A new study from Japan develops a model for cities to maximize their use of rooftop PV electricity, using the batteries in electric vehicles to balance the grid. Applied to nine different Japanese cities (Kyoto, Hiroshima, Korimaya, Okayama, Sapporo, Sendai, Niigata, Kawasaki and the special districts of Tokyo), the model suggests that if properly implemented, such a system could bring about significant reductions to both pollution and energy costs.
In the model, researchers led by Japan’s National Institute for Environmental Studies assume that 70% of rooftop space in each city is available for PV installations, that all private vehicles in the city are converted to electric vehicles, and that half of the battery capacity of these vehicles is available to help balance the grid. Factors such as population density – and both rooftop space and vehicle ownership per capita, industries operating in each region and the local climate, led to variability in what this model could achieve, however it demonstrates benefits for all regions analyzed.
For the nine Japanese cities included in the study, the model could meet between 53% and 95% of total energy demand, reduce CO2 emissions (from vehicle use and electricity generation) between 54% and 95%, and cut costs by between 26% and 41%. The researchers suggest that given these disparities, the concept may be most applicable to cities in lower latitudes. Full details of the model are published in the paper SolarEV City concept: Building the next urban power and mobility systems, currently an accepted manuscript in the journal Environmental Research Letters.
The group noted that factors not included in the model could also lead to even higher overall cost savings – such as the potential for batteries to provide other ancillary services to the grid, and potentially lower maintenance costs for electric vehicles versus internal combustion engines.
The group states that the scenarios in its model should be realistic based on implementation by 2030, and calls on Japan’s government to implement supportive policies over the coming decade, including financial support for EV purchases along with support for vehicle to home and vehicle to grid schemes, tighter regulations on CO2 emissions, and changes to Japan’s current system of network fees for use of distribution lines.
“We demonstrated that coupling PV with EV in the SolarEV City concept could be a highly cost-effective strategy to decarbonize the urban energy and transport system,”. The idea can be a basis for the next urban systems for developed and developing countries alike, and should be further explored by policymakers, researchers, industries, and communities. That should also help to fulfill SDG 7, which is one of 17 Sustainable Development Goals established by the United Nations General Assembly in 2015. It aims to ensure access to affordable, reliable, sustainable and modern energy for all. Particularly, at the time of recovery from COVID-19, our society is in the right moment to get a start in this direction.
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