Revolution of Urban Energy System

Fragility of energy supply structure in Japan was exposed with Great East Japan Earthquake as a turning point. Then it is required to reduce consumption of fossil fuel and utilize renewable and unused energy for securing the safety of society. Also shift of energy supply from centralized system to decentralized one for improving efficiency of system. There are many kinds of unused energy such as river/sea water and waste heat in city. However, it is difficult to use these energy by individual buildings. Therefore area energy system and energy network play an important role. Also networking of energy system functions as a mutual help system in the city at an emergency. Under this background in this paper energy interchange in urban central district and utilization of waste heat from heating/cooling of building are discussed with the results of studies on these topics.