Storage is needed to harvest the full yield available from intermittent sources of energy like wind and solar. One of the options is compressed-air storage; till now only possible in underground caverns. But SustainX Energy Solutions; a Dartmouth College start-up that got $4 million in VC funding from Polaris Venture Partners and Rockport Capital this year is working on compressing and storing air in cheap off-the-shelf shipping containers.
Over the next two years SustainX will try to develop a way to cram 4 megawatt-hours worth of stored energy into each 40-foot long container and to reduce the energy that it currently takes to compress and release air by about 70%.
The goal? A renewable energy storage system with the portability and scalability of a battery and the economy and capacity of a cave. Make that a portable cave.
Cheap storage is needed. A lot of research dollars are going into building a variety of storage options for renewable energy to extend their contribution to the grid. We have too much wind at night and too much solar in the day: but seldom overlapping in any one region.
The breakthrough better battery is being funded by ARPA-E and sought by hundreds of researchers and companies from the traditional fly-wheel manufacturers to new nanotech start-ups.
Utilities are looking into storing energy in compressed-air in caves, in gravity; by pumping water up – to let it drop when needed – or in rolling batteries; by loading up extra juice at night into electric cars – to be dispatchable back to the grid again at peak with interactive vehicle-to-grid technology.
PG&E is one public utility scouting for caves suitable for compressed-air storage capable of storing 3,000 megawatt-hours (or 300 megawatts for ten hours). There are already a few compressed-air facilities in the world where off-peak electricity is used to pump air underground for storage. During peak-demand times, the air is released and pushed through a turbine to make electricity. Utility-scale battery storage systems only deliver 1 or 2 megawatts for a few hours.
But underground limestone caverns aren’t always right where you need them; at least with the right geological attributes that make them safe as depositories. You need the portability and scalability of a battery and the economy and capacity of a geological feature.
The president of SustainX; Dax Kepshire conceived his modular scalable portable “cave” system to find that solution. Portable compressed air storage could be big simply because it is a very cheap tech. Even more so now, since Dan’s portable “caves” could be the unused shipping containers that are piling up in ports around the world.
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