A small scale pumpless ORC (organic Rankine cycle) system which can recover waste heat from low temperature heat resource is established to investigate the performance of the cycle. The system is mainly composed of two high efficient heat exchangers

one scroll expander

one generator

four refrigerant valves and eight water valves. The flow direction of the water and refrigerant is controlled by the valves. The water heated by electric heating boiler is used to simulate the low temperature heat resource. The temperature of the hot water ranges from 75℃ to 95℃ and the temperature gradient is 5℃. The cooling water from the cooling tower is 25℃ accordingly. The refrigerant R245fa is selected as the working fluid. The results show that the largest power output is 232 W

and the stable power output is about 230 W when the inlet water temperature is 95℃. The total time of power generation last 380 s. One more thing is that the higher inlet water temperature

the less time of power generation process. For the average steady power generation

the maximum energy efficiency is 3.92% and the minimum energy efficiency is 3.02% when the inlet water temperature is 95℃ and 85℃

respectively.