Publication date: April 28, 2025 Weathering the Storm: Weather Forecasting and Battery Energy Storage Systems in Japan’s Changing Climate

Weathering the Storm: Weather Forecasting and Battery Energy Storage Systems in Japan’s Changing Climate

Shulman Advisory is delighted to present the following article in collaboration with Atmospheric G2, on how weather, growing gradually more extreme under Japan’s changing climate, can affect BESS and how weather forecasting could facilitate BESS management. 

BESS deployment in Japan is expanding rapidly as part of a broader push to support renewable energy integration and ensure grid reliability. Government initiatives such as the Long-Term Decarbonization Auction (LTDA) and the issuance of Climate Transition Bonds are accelerating installations, particularly in regions with high renewable energy potential like Hokkaido and Kyushu (METI). Temperature plays a critical role in the performance, safety, and lifespan of lithium-ion batteries—the core technology behind most BESS operating in the market today (Nature). While these systems are generally designed to operate within a temperature range of 5°C to 30°C, optimal performance is typically achieved around 20°C.

Beyond the growing unpredictability of extreme weather events, Japan’s geographical diversity adds another layer of complexity to BESS operation and positioning. The country spans multiple climate zones, leading to substantial regional variations in temperature and humidity. For example, northern regions such as Hokkaido, bordering the Siberian climate zone, face long, severe winters and heavy snowfall. In contrast, southern areas like Kyushu experience hot, humid summers that regularly test the upper thermal limits of battery systems. These climatic differences demand region-specific approaches to BESS planning and management. 

Weather forecasting can play a vital role in improving the operational efficiency, safety, and financial return of BESS. Maintaining batteries within their optimal temperature range not only enhances performance but also significantly extends system lifespan by reducing thermal stress and chemical degradation. Therefore, the implications of external temperatures must be carefully considered in project design and implementation.

Short-term but high-resolution weather forecasting services can enhance the predictability of weather shifts, enabling BESS operators to optimize charging and discharging schedules. Since BESS is often used to compensate for mismatches between predicted and actual renewable energy generation, accurate forecasting is essential. Additionally, because electricity prices fluctuate with demand and weather conditions, timely forecasts can help operators discharge energy when prices are higher, such as during adverse weather, maximizing revenue and grid support services.

Adjusting to extreme seasonal weather can also minimize potential accident risks and protect the business assets. For instance, hot summer days present significant challenges for BESS developers. Although longer, sunnier days support renewable energy generation, the accompanying high temperatures can place heavy stress on battery cooling systems. This increases the risk of thermal runaway conditions that can lead to fires or explosions, posing both safety hazards and financial liabilities.

Historical weather data (provided by Atmospheric G2) highlights a growing frequency of weather anomalies in recent years, many of which could likely have tested the resilience of storage systems. For example, in July 2024 alone, Japan experienced five significant heat spikes (Figure 1). On July 22, the recorded temperature exceeded the historical average by +6.3°C (Table 1), pushing operating conditions well beyond the optimal thermal range for BESS. Such elevated temperatures increase the risk of thermal stress, accelerated battery degradation, and other potential safety concerns.
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Table 1. Observed vs. Normal Temperatures in Japan, July 2024 (source: Atmospheric G2). 

Cold-weather events, while generally less extreme than heat-related events, can also pose challenges (Figure 2). As shown in Table 2, several cold spikes in early 2025 saw temperatures fall well below seasonal norms. The most pronounced of these occurred on February 23, when the temperature dropped 3.4°C below the average for that time of year. Although less dramatic than the summer spikes, cold extremes can impair battery efficiency and output, underscoring the need for both heating and cooling strategies in system design.
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Table 2. Observed vs. Normal Temperatures in Japan, February 2025 (source: Atmospheric G2). 

The operational safety of BESS is mandated by the Electrical Appliance and Material Safety Act for manufacturers and by the Electricity Business Act for installers (Cabinet Office). The recent revision of the Electricity Business Act in 2022 outlines increasing support for the adoption of BESS. It clarified the treatment of BESS and positioned projects discharging 10 MW or more from BESS as ‘power generation businesses’,  thereby improving the environment for connection to the grid (METI). 

Regarding the LTDA, in FY 2024, METI updated the guidelines for participation of BESS operators to include submission of a business plan. Aside from general management requirements for BESS, the business plan should include details in safety measures, such as safety design features, measures to prevent and respond to accidents (e.g., fire or smoke), public safety measures, and security measures. Increased attention to safety suggests the government is already mindful of increasing weather-related hazards that can affect BESS safety and operations. 

Improving weather forecast predictability offers advantages and is directly linked to effective BESS management. The optimal use of weather forecasts is a crucial tool for BESS operators, enabling better foresight and scheduling of battery charge and discharge, enhancing the safety and durability of BESS operations over the long term, and reducing the operational costs associated with extreme weather. 

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Thank you for reading. This report is also available as a PDF for download here.

This is the forth article in our mini-series on harnessing weather intelligence to optimize renewable asset performance. If you missed the previous articles, you can catch up here:

• First article: Harnessing Weather Intelligence for Renewables to Optimize Asset Performance in Japan: Solar
• Second article: Understanding & Forecasting Wind Power Generation in Japan 
• Third article: Understanding & Forecasting Hydroelectric Power Generation in Japan

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