Economic Analysis of a Micro Humid Air Turbine for Domestic Applications

Micro Gas Turbines (mGT) appear as a promising technology for small-scale (up to 500 kW) Combined Heat and Power (CHP) production. However, their rather low electric efficiency limits their profitability when the heat demand decreases. Hot liquid water injection in mGTs -particularly within the micro Humid Air Turbine (mHAT) cycle allows increasing electric efficiency by making use of the flue gas residual heat in moments of low heat demand. Based on simulations performed on a Turbec T100 mGT -modified to operate as an mHAT installed at the VUB, this paper presents an analysis of the economic profitability of such facility running on real network conditions. The study is performed assuming typical electricity and heat demand profiles for a domestic consumer. 25 natural gas and electricity price combinations have been taken into consideration, along with two types of domestic customers with higher and lower heat demands. Results show that the profitability of the mHAT with respect to the equivalent CHIP facility increases with higher electricity and lower natural gas prices. In particular, given a certain number of CHIP running hours and a natural gas price, there is a threshold for the electricity price above which the net income of the mHAT unit is always higher than that of the corresponding CHIP unit. In addition, water-cleaning costs for the mHAT case appear to constitute only 1 to 2.5% of total running costs. (C) 2014 The Authors, Published by Elsevier Ltd.