Life below the wet bulb: The Maisotsenko cycle
POWER magazine, by Platts/McGraw Hill
For several years, the humid air turbine (HAT) cycle has promised a new way to generate electricity more efficiently and cost-effectively than combined-cycle power plants. However, practical limitations have prevented the HAT cycle from being commercialized. In response, Idalex Inc. an R&D firm based in Arvada, Colo. has developed and proven a new technology called the Maisotsenko (M) cycle that it claims solves the HAT cycle’s limitations. The major limitation of the HAT cycle lies in its humidification process, which uses a column saturator that ties evaporation to the boiling temperature of water at compressed air pressure. Raising humidity past this point would require a separate boiler another piece of equipment whose cost, maintenance, and pressure and temperature losses are significant drawbacks.
According to researchers at Idalex, the M cycle lacks those drawbacks because in it, humidity gains are limited only by the amount of waste heat available from the turbine’s exhaust gas. Leland Gillan, a senior R&D engineer at Idalex, claims that the M cycle could achieve efficiencies as high as 60% while simultaneously lowering emissions all with lower equipment costs and a smaller footprint than the HAT cycle. Gillan also claims that the M cycle can be scaled to work with any size turbine, from micro to large, and that it would not suffer from the drops in efficiency that conventional gas turbines suffer at partial loads. “Rather,” he states, “the ability to add moisture using waste heat allows the Maisotsenko cycle to run at high efficiency at any load from 50% to 100%.”
Although this new combustion turbine technology is still at the theoretical stage, it has some high-powered supporters. One, Dr. Myron Tribus, is a former assistant secretary for science and technology at the U.S. Department of Commerce. When he first studied the M cycle, he thought it violated the second law of thermodynamics. (One way to state the law is as follows: In a closed system, you can’t finish any real physical process with as much useful energy as you had to start with some is always wasted, in the form of entropy.) However, once Tribus understood what Idalex was doing and how the cycle works, he was impressed. “The Maisotsenko cycle should have many applications for increasing the efficiency of power systems,” he says.
The new thermodynamic cycle is named for Dr. Valeriy Maisotsenko, Idalex’s chief scientist. It gets its latent heat of evaporation from a heat and mass exchanger. Dr. Maisotsenko claims, “The cycle works at any temperature and pressure, and can dramatically improve any process that needs fluid cooling and/or saturated air.”