In a project funded by the U.S. Army, two University of Florida (UF) engineers have designed, built, and tested a combined power-refrigeration system that was designed to provide water, electricity, and refrigeration in emergency situations. Those involved in the project said that with additional research, the system can be made compact enough to fit inside a military jet or large truck.

William Lear, a UF associate professor of mechanical and aerospace engineering, and S.A. Sherif, a UF professor of mechanical engineering, have published several papers on the system that is being patented by the university.

Currently, both the military and the Federal Emergency Management Agency (FEMA) now rely on large generators to produce electricity in hazard zones. For cooling, they often haul in ice refrigerators that can often be energy inefficient. Depending on the location, imported fresh water may be another major logistical challenge and expense.

The engineering researchers' solution was a small system that ties a gas turbine power plant to a heat-operated refrigeration system. The refrigeration is used 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, but often lose efficiency when not operated at full power or in warm temperatures. Seeking to erase this loss, he rerouted the path of gases passing through the turbine, cooling via the heat exchanger. Sherif then tied the system to absorption units, cooling the gas 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 for the other, depending on your needs," Sherif said.

The system makes water by condensing the turbine's combustion gases. It is capable of producing about one gallon of water for every gallon of fuel burned, he said. The water would need to be treated because it is potable. But even if untreated it could be used for cleaning and other purposes.

A working prototype of the plant has been built at the UF engineering college laboratory. The maze of tubes and pipes are arranged into a ‘flow pattern' to route gases through and around a small gas turbine. There are also dozens of electronic and pneumatic monitoring probes.

Lear said further research is required to make the plant more compact and otherwise enhance its performance. He also said there is a possibility the concept could be developed for use in fixed locations as part of a normal power grid. For example, he said, utilities could build the plant nearby a supermarket warehouse that required both electricity and cooling.

Publication date: 11/06/2006