Researchers from University of Glasgow built a small-scale experimental rig that can switch between regenerative and non-regenerative modes
Increasing population and industrialization has led to high demand for power generation worldwide. However, adverse impacts of power generation techniques such as carbon dioxide emission are also needed to be considered while catering to increasing demand for energy. According to the paper – A novel design methodology for waste heat recovery systems using organic Rankine cycle — published in Energy Conversion and Management in 2017, 20–50% of the primary energy to industry is released to the environment in the form of waste heat. The Stirling cycle, reversed Brayton cycle, the Kalina cycle, and the Organic Rankine Cycle (ORC) are some of the technologies suitable for utilization of the low-temperature heat sources.
ORC offers simplicity and low operating pressures and therefore, is the most potential technology for the utilization of low-temperature heat sources. However, the technology has some drawbacks such as low thermal efficiency and consequently low cost-effectiveness. Now, a team of researchers from University of Glasgow built a small-scale rig (rated at 1 kW) to isolate and examine the effect of a regenerator on the performance of an ORC using a scroll-type positive displacement expander. The team measured temperature, power output, and pressure at various points in the cycle to examine the efficiency and pressure losses in the cycle.
The team found that the first-law efficiency increased when a regenerator was introduced into the cycle. Moreover, better increase in efficiency was observed when the heat source temperatures further increase. The team also reported an increase in the second-law efficiency of the cycle when a regenerator was added and heat source temperature was increased. For a regenerative cycle, the peak efficiency of the cycle was recorded at 8.61% when the heat source temperature was 95 °C. In terms of efficiency, the regenerative cycle was superior to the non-regenerative cycle. Moreover, the efficiency of regenerative cycle was much higher when the heat source temperatures were above 75 °C. This can be due to reduced heat demand in the evaporator and increased output power of the cycle when the regenerator was added. The research was published in the journal MDPI Energies on April 16, 2019.
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