Technical and economic performance comparison between recuperated and non-recuperated variable-speed microturbines in combined heat and power generation

This paper presents a technical and economic analysis for a microturbine in combined heat and power generation. In the studied case, the microturbine follows the electrical load, replacing purchased electricity and produced heat in an existing boiler. The influence of recuperation and different power control methods on the part load operation of the microturbine is investigated in the performance analysis. The control methods include using the turbine inlet temperature and the rotational speed of the shaft as control parameters. A steady state model has been constructed for the microturbine, using realistic component models. The operating values of the microturbine are obtained by solving the system of non-linear equations formed by the governing relations. In the economic analysis, maximum investment costs are determined that can be allowed for applications that use different microturbine configurations and control methods. Apart from the microturbine specifications and the case-specific heat and power demand, the results are strongly dependent on the economic parameters. Sensitivity analysis is presented for the main affecting factors.