Operation strategy of a solar-gas fired single/double effect absorption chiller for space cooling in Indonesia

Abstract

A solar-gas fired absorption cooling system has been installed and tested in a real environment at the University of Indonesia, Depok, Indonesia. The cooling system provides chilled water to the building of the Mechanical Research Center of the university. This system has a unique single/double-effect water/Lithium Bromide absorption chiller with a nominal cooling capacity of 239 kW. In addition, the system consists of evacuated tube solar collectors (~181 m2 total aperture area) and fan coil units installed in the building. The absorption chiller is driven by (i) hot water (75 – 90 °C) produced by the solar collectors which supply heat to the single-effect generator and (ii) by a direct gas-fired burner at the double-effect high-temperature generator when it is needed. The driving heat supply from the gas-burner is 113.2 kW and 93.3 kW (at 90 °C) from the solar collector field. This study focuses on the control strategy of the solar-gas fired absorption chiller system based on operational data obtained from the field test carried out in an Asian tropical climate, particularly Indonesia. The proposed and implemented control strategy consists of the control of both external and internal operation variables. The external control strategy includes the control of three water flow loops (hot water, cooling water, and chilled water) that are controlled according to the cooling load of the building and weather conditions (i.e., solar irradiation and ambient temperature). The internal operation variable (total solution flow rate) and gas flow rate are adjusted according to the required cooling capacity. The field tests of thermal and electrical COP are around 0.9–1.1 and 4.5–5.5, respectively. The field test results demonstrate the feasibility of the implemented control strategy for the optimum and safe operation of the system in an Indonesian climate, with the possibility of adapting to other similar Asian tropical climates.