Since the Great East Japan Earthquake, although it has been required to introduce renewable energy and save energy in houses, the supply and demand of electric power remains an important issue. This study’s purpose is to verify the effectiveness of combined power generation using photovoltaic power generation (PV) and solid oxide fuel cells (SOFCs) by lifestyle. We created a simulation model for a household distributed energy system with PV, SOFC, and a storage battery (BT). Focusing on understanding the impact of different lifestyles on energy consumption and the equipment capacity and power generation method to achieve a zero energy house (ZEH), we evaluated the equipment introduction effect and economic efficiency in multiple life patterns.
The following observations are reported in this article:
1) With regard to the energy evaluation, in single power generation, which uses only PV power generation, as the amount of PV power generation increased, the amount of sales energy increased, and the amount of purchased energy decreased. On the other hand, in combined power generation, which uses PV and SOFC, the amount of sales energy increased, however, there was no amount of purchased energy. The self-consumption decreased with the increase in PV capacity in single power generation and combined power generation.
2) With regard to the evaluation of primary energy reduction rate and ZEH achievement ratio, the average primary energy reduction rate was 17% for single power generation, 37% for combined power generation (selling only PV surplus power), and 56% for combined power generation (selling surplus power of PV and SOFC). By selling surplus power from the PV and SOFC, the primary energy reduction rate increased by 19% on average. In addition, the ZEH achievement ratio increased as the amount of PV power generation increased in single power generation and combined power generation.
3) With regard to the economic evaluation, the annual cost was evaluated in terms of the combination of equipment capacity by lifestyle. When selling only the PV surplus power, combined power generation reduced the annual cost by an approximately JPY 21,000 under two-person household condition and an approximately JPY 84,000 under four-person household condition compared to single power generation. When selling surplus power of PV and SOFC, combined power generation reduced the annual cost of approximately JPY 118,000 compared to single power generation.
In this study, when introducing single power generation and combined power generation, we propose appropriate equipment capacity according to each power method by lifestyle and evaluated the economic efficiency. The results confirmed that combined power generation has a higher primary energy reduction rate and ZEH achievement ratio than single power generation. Moreover, the annual cost of combined power generation was less than that of single power generation. However, in this study, we fixed the BT capacity at 7.2kWh, and there were restrictions on the capacity and price of PV and SOFC, and the power price of selling and purchasing with the grid. The evaluation of equipment combination considering the BT capacity and power generation mode of SOFCs is a future task.