Defining “Waste Heat” for industrial processes

This paper aims at presenting a method for identifying, characterising and quantifying the available waste heat of an industrial system that can be converted into a useful form. A distinction is made between avoidable and unavoidable waste heat. This distinction is especially important when it comes to deciding on an investment for the integration of a waste heat valorisation process. In the proposed methodology, process integration techniques and exergy analysis are used to measure the useful potential of waste heat. It results in a definition of waste heat as a resource and a reserve in analogy to the definitions of natural resources and reserves. © 2013 Published by Elsevier Ltd. All rights reserved.

Defining the potential of usable waste heat in industrial processes with the help of pinch and exergy analysis

Matthias Bendig, Daniel Favrat, François Maréchal

This paper aims at giving a definition for waste heat in analogy to the definitions of natural resources and reserves. It aims also at presenting a method for identifying, characterizing and quantifying the available waste heat of an industrial system that can be converted into a useful form. A distinction is made between avoidable and unavoidable waste heat. In order to measure the entire useful potential of waste heat, exergy is used for characterization

Czech Society of Chemical Engineering and Italian Association of Chemical Engineering2012

Enthalpy and exergy analysis in the framework of a district scale energy balance

Cédric Lambiel

This report presents a study of an enthalpy and exergy analysis in the framework of a district scale energy balance. Energy demand (heating, cooling and lighting) for buildings represents more than 30 % of the total worlds energy use. Main eﬀorts have been made on increasing performances of new building envelop and on the use of low temperature processes in order to increase the exergy eﬃciency. On a district scale, diﬀerent temperature and energy ﬂow levels are present, meaning a great potential to make use of synergetic eﬀects by rationally managing energy ﬂow interactions between buildings as synergies by enhanced energy management and the usability of waste heat source. An optimisation of exergy ﬂows for the heating systems allows to identify the temperatures levels according to the energy demand, which helps to implement the best choice of available technologies. A number of connection cases will be described and studied to show the potential gain in terms of thermal and economical performances, where the thermal performances are deﬁned by both the energy and the exergy eﬃciency. This study shows an improvement of the thermal performances of connection cases where in all scenarios the heat losses are lower than the waste heat recovery. These gains on thermal performances may increase further by the integration of appropriate technologies such as heat pumps. The use of primary resource like gas can also be decreased.

2012

Integration of Organic Rankine Cycles for Waste Heat Recovery in Industrial Processes

Matthias Bendig

Developing a methodology that allows identifying maximumelectricity production with the help of Organic Rankine Cycles (ORC) from the waste heat of an industrial process, at the lowest specific cost, without jeopardising the increase of the industrial process’s thermal efficiency. Such is the goal of this thesis. In order to reach this goal, a software tool which is able to identify the most suitable cycle for a heat source regarding electricity production and cost efficiency is developed and explained in detail. Threemain areas of research can be identified, the definition of waste heat, the analysis of experimental data with the help of data reconciliation and the identification of a suitable working fluid and operation parameters of an ORC for any given heat source. A method for identifying, characterising and quantifying the available waste heat, which can be converted into a useful form, for any industrial system, is presented. A distinction is made between avoidable and unavoidable waste heat. Combined pinch analysis and exergy analysis is used to characterise the waste heat potential of a given process. Based on the study of two industrial processes, it will become clear how the constraints of a waste heat analysis influence the outcome and the potential for the integration of ORCs. The studies illustrate how the increase in energy efficiency and degree of heat recovery and integration of a process can be contradictory to the production of electricity with ORCs. The concept of data reconciliation is needed for the measurements, collected from two ORC demonstrators. Apart from "classical" data reconciliation, a new method is presented, which consists in including parameters as virtual measurements and time dependency of measurements. This increases the redundancy of the system and thus the overall accuracy of the reconciled values. A methodology, capable of choosing the designpoint, a suitable working fluid and a cycle configuration, for the lowest specific investment cost while at the same time maximising the electricity output, for a given process environment is developed. The new methodology uses a multi objective optimisation (master optimisation) andMixed Integer Linear Programming (MILP) problem (slave optimisation). A novel approach of combining multi objective nonlinear master optimisations with single objective linear slave optimisations is introduced, increasing the reliability of the algorithm.

EPFL2015

Integration of Organic Rankine Cycles for Waste Heat Recovery in Industrial Processes

Matthias Bendig

EPFL2015