Pilot Project Study for Industrial Surplus Heat Transportation

Abstract: Primary energy use in Sweden today can to a large extent be traced to manufacturing industries. In parallel, improved energy efficiency is a goal set out by Swedish authorities and the EU. One way to improve efficiency in the industry is to harvest the excess energy in form of heat that is currently going to waste in the various processes. This thesis has investigated the feasibility of employing a mobile thermal energy storage (M-TES), developed at KTH, as a method of transporting excess heat from a steel plant in Sandviken to a local hotel and conference centre. The M-TES performance had previously been determined on a small scale prototype, and the effects on performance and cost of up-scaling the M-TES for real use was studied theoretically. An estimation of the cost for up scaling the M-TES from its current laboratory scale to the intended large scale was obtained. The study concludes that the construction cost can be affected mainly by two parameters: the number of tubes and tube diameter inside the M-TES. Changes to the performance parameters of the M-TES, caused by varying these parameters, were investigated using theoretical correlations. It was found that performance of the M-TES can drastically change with changes to the design parameters. The exact changes in construction costs were not obtained, however, a cost effective design uses as few tubes as possible, meaning the tube diameter has to be increased. Using the theoretically based performance values, an M-TES operation was mapped towards two scenarios; one scenario where a greenhouse is supplied with heat, with comparatively low heating demand to the other scenario, where the greenhouse and hotel are both supplied. In the hotel-scenario, the M-TES complements the boiler that is already in place and provides heat for the hotel today. It was found that increased heating demand and number of heat deliveries significantly improved the economic performance of the M-TES system. The levelized cost of transported energy (LCOTE) was used as parameter for measuring this performance and LCOTE:s of 470 and 1380 SEK per MWh were found in the high and low demand scenarios, respectively. A sensitivity analysis showed that the M-TES itself is among the most influential parameters on the LCOTE, while also being deemed as the most uncertain in terms of cost and performance. It is recommended for future work that the MTES is investigated extensively with regard to design choice, performance and costs.