that could be recombined to generate energy at night in a fuel cell.

"If you can only use photovoltaics when the sun's shining, that's not good," Nocera said. "If you can make a cheap, affordable, easy-to-use storage mechanism, then it's a 24-7 industry; then people start investing and driving technology."

Batteries, from lead acid to more futuristic types, are being tried, too.

But progress has been relatively slow "because of how difficult the problem is," said Donald Sadoway, a professor of materials chemistry at MIT who is working with a graduate student in his lab to develop a battery that could be used for large-scale utility storage. Other types are already being integrated into wind farms and electricity grids.

"I don't want to say this is as complicated as getting humans on the moon, but it is a major challenge and we don't have a NASA price-point here," he said. "You've got to get the electricity back to the grid at pennies a kilowatt-hour."


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