Title: Exergy analysis and optimisation of a two-stage solar thermoelectric generator with tapered legs
Authors: Mkpamdi N. Eke; Chika C. Maduabuchi; Ravita Lamba; Howard O. Njoku; Xiaoli Ma; Yuri G. Gurevich; S.K. Tyagi; Onyemaechi V. Ekechukwu; Emenike C. Ejiogu; Chibuoke T. Eneh
Addresses: Department of Mechanical Engineering, University of Nigeria, Nsukka 410001, Enugu, Nigeria ' Department of Mechanical Engineering, Federal University of Agriculture, P.M.B. 2373, Makurdi, Nigeria ' Department of Electrical Engineering, Malaviya National Institute of Technology, Jaipur 302017, India ' Department of Mechanical Engineering, Applied Renewable and Sustainable Energy Research Group, University of Nigeria, Nsukka, 410001, Nigeria; Department of Mechanical Engineering Science, University of Johannesburg, Auckland Park, 2006, South Africa ' Research Centre for Sustainable Energy Technologies, University of Hull, HU6 7RX, UK ' Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, 07360 México, CDMX, México ' Department of Energy Science and Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, Delhi 110016, India ' Department of Mechanical Engineering, University of Nigeria, Nsukka 410001, Enugu, Nigeria ' Africa Centre of Excellence for Sustainable Power and Energy Development, University of Nigeria, Nsukka, Nigeria; Laboratory of Industrial Electronics, Power Devices and New Energy Systems (LIEPNES), University of Nigeria, Nsukka, Nigeria ' Department of Mechanical Engineering, University of Nigeria, Nsukka 410001, Enugu, Nigeria
Abstract: Numerous previous studies indicate that the performances of thermoelectric generators are enhanced by incorporating legs with variable area geometries. However, there is a dearth of comprehensive optimisation studies on these new thermoelectric generator designs. More so, the few optimisation studies that exist have rather employed unrealistic isothermal boundary conditions in their numerical models. Furthermore, these new leg geometries have not been applied to multi-stage systems. Accordingly, to address these gaps, a numerical optimisation, using ANSYS 2020 R2 software, is performed on a two-stage thermoelectric generator with variable area leg geometries; with optimisation parameters that include: leg geometry (height and area), intensified insolation with external load resistance, i.e., geometrical, thermal and electrical operation of the device. An exergy/irreversibility analysis is also carried out and techniques of minimising thermodynamic losses while allowing for the useful exergy output after solar energy conversion are proposed. Results indicate that, for an optimum leg height, area, concentrated solar radiation intensity and load resistance of 10 mm, 0.7 mm2, 20 suns and 1.3 Ω, respectively. Maximum energy and exergy efficiencies of 7.03% and 7.55% respectively, were obtained for the proposed system. This improves the energy and exergy efficiencies of the standard device by 23.44%.
Keywords: solar thermoelectric generator; variable area leg geometry; two-stage thermoelectric generators; numerical optimisation; thermodynamic analysis.
International Journal of Exergy, 2022 Vol.38 No.1, pp.110 - 136
Received: 11 Jan 2021
Accepted: 22 Jul 2021
Published online: 19 Apr 2022 *