A comparative study of sustainable industrial heat supply based on economic and thermodynamic factors

Three different process types of heat supply for industrial production processes requiring low temperature heat at 140°C are analyzed and compared with each other. The thermodynamic and economic efficiency of a gas turbine process with a heat recovery boiler (GT), a gas and steam turbine combined cycle process with a back-pressure turbine (GT-CC) and a high temperature heat pump (HTHP) system recovering waste heat from humid exhaust air between 90°C and 50°C are assessed based on energy flows, exergy flows and costs of heat provided as 4 bar (abs) saturated steam. The economic analysis bases on the comparison of the consumption-related costs of heat, the capital-related costs of heat and the operation-related costs of heat. The payback-times are calculated for different HTHP investment cost levels (1000 EUR/kWQ, 750 EUR/kWQ, 500 EUR/kWQ and 250 EUR/kWQ). To evaluate the effects of fluctuating energy costs, a sensitivity analysis with varying gas and electricity prices has been carried out