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Aruba, June 11, 2014 - The first thing Dax Kepshire shows a visitor to SustainX is foam. When he flips a switch on a 10-foot-tall assemblage of pneumatic tubes and mesh screens, the machine starts spewing a creamy white goo that resembles soft-serve ice cream into a 300-gallon plastic tub. In a few minutes the foam is 3 feet deep, and Kepshire plunges his hand in. “It’s completely nontoxic,” he says, and derived from an industrial foaming agent found in shampoo and carwash soap. The seven-year-old company is betting the substance can solve the biggest challenge for renewable energy: how to store it.
The difficulty of holding on to enough wind and solar energy to power a city remains an obstacle to the commercial viability of renewables. Because excess electricity from wind farms or solar panels can’t easily be saved, utility companies can’t rely on them when the wind stops blowing or the sun goes down. In the race to develop commercial storage systems that can meet utility-scale demand, SustainX is up against technologies that include powerful but short-lived batteries. Kepshire, a vice president and general manager at Seabrook (N.H.)-based SustainX, says the foam his company creates can help effectively store power at the scale needed to keep cities humming.
The SustainX system relies on compressed-air energy storage, a technology that has been tested on and off for decades with mixed results. The idea is to save surplus electricity by using it to drive an air compressor, keep the compressed air in tanks or underground, and then tap it at will to spin electricity-generating turbines. The problem with this approach is temperature control. Compression superheats air, while decompressing it makes it very cold, and the swings result in a lot of wasted energy. (The heat also threatens to explode a compressor’s cylinders.) The world’s only two operational compressed-air facilities, built decades ago in Alabama and Germany, require the use of natural gas as an external fuel source to stabilize air temperatures—raising costs and defeating the purpose of using clean energy.