Micro gas turbine cogeneration system with latent heat storage at the University: Part I: Plan and energy flow test

Abstract Overcoming the spatiotemporal mismatch between heat and electricity utilization is a major issue in distributed energy systems. Latent heat storage systems are able to store heat for a long period of time with little heat loss. The Energy Technology Research Institute (ETRI) of the National Institute of Advanced Industrial Science and Technology (AIST) demonstrated a micro gas turbine cogeneration system with latent heat storage at Sapporo City University. Since there had been no cogeneration system with the latent heat storage under service condition, this system was the first demonstration and its characteristic was very important. The proper use of the latent heat storage system will save energy economically, store high energy density, reduce exhaust emissions, and save operational costs. The latent heat storage system operated well and was able to repeat 407 cycles of heat storage and heat release. The efficiency of the electricity generation was about 20%, although the efficiency of the total system remained at 55%, which was lower than the nominal specifications. Heat loss, which amounted to 45%, was from a decrease in the efficiency of the heat exchanger, piping loss around the heat exchanger, heat loss due to cooling of auxiliary equipment, and heat loss due to exhaust gas out of the building. Heat loss of the heat exchanger system and piping loss can be diminished by making better use of the highly sophisticated system. The proper solution is to operate the system for more than 4 h until sufficient heat is stored in the latent heat storage system. This would decrease the heat loss from both the heat exchanger system and the piping. In Part II [1], 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 latent heat storage system. In Part III [2], a temperature control schedule of the system was demonstrated in winter morning using a new programmable logic controller (PLC). If the more larger latent heat storage system will be developed in the future, it will be expected greatly that the temperature of the classrooms are kept more comfortable with less energy consumptions and less CO 2 emission.