Abstract

The development of improved means of thermal storage is an aspect of energy conservation which has lagged other advances in this field. The intent of the present work is to address this need. To that end, concrete building materials were selected as ideal candidates for improvement in respect to their thermal storage capability. This was achieved by the incorporation of organic phase change materials (PCM's) in the concrete. These PCM's absorb or release the latent heat of fusion at a selected temperature and thereby greatly enhance the heat storage capacity of the impregnated concrete over a small temperature range. Modification of the concretes were performed to enhance their compatibility with the PCM's. Four types of aggregate were studied, three of which also found to be suitable for pre-impregnation. The energy storing concretes developed in this research have a very wide range of use in the storage of waste heat, heat from solar collectors of off-peak, low cost heat. In addition, they can also be used to improve the performance of burners and chillers through reduction of operating frequency by thermal storage. Their application is cost effective in areas with an appropriate diurnal temperature swing and, as fuel costs rise, they may be applied in colder regions as well. Original aspects of energy storage developed in this work comprise: (i) new concrete modules with organic PCM's including fatty esters, fatty alcohols and C22-C24 paraffins; (ii) the application of lightweight aggregates such as pumice, expanded shale and expanded slag as PCM carriers for direct incorporation in concrete; (iii) various techniques for direct incorporation of PCM's without carriers; (iv) the use of pozzolans to modify concrete to permit use of alkali sensitive PCM's; (v) development of theoretical considerations of PCM diffusion in concrete and the determination of absorption characteristics; (vi) development of technique for defining absorption constants; (vii) the use of PCM's as protective substances in concrete; (viii) development of means to use walls, floors and ceilings for enhanced thermal storage.