Managing decarbonization and contributing to communities through floating solar power generation

In its Roadmap to Carbon Neutrality in 2050, the company has set a long-term vision of becoming virtually carbon neutral, i.e., balancing greenhouse gas emissions and absorption, by 2030. Specifically, the company aims to (1) engage in renewable energy power generation projects to promote the sale of electricity, and (2) participate in projects that promote carbon neutrality initiatives by private-sector customers and local government. For the company, the business of selling electricity is also an opportunity to help companies manage decarbonization and to contribute to local communities.

To realize this vision, in 2022 the company established the Business Creation Division whose Renewable Energy Promotion Department has been setting the pace in commercialization of floating solar power generation.

The company is notable for its focus on exploiting reservoirs as sites for solar power plant. According to the “Technology White Paper on Renewable Energy” (2013) by Japan’s New Energy and Industrial Technology Development Organization (NEDO), potential solar power generation capacity that could be sited on lakes, dam reservoirs and the like is approximately 38 GW (gigawatts), exceeded only by potential capacity on cultivated land. However, noting that construction projects in Japan for solar power plant sited on water bodies were still relatively few in number, Sumitomo Mitsui Construction decided to exploit this untapped potential. Another strength of the company is its ability to develop business by leveraging the capabilities of its nationwide branch network.

Compared to plants on land, floating plants have several advantages in terms of environmental conservation, such as (1) no cut and fill construction; (2) no pile foundations or groundwork; and (3) no deforestation. Construction is straightforward and installation can be completed within as little as 6 months, from the start of construction to its completion. Furthermore, because the cooling effect of the water surface suppresses the temperature rise of the solar panels, power generation is more efficient than on land.

The plant in Izumisano City operates under a power purchase agreement (PPA), a business model that has been attracting attention in recent years. It is a type of long-term contract, typically 20 years or longer, under which electricity generated by the renewable electricity producer (Sumitomo Mitsui Construction) is purchased by the electricity consumer (Izumisano Power Company). It is called an off-site PPA because the power lines used to distribute electricity to customers do not belong to the electricity producer.

On the other hand, there is also an on-site PPA business model, in which case the electricity producer’s lines distribute electricity to customers. In February 2024, Sumitomo Mitsui Construction began operating a floating solar power generation system in a balancing reservoir within the site a company’s factory in Ozu Town, Kumamoto Prefecture.

With a view to promoting renewable energy, a government-initiated feed-in tariff (FIT) scheme has been available since 2012, but the purchase price has fallen and this scheme’s attractiveness as the basis for a power generation business has declined. Hence, Sumitomo Mitsui Construction has been shifting its business from FIT to power sales through PPA.

Most important is securing the understanding of local residents and building a consensus in the community. There is a widespread perception that solar power generation, which hitherto has been sited mostly on land, is detrimental to the environment. Therefore, Sumitomo Mitsui Construction thoroughly explains the advantages of floating solar power generation, not least its safety, in briefings for local residents.

For example, safety measures are implemented to cope with storms and torrential rain. To ensure the solar panels do not sink in the event of a typhoon or a downpour, the company has developed its proprietary PuKaTTo float filled with Styrofoam, as well as a robust mooring system to prevent the panels from being washed away. The mooring technology draws on expertise that the company has cultivated in the course of construction projects in littoral or riverine environments.

The company also monitors impacts on flora and fauna in accordance with the guidelines of the Ministry of the Environment and the Ministry of Agriculture, Forestry and Fisheries. Fixed-point cameras have been installed to not only continuously monitor the solar plant, but also to observe birds and other native fauna frequenting the sites. Environmental monitoring at the Meima Pond Floating Solar Power Generation Plant, Kagawa Prefecture, which started operation as a FIT project in 2020, has already confirmed that the natural environment has been maintained without adversely affecting flora and fauna.

Furthermore, the company has begun initiatives to install emergency power sources at power plants so that local residents can charge their smartphones, computers, and other devices in the event of a power outage due to a natural disaster. Such meticulous consideration is essential for gaining the understanding of the community.

Going forward, while maintaining the pace of technological development, the company intends to identify many sites suitable for floating solar power generation throughout Japan, including large dam reservoirs, windswept sites, remote islands, and offshore sites, as well as sites that are snowbound for much of the year. By exploiting the advantages of water-based solar power generation, Sumitomo Mitsui Construction aims to realize a safe, secure, and sustainable society with systems rooted in the community.