Energy and economic performance comparison of heat pump and power cycle in low grade waste heat recovery

Abstract

For the sake of making an appropriate choice for the reuse of low grade waste heat, the mechanical heat pump, steam turbine (ST), and organic Rankine cycle (ORC) are modeled by Aspen Plus. The working conditions of 100–150 °C waste heat temperatures, as well as 10–30 °C heat pump temperature lifts are simulated and calculated. The price ratio of electricity to heat is introduced as an important economic variable. The energy and economic performance of the three technologies in low grade waste heat recovery are compared and analyzed based on the exergy efficiency and annual revenue. The results indicate that in terms of the exergy efficiency, the mechanical heat pump is always the best choice. From the perspective of the annual revenue, the mechanical heat pump is the best choice in most cases. The chance that the annual revenue of the ORC and ST is greater than that of the mechanical heat pump arises only when the price ratio of electricity to heat is greater than 5. As for the payback period, all the cycles can meet the requirements of enterprises. A guide of the selection of waste heat recovery technology based on economics is drawn.