In a project funded by the US Army, two University of Florida engineers have designed, built and successfully tested a combined power-refrigeration system that can provide water, electricity and refrigeration. With further development, the system could be made compact enough to fit inside a military jet or large truck.
‘If you’re in a forward base in
Lear and UF mechanical engineering professor SA Sherif have published several academic papers on various aspects of the system, which is being patented by UF. In November, they will present a paper discussing the system’s experimental results at the International Mechanical Engineering Congress & Exposition in
The US Federal Emergency Management Agency and the military now rely on large generators to produce electricity in hazard zones. For cooling, they either haul in ice or electricity hungry refrigerators. Depending on the location and emergency, imported fresh water may be another major logistical challenge and expense.
Hoping to cut costs and simplify the process, the Army has provided a $750,000 grant to a small
The engineering researchers’ solution: a small system that ties a novel gas turbine power plant to a heat-operated refrigeration system. The refrigeration is said to make the gas turbine more efficient, while also producing cool air and potable water. The turbine can run on conventional fossil fuels as well as biomass-produced fuels or hydrogen.
Lear said gas turbines are a common power generator used in everything from jet engines to electricity plants. The problem with traditional versions is that they lose efficiency both when not operated at full power and in warm temperatures, he said.
Seeking to erase this loss, he rerouted the path of gases passing through the turbine, cooling them via heat exchangers. Sherif, an expert in refrigeration, then tied the system to absorption units, cooling the gases still more.
Users can either tap all the cooling power to obtain peak efficiency for the turbine, or divert some for refrigeration or air conditioning. “You can decide how much of one you want versus how much of the other, depending on your needs,” Sherif said.
Lear said his experiments and computer models suggest that with all the cooling devoted to the turbine, it will be five percent to eight percent more efficient than traditional turbines. With some cooling siphoned for other purposes, it was still three percent to five percent more efficient than the turbines. Contrasting traditional gas turbines, the system maintains its efficiency whether operated at peak or partial power.
A few percentage points might not seem like much, but it makes a big difference when fuel is scarce or expensive, particularly if refrigeration and water are added bonuses, Lear said. “Power companies would kill for a one percent gain,” he said.
Bill Lear, a UF associate professor of mechanical and aerospace engineering, stands in front of a prototype system that provides power, water and refrigeration. The system, which is intended to be compact enough to fit inside a military jet or large truck, is designed for use in war zones, hurricanes or other emergencies
The system, which makes water by condensing the turbine’s combustion gases, is capable of producing about one gallon of water for every gallon of fuel burned, Sherif said. The water would need to be treated to be potable, but even if untreated it could be used for cleaning or other purposes. Because the plant reuses gases so extensively, the power plant also has very low polluting emissions, Lear added.
Sherif, Lear and colleagues have built a working prototype of the plant for experiment and testing purposes. The system routes gases through and around a small gas turbine, with dozens of electronic and pneumatic monitoring probes. Operators run the test plant from an adjacent control room.
Lear said further research is required to make the plant more compact and otherwise enhance its performance. That’s one of the goals of the Army’s Small Business Innovation Research Grant to the