Design and operation of an air-conditioning system fueled by wood pellets

A room-cooling system of 2kW capacity fueled by wood pellets was designed, built and tested. The system was demonstrated during summer at the Yakushima Field Station of Kagoshima University, Japan. It contained a pellet feeder, a pellet burner, a heat exchanger, a lithium bromide–water absorption heat pump and a control unit. The volume of the test room was 36.9m3 and ambient temperature 30°C. The airflow temperature from the room unit was decreased to 16°C by the system, and the room temperature could be successfully controlled to 24°C steady state. Room heating in winter was also demonstrated. Since the air was heat exchanged, the overall energy efficiency of the cooling system was low at about 19%. However, the calculation based on the heat flow showed that the efficiency could be enhanced to about 75% by direct heating of the regenerator by the flue gas.