By integrating waste heat driven cooling and heating with the electric power system, fuel use and cost can be reduced
by 66%. This is a substantial savings, which makes these systems more competitive with grid based power. In order
to realize these benefits, efficient engines must be combined with cooling and heating systems. Altex has identified
and is developing an innovative closed cycle gas turbine engine with partners, which is well-suited to combined heat
and power. Besides achieving high efficiency at both full and part load, the engine is quiet and clean. Also, because it is
indirectly fired, a fuel compressor is not needed for gaseous fuels. This saves costs and reduces system
complexity. One application of the engine is to provide power, and cool and heat a Lightweight Multipurpose
Shelter, for military applications.
The power unit, illustrated in the drawing above, produces 8 kilowatts power, 5.3 kilowatts
cooling and 4.4 kilowatts heating. While under development, the engine's indirect firing capability has been shown in
tests at larger scales. Given the separation of combustion gases and working fluids in this approach, solid fuels, as
well as liquid and gaseous fuels can be burned to provide heat. In particular, the Altex indirectly fired gas turbine tests
were accomplished by using dried dairy manure as the fuel. This system, mounted on trailers, utilized a rotary dryer
with waste heat to dry the fuel and a staged cyclonic combustor to burn the
manure, while controlling NOx by over 80%. Heat from the manure combustion was then transferred through an
alloy heat exchanger to the gas turbine working fluid. Because the combustor used cyclonic flow, ash was captured
in the combustor and discharged, allowing the heat exchanger to operate with only modest particulate
deposition. This increases the reliability of the system. While burning dairy manure to drive the gas turbine is an
extreme example, the test results show the flexibility of the system to address several fuel types and applications.