Cold-to-electricity conversion using a piston based engine in cold energy storage (CES) system, part one: a theoretical study

This study concerns the cold-to-electricity conversion in a piston based engine. A theoretical model was developed to predict the power generation rate in the engine. Parametric study showed the significant effect of p-crank angle, motor speed, gas pressure and temperature and chamber volume on the power generation by the piston based engine. It was found that optimal p-crank angle was normally in the range of 55°∼76°. The minimum inner diameter of the valves connected to the engine was a crucial factor that limited the power capacity of the engine system. Based on the experimental data, the large engine (1900 cm3) and small engine (162 cm3) had an actual efficiency of 24.1% and −23.6%, respectively. This implied that the large engine was feasible to be used in CES system for electricity re-generation during peak hours. However, the induced CES efficiency was 18.9% and 52.1% in two different situations. The results indicate the importance of engine development in promoting the CES technology.