Model of a centrifugal-force-aided convective heat engine - An attempt to miniaturise solar updraft tower technology

This paper presents the idea of a centrifugal-force-aided convective heat engine where convective flow of a working fluid in a closed loop is used for the conversion of heat to mechanical energy. Centrifugal force is used for the conversion of a large pressure-head developed in a small volume of gas by heating into a large-volume bulk flow at much lower pressures. This flow is used to run a low-pressure turbine. Theoretical and numerical model calculations have been performed on an ideal system, without friction. The energy output per cycle and the efficiency of conversion have been calculated for different parameters. Considering linear heat flow at source and sink, efficiencies have been obtained that closely match the Curzon-Ahlborn efficiency, validating the model. Use of centrifugal force on the working fluid is seen to be a very effective way to increase efficiency and work done per cycle. The closed loop of the system allows suitable working fluid selection, thermal-linkage options and pressurisation, increasing efficiency and work done. This technique has the potential to reduce the complexity and cost substantially and simplify tolerance requirements. Coupled with a concentrating collector, this system can be used for sustainable conversion of energy through the CSP route. (C) 2019 Elsevier Ltd. All rights reserved.