Scope #16

Mibugawa Electric Power,
Tsuruga Greenpower

The Domestic Power Business of Marubeni Group: Producing Sustainable Electricity, Rooted in the Local Community
Small Hydropower: “We use water taken from Nature, clean it, and return it to her.”

Mibugawa Power Company has eight hydropower plants in Nagano, a mountainous prefecture located northwest of Tokyo. The region, surrounded by the magnificent Japanese Alps, boasts picturesque landscapes and is among the top tourist destinations in Japan.

The mention of hydroelectricity often makes people think of damming up a river with a massive concrete structure, but all the eight power plants of Mibugawa are of small hydro type; they generate electricity utilizing the energy of falling water. The water is supplied either from an irrigation canal or a natural stream and it flows rapidly down a steep hill through a penstock into the water-turbine generator, which converts the motion into electrical energy. The used water goes back to its sources.


The geography of Japan is suitable for small hydropower; more than 70 percent of its islands are covered with mountains, and rivers run quickly through steep-sided valleys. Mibugawa Power Company has 17 small hydropower plants across the county and vigorously continues to develop new ones.

“We use water, but we do not consume it. We borrow water and then we return it,” says Takahiro Kaneko, head of the operations management office that monitors and controls all of the company’s power plants. The “borrowed” water becomes even cleaner by the time it is “returned” to an irrigation canal and a natural stream. Before entering a pipeline, the water is stilled in a reservoir allowing dirt and other sediments to settle. Leaves, twigs, and other debris are also removed by a trash filter. Farmers, who share the water, are happy that their canals are cleaner and sustain less damage.

Living in Harmony With Nature

Small hydropower requires a rich, dependable flow of water as well as a steep incline for the water to fall. When such a place is proposed, the project development team visits the candidate site to study its geographical features and water supply. To be safe and successful, since they are exploring nature, being prepared is of utmost importance. In fact, the team members often encounter bears or boars during their expedition, and they carry a bear bell and use a safety rope to descend cliffs.


During the rainy season and the typhoon season, operational managers need to take extra precautions. They shut down a power plant if its surrounding area is at risk of torrential rain, flooding or landslides. Experienced engineers have a thorough grasp of the landscape of each site. Based on the stream flow, they can estimate the amount of mud any excessive water will pour into the reservoir. It takes at least six years before one becomes a full-fledged engineer, Kaneko says. He keeps pushing his young subordinates to learn more about how nature works.

For Tomoya Matsuda, a young engineer who joined Mibugawa Power Company five years ago, regular inspection and maintenance of the plant is one of his important duties. He does this duty on a nearly daily basis during the two seasons when water contains extra debris. In early summer, all farmers start to mow weeds. In autumn, leaves and nuts continue to fall. The clogging of a trash filter will cause a water-turbine generator to stop, and this means a loss in electricity production. To prevent a shutdown, Matsuda needs to regularly check the power plants and remove heaps of debris disgorged by the trash cleaners. “I feel happy and fulfilled on a day when we manage to avert any production losses,” he says.

Building a Strong Bond With the Local Community

Tateshina Power plant 2 (output power: 141kilowatts), one of Mibugawa Power Company’s eight power plants in Nagano, has provided electricity to the local community since 2014. Its annual production is in proportion with the aggregate annual consumption of the local 250 households, many of whom are rice growers. The power plant takes water from their irrigation canal that stretches 10 kilometers across the area. The water flows into the generator unit through the penstock; the “head of water,” the vertical distance between the intake and the turbine, is 33.6 meters.

It goes without saying that the company needs the support of local farmers when it comes to developing a new power plant within their agricultural water-supply system. Until all farmers in the area are convinced that the impact on the environment will be minimal, the development team will continue to explain that a small hydropower plant only requires a compact facility.


Reinforcing relationships with the local communities is extremely important. Once trust is built, they become eager to support the company on various fronts. For example, farmers provide valuable input on the water conditions or potential sites for new development. Likewise, the company supports the local communities; it sponsors their festivals and traditional performing-arts events.

“Small hydropower plants can continue to operate for more than 100 years, so our relationships with people in the local communities will last for generations to come –their grandchildren, great-grandchildren and beyond,” says Wataru Ikushima, president of Mibugawa Power Company and general manager of Marubeni’s domestic power business department. Whenever he has a chance to meet people in the local community, Ikushima emphasizes the company’s long-term commitments and the value of long-lasting relationships.

Bringing International Expertise to the Japanese Market

Japan relies heavily on imported fossil fuels to meet its energy demands; its self-sufficiency rate remains low at 6 percent. Nonetheless, electricity production from renewable energy sources has not sufficiently prevailed because of its high costs. Excluding large-scale hydropower, it accounts for just 3.2 percent of the nation’s total electricity production. In 2012, the government introduced a feed-in tariff to promote renewable energy. Under this scheme, electric utility companies offer producers fixed prices based on fixed-term contracts to purchase electricity generated from renewable energy sources. Their purchasing costs are covered by the surcharge that all consumers, including private households, pay.

All nuclear reactors in Japan were shut down in 2011 in the aftermath of the massive earthquake and tsunami, which devastated the eastern region of Japan. This resulted in a nationwide electricity crisis and underscored the need to accelerate investments in the development of alternative energy sources.

In response to these events, Marubeni boosted its domestic power business by speeding up projects to create power plants: small hydro, solar, wind, and biomass. Out of all of the power plants the company currently owns, 43 percent uses renewable energy sources to generate electricity (as of October 2017).

With the acquisition of Mibugawa Power Company in 2000, the Power Business Division of Marubeni entered the domestic arena. Its extensive know-how based on many years of experience in the power business around the globe helped the company quickly expand its business in Japan, which includes power plant development and retail sales. The retail business was then transferred to its wholly-owned subsidiary, Marubeni Power Retail, which was established in 2015. Now, Marubeni is applying itself to cutting-edge technologies to increase efficiency in various aspects of its power business. Demand forecasting by artificial intelligence is one of the most recent projects.

“We do all sorts of things, and this is exactly the strength of Marubeni Group. We can get more input, come up with new ideas, and find new partners, by doing many different things,” Ikushima says.

How Voices of the Local Community are Incorporated in the Plant Management

In July 2017, Marubeni commenced commercial operation of a biomass power plant owned by its subsidiary company, Tsuruga Green Power, which is based in Tsuruga, a city in the southwest of Fukui. In biomass power, electricity is generated by burning fuels derived from organic materials such as wood or animal waste. Tsuruga Green Power uses primarily woodchips and has a total capacity of 37 megawatts, equivalent to the annual aggregate consumption of electricity by 70,000 households.


Steam that comes from a boiler burning woodchips spins a turbine, which generates electricity. Carbon dioxide (CO2) is emitted during this process, but biomass power is considered carbon neutral because plants absorb CO2 as they grow through photosynthesis. By the same token, biomass power offsets methane emissions. One of the main sources of woodchips is forest thinning. It is believed that if the thinned trees are abandoned and unutilized, they will contribute to global warming because they emit methane as they decompose.


Tsuruga Green Power is situated near the city center, surrounded by retail stores, condominiums, and schools. When the construction project was initially announced, some residents in the local community expressed their concerns over noise and air pollution. Others worried that if the plant took up a large volume of groundwater, which they use for daily living, water would be scarce.

“Since the design phase of our plant, we have incorporated voices of people in the local community as much as possible. We are trying to be mindful of their needs,” says Shuki Sakaguchi, general manager of the plant. The height of the stack is 80 meters while in fact only 50 meters was sufficient in terms of air-pollution control. The boiler is enclosed with sound-blocking panels. The cooling system utilizes industrial wastewater, so groundwater does not need to be pumped up. The plant is also committed to minimizing the impact of its fuel transportation on people’s daily lives. Transport trucks go back and forth between the plant and the port where woodchips are being stockpiled, however during the hours that children walk to and from school, the number of trucks on the road is reduced.

Creating Synergy in Fuel Procurement

The key to maintaining the stable operation of a biomass power plant is its owner’s ability to procure fuels. At Tsuruga Green Power’s plant, 280,000 tons of woodchips per year are needed to produce electricity, and they are imported from overseas by Marubeni’s Forest Products Division. “It’s our strength as a sogo shosha (general trading company) that create this synergy,” says Shota Anzai, a young member of Marubeni’s domestic power business department. He joined the company only four years ago, but he has been engaged in this biomass business since the project was launched. He is currently based in Tsuruga dealing with all aspects of the plant management. “I feel a strong sense of pride that our plant is part of the infrastructure that helps ensure the quality of life of people,” Anzai says.

Being at the Forefront

Marubeni strives to develop next-generation technologies of renewable energy.
The most promising among them is offshore wind power. Compared with wind farms on land, offshore wind farms can produce electricity more efficiently. First, wind conditions are more stable. Second, large turbines can be installed because they are less obtrusive when placed in the ocean. While offshore wind power has not been commercially developed in Japan, Marubeni operates two farms in Europe. The company also has some ongoing projects in Japan including an empirical study. “Being armed with these achievements and knowledge, we aim to be the top player in Japan,” Ikushima says.

It is crucial to pursue sustainability while ensuring the supply of electricity for the society. In its quest to fulfill this social responsibility, Marubeni continues to venture into new businesses as the leader of the power industry, leveraging its very strength: filling many different crucial roles.

* Electricity generated by Mibugawa Power Company and Tsuruga Green Power is delivered to consumers by Marubeni Power Retail.

#15
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Scope Index #17
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