EXPERIMENTS AND EVALUATION OF LOW ENERGY HOUSE WITH SEASONAL THERMAL ENERGY STORAGE

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The purpose of this study is to evaluate the effectiveness of a low energy house, which is assisted by hybrid energy resources, unused energy and a thermal energy storage system, and a desirable energy system for urban areas. Some of the findings are briefly described in the following.1. The possibility of solar energy and wind power in snowy regions was evaluated. It was shown that the efficiency of a photovoltaic system in winter could be improved by utilizing high albedo of the surface of the snow. Next, experiments and analyses on hybrid solar collectors, which produce both electric power and heat, were examined. The hybrid collectors' efficiency was superior to photovoltaic cells and conventional solar collectors. We also carried out computer simulations on a combined system both photovoltaic cells and wind power generators. As a result, an indication of the existence of an optimal solution to achieve self-sufficiency in electric power was given.2. We have measured the earth tempe … More rature for about two years and prepared a calculation method of the temperature for snowy regions in order to make a fundamental data base for an underground thermal energy utilization system. Next, a new concept on evaluation of characteristics of annual energy storage was proposed. On the basis of long term experiments, it is possible to say that this system could be utilized over a long period.3. A low energy house was built in Hokkaido and annual experiments were examined. As a result of the operation, 80 % of its energy demand was supplied from natural energy resources and unused energy. 36 % of the total energy demand was from an underground thermal energy utilization system. Therefore, the effectiveness of the system was clarified. Annual purchased energy of this house was 12.5 % of energy consumption of a typical house in Hokkaido. Next, a calculation program for the low energy house was developed. From aspects of energy saving and environmental protection, the calculation results showed the possibility of self-sufficiency in other domestic regions.4. The effectiveness of desirable energy system for urban areas was evaluated. From analyses on a combined heat and power system, annual primary energy reduction rate was 10 to 30 %. Next, quantitative analyses were examined on the influence of natural free convection on heat recovery ratio of an aquifer for thermal energy storage. Through experiments, it was verified that the heat recovery ratio was very high from the viewpoint of long and short term energy cycles. In order to realize a successful high temperature aquifer thermal energy storage system, it is necessary to take account of the influence of natural free convection. Less