Conceptual study of combined cycles with thermally coupled micro gas turbines and high temperature heat pumps for trigeneration

Abstract

In the context of climate change low-emission technologies need to be developed to cover the high thermal energy demand of the industrial sector. Because of the ongoing transition to renewable energy sources and their limited availability, combustion-based technologies will be required to support this transition. This paper presents fundamental, application-independent conceptual studies of thermally coupled micro gas turbines (MGT) and high temperature heat pumps (HTHP). The MGT provides electrical power to drive the compressor of the heat pump, while the heat of the exhaust flow is used as a heat source. This self-sufficient system is expected to provide high thermal output at temperature levels beyond available heat pump technology. In addition, low temperatures can be achieved for cooling processes. Within the scope of this study, several process architectures with different integration of heat sources are analyzed by performing thermodynamic cycle simulations. The results demonstrate attainable temperature levels and it can be shown that heat can be provided at temperatures above 300 °C. Cooling processes can be effectively integrated in some of the investigated cycle configurations so that temperatures below -30 °C can be reached. Thermal coupling enables high utilization rates of primary energy and values over 100% are possible. The present work provides the basis for future studies, which will take the economic feasibility in comparison with competing technologies into consideration.