Applicability study of micro Kalina cycle for regional low grade geothermal heat in Japan

In this study, the micro Kalina cycle (Micro KC) was designed as 10 kW class power generation system to utilize the low grade thermal heat sources (hot spring) at a temperature of 373 K with applying characteristic of the Lorenz cycle. The utilization of low grade geothermal energy which is not currently the focus of attention, is important as an energy source for distributed energy systems in small villages in mountainous areas of Japan. In the case of low grade geothermal heat utilization, it is difficult to utilize for power generation due to its large temperature gradient caused by the low temperature and small flow rate of the heat source. This condition is suitable for applying the Lorenz cycle. It was found that micro KC could generate 9.42–11.0 kW of electricity under realistic hot spring water conditions (373 K, 4000 kg/h) of Japan. The micro KC showed in 50% higher power performance than a micro ORC using R245fa.