Abstract
The current research study focuses on the feasibility of stand-alone hybrid solar-geothermal organic Rankine cycle (ORC) technology for power generation from hot springs of Bhurung Tatopani, Myagdi, Nepal. For the study, the temperature of the hot spring was measured on the particular site of the heat source of the hot spring. The measured temperature could be used for operating the ORC system. Temperature of hot spring can also further be increased by adopting the solar collector for rising the temperature. This hybrid type of the system can have a high-temperature heat source which could power more energy from ORC technology. There are various types of organic working fluids available on the market, but R134a and R245fa are environmentally friendly and have low global warming potential candidates. The thermodynamic models have been developed for predicting the performance analysis of the system. The input parameter for the model is the temperature which was measured experimentally. The maximum temperature of the hot spring was found to be 69.7°C. Expander power output, thermal efficiency, heat of evaporation, solar collector area, and hybrid solar ORC system power output and efficiency are the outputs from the developed model. From the simulation, it was found that 1 kg/s of working fluid could produce 17.5 kW and 22.5 kW power output for R134a and R245fa, respectively, when the geothermal source temperature was around 70°C. Later when the hot spring was heated with a solar collector, the power output produced were 25 kW and 30 kW for R134a and R245fa, respectively, when the heat source was 99°C. The study also further determines the cost of electricity generation for the system with working fluids R134a and R245fa to be $0.17/kWh and $0.14/kWh, respectively. The levelised cost of the electricity (LCOE) was $0.38/kWh in order to be highly feasible investment. The payback period for such hybrid system was found to have 7.5 years and 10.5 years for R245fa and R134a, respectively.
Highlights
Renewable energy sources such as solar, biomass, geothermal, and hydro are the alternative energy sources for power generation
Two working fluids R134a and R245fa had been taken for investigation of the system performance
The Carnot efficiency of the system ranged from 16% to 23% for both of the working fluids when the heat source temperature lies between 70 and 99°C
Summary
Renewable energy sources such as solar, biomass, geothermal, and hydro are the alternative energy sources for power generation. The renewable energy should be deployed and implemented in every aspects of power production. According to International Energy Agency (IEA), renewable energy will have the fastest growth in the electricity sector which provides almost 30% of power demand in 2023 globally. During this period, solar PV which is one of the renewable energy technologies is forecasted to meet more than 70% of the global electricity generation followed by wind, hydro, and bioenergy [1]. A geothermal source is not exploited till in Nepal for power generation.
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