Abstract
Global warming and energy security concerns have been causing increasing expectations to be posed on energy conservation . Although energy conservation after the oil shock has centered on the improvement of thermal insulation and development of new energy-conserving machines, the present age calls for the promotion of systematic energy conservation. About 65% of the total energy consumed in Japan being discarded while still unexploited, the construction of energy systems for rational utilization of unexploited energy is severely needed . Particularly in downtown urban areas, where non-industrial demand for heat has been growing dramatically, highefficiency utilization systems are increasingly needed for not only high-temperature waste heats from garbage incineration or electric power plants, but also low-temperature heat sources such as rivers, sewage, electric power substations and subways.In this article, the background for rational unexploited energy utilization is presented. Subsequently, representative system components such as heat pump and heat storage technologies are addressed and their main technological development requirements are clarified. Finally, the concept of cascaded energy utilization is presented as the ultimate energy-conservation system.
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