Micro gas turbine cogeneration system with latent heat storage at the University: Part III: Temperature control schedule

Abstract The latent heat storage system is a novel heat storage system. At the University under service conditions, it was demonstrated with a micro gas turbine (MGT) cogeneration system (CGS). Expanding the latent heat storage system into new applications is expected to save energy economically with high density energy storage and reduce exhaust emissions and reduce operational costs. This is the first demonstration of using a latent heat storage system with CGS under service condition and its characteristics are very important. In Part I, a fixed operating schedule of the system was planned and demonstrated at the University. The charge/discharge cycles of the latent heat storage system were repeated for 407 times. The energy flow test of the system shows the importance of the heat release source and total system design. In Part II, an irregular charge case of the latent heat storage system was discussed when the prime mover of the system was operated at a part load and thermal priority mode. A highly sophisticated system design that solves these problems was necessary for extending the applications of the latent heat storage system. In Part III, a temperature control schedule of the system was demonstrated during winter mornings using a new programmable logic controller (PLC). Using a fixed schedule, the MGT-CGS with latent heat storage reduced the CO2 emission when the energy utilization factor was above 50%. The temperature control schedule was considered to be better than the fixed schedule, both in terms of the operational efficiency of the overall system and CO2 reduction. The temperature control schedule was executed using an empirical formula for the temperature rise in a classroom. The restriction on the operation time by the contract with the gas supplier and the low heating capacity of the CGS affected the heating time and temperature rise. The temperature rise in the classroom was almost proportional to the integrated temperature difference across the hot water header of the heating system. On cold days, the rate of temperature rise produced by the CGS was very slow, therefore, additional heat supplied by the original boiler was used to increase the temperature rise. If larger latent heat storage systems will be developed in future, it will be expected that the temperature of the classrooms are kept more comfortable with less energy consumptions and lower CO2 emission.