Electricity generation from low temperature industrial excess heat – an opportunity for the steel industry

Awareness of climate change and the threat of rising energy prices have resulted in increased attention being paid to energy issues, and industry seeing a cost benefit in using more energyefficient production processes. One energy-efficient measure is the recovery of industrial excess heat. However, this option has not been fully investigated and some of the technologies for recovery of excess heat are not yet commercially available. This paper proposes three technologies for the generation of electricity from low temperature industrial excess heat. The technologies are thermoelectric generation, organic Rankine cycle and phase change material engine system. The technologies are evaluated in relation to each other, with regard to temperature range of the heat source, conversion efficiency, capacity and economy. Because the technologies use heat of different temperature ranges, there is potential for concurrent implementation of two or more of these technologies. Even if the conversion efficiency of a technology is low, it could be worthwhile to utilise if there is no other use for the excess heat. The iron and steel industry is energy intensive and its production processes are often conducted at high temperatures. As a consequence large amounts of excess heat are generated. The potential electricity production from low temperature excess heat at a steel plant was calculated together with the corresponding reduction in global CO2 emissions.