Stop a dozen people on the street and ask them what the biggest challenge facing alternative energy is, and most would probably answer along the same lines. There would be some vague notion of finding, or maybe developing, clean energy sources to prepare for the day when we exhaust the Earth’s supply of fossil fuels.
Ask many experts, though, and they will tell you that we already have viable solutions and now just need to solve one central problem: storage.
The answer to that may be something as simple as giant bags of air.
Clean energy sources have a major storage problem, because the big ones at least -- wind, wave and solar -- are neither constant nor adjustable. Obviously, the wind doesn’t blow constantly, nor are a calm ocean or cloudy days unknown. Energy from those sources, then, must be produced when possible and stored for use when needed. Even if a more consistent flow of energy could be achieved, demand fluctuates to such an extent that storage would still be necessary.
Various solutions already exist. Pumped hydro, where water is pumped to higher elevation at peak production times and then released to drive turbines when demand outstrips supply, is one solution. There are limitations, though, most notably those related to geography; nearby high ground is needed if massive construction costs are to be avoided.
Compressed air has also already been used in some cases, with storage either underground or in tanks, but cost, storage space, and inefficiency have all presented their own problems.
Enter Canadian start up Hydrostor and their underwater air storage system. The company's website explains how the system works, but the basic principle is straightforward. Large bags of pressurized air are kept deep underwater, preferably at depths of over 300 feet, where the pressure of the water above acts as a compressor.
Power at peak generation times is used to pump the air down into the bags. Then the air is released at times of peak demand and used to power a turbine, which produces electricity.
The system isn’t perfect -- no energy storage system is -- but the 70 percent efficiency rate that the company claims is acceptable, especially in the light of other serious advantages. Most notably, two popular alternative energy collection methods, wave and wind power, are often located offshore, where the pre-requisite for Hydrostor’s system, deep water, exists naturally.
There have been previous attempts at doing similar things, but none have achieved the degree of efficiency claimed by Hydrostor. Those claims will be tested soon, when completion of their first project -- in Lake Ontario – happens later this month. If there are no problems, we will have the world’s first commercial underwater compressed air storage facility.
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Martin Tillier of Oilprice.com
