Title: Methodology to evaluate the effect of cascaded use of heat on energy conservation

Authors: Atsushi Akisawa; Rikiya Ito; Takao Kashiwagi

Addresses: Department of Mechanical Systems Engineering, Tokyo University of Agriculture & Technology, 2–24–16 Nakacho, Koganei, Tokyo 184, Japan ' Department of Mechanical Systems Engineering, Tokyo University of Agriculture & Technology, 2–24–16 Nakacho, Koganei, Tokyo 184, Japan ' Department of Mechanical Systems Engineering, Tokyo University of Agriculture & Technology, 2–24–16 Nakacho, Koganei, Tokyo 184, Japan

Abstract: This study aims to develop a methodology to evaluate the effect of cascaded heat use quantitatively and apply it to Japan to estimate the possibility of energy conservation. It is essential for heat cascading to utilise discharged heat of high temperatures in those processes that demand lower temperatures. Heat input and output of industrial processes are specified in terms of temperatures of heat use and discharged heat, which are finally expressed as a matrix. To investigate the optimal configuration of primary energy input into each temperature segment, the authors formulate a heat cascading model based on linear programming, whose objective function represents total exergy of wasted heat, with primary inputs as control variables. Energy conservation is estimated by comparing actual energy consumption with the optimal one that results from the LP model. The estimation of energy saving by heat cascading is presented together with the formulation, which suggests that 30% of primary energy could be reduced in Japan.

Keywords: cascaded heat use; energy conservation; exergy; discharged heat utilisation; Japan; modelling; waste heat; energy consumption; heat cascading; linear programming.

DOI: 10.1504/IJGEI.1998.071444

International Journal of Global Energy Issues, 1998 Vol.11 No.1/2/3/4, pp.188 - 194

Published online: 27 Aug 2015 *

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