The Development and Demonstration Project for Optimal Control Technology of Renewable Energy based on Time-of-Day CO2 Emission Coefficients has Completed - Visualization of CO2 Reduction Effects through Optimal Control of Digestion Gas Power Generation -
PACIFIC CONSULTANTS CO., LTD. (Address: Chiyoda-ku, Tokyo, Representative Director, President Executive Officer: Osamu OMOTO, hereinafter referred to as "PACIFIC CONSULTANTS") has a group company of Pacific Power Co., Ltd. (Address: Minato-ku, Tokyo, President and Representative Director: Michiko GOUZU, hereinafter referred to as Pacific Power) which has been participating as a co-implementer in the Ministry of the Environment's FY Reiwa 4 Regional Co-Creation and Cross-Sectoral Carbon Neutral Technology Development and Demonstration Project (Development and Demonstration Project for Optimal Control Technology of Renewable Energy Power Generation Based on Real-Time CO2 Emission Coefficients) and has been promoting technology development.
We are pleased to announce that we have completed the Development and Demonstration Project for Optimal Control Technology of Renewable Energy Power Generation Based on Time-of-Day CO2 Emission Coefficients, and in February 2025, we will conduct a demonstration of the system developed at the Chubu Water Treatment Center in Fukuoka City, and have succeeded in optimally controlling the operation of digestion gas power generation using the time-of-day based CO2 emission coefficients as an index and quantitatively evaluating its effectiveness.
Objective and Overview of the Developed Technology
Our company and Pacific Power, as shown in the press release on September 9, 2024, have independently calculated and published our time-of-day CO2 emission coefficients. The CO2 emissions when generating electricity that flows through the power grid (the electricity we use every day), are not the same every day, but actually vary greatly depending on the time-of-day. For example, electricity during times when the renewable energy ratio is high, such as on sunny days, emits less CO2. On the other hand, CO2 emissions are low during rainy days and in the mornings and evenings when the ratio of thermal power generation is high. The CO2 emission coefficients by time-of-day cannot be grasped by using the annual CO2 calculated under the current system and we aim for the visualization of changes in CO2 emission intensity over time. As an application of the time-of-day based CO2 emission coefficients, even if you generate or consume the same amount of electricity at different times of the day, one advantage is that it is easy to show how it can lead to savings of CO2.
Furthermore, this time, we developed technology to predict the time-of-day CO2 emission coefficients of grid power from the next day onwards, and then controlled biogas power generation (digestion gas power generation) at sewage treatment plants, renewable energy is relatively easy to control, and successfully demonstrated this technology. As a result, the series of systems shown in the diagram below that were planned for this project was completed, and optimal control of biogas power generation that maximizes the CO 2 reduction effect and its quantitative evaluation were achieved.
Image of the developed system
Overview of the Demonstration Project
This demonstration project was carried out at the Fukuoka Chubu Power Plant (rated output 1,999kW) operated by Tsukishima JFE Aqua Solutions Co., Ltd., a joint implementer of this project. The facility is installed in the Chubu Water Treatment Center in Fukuoka City, and currently sells all of its electricity under Feed-in tariff (FIT) scheme. The system developed this time creates a plan to maximize power generation during the time periods when the time-of-day based CO2 emission coefficient of electricity is high, as predicted by the previous day, and actually sends commands to the on-site generator to control power generation. In this case, gas is temporarily stored in the gas holder shown in the figure below to shift the amount of generated power, and the system predicts the amount of gas generated from the sewage treatment plant and creates a plan to keep it within the upper and lower limits of the gas holder.
Image of power generation time control using a gas holder
Biogas generator
Gas holder
Demonstration Project Results and Future Outlook
The amount of electricity sold during the demonstration project from February 12 to 21, 2025, was highly correlated with the time-of-day based CO2 emission coefficient, which was used as a control index, and the CO2 reduction effect of the electricity generated was improved by approximately 5% compared to the operation method outside the demonstration period. In addition, although this is a calculation assuming a transition from the current FIT system to the FIP system, it was confirmed that the revenue from electricity sales would also increase by approximately 7% when evaluated at the spot market price, which is the economic value of electricity. During this period, the gas holder remained within certain upper and lower limit values, and it was demonstrated that it is possible to optimize the time of power generation while using up all of the generated digester gas as before.
Actual optimal control results
PACIFIC CONSULTANTS and Pacific Power aim to spread the system they have developed to biogas power generation facilities across the country. This system can also be used to generate biogas from food waste and livestock manure in addition to sewage sludge. As announced in a press release on the Pacific Power website on February 25, 2025, the system can be applied not only to facilities that sell electricity under the FIT system, but also to facilities that consume the electricity they generate, and they will roll it out to both.
PACIFIC CONSULTANTS GROUP will continue to contribute to the revitalization and development of cities and the progress of carbon neutrality through its local energy business.