By 2030, renewable sources are expected to provide more than a third of the electricity used in countries such as Japan. Yet the variability of solar and wind power poses a number of challenges — such as a mismatch in supply and demand in the evening when people return home and begin to use appliances, but the power generated from solar panels also begins to decline.

One way to ensure that the grid can meet demand is to store the electricity generated during sunlight hours in batteries, using these to feed electricity back into the grid when production is low. But industrial-scale batteries are expensive and resource intensive.

Researchers at Japan’s largest utility provider, Tokyo Electric Power Company Holdings, Incorporated (TEPCO), see promise in a largely untapped battery resource — electric vehicles (EVs).

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Bidirectional charging

EVs could serve as ‘distributed energy resources’ (DERs) — small electricity storage systems owned by consumers that store excess energy to feed back to homes or the grid when needed. And — as is already happening in many parts of the world with household solar panels — utility companies could provide incentives to consumers contributing to the grid, says Kenichi Saruta, a manager at TEPCO.

Saruta says that up until now EVs have been largely disregarded for use as DERs, due to low EV uptake and challenges in predicting when drivers might charge their vehicles. But, as EVs have grown in number, “they now hold immense potential,” he says.

TEPCO estimates that by 2050, DERs could supply more than twice the power needed in the Tokyo metropolitan area, and store up to four times more energy than exists in Tokyo’s current backup systems.

Key to this vision are new bidirectional charging devices that attach to EVs, which help provide energy to the vehicles and can also feed energy from EVs back to homes or the grid.

TEPCO has developed a bidirectional charging device with electrical equipment manufacturer Diamond & Zebra Electric Mfg. Co., Ltd., based in Osaka, Japan.

TEPCO’s devices uses artificial intelligence (AI) to optimize the timing of charging or release of power based on factors including time of day and year, weather forecasts and the prediction of fluctuations in demand.

In addition to future incentives to feed power back into the grid, consumers can expect lower annual electricity costs as batteries in their homes and cars provide power when electricity prices are high. These batteries could also serve as a backup power source during extended outages caused by natural disasters, such as earthquakes and typhoons.

Catalysing EV adoption

Crucially, the new bidirectional charging device is designed to meet Japanese charging standards, also known as the ‘charge de move’ (CHAdeMO) standards. These were developed by an association formed by TEPCO and five major Japanese car manufacturers a decade ago, and were the first international standards for fast charging.

Saruta also emphasizes that standardized fast-charging is crucial to increasing the number of EVs in the market.

“Fast charging is key to making EVs more convenient and appealing,” he explains. For example, in a Nissan Leaf — one of the most popular EV models in Japan — a CHAdeMO connector charges the battery to 80% full in 40 minutes, while a regular charger could take up to eight hours to reach the same level.

CHAdeMO are also one of the few international standards for bidirectional charging and TEPCO is using their experience in developing these standards to help guide the creation of new, stabilized power supply systems that harness bidirectional charging devices. An important goal, for example, is to implement innovative pricing methods that help to balance the grid more efficiently, says Saruta.

Building on these advances is one of the reasons that TEPCO has led efforts to facilitate the adoption of CHAdeMO globally since the standards were developed, says Saruta.

The implications for these advances are wide reaching, with pilot studies currently underway using the bidirectional charger systems in areas of the United States operated by the Hawaiian Electric Company in Honolulu and the Sacramento Municipal Utility District in Sacramento.