Extending building simulation software to include the organic Rankine cycle for factory waste heat recovery

Panel: 4. Technology, products and systems

This is a peer-reviewed paper.

Authors:
Richard Greenough, Institute of Energy and Sustainable Development, United Kingdom
Ivan Korolija, Institute of Energy and Sustainable Development, De Montfort University, United Kingdom
Michael Oates, Integrated Environmental Solutions Limited., United Kingdom

Abstract

Generators based on the organic Rankine cycle (ORC) are used in some industries to generate electricity from waste heat. The supply of heat is rarely constant since it is linked to the operation of processes whose energy use is determined by the manufacturing schedule. The performance of the ORC depends on many factors including the working fluid, the choice of condenser type and whether or not to use a recuperator. The performance of the condenser is influenced by the climate and therefore the location of the factory.

This paper describes an extension of the functions of a commercial building energy modelling software IES to include ORC simulation. Some of the features of IES such as the modelling of energy profiles, the ability to input weather data and the modelling of typical energy system components make it well suited to this task.

The model of a typical ORC system includes the evaporator heat exchanger with its thermal oil pump, the condenser with its pumps and fans and the option of a recuperator, as well as the ORC device itself. As well as selecting the configuration of the ORC system, the software user is able to choose from a wide range of working fluids. The auxiliary energy used by the pumps and fans is modelled since this can significantly offset the electricity generated by the ORC and therefore impact the cost benefits. The user may select an air-cooled or water-cooled condenser, and the psychrometric behaviour of the cooling tower is modelled so that the impact of location on annual performance can be analysed. The use of the software is illustrated by its application to the waste heat from an iron foundry, which is typical of industries with significant waste heat.