# Feasibility Analysis of Industrial High-Temperature Heat Pumps in Greece
## 4 Conclusions  
Electrification of industrial processes is an important step for the decarbonization of the industrial sector. This work examines the sustainability of using high-temperature heat pumps (HTHP) for process heat production at temperature levels of 100 \({}^{\circ}\)C to 180 \({}^{\circ}\)C. The ambient-source HTTP and the waste heat source (WHS)-driven HTHP were examined and compared with the baseline scenario of using a natural gas boiler. The core of this work is a parametric thermodynamic investigation of HTHPs with cyclopentane as a working medium for different design conditions. Moreover, energy and environmental indexes are calculated, aiming to determine the overall sustainability of the studied solutions. The most critical outcomes of this analysis are as follows:  
* The utilization of low-grade waste heat sources is beneficial for increasing the COP of the heat pump, with this scenario outperforming the ambient-source heat pump. In terms of exergy efficiency, there is an optimal waste heat source temperature for maximizing the unit performance for every scenario. * It was concluded that rises in the heat temperature reduce the performance due to the difficulties that the heat pump faces in achieving a high-temperature lift. The waste heat-driven system can produce useful heat up to 180 \({}^{\circ}\)C, while the ambient-source system does so up to 160 \({}^{\circ}\)C.
* The results indicate system economic sustainability for process heat temperatures up to 160 \({}^{\circ}\)C and in the cases with higher waste heat input temperatures. For the ambient-source high-temperature heat pump, the economically viable scenario was found only for the case of heat production at 100 \({}^{\circ}\)C due to significant efficiency reductions at higher temperatures. * For the waste heat source-driven system, the LCOE ranged from 0.0220 EUR/kWh to 0.1024 EUR/kWh, while for the ambient source, it ranged from 0.0562 EUR/kWh to 0.0977 EUR/kWh, and for the natural gas boiler, it was found at 0.0602 EUR/kWh. Therefore, the application of heat pumps is not always an economically viable choice. * For the ambient-source heat pump, economic viability is only found for the cases with T\({}_{\text{process}}\) = 100 \({}^{\circ}\)C. For the cases with the waste heat stream-driven heat pump, economic viability always exists for T\({}_{\text{process}}\) = 100, 110 and 120 \({}^{\circ}\)C, while for T\({}_{\text{process}}\) = 170 and 180 \({}^{\circ}\)C, the economic results are less favorable. For the intermediate cases, economic viability is achieved from a minimum waste source temperature. Specifically, for T\({}_{\text{process}}\) = 130 \({}^{\circ}\)C, the economically viable designs need T\({}_{\text{win}}\) \(\geq\) 55 \({}^{\circ}\)C; for T\({}_{\text{process}}\) = 140 \({}^{\circ}\)C, the economically viable designs need T\({}_{\text{win}}\) \(\geq\) 65 \({}^{\circ}\)C; for T\({}_{\text{process}}\) = 150 \({}^{\circ}\)C, the economically viable designs need T\({}_{\text{win}}\) \(\geq\) 80 \({}^{\circ}\)C; and for T\({}_{\text{process}}\) = 160 \({}^{\circ}\)C, the economically viable designs need T\({}_{\text{win}}\) \(\geq\) 90 \({}^{\circ}\)C.
* Both waste heat- and ambient-source-driven heat pumps lead to CO\({}_{2}\) emission reductions compared to the scenario of using a conventional natural gas boiler. The CO\({}_{2}\) emission reductions for the waste heat source-driven heat pump were found to vary from 13.38% to 82.61% compared to the natural gas boiler, while for the ambient-source heat pump, they ranged from 26.76% to 72.60% compared to the natural gas boiler. In the future, different heat pump configurations should be examined, as well as applications of mixtures of working fluids, in order to optimize the heat transfer and minimize the exergy destruction in the heat exchanges.