Investigation on a novel pumpless module driven by thermal energy and gravity and its application in an ORC system

Abstract

The “virtual” pump without power supply is a potential replacement for the electrically-driven pump in the conventional Organic Rankine Cycle (ORC) system. In this paper, a pumpless module and a 10 kW ORC system are designed and constructed, and the optimization for the system control method is studied with the performance evaluation of the pumpless module. The experimental results show that the generated power fluctuates periodically with applying the pumpless module. There exists an optimal liquid level range of (280–340) mm in a pumping cycle to stabilize the output power near the peak. By optimizing the input vapor flowrate, pressure balance time, and upper and lower limits of the liquid level of the pumpless module, the liquid flowrate and the average power generation can reach 1.25 kg/s and 11.76 kW respectively. In addition, the heat consumption and the equivalent power consumption of the pumpless module are analyzed. The heat consumption as a percentage of the total input heat increases from 4.2% to 14.7% as the heat source temperature increases from 90 °C to 130 °C, and its equivalent power consumption can save 36.1% at 90 °C compared to the electrically-driven pump while consumed 7.8% more than the electrically-driven pump at 130 °C.