Feasibility of 100% renewable energy system in residential area and a multi-dwelling building with photovoltaic and electric vehicle

The utilization of "100% renewable energy" has recently attracted considerable interest in view of the objective of achieving a low-carbon society. An approach that seems effective to realize this goal is the purchase of renewable electricity from the power grid. However, the amount of renewable electricity that the power grid can supply at various seasons and periods is limited. In view of this, it is necessary to consider the use of energy systems that can exploit renewable energy, such as the installation of photovoltaics in households. The purpose of this study is to investigate the feasibility of 100% renewable energy systems in residential areas and multi-dwelling buildings. The area and building examined are limited to a set of "all-electric houses" with electric vehicles, photovoltaics, and heat pump water heaters. In each case, the electricity self-sufficiency ratio and electricity self-consumption ratio resulting from the use of photovoltaics are derived. In this study, an operation that minimizes CO2 emissions during the evaluation period is developed. It is found that the use of 100% renewable energy in residential areas without relying on the renewable electricity from the power grid is possible as demonstrated by the high feasibility of using 100% renewable energy in rural areas. In multidwelling buildings, this feasibility is lower than that in residential areas. To achieve the utilization of 100% renewable energy using the renewable electricity from the power grid, the grid should increase its supply of renewable electricity at dawn and in the evening. In winter, the renewable electricity from the photovoltaic power alone is insufficient; hence, the power grid requires other renewable electricity sources, such as windgenerated power. To improve the electricity self-sufficiency ratio of multi-dwelling buildings, the use of an energy system that allows electricity sharing from the residential areas to multi-dwelling buildings is found effective.