Enhancing micro gas turbine performance in hot climates through inlet air cooling vapour compression technique

Microturbines (MGTs) are power generation devices showing very interesting performance in terms of low environmental impact, high-grade waste heat and very low maintenance cost. One of the main issues that affect the output of MGTs is their strong sensibility to inlet air temperature. Both in literature and in practical applications, several solutions have been applied to control the inlet air conditions and reduce the sensibility of this kind of machines to ambient conditions. One of the most interesting technology is the refrigerating vapour compression technique. This solution has already been used for medium/large GTs, but there are very limited inlet air cooling applications on MGTs and few experimental data are documented. This paper describes a test bench that has been designed to apply the direct vapour expansion technique to a 100 kWe MGT and reports the power and efficiency augmentation of the machine when operating in hot summer days. The chiller was designed to treat the MGT's air flow rate under specific working conditions and cool the inlet air temperature down to 15 degrees C. Thanks to the reduction of the inlet air temperature, the MGT showed a benefit in terms of electric power gain up to 8% with respect to the nominal power output in ISO conditions while the electric efficiency increased by 1.5%. Results indicate that an almost linear trend can be obtained both in the electric power increase and in the electric efficiency increase as a function of the inlet air temperature when the chiller operates under nominal working conditions. When the IAC device operates at a higher temperature or a higher humidity than the design one, the gain is limited; in some working conditions with high relative humidity, most of the beneficial effect can even be lost. (C) 2015 Elsevier Ltd. All rights reserved.