OPTIMIZED OPERATION OF A COMBINED SOLAR AND WASTE HEAT DRIVEN HIGH TEMPERATURE HEAT PUMP FOR A FOOD INDUSTRY

Kurzfassung

Heat upgrade to high-temperature levels is a significant challenge in the industry that accounts for high annual CO2 emissions. This research aims to develop a novel concept for solar energy and waste heat exploitation to enable high-temperature heat upgrade through a heat pump. The design incorporates the use of solar thermal collectors connected with a thermal energy storage tank, with thermal oil as the storage medium. The stored heat in coalition with a waste heat recovery unit will operate a reverse air Brayton heat pump to achieve the required temperature. A Matlab algorithm has been developed to simulate the operation of the system dynamically. The analysis is conducted for a food industry located in Kreba-Neudorf, Germany where a temperature upgrade from 245oC to 255oC of a 20.7 kg/s mass flow rate of diathermic oil is required. The solar thermal collecting area installed is 500 m2 with a 15 m3 storage tank volume, while the waste heat availability is 2.6 kg/s flue gas mass flow rate at 230oC. The plant is operational for 8 hours a day and 5 days per week for the year. The present work will calculate important metrics such as the average daily coefficient of performance (COP) and the daily heat production. Furthermore, a parametric investigation of various parameters of the system is conducted to achieve the highest efficiency, while the significance of the temperature of the thermal energy storage to the COP of the system is illustrated.