Toshiba and TNK to Improve the Accuracy of Forecasting the Amount of Renewable Energy Generation and Achieve Approximately 70% Reduction of Imbalance Amount by Utilizing Storage Batteries

~Results of the FY2022 Renewable Energy Aggregation Demonstration Project~

  • Renewable Energy
  • R & D / Technology

March 29, 2023

Toshiba Energy Systems & Solutions Corporation
Next Kraftwerke Toshiba Corporation

KAWASAKI, JAPAN-Toshiba Energy Systems & Solutions Corporation (hereinafter, “Toshiba ESS”) and Next Kraftwerke Toshiba Corporation (hereinafter, “TNK”) have previously announced to be selected for the “FY2022 Renewable Energy Aggregation Demonstration Project” *1, with Toshiba ESS as consortium leader. Throughout this demonstration project, publicly facilitated by the Ministry of Economy, Trade and Industry, new forecasting methods were developed and demonstration experiments mainly from December last year through January this year were conducted.
Successfully, this demonstration experiment improved the accuracy of renewable energy power generation forecasts and reduced imbalance risk*2 through the use of storage batteries.

This demonstration project has been promoted by a consortium*3 of 14 renewable energy aggregators, including Toshiba ESS, and 9 collaborator companies with the aim of building a stable and efficient power system utilizing highly unstable renewable energy sources and showcase the feasibility of expanding the use of renewable energy.
Following FY2021, the consortium including Toshiba ESS and TNK conducted imbalance reduction assessments, renewable energy generation forecasts, and aggregator profitability assessments using approximately 200 resources, including solar power, wind power, and storage batteries.
This demonstration used REBSetTM, a renewable energy balancing system jointly developed by Next Kraftwerke and Toshiba ESS (Figure 1).

For the imbalance reduction evaluation, multiple methods were developed utilizing storage batteries and intraday trading in the electricity market. The control method that utilizes storage batteries where reflecting the real-time actual amount of renewable energy generation (feedback control method) was considered the most successful in reducing imbalance.
The demonstration system on the cloud-controlled storage batteries (actual equipment) successfully achieved an average of approximately 70% reduction of imbalance amount compared to the imbalance amount that would have occurred if storage batteries would not have been used*4.

In the evaluation of renewable energy power generation forecasts, Toshiba ESS and Next Kraftwerke developed eight new forecasting methods for solar and wind power generation. In addition, Toshiba ESS and Next Kraftwerke increased the frequency of power generation forecasts and made forecasts at times closer to actual power generation.
As a result, the minimum forecast error for solar was reduced to approximately 1.5% (Tokyo area/January) *5 and for wind to approximately 11.8% (Tohoku area/January) *6. The forecast errors for solar and wind power in the same area last year were approximately 2.9% and 25.6%, respectively. In conclusion, the accuracy of both solar and wind power forecasts has improved.

The profitability assessment of the aggregator confirmed that the new market transaction planning technology, which is part of REBSetTM, will result in greater revenues under the Feed-in Premium system than under the Feed-in-Tariff system.
In addition, the demonstration taking into account the forecast of renewable energy power generation and the forecast of day-ahead market prices in the electricity market, we confirmed that creating a charge/discharge plan for storage batteries can increase aggregators' income. The suggested battery schedule charges renewable energy during times of high generation and low market prices, and discharges and sells electricity during times of low generation and high market prices, in months when electricity generation is high and the market price is at its lowest (0.01 yen/kWh), the results showed that the aggregator's income could be increased up to approximately three times.

Toshiba ESS and TNK will continue to develop control technologies using renewable energy power generation forecast and storage batteries to solve the issues identified through this demonstration, and through the renewable energy aggregation business, contribute to the realization of a stable and efficient power system that utilizes renewable energy.


Figure 1: Jointly developed demonstration system (screen for checking predicted/actual power generation)

*1: The official name of the project is “FY2022 Subsidy for Demonstration Project for Establishing Next-Generation Technologies Using Distributed Energy Resources such as Storage Batteries (Renewable Energy Aggregation Demonstration Project within the Renewable Energy Generation Aggregation Technology Demonstration Project).”

*2: Imbalance is the difference between the amount of electricity demanded (used) and the amount of electricity supplied that occurs when a renewable energy power generator is unable to achieve the same amount of electricity as planned and actual simultaneously. If the amount of renewable energy power generation deviates from the planned value and the imbalance becomes large, it may cause a decline in the quality of the electricity supplied and power outages. In addition, an imbalance fee must be paid as an adjustment cost due to the imbalance.

*3: Consortium member:
Consortium leader
Toshiba Energy Systems & Solutions Corporation

Renewable Aggregators 14 companies
・Urban Energy Corporation
・ENEOS Corporation
・The Kansai Electric Power Co., Inc.
・Kyushu Electric Power Co., Inc.
・Cosmo Eco Power Co., Ltd.
・Japan Renewable Energy Corporation
・The Chugoku Electric Power Co., Inc.
・TEPCO Energy Partner, Inc.
・Nippon Koei Co., Ltd.
・NEC Corporation
・Hokkaido Electric Power Co., Inc.
・Eurus Green Energy Corporation
・Toshiba Energy Systems & Solutions Corporation

Demonstrating collaborators 9 companies
・Idemitsu Kosan Co., Ltd.
・Energia Solution & Service Co.
・Kanden Energy Solution Co., Inc.
・Japan Weather Association
・First Solar Japan G.K.
・Mitsui Sumitomo Insurance Co., Ltd.
・Next Kraftwerke Toshiba Corporation

*4: Average percentage reduction in daily imbalance volume

*5: Evaluation results for the consortium as a whole in the Tokyo area. Prediction error is calculated by normalizing the difference between predicted and actual power generation every 30 minutes by the rated capacity of the generator.

*6: Results of the evaluation of the consortium as a whole in the Tohoku area


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