Is there a New Case for Non-Conventional Hydropower Technologies?

Sure there’s the old hydropower technologies that we’re all familiar with but I believe it could be more efficient to use the water power to compress air, using the principle of hydraulic air compression. The compressed air would be used in gas turbines, fired with fossil fuel or biofuel. Solar power might be able to supply some of the heat. In other words, turn the dam into a hydraulic air compressor. George F. Massillon OH

George, Water power technologies are one of the most under-estimated power sources. The US Department of Energy RD&D program has focused on upgrading existing hydropower turbines on existing dams significantly increasing electric power output and fish friendliness. This program for FY’07 is proposed to be shut down by The Bush Administration but hopefully Congress will instead vote to continue it and even significantly expand it. All the technology approaches below deserve aggressive RD&D and utilization. Pumped storage technologies have been well known in the hydropower industry. At a pumped storage hydropower plant, flowing water is used to make electricity and then stored in a lower pool. Depending on how much electricity is needed, the water may be pumped back to an upper pool. Pumping water to the upper pool requires electricity so hydropower plants usually use pumped storage systems when there is a big demand for electricity. It’s not an efficient process but the economics of time-of-use energy often make it so. Frequently, these facilities generate power by releasing water from the top reservoir during the day when power is most needed. At night, when the demand, and therefore the cost for power, has gone down, the facility then pumps the water back up to the top reservoir. Compressed air systems for storage deserve greater attention as well. The concept of compressed-air energy storage to help generate electricity is more than 30 years old. Two plants currently exist – an 11-year-old plant in McIntosh, Alabama, and a 23-year-old plant in Germany, both in caverns created by salt deposits. According to USDOE, off-peak electricity is used to power a motor/generator that drives compressors to force air into an underground storage reservoir. Similar to the aforementioned pumped hydro storage approach, this process typically occurs when utility system demands and electricity costs are the lowest. When electric power demand peaks during the day, the process is reversed. The compressed air is returned to the surface, heated by natural gas or renewable fuels in combustors and run through high-pressure and low-pressure expanders to power the motor/generator to produce electricity. You’re right that this technology has great benefits particularly incorporating other renewable technologies including biopower, geothermal, and solar thermal. Other water-based power technologies also deserve greater utilization. Kinetic wave technologies have attracted the US Navy which recently procured “power buoys” from Ocean Power Technologies (OPT), a wave energy company based in New Jersey. According to Dr. George W. Taylor, CEO of OPT, all the power needs of the US’s west coast could be provided from less than 200 square miles of ocean adjoining that coastline. This would account for approximately 75,000 MW of power capacity. Another promising water technology is freeflow microhydropower being commercialized by Verdant Power (VA). Says Verdant, the scope of the US market for “free-flow” technology is more than 12,500 MW, which is based on tidal and riverine system sites nearest to urban areas, such as New York Harbor, San Francisco Bay, and Puget Sound. Additionally, “accelerated-flow” technology is more than 12,000 MW, which is based on manmade channel system sites in rural areas, such as within by-pass channels at dams, irrigation canals, and aqueducts. Trey Taylor, Verdant Power’s CEO said that the first two of six tidal turbines (Phase 2 of 3, of the Roosevelt Island Tidal Energy Project) will be deployed in March 2006 with the remaining four following in April 2006. Scott