A research group led by Japan’s Nagoya University has conducted a feasibility study of PV-powered temporary housing solutions tailored to Japan’s unique climatic and disaster-prone conditions.
“The novelty of this research lies in its application to Japan, a country highly susceptible to seismic disasters, where the potential for energy self-sufficiency in mobile homes has been relatively unexplored,” corresponding author, Sihwan Lee, told pv magazine. “By integrating PV panels with energy storage, the study demonstrates how renewable energy can enhance resilience in temporary housing solutions, reducing reliance on external power sources.”
The experimental set-up was based on a commercially available mobile home that includes a bedroom and living room with an integrated kitchen, bathroom, restroom, and lavatory. A single air conditioner located in the bedroom provides heating and cooling for the entire unit. Exhaust fans located in the living room, bathroom, and lavatory provided ventilation. On that unit, the team installed eight 300 W PV panels to achieve a total input of 2,400 W. A lithium-ion iron phosphate (LiFePO4) battery with a capacity of 3 kWh was installed inside the house.
The system was tested on January 19, 2024, in the Japanese city of Nagano. The maximum air temperature recorded on the measurement day was 7.4 C at 13:40, with an average temperature of 3.8 C throughout the recorded period. The global horizontal irradiation (GHI) peaked at 12:12, reaching a magnitude of 744.0 W/m2.
“On the day of measurement, the total electricity generated by the solar panels was approximately 4.2 kWh, whereas the air conditioner consumed approximately 8.3 kWh,” the research team said. “Although the power-generation efficiency varied with the surface temperature of the solar panels, the average power-generation efficiency during the day was approximately 16.0%, which was lower than the catalog-specified value of 19.3%.”
Image: Nagoya University, Sustainable Cities and Society, CC BY 4.0
Following that measurement, the unit was numerically simulated using different software. The group selected six cities to test and analyze the feasibility of operating mobile homes in other latitudes, longitudes, and weather conditions. Namely, they were Sapporo, Tokyo, Niigata, Nagano, and Takamatsu. In addition, the models were asked to optimize the PV installation angle, the total area of the panels, the battery capacity, and the total costs.
“Mobile homes equipped with eight commercially available photovoltaic panels can generate over 3,000 kWh of electricity annually in any region of Japan,” they found. “Mobile homes with eight solar panels and 3 kWh storage batteries demonstrated high self-sufficiency during cooling periods in regions with lower cooling loads. However, maintaining self-sufficiency during heating proved challenging in most areas, except Naha, due to significant heating loads during non-generating hours.”
In addition, the results showed that increasing the number of solar panels and storage battery capacity enhanced self-sufficiency rates to over 80% in non-cold regions. However, these improvements were limited in cold regions, even with additional solar panels and storage capacity.
“In colder regions with high heating demands, optimal solar panel angles ranged from 59◦ to 63◦, maximizing winter electricity generation. Conversely, warmer regions with lower heating demands required significantly lower angles,” they concluded. “Achieving off-grid electricity self-sufficiency necessitates region-specific optimization of panel angles and storage battery capacities based on local climatic and energy demand conditions.”
Their findings were presented in “Electricity self-sufficiency of off-grid mobile homes as temporary housing: A feasibility study in Japan,” published in Sustainable Cities and Society. The research was conducted by scientists from Japan’s Nagoya University and mobile home manufacture Cumberland Japan.
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