City Research Online

Abstract

The integration of thermal-energy storage (TES) within waste-heat recovery power generation systems has the potential to improve energy-efficiency in many industrial processes with variable and/or intermittent waste-heat streams. The first objective of this paper is to present a novel model of these systems that can be used at an early design stage to provide fast and accurate estimates of performance. More specifically, the method can identify the optimal temperature of latent-heat TES systems for waste-heat recovery applications based only on the known heat-source and heat-sink conditions (i.e., temperature, mass-flow rate and specificheat capacity), and can assess both single-stage and cascaded systems. The model has been validated against optimal organic Rankine cycle systems identified from a thermodynamic cycle optimisation. The second objective is to identify the characteristics of optimal systems for different heat-source profiles. The results indicate that, for a given application, there exists an optimal temperature for the latent-heat TES system that depends primarily on the relative size of the heat sink. Moreover, it is found that, for a heat engine operating with TES, the power rating ranges between 25% and 60% of the corresponding power rating for an optimal heat engine, operating without TES, that adapts instantaneously to heat-source fluctuations, whilst the total energy production is reduced by between 45% and 85% respectively. Finally, a small deviation is observed between the results obtained for the different heat sources considered, which suggests that these findings can be extrapolated to other heat sources not considered within this study.

Publication Type:	Article
Additional Information:	© 2020 The Authors. Published by Elsevier Ltd. This is an open access article made available under a Creative Commons Attribution 4.0 Licence.
Publisher Keywords:	latent-heat thermal-energy storage; TES; waste-heat recovery; WHR; power generation; ORC
Subjects:	T Technology > TJ Mechanical engineering and machinery T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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