Researchers from the University of Texas in the US have calculated that if solar panels were installed on available roof space in the greater Tokyo area, the region could generate up to 26.5% of the electricity it received from nuclear power before the Fukushima disaster.
"That's a sizable fraction of the base load that used to be generated by nuclear power," said lead author Brady Stoll. "The reason this is possible is because Japan is in the unique position of already possessing the largest capacity of pumped hydroelectric storage in the world."
Stoll and her colleagues estimated the suitable rooftop area in the greater Tokyo region to be around 300 km2. Such an array would have an installed capacity of 43.1 GWp. The researchers used this information, together with the reported availability of pumped hydroelectric storage for the region – 7.28 GW – and daily average surface solar irradiances from a 34 year database, to determine the level of base-load power that could be provided by the distributed photovoltaic system, as well as the overall amount of energy that could be expected per year.
The combined system was found capable of providing 4.8 GWe for 91% of the time. The team also estimated that a photovoltaic array of 1700 km2, coupled to 18.1 GW of storage capacity would be sufficient to replace the 2010 nuclear capacity of the Tokyo Electric Power Company.