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Maintaining a stable supply of high-quality electricity is becoming an urgent issue as larger amounts of renewable energy are being introduced to the power grid. Battery energy storage systems are gaining popularity as a promising option to replace variable speed pumped storage hydroelectric plants. Hitachi has been working towards the commercialization of safe and economical battery energy storage systems to provide a solution for this challenge.
In Japan, a shift in energy policy is accelerating the utilization of energy from renewable sources such as wind and solar power.
However, a new problem has surfaced. Bringing large amounts of energy from renewable sources into the grid tends to destabilize the power supply due to fluctuations in frequency. Providing a stable supply of power is a constant balancing act. When supply and demand do not match, it causes fluctuations in frequency. Normally, utility companies try to keep fluctuations in frequency down to less than 0.2 Hz, as greater fluctuation would have negative effects on control systems and sensitive devices. If the fluctuation becomes greater than several Hz, generators in power plants would stop working, causing greater effects that could destabilize the power supply. The output of power from renewable sources fluctuates with changing weather conditions. Therefore, introducing large amounts of renewable energy to the grid can throw off the balance between supply and demand as well as cause fluctuations in frequency that could destabilize the entire system. To resolve this problem, Hitachi has been working on the development of battery energy storage systems. It has been making progress on projects inside and outside of Japan, including a demonstration project in Hawaii. Hitachi also participated in the project to develop technology for safe and economical large-scale energy storage systems supported by NEDO (The New Energy and Industrial Technology Development Organization) which started in 2011 and ended in February 2016.
Battery energy storage systems have been gaining popularity as a way to stabilize the supply of power, but there are many problems to solve. One of those problems is that there are two different kinds of fluctuation in frequency: short cycle and long cycle. Battery energy storage systems need to be able to work with both. In addition to being safe, systems used by utility companies must also have a long life. It is also important to lower costs to be able to popularize their use. To achieve these goals, Hitachi decided to develop a new hybrid battery energy storage system that combines lead-acid batteries and lithium-ion capacitors. Lead-acid batteries have large capacity and endurance, but they are not suited to absorb sudden short-cycle fluctuations. On the other hand, lithium-ion capacitors have high-power output capability to respond sudden fluctuations, but their capacity is small and not suited for long-cycle fluctuations. That's why Hitachi decided to combine the strengths of both systems to be able to deal with both long-cycle and short-cycle fluctuations. For the development of hybrid battery energy storage systems, Hitachi is aiming to cover the same range of needs as variable speed pumped storage hydroelectric plants. For this purpose, Hitachi co-developed a 1.5 MW hybrid battery energy storage system with a group company, Shin-Kobe Electric Machinery Co., Ltd. (now Hitachi Chemical Company, Ltd.), as part of project subsided by NEDO.
High-power input-output, long-life, lead-acid batteries are well suited for energy storage to even out fluctuations in power supply.
Lithium-ion capacitors are effective in addressing short-cycle frequency fluctuations.
In cooperation with TEPCO* Power Grid, Inc., Hitachi has been conducting a demonstration project on its large-scale battery energy storage system on Izu Oshima Island south of Tokyo. The island has an independent power grid and is a suitable testing site to assess the effect of introducing large amounts of energy from renewable sources on the grid. In the demonstration project, which is aiming toward the commercialization of the system, the durability of the battery energy storage system was an especially important concern. Hitachi Chemical Company, Ltd., the developer of the lead batteries, has more than 10 years' experience in delivering devices to reduce power fluctuation. The company has been researching and analyzing batteries for longevity and has accumulated a knowledge base on the improvement of battery performance. In the Izu Oshima Island demonstration, Hitachi has also evaluating the durability and performance of the battery energy storage system through deterioration analysis utilizing data from Hitachi Chemical Company, Ltd. Further, Hitachi is creating control systems to monitor the operational status of the battery energy storage system for the demonstration project, not just for onsite monitoring but also for remote monitoring from the TEPCO's Oshima Power Plant at Izu Oshima Island in Tokyo and Hitachi's Omika Works in Ibaraki Prefecture. Hitachi is striving to develop control technology from research and analysis of the data for the operation of battery energy storage systems.
As Izu Oshima Island has been relying on diesel power generation, one of the purposes of this demonstration project is to evaluate the effect of using the battery energy storage system in reducing fuel costs. Hitachi is looking to find economical solutions to improve power grids in other island regions that have been relying on fossil fuels for their power supply. Hitachi is working towards optimal utilization of renewable energy and diesel power generation.
Diesel power plant by TEPCO Power Grid, Inc.
Control system used to monitor the battery energy storage system in the demonstration project.
The demonstration project in Izu Oshima Island began in 2015 and has entered into a new stage as a joint research project with TEPCO Power Grid, Inc. The companies have been evaluating the efficacy of the monitoring control system and its effects on the operation of existing power plants. Hitachi is aiming for the commercialization of the system by 2018 to contribute in stabilizing the supply of power in island regions.
Besides Izu Oshima Island, Japan has many other regions with small islands that have independent power grids. In order to introduce more renewable energy to take advantage of island climates, it is essential to have measures in place to deal with fluctuations in output related to weather. Hitachi will continue to strengthen its efforts to commercialize safe and economical battery energy storage systems as quickly as possible to stabilize the supply of power and provide solutions for other social issues stemming from the large-scale introduction of energy from renewable sources in island regions.
Hitachi is contributing to stable electric supply throughout the island regions.