Low grade heat driven adsorption system for cooling and power generation with small-scale radial inflow turbine

Abstract

Adsorption system is a promising technology that can exploit the abundant low grade heat sources (∼150°C) from renewables like solar, geothermal and industrial waste heat leading to reduction of fossil fuel consumption and CO2 emissions. In this work, the effect of using advanced adsorbent materials like AQSOA-Z02 zeolite (SAPO-34) and Metal Organic Framework (MOF) like MIL101Cr and Aluminium fumarate on power and cooling performance compared to that of commonly used silica-gel was investigated using water as refrigerant. A mathematical model for a two bed adsorption cooling cycle has been developed with the cycle modified to produce power by incorporating an expander between the desorber and the condenser. Results showed that it is possible to produce power and cooling simultaneously without affecting the cooling output. Results also showed that for the four pairs used as the heat source temperature increases, the cooling capacity and power generated increase. As the condenser cooling temperature increases, the cooling effect and power output will decrease while for the chilled water temperature, the cooling capacity and power generated increased as the chilled temperature increased. Also, it is shown that SAPO-34 achieved the maximum average specific power generation (SP) and specific cooling power (SCP) of 67W/kgads and 622W/kgads respectively. A detailed CFD modelling has shown that a small-scale steam radial inflow turbine with mass flow rate of 0.0046kg/s generated using 8.55kg/bed of SAPO-34 adsorbent with heat source temperature of 160°C can achieve efficiency of 82% and power output of 785W.