Effects of steam injection on microturbine efficiency and performance

Microturbines offer new perspectives in small-scale heat and power production. Non-continuous heat demand however often leads to a reduced number of yearly running hours. This paper proposes an alternative by introducing water or steam injection without significantly increasing the overall cost. Steam injection (STIG®) has been successful to boost performance and efficiency in industrial gas turbine cycles and similar effects are expected in the case of microturbines. Owing to the different way of controlling microturbines at non-constant shaftspeed, the response to steam or water injection differs from current STIG® cycles. The purpose of this study was to examine the effects of steam injection on microturbine behavior by simulating its off-design characteristics in Aspen.The dry behavior of a microgasturbine has first been simulated and validated against a limited number of available measurements. After increasing steam injection up to the surge limit, we concluded a large amount of steam can potentially be injected. Next, the heat required to generate steam was rerouted from the water heater. When CHP mode is disabled and all residual heat after the recuperator is used in a STIG® route, 3.3% water can be injected and electric efficiency rises by 5.1%.