Development and experimental investigation of a novel solar-powered cooling system

Abstract

The development of novel and improvement of existing technologies for utilising solar thermal energy for cooling purposes traditionally attracts increased attention in both industry and academia. This work presents the development of a novel cooling system with a simple design and direct utilisation of solar thermal energy. The cooling system combines a liquid piston engine and cooling machine and is driven by an evacuated tube solar collector. A prototype of such the system was designed, built and tested in laboratory conditions using a solar radiation simulator. Variations in pressures, temperatures, and the fluid piston oscillation amplitudes in the system during its operation were recorded, and the indicated power of the engine and cooling capacity of the system were determined for a range of operation and design parameters. For the heat input range of 700–900 W and the constant temperature of the cooling water equal to 26.0 °C, the engine indicated power and cooling capacity of the system varied in the range of 70.0–88.0 and 51.0–61.0 W. The corresponding indicated efficiency of the engine and cooling system were in the range of 10.0–9.7 and 7.2–6.7%. The temperature in the cooling chamber was registered in the range of 20.0–18.2 °C at an ambient temperature of 24.0 °C. The COP of the cooling machine decreased from 0.71 to 0.69. The system performance improved in tests with a constant heat input (700 W) and reducing cooling water temperature. For cooling water temperature reduction from 26.0 to 18.0 °C, the engine indicated power and cooling capacity of the system varied in the range of 70.0–111.9 and 51.0–72.0 W. The corresponding indicated efficiency of the engine and cooling system were in the range of 10.0–16.0 and 7.2–10.3%. The COP of the cooling machine decreased from 0.71 to 0.64. The temperature in the cooling chamber was registered in the range of 20.0–14.4 °C at an ambient temperature of 24.0 °C. Experimental results obtained using the system's initial design demonstrate that the engine has efficiency comparable to low-temperature steam and Organic Rankine Cycle turbines. The Coefficient of Performance of the system is similar to that of single-stage absorption chillers.