Novel hybrid thermochemical cycles for low-grade heat storage and autothermal power generation: A thermodynamic study

• Published in: Applied energy 2020-07, Vol.270, p.115111, Article 115111
• Main Authors: Godefroy, Alexis, Perier-Muzet, Maxime, Mazet, Nathalie
• Format: Article
• Language: English
• Subjects: Chemical and Process Engineering; Engineering Sciences; Hybrid cycles; Power and refrigeration cogeneration; Sorption; Thermal storage; Thermochemical cycles; Thermodynamic analysis
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2020.115111

•Hybrid thermochemical cycles targeting power production are proposed.•New cycles enabling autothermal power generation and cold production are achieved.•They can be driven by low-grade heat sources at temperatures between 100 and 250 °C.•They provide an intrinsic storage feature, the exergy densities reach 722 kJ/kgNH3.•The highest energy and exergy efficiencies are respectively 0.24 and 0.40. The principle of hybridizing a solid/gas thermochemical refrigeration cycle with a power cycle is extended to two novel hybrid cycles (called operating modes). They can be driven by low-grade heat, and they allow storing this energy and converting it predominantly into mechanical power. For this purpose, they integrate an original autothermal power production during their discharging step, which is deeply analyzed. In addition, depending on the operating mode, power can be produced in both charging and discharging steps and an additional cold production can be provided. A deep thermodynamic study was carried out to assess the performance of these cycles, for 103 solid/gas pairs. These cycles allow converting low-grade heat sources from 87 °C to 250 °C. The maximal energy and exergy efficiencies for power and cold cogeneration are 0.24 and 0.40, respectively, and the maximal exergy density is 722 kJ/kgNH3. The part of power production reaches 62% (when it occurs only in discharging step) to 78% (when it occurs in both steps).