Abstract
A photovoltaic/wind/diesel generating system with a battery (PWD system) is discussed from a view point of total CO2 gas emissions during life time. The total Emissions is the sum of the emissions occurring at manufacturing and operating. First, the manufacturing CO2 emissions of the photovoltaic generator and the wind turbine generator are calculated by “the process analysis method”. The method considers the material used in each generator, its weight and its CO2 emissions rate. On the other hand, the manufacturing CO2 emissions of the diesel generator and the battery are calculated using “the interindustry (input-output) table”. Secondary, the PWD system is operated on a computer so that the fuel consumption of the diesel generator is minimum assuming that hourly series data of electric load, insolation intensity, wind speed and air temperature are known during a year. And CO2 emissions occurring at the system operation is obtained from the annual fuel consumption of the diesel generator.
The result show that the CO2 total emissions of the PWD system is lower than that of the conventional diesel generator system. The CO2 total emissions has a minimum when photovoltaic/wind generating ratio is at 50/50. The CO2 emissions of manufacturing decreases with increasing of the wind generating ratio from 100/0 to 0/100. The CO2 total emissions decreases as the natural energy ratio increases. It is, however, saturated to about 60% when the ratio is more than 60%. And the CO2 total emissions increases with increasing of the battery capacity. It is concluded that the PWD system plays an important role in decreasing considerably the CO2 total emissions while the total system cost is high under the present price circumstances.
