Recent research led by Ran Chen from the State Key Laboratory of Petroleum Resources and Prospecting at China University of Petroleum-Beijing has shed light on a critical aspect of geothermal power generation using the Organic Rankine Cycle (ORC). This innovative study, published in ‘发电技术’ (translated as ‘Power Generation Technology’), focuses on the effects of subcooling within the ORC system that utilizes zeotropic mixtures, a blend of refrigerants that can enhance thermal performance at medium-low temperatures.
Geothermal energy, typically harnessed at temperatures below 150℃, represents a significant opportunity for sustainable power generation. However, the study reveals that as zeotropic mixtures condense into a subcooled state, the thermal efficiency of the ORC can be compromised. “The condensation subcooling affects the temperature profile match between the working fluid and the heat sink,” Chen explains. This mismatch can lead to a rise in condensation pressure, which in turn impacts the overall power output of the system.
Chen’s research emphasizes the importance of optimizing evaporation pressure to maximize net power output. The findings indicate that even a modest subcooling of just 2℃ could result in a reduction of net power output by 4.36% for isobutene/isopentane mixtures, highlighting the sensitivity of these systems to thermal conditions. This insight is particularly valuable for geothermal power operators looking to enhance efficiency and profitability.
Moreover, the study introduces the concept of an internal heat exchanger (IHE), which can recover waste heat from the expander exhaust to preheat the working fluid. This innovative approach allows the subcooled ORC system to increase net power output by 0.55%. “By integrating an IHE, we can significantly improve the thermal performance of ORC systems, making them more viable for commercial applications,” Chen noted.
The implications of this research extend beyond theoretical analysis. With the global push towards renewable energy sources, optimizing geothermal systems could lead to more efficient power generation, lower operational costs, and ultimately, a more sustainable energy future. As countries seek to reduce their carbon footprints, advancements in ORC technology could play a pivotal role in harnessing geothermal resources more effectively.
This research not only contributes to the scientific understanding of ORC systems but also provides actionable insights for industry stakeholders. As the energy sector continues to evolve, studies like Chen’s could pave the way for innovative solutions that enhance the viability and efficiency of geothermal power generation.
For more information on this groundbreaking research, visit State Key Laboratory of Petroleum Resources and Prospecting.
