Shikaoi-cho in Hokkaido, which promotes itself as “Shikaoi, an eco-friendly town”, is actively pursuing local energy production and consumption. In addition to its existing biogas plant, the town planned a solar power plant utilizing idle land, but faced the challenge of securing sufficient demand for the renewable electricity generated. Pacific Consultants proposed a new thermal and electrical energy system, including the construction of a private transmission line network, and supported the maximum deployment and utilization of renewable energy. We spoke with Hiroomi Ono of the GX Promotion Dept., Social Innovation Div. and Daiki Yamashita of the Energy Business Development Support Sec., who spearheaded the project.
INDEX
- Challenges that had to be overcome to expand renewable energy adoption
- Planning to supply electricity to public facilities through a private transmission line network
- Storing surplus electricity as heat for effective use
- Controlling the entire system with an energy management system
- Operation of the private transmission line network increases revenue by approximately 10 million yen per year
- Recipient of the Grand Prize in the Ministry of Economy, Trade and Industry's Northern Region Energy-Saving and New Energy Award
Challenges that had to be overcome to expand renewable energy adoption
Shikaoi-cho is located almost in the center of Hokkaido.
Shikaoi-cho is located in the northwestern part of the Tokachi Plain, at the southern foot of Daisetsuzan National Park in central Hokkaido. It is a small town with a population of about 5,000 people and 2,200 households, but building on its thriving dairy farming industry, the town is promoting biomass-based regional circular community development that is environmentally friendly and beneficial to local communities and residents, including power generation using livestock manure and food waste. Two biogas plants are already in operation. In order to further promote the use of renewable energy, the town considered constructing a solar power plant on a vast area of idle land owned by the town and located adjacent to the town hall. The town had been struggling to find an effective use for the land, which was formerly a cemetery, but developing the site as a solar power plant would further advance local energy production and consumption and would be a fitting initiative for "Shikaoi, an eco-friendly town".
However, the town encountered a major challenge. Due to the large size of the site, the planned solar power plant would be large-scale, significantly increasing the supply of renewable electricity in addition to that generated by the existing biogas plants. It was therefore necessary to secure sufficient demand for this additional power supply.
Generating electricity from renewable energy sources is not simply a matter of producing more power. Even with battery storage, there are limits, making it necessary to secure sufficient demand that matches the amount of electricity generated. While there is the option of feeding the electricity into the existing grid and selling it, Shikaoi-cho is already using the FIT (Feed-in tariff) to sell surplus electricity generated by its biogas plants. Further renewable electricity could not be fed into the existing grid. Under these constraints, the question was how to secure new uses for electricity generated by the planned solar power plant. Without a solution, the solar power plant could not be built, even though suitable land was available. Solving this problem was a major theme for future regional circular community development.
Planning to supply electricity to public facilities through a private transmission line network
"How to develop new uses for the electricity?" — Pacific Consultants joined the discussion on this matter. That was in 2016. Ono, who led the discussion, recalls:
"Solar power generation on unused land can generate a considerable amount of electricity because the site is so large. However, no additional electricity can be fed into the existing grid. Therefore, our proposal was based on the construction of a microgrid that would create a private transmission line network and supply electricity to many public facilities."
Yamashita, who was in charge of the basic plan for the microgrid in Mutsuzawa Town, Chiba Prefecture, joined the discussions and helped develop the concept further.
"This is common in small municipalities in Hokkaido, but in Shikaoi-cho, various public facilities are located close together in the same area, making it easier to build a network," said Yamashita.
"We decided to create a substantial demand base by networking nine facilities, including the town hall, the national health insurance hospital, the community hall, the elementary school, the Trim Center (a health and welfare service hub), and the heated swimming pool, using 44 privately owned poles with a total distance of approximately 3 km, and supplying a maximum of approximately 440 kW of electricity from solar power generation. We also planned to install a 270 kWh battery storage system to accommodate surplus power generation and provide backup during power outages caused by disasters. However, if power generation is at full capacity, there will still be excess power even after storing it in the battery storage system. We considered reducing the scale of solar power plant, but since this idle land was originally a cemetery, it seemed difficult to utilize even if some of it remained. Another option was to further increase battery storage capacity, but batteries are expensive, and in a cold region like Shikaoi-cho, where winter temperatures can drop to minus 20°C, specially designed, high-priced products are required, and increasing the number of units would result in significantly higher electricity costs. This is also not realistic. While maintaining the basic policy of generating the maximum amount of power and utilizing it to the fullest extent, we continued exploring additional opportunities to utilize the electricity."
It was Ono who found a promising answer to this problem. Ono is an expert in architecture and thermal energy systems, and has previously worked on a number of unique local energy production and consumption projects across Japan. He is an engineer whose motto is, "I never say it can't be done."
Storing surplus electricity as heat for effective use
Overall system diagram for maximizing renewable energy deployment and utilization,
Comprising a private transmission line network and electricity and heat utilization systems
Source: "Shikaoi private transmission line network" (Shikaoi-cho, Hokkaido)
Details of the electricity and heat utilization system (using two heat pumps,
Using surplus electricity to power a geothermal heat pump,
(Used to heat the hot water in the heat storage layer)
Source: Renewable energy utilizing private transmission line network etc.
Maximum introduction and utilization project” March 19, 2021 (Shikaoi-cho)
Ono's idea was to "store excess electricity by converting it into heat."
"At the Trim Center, which has a heated swimming pool and bathing facilities, we previously supplied hot water using a fossil fuel boiler, but we decided to replace this with a heat pump system that utilises ground-source heat. Two heat pumps are connected in series; one efficiently uses ground-source heat to produce low- temperature hot water, and the second heat pump uses that hot water as a heat source to raise the temperature to around 70°C and supply it to the facilities. This forms the "electricity and heat utilization system." When the amount of electricity generated by solar power exceeds demand, it is first stored in the battery storage system, but if there is still a surplus, the temperature setting of the water in the heat storage tank is raised from the usual 30°C to 40°C, and the second ground-source heat pump is activated. In other words, the surplus electricity is used to raise the temperature of the water, and the heat equivalent to an additional 10°C is stored. If 40°C water is used as the heat source, the first heat pump can produce 70°C hot water with less energy, making the system more efficient and providing an additional benefit."
The idea of a two-stage heat pump system incorporating a hot-water thermal storage tank was unusual in Japan. While the concept of two-stage heating itself is not new, the system that integrates it into a private transmission line network and uses surplus electricity generated by solar power to heat the thermal storage tank originated from Ono's proposal.
Controlling the entire system with an energy management system
By incorporating Ono's ideas, the basic framework of a renewable energy-based private transmission line network system was established. However, meticulous control is essential for actual operation. While the system efficiently uses electricity supplied by solar power generation, it is not intended to meet the electricity demands of all nine facilities connected through the private transmission line network. Doing so would require a significant increase in renewable energy generation and a greater number of storage batteries, which is not realistic. Even if it were realized, electricity costs would rise dramatically. It is more realistic to continue receiving electricity from the grid while integrating renewable electricity into the overall power supply. This requires careful management to determine how to distribute the electricity more efficiently and economically, and for solar power generation, it is necessary to predict how the amount of electricity generated will change throughout the day. Based on this, meticulous management is essential to determine how to distribute the electricity to the facilities that use it, store any surplus in storage batteries, and, if excess power still remains, the temperature setting of the thermal storage tank must be increased and the ground-source heat pump activated. Such detailed energy management is essential to the system's operation.
The system had to consider a vast number of parameters, and the construction of a Community Energy Management System (CEMS) to manage them using appropriate algorithms was a prerequisite for its operation. Without it, the proposed electricity and heat utilization system would never become a practical reality. In this regard, Yamashita developed and proposed the basic algorithm, on which the design and construction companies based their system development.
Operation of the private transmission line network increases revenue by approximately 10 million yen per year
In April 2021, five years after the project was conceived, the Shikaoi private transmission line network began operation. The system is running smoothly and is showing economic benefits. First, the basic electricity charges have decreased significantly. Previously, the nine facilities had individual contracts with the power company, but with the establishment of the private transmission line network, these were consolidated into a single demand. As a result, the total contracted power of the nine facilities, previously 759kW, was consolidated into a single contract of 450kW (FY2021 results), resulting in an annual reduction of approximately 7 million yen in basic charges alone. In addition, the reduction in electricity purchases due to solar power generation amounted to 15 million yen, and the reduction in heavy oil purchases for boilers amounted to approximately 4.7 million yen, resulting in a total annual financial benefit of 26.35 million yen. Expenses, including maintenance costs, electricity consumption for the electric heat pump, and additional costs for the Chief Electrical Engineer hired for system management, totaled approximately 15.86 million yen, resulting in a net annual financial benefit of approximately 10.48 million yen. Excluding subsidies from the Ministry of the Environment, the investment amounted to 113.5 million yen, which is expected to be recouped in approximately 10.8 years. Currently, Pacific Consultants continues to support the project, aiming for even more efficient operation by promoting ZEB (Net Zero Energy Building) conversion at the facilities connected through the private transmission line network. *.
Recipient of the Grand Prize in the Ministry of Economy, Trade and Industry's Northern Region Energy-Saving and New Energy Award
The private transmission line network project in Shikaoi-cho received the Grand Prize in the FY2021 Northern Region Energy-Saving and New Energy Award, organized by the Hokkaido Bureau of Economy, Trade and Industry of the Ministry of Economy, Trade and Industry, in recognition of its excellence as a self-sufficient regional energy system that produces and consumes energy locally. (Lead Partner: Shikaoi-cho; Partners: Pacific Consultants Co., Ltd., Ars Zeta Limited Company, and Itogumi Construction Co., Ltd.) The project also received the Chairman's Award of the New Energy Foundation at the FY2024 New Energy Grand Award (awarded by the New Energy Foundation) and the Solar Week 2023 Special Award from the Japan Photovoltaic Energy Association.
Looking back on the project, Ono recalled:
"There were no particularly new technologies involved. However, in terms of how to combine and utilize those technologies to solve challenges, we were able to devise and implement something unprecedented in Japan. I think that taking on challenges that no one else has attempted and creating something that does not yet exist is something unique to Pacific Consultants."
Yamashita, who played a leading role in the project through the construction of the private transmission line network and the development of the basic plan for the EMS control program, said, "The private transmission line network for Shikaoi-cho was large in scale and unprecedented, and its impact on the power grid was unknown, so there was considerable skepticism about the project. I believe that persistent negotiations, addressing each concern one by one, led to this positive result. Currently, the society has shifted from 'low carbon' to 'decarbonization', and the business environment has changed, with a certain degree of acceptance of grid constraints. The construction of the private transmission line network is one promising approach to regional energy policy, but the optimal energy system differs from municipality to municipality. We will continue to explore heat and power systems that contribute to solving the challenges of each region, and we will continue taking on new challenges rather than hesitating because no one has done it before."
The development of locally produced and consumed energy systems that utilize unique regional resources is attracting significant attention as a region-driven decarbonization initiative and as a means of fostering local industries. Pacific Consultants plans to further strengthen its support for both the formulation of basic plans and the implementation of such projects in local communities.
