Finite-time thermoeconomic optimization of a nonendoreversible heat engine

In 1995, Alexis De Vos introduced a thermoeconomical analysis of a Novikov plant model considering the power output per unit of running cost of the plant exploitation as an objective function. In his study he assumed that the running costs of the plant consist of two parts: a capital cost that is proportional to the investment and, therefore, to the size of the plant and a fuel cost that is proportional to the fuel consumption. De Vos showed how the optimal efficiency smoothly increases from the maximum-power point (Curzon-Ahlborn efficiency) corresponding to energy sources where the investment is the preponderant cost up to the Carnot value (Carnot efficiency), that is, for energy sources where the fuel is the predominant cost when the heat fluxes in the Novikov model are given by a linear Newtonian heat transfer law. Recently, Barranco-Jiménez and Angulo-Brown also studied a Novikov engine following the thermoeconomical approach used by De Vos, but by means of the so-called modified ecological optimization criterion. By means of the maximization of an objective function defined by the quotient of the characteristic functions (power output, ecological function) and the total costs considered in the performance of the power plant, we show that under maximum ecological conditions the wasted energy towards the environment is diminished in comparison to the wasted energy under maximum power conditions. In this work, we again study the termoeconomics of a non-endoreversible simplified thermal power plant model (the so-called Novikov engine). In our study, we use different heat transfer laws: The so called Newton's law of cooling, the Stefan-Boltzmann radiation's law, the Dulong-Petit's law of cooling and another linear phenomenological heat transfer law. We use two finite-time thermodynamics optimization criteria: the maximum power regime and the so-named modified ecological criterion for the performance analysis. This last criterion leads the engine model towards a mode of performance that appreciably diminishes the engine's wasted energy. It is shown that under ecological conditions the plant dramatically reduces the amount of heat rejected to the environment, and a loss of profits is translated in an usage of fuels that dramatically reduces the heat rejected towards the environment respect to that of a maximum power regime. Besides, we analyzed the effect on the reduction of power output in terms of an internal irreversibility parameter which characterizes the degree of internal irreversibility that comes from the Clausius'inequality.