A Solar Powered Tokyo?

Much of Tokyo’s power needs once supplied by nuclear power could be met by rooftop solar along with energy storage systems already in place.

Nuclear is still a dirty word to many in Japan following the Fukushima crisis, a disaster that will continue to negatively affect a large area for many years to come.

While solar power offers an attractive alternative; the issue remains of continual supply – particularly at night and during heavily overcast days.

A recent study examining the potential for rooftop solar panels in Tokyo to replace nuclear capacity reveals some of the answer is already in place – pumped hydroelectric storage.

“Japan is in the unique position of already possessing the largest capacity of pumped hydroelectric storage in the world, a total of 24.6 GW… and it has been used largely as a way of storing excess nuclear power for use during peak demand. TEPCO itself owns 7.28 GW,” states the study.

TEPCO is the Tokyo Electric Power Co., Ltd.; the largest electric utility in Japan and the 4th largest electric utility in the world. TEPCO has 17,308 MW of nuclear capacity in its portfolio, including the power plant at Fukushima Daiichi.

The authors say if the storage owned by TEPCO were instead coupled to current generation rooftop solar system potential in Tokyo, this could help meet the city’s peak requirements and provide over a quarter of the electricity Tokyo used to source from nuclear power – and for the vast majority of the time.

Analyzing the available rooftop area in the Kanto region of Japan, the authors estimate that a total area of 297.5 km2 is currently available for solar power systems.

“When coupled to the 7.28 GW of pumped hydroelectric storage owned by TEPCO, the combined system was found capable of providing 4.8 GWe 91% of the time. It was also estimated that a photovoltaic array of 1700 km2, coupled to 18.1 GW of storage capacity would be sufficient to replace TEPCO’s 2010 nuclear capacity.”

The full text of the study can be viewed here.