Analysing the use of waste factory heat through exergy analysis

When analysing the energy efficiency of a factory, it is useful to consider the whole system including both the manufacturing processes and the factory building. The latter is included due to its significant energy usage associated with production. The depletion of natural resources can be linked to the consumption of stocks of non-renewable exergy, and an analysis of this can be used to quantify the impact on natural resource consumption. This paper presents a case study into the use of waste heat from a factory building to supplement the heating system. An engine machining line within an automotive factory is analysed, using a simulation based approach in which the factory heating system is compared with and without heat reuse. The results quantify and compare the changes in efficiency and resource use based on both energy analysis and exergy analysis; effectively quantifying natural resource consumption due to changes in the manufacturing system.