Abstract
Recently, the need for energy-saving and eco-friendly energy systems is increasing as problems such as rapid climate change and air pollution are getting more serious. While research on a power generation system using hydrogen energy-based fuel cells, which rarely generates harmful substances unlike fossil fuels, is being done, a power generation system that combines fuel cells and Organic Rankine Cycle (ORC) is being recognized. In the case of High Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC) with an operating temperature of approximately 150 to 200 °C, the importance of a thermal management system increases. It also produces the waste heat energy at a relatively high temperature, so it can be used as a heat source for ORC system. In order to achieve this outcome, waste heat must be used on a limited scale within a certain range of the temperature of the stack coolant. Therefore, it is necessary to utilize the waste heat of ORC system reflecting the stack thermal management and to establish and predict an appropriate operating range. By constructing an analytical model of a combined power generation system of HT-PEMFC and ORC systems, this study compares the stack load and power generation performance and efficiency of the system by operating temperature. In the integrated lumped thermal capacity model, the effects of stack operating temperature and current density, which are important factors affecting the performance change of HT-PEMFC and ORC combined cycle power generation, were compared according to operating conditions. In the comparison of the change in power and waste heat generation of the HT-PEMFC stack, it was shown that the rate of change in power and waste heat generation by the stack operating temperature was clearly changed according to the current density. In the case of the ORC system, changes in the thermal efficiency of the ORC system according to the operating temperature of the stack and the environmental temperature (cooling temperature) of the object to which this system is applied were characteristic. This study is expected to contribute to the establishment of an optimal operation strategy and efficient system configuration according to the subjects of the HT-PEMFC and ORC combined power generation system in the future.
Highlights
Today, the need to expand power generation systems utilizing eco-friendly and waste heat energy to tackle climate changes is increasing, and active research on hydrogen fuel cell generation and a cogeneration system capable of utilizing waste heat is being done
A system analysis was conducted to predict system performance and efficiency according to changes in operating conditions such as stack operating temperature, current density, and Organic Rankine Cycle (ORC) cooling temperature for a combined power generation system composed of a lumped thermal capacity model
Case of HT-PEMFC, thermal is formed important as a relatively operating and in the case ofmanagement a heat exchange system as that utilizes waste heat, sincehigh the operating range temperature, and intaking the case of a heat exchange system that utilizes waste heat, the operating and strategies account of the thermal management of the stack must besince selected, operating range and strategies taking account of the thermal management of the stack must be it is necessary to predict the power generation performance and efficiency according to the operating selected, it is necessary to predict the power generation performance and efficiency according to the conditions
Summary
The need to expand power generation systems utilizing eco-friendly and waste heat energy to tackle climate changes is increasing, and active research on hydrogen fuel cell generation In the case of HT-PEMFC, the inlet temperature and mass flow rate of the coolant must be kept relatively constant in order to secure appropriate power efficiency at a relatively high operating temperature [19] This is a limiting factor that must be reflected in the operational design of waste heat utilization systems such as ORC power generation and is the reason for the need to optimize the integrated system linked to the stack thermal management system. To this end, it may be useful to introduce a HT-PEMFC and ORC power generation integrated system modeling, as well as a confirmation and verification process of power generation performance and efficiency range according to the application subject and operating conditions. A system analysis was conducted to predict system performance and efficiency according to changes in operating conditions such as stack operating temperature, current density, and ORC cooling temperature for a combined power generation system composed of a lumped thermal capacity model
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