Alternative thermal regenerative osmotic heat engines for low-grade heat harvesting

Rui Long, Yanan Zhao, Zuoqing Luo, Lei Li, Zhichun Liu and Wei Liu

Energy, 2020, vol. 195, issue C

Abstract: Low grade heat below 80 °C could offer a considerable energy supply. The utilization for this energy is limited with existing heat-to-power technologies for rather small differences between the heat source and environment. To efficiently harvest such low-grade heat, an alternative kind of thermal regenerative osmotic heat engine (TROHE) is proposed, which employs power-driven separation processes that run at a lower temperature, and the salinity gradient power technologies for power extraction after heating. For a TROHE that employs the reverse osmosis in the solution separation process, and pressure retarded osmosis in the energy extraction process, a figure of merit for selecting appropriate solutions is proposed. Salt solutions with a smaller specific heat capacity and density, and higher solubility are preferred to achieve a larger heat-to-work conversion efficiency. When operating between 60 °C and 20 °C, a maximum energy efficiency of 1.4% was achieved at 7 M LiCl-Methanol solution with a regenerative efficiency 90%. With advances in high performance regenerators and membrane technologies, the proposed TROHE can offer an alternative way for efficiently utilizing the vast low-grade heat.

Keywords: Low-grade heat; Thermal regenerative osmotic heat engine; Reverse osmosis; Pressure retarded osmosis (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:195:y:2020:i:c:s0360544220301493

DOI: 10.1016/j.energy.2020.117042

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