MAY 20

One of the most frequent objections to renewable energy systems is that their production is too variable. But technologies continue to be developed that will allow storage of power generated from wind, solar, and other intermittent renewable sources. The latest development comes from researchers at Isentropic in Cambridge, England who propose giant batteries filled with gravel and argon gas. These batteries would provide a number advantages over pumped hydro, which is presently used for almost all electricity storage today, as well as over underground compressed air storage.

The gravel battery system would use excess capacity generated by a renewable source to heat and pressurize the argon gas and then pump it through a gravel filled silo to store energy. Then, when demand calls for electricity, the system is simply operated in reverse to generate electricity. According to the company, the system's "round trip efficiency is over 72% - 80%." This is comparable to the efficiency of pumped storage hydro, which has an efficiency of 70 - 85%. But gravel batteries are much more compact, and can be more readily installed in relatively flat areas characteristic of many areas with good windpower potential, such as the American Great Plains. A gravel battery can use far less land (1/300th) than that required for a pumped hydro lake, as well.

Underground compressed air storage is another technology that has been suggested, but that requires the presence of underground caverns, which are not always present where you might want to put a power storage facility. In addition to being able to be located anywhere, gravel batteries could be relatively inexpensive because they do not need costly materials. Costs could be as low as $55/kWh, and $10/kWh at scale for large installations.

via: Worldchanging

Comments (10)

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What is the obsession with storing the energy on-site?
written by BruceMcF, May 20, 2010

The notion that energy to stored wind farm by wind farm that some people seem to have is a bit nutty, and it seems to be echoed in the suggestion that electricity from the Great Plains wind resource needs to be stored near where it is generated.

Where precisely is the massive demands for electricity consumption where there is nothing both plains from the Great Plains to the final consumer? The west coast (via the Rockies)? Chicago (via, eg, Wisconsin's Iron Range)? The East Coast (via the Appalachias)?

And of course, many research power storage oversell the important of energy storage in a renewable, sustainable grid by focusing on volatility of individual wind farms rather than of all the wind resource areas that are available to the different consuming grids, and by ignoring the normal changes in the use of conventional hydro when there are a range of volatile energy supplies on hand.

But most notably, you are burying the lede here: it's all about the capital cost per kW capacity. That's the story.

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Would it fit in the tower?
written by Jon, May 20, 2010

Would those gravel batteries fit in the tower of the wind turbines, that would be convenient?

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@Will it fit in the tower
written by Gary, May 21, 2010

Jon, I expect that given just a few years, the Chinese will be making synthetic gravel from recycled human waste that fits in the wind mill towers.

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Why store locally ?
written by Andy Simpson, May 21, 2010

Bruce,
By storing the energy locally, you can smooth the supply to the grid. For example a large solar installation can smooth out the effects of passing clouds. This is an obsession of the guys ensuring distribution, they want any renewable source to supply energy in a predictable way.

Andy

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@Andy, Low-rated comment [Show]

Argon?
written by Kevin, May 21, 2010

I couldn't find anything about Argon in the original article at Isentropic. They seem to me to be talking about heating air, rather than Argon.

Their main innovation is the heat pump, which is supposed to very efficient. If so, then it will have a great many more applications.

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...
written by P Proefrock, May 21, 2010

Good questions Bruce. Storage near the source can be important if the grid doesn't have the capacity to handle the load (though we're talking about dealing with storing off-peak production, so that may not be much of an issue). Also, since demand is variable and production from a solar field or wind farm will not necessarily serve only one location, on-site storage can be dispatched where it is needed.

From an economic perspective, owning the storage as well as the production is probably a way for a power producer to optimize their business model. If a wind farm is selling off-peak power, they aren't getting paid much. If, on the other hand, they are better able to serve as a peaking plant, and help when demand is high, they can get premium rates, and can belong to the grid as a more reliable source.

Also, if a storage system is located near a municipality, land costs are going to be much higher, and NIMBY reactions will be much more likely, whereas land near the production source is likely to be far less expensive, and some amount of land is already being acquired to install the production facility, so it might be only an incremental add.

These absolutely WOULD NOT fit inside a turbine's tower; they are far larger than that. Isentropic is talking about a pair of 50m tall and 50m diameter structures (that's about 165 ft), which would be difficult to locate too near a municipality. However, using these to raise towers even higher to get greater access to wind could be an interesting idea.

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Storage system for power
written by Arvind Kumar, June 20, 2010

for the years, power engineers are trying to store the power for whenever use, but alas they have failed. Pumped storage technology was good but to some extend it demand power to produce power....Not a good option....But this kind of battery system storage can play a big role.

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Renewable energy sources
written by jekin, July 09, 2010

It would be great if renewable energy would someday cost consumers less. The fact is, if everyone in the world had a hydrogen generator or solar panels, the cost would be shifted to purchasing and maintaining this equipment. Unless you have the capabilities to build and maintain it yourself, you will still be paying for it. At least we're saving the world physically while it falls apart economically.
http://www.globalwarming360.net/

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melting wires
written by ron davison, July 16, 2010

Why store on site of intermittent power? Because the wires will melt if you try to put peak power through them. if you size them for peak loads then they cost 2x to 3x due to the upsizing of cable diameters and tower structures.

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