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1. Gravel Batteries Offer a Solution for Renewable Energy Storage
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2. Oyster Offshore Wave Generator Is 2.5x Better Than Predecessor
Gravel Batteries Offer a Solution for Renewable Energy Storage
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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
Oyster Offshore Wave Generator Is 2.5x Better Than Predecessor
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Power generation from waves continues to develop as Aquamarine Power has unveiled its new, second-generation Oyster 2 wave power generator. According to the company, "The new 800kW device will measure 26 metres by 16 metres and will deliver 250 per cent more power than the original Oyster 1 which was successfully deployed at the European Marine Energy Centre (EMEC) in Orkney last summer." A test installation is planned for 2011 and will use three wave devices connected to a single power generation station to produce 2.4 megawatts of electricity.
Like the Pelamis wave generator (now, sadly, sitting on the shore for lack of maintenace funds), the Oyster rides on the surface to harness wave power. This means that Oyster cannot coexist with surface vessels, unlike other underwater systems. But, instead of housing the generator at sea, where conditions are harsh and maintenance and repair are costly, the Oyster system harnesses wave power to drive hydraulic systems and on-shore turbines to produce electricity.
The new Oyster incorporates many improvements over the original design, including simplified construction requiring less steel to produce and design to enable easier mass production. Aquamarine Power expects to deploy Oyster in farms of 100MW generating capacity or more. An animated Oyster video shows more about how the system operates.
via: Inhabitat
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