Grid Level Storage: Regenerative Air | EDN

LightSail Energy in Berkeley, CA, founded by Danielle Fong, has come up with an almost-too-obvious, but clean energy source—compressed air. Although not a new idea, this team has solved the stumbling block to the process of using compressed air for energy storage—the energy lost in the form of heat when the air, while being compressed, can reach temperatures of almost 1,000 oC.

LightSail’s innovation captures the heat energy before it is lost and regenerates useful energy from it. A fine, but dense mist of water is sprayed and quickly absorbs the heat energy of the compressed air and alternately provides that heat energy back during expansion. See Figure 1.

Figure 1: LightSail’s approach to efficient compressed air storage (Courtesy of LightSail)

The system is fully reversible

Storing the energy: An electric motor drives an air compressor.

Delivering the energy: Reverse the process and the air compressor becomes an expander with the electric motor becoming the generator!

Heat from the compression can be stored or sent to a building to provide heating, for example. During expansion, heat can be extracted from storage or buildings to provide air conditioning, thereby increasing the energy efficiency of the building. See Figure 2.

Figure 2: The system is fully reversible (Courtesy of LightSail)

LightSail’s experimental results have shown that high thermodynamic efficiency can be achieved without a sacrifice in performance. These efficiencies have been achieved at higher RPMs than previously thought possible. As it turns out, the higher the RPM, the higher the power of that same machine and subsequently, the lower the cost per kW! See Figure 3.

Figure 3: Experimental efficiency results are shown (Courtesy of LightSail)

Storage

The air can be stored in simple, low cost storage tanks, then packed in a shipping container using industry standard pipes and meeting ASME and ISO safety standards. For unusually large installations, air can be stored in underground caverns, which is similar to the standard for large scale natural gas storage. See Figure 4.

Figure 4: Air can be stored in standard piping, low cost storage tanks within a simple shipping container (Courtesy of LightSail)

So let’s get ready for our plentiful air supply as a natural source of energy! Save the rain forests!!!! We need more air!

Source:  http://www.edn.com/electronics-blogs/other/4395690/Regenerative-air-energy-storage

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