COST-EFFECTIVENESS OF A HEAT ENERGY DISTRIBUTION SYSTEM BASED ON MOBILE STORAGE UNITS : TWO CASE STUDIES

Today, the most common way to transport heat energy from the location where it is generated to the application where it is needed is by means of a heat transfer fluid (e.g. water, steam or oil) pumped through pipelines. However, with increasing distances to cover, the construction costs for such a pipeline system become considerable. For local heating networks, it has turned out that per meter pipeline, energy consumption should be higher than 1.5 MWh/a and the requested load higher than 1 kW for cost efficient operation [Krapf 2001]. Therefore, for medium scale applications on a range of several kilometres, pipeline-bound systems are economically not feasible. In these cases, energy transportation via mobile storage units moved by truck becomes an interesting alternative. To use waste heat from industry in order to supply energy in a remote location represents an especially promising field of application for this kind of systems. For the mobile storage unit itself, several technical concepts based on phase change materials have been proposed in the last decades [Lindner 1981, Schneider 2000] and in Germany, several players are currently trying to enter the market. Another promising mobile storage concept is based on the adsorption of water vapour on zeolite in open systems. The viability of the technology in a stationary application has already been proven [Hauer 2002]. In an ongoing research project, the technical and economical prospects for applying the principle to mobile storage units are being evaluated. First results from two case studies are presented in this paper. As potential waste heat sources, an aluminium processing factory and a waste incineration plant have been studied in detail. Several heating, drying and air conditioning applications have been considered as possible energy consumers, namely indoor and outdoor swimming pools, office air conditioning, and an industrial drying process. The aim of this work was to clarify the circumstances that allow the proposed distribution system to run profitably. Therefore, investment and running costs have been calculated for different combinations of waste heat source and user application as well as for varying operation conditions in order to calculate the effective costs per MWh for energy delivered within the proposed distribution system.