Renewable energies such as wind power or photovoltaic energy are getting attentions for view points of energy conservation and environmental issue. However, fluctuation of output power of renewable energies may cause excess variation of voltage or frequency of the grid. Increase of the amount of renewable energies would violate the quality of the grid. The micro grid in which dispersed energies compensate the variation from the renewable energies can expand the installation limit of the renewable energies by maintaining the quality of the interconnected grid. In this paper, evaluation of ratio of gas turbines, gas turbines and batteries is discussed from the point of power flow stability of the grid, efficiency and economy. Gas turbines have quicker response and lower efficiency, whereas gas engines have slower response and higher efficiency. Best ratio is discussed for higher efficiency while fluctuation of output power of the micro grid is kept in a small amount. Additionally, introducing batteries is discussed to introduce more gas engines he point of power flow stability of the grid, efficiency and economy.
The biomass energy production by intensive cultivation is expected in future. In this study, we assumed large-scale plantation in an arid land of Western Australia. We analyzed inventory about conversion processes to various fuels from produced wood. Our evaluation indexes are calorific yield as fuel (energy in produced fuel per one ton dry-wood), CO2 emission (CO2 emission from fuel production process per one ton dry-wood) and external energy consumption per one ton wood (primary energy basis). Calorific yield as fuel was also evaluated for the independent case where all input energy was assumed to be supplied from biomass itself or fuel from it. From the results on energy consumption and CO2 emission analyses with external energy input, transportation of wood or fuel was found to be negligibly small in case that the conversion process was located in Australia. But in case that conversion process was located in Japan, that was considerably high (15-40%). From the independent scenario (without energy input except that from biomass itself) analysis, in case of conversion process in Australia and transportation of produced fuel to Japan, 34% of the energy in the whole wood (at the maximum condition of 50% in the feedstock except felling loss) was at the maximum, expected to be recovered as energy in fuel for methanol production case. More than 30% (up to 55%) of the energy in the wood was exhausted in the conversion process. Energy based yield of fuel and CO2 emission were much more influenced by the difference of target fuel or conversion process than the conditions of location and transportation.