Study on Environment Friendly Urban Energy System

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This study aims at assessing various key measures for more benign urban energy systems. They are :1) cogeneration, , 2) photovoltaics and 3) heat cascading. The results of the study on these measures are summarized as follows.1.Among various measures which facilitate penetration of cogeneration into the urban energy market retail sales wheeling is very promising in the sense that it provides with flexible demand as buffer. Heat/electricity ratio of the cogeneration plant is a key parameter affecting the usefulness of the plant.2.While the advantage of photovoltaics located on the roofs of houses is the low cost in power distribution, its disadvantage comes mainly from changeability of its outputs. The economic analysis of PV indicates that more than a half of its value comes from its substitutability of conventional power plants, rather than from reduction in energy cost. According to our analysis PV's breakeven cost is of 1 order lower than it pressent cost ; it indicates that much efforts are indispensable for reduction in PV costs. Impacts of PV on LFC capacity of the power system are also evaluated in this study.3.Energy cascading is one of the effective measures for improving energy efficiency in a society. Cascading within energy intensive industries will save a few per cent of the total primary energy, but cascading together with residential and commercial sectors is more effective in the sense that low temperature waste heat from industries may be utilized in heat and hot water supply to these sectors.