Carbon Dioxide Emissions and Energy Self-Sufficiency of Woody Biomass Utilization for Residential Heating: A Case Study of Nishiwaga, Japan

Renewable energy sources, including bioenergy, are presently attracting considerable attention as possible substitutes for fossil fuels. Among the various sources of bioenergy, biomass can arguably play a significant role in the reduction of greenhouse gases and the provision of a stable energy supply. However, the use of fossil fuels continues in the production of bioenergy. Consequently, the overall extent to which biomass utilization for energy can reduce carbon dioxide emissions as a substitute for fossil fuels and whether this can improve the energy self-sufficiency rate remains largely unknown. This study responds to these questions using a case of a Japanese rural community using firewood for residential heating. The results showed that woody biomass utilization for energy is able to both reduce the dependence on fossil fuels and mitigate climate change. These findings offer new insights into the development of sustainability in rural communities.

On-site solar PV generation and use: Self-consumption andself-sufficiency

As energy storage systems are typically not installed with residential solar photovoltaic (PV) systems,any “excess” solar energy exceeding the house load remains unharvested or is exported to the grid.This paper introduces an approach towards a system design for improved PV self-consumptionand self-sufficiency. As a result, a polyvalent heat pump, offering heating, cooling and domestic hotwater, is considered alongside water storage tanks and batteries. Our method of system analysisbegins with annual hourly thermal loads for heating and cooling a typical Australian house inGeelong, Victoria. These hourly heating and cooling loads are determined using Transient SystemSimulation (TRNSYS) software. The house’s annual hourly electricity consumption is analysed usingsmart meter data downloaded from the power supplier and PV generation data measured with aPV system controller. The results reveal that the proposed system could increase PV self-consumptionand self-sufficiency to 41.96% and 86.34%, respectively, resulting in the annual imported energybeing reduced by about 74%. The paper also provides sensitivity analyses for the hot and coldstorage tank sizes, the coefficient of performance of the heat pump, solar PV and battery sizes.After establishing the limits of thermal storage size, a significant impact on self-efficiency can berealised through battery storage. This study demonstrates the feasibility of using a polyvalent heatpump together with water storage tanks and, ultimately, batteries to increase PV self-consumptionand self-sufficiency. Future work will concentrate on determining a best-fit approach to systemsizing embedded within the TRNSYS simulation tool.