Mitsubishi Heavy Industries, Ltd., (MHI), has developed Japan’s first cargo container-type large-capacity energy storage system that uses a lithium-ion rechargeable battery. The system is capable of providing power of up to one megawatts (MW), and its mobility makes the system suitable for a wide range of applications, including emergency use. The actual system has been installed at the Nagasaki Shipyard & Machinery Works of MHI in Nagasaki Prefecture, Japan, to begin verification testing for a power stabilization system application from early July towards the commercialization of the system.

The container-type “megawatt-class large-capacity energy storage system (ESS)” consists of a 40ft-long container unit, which houses more than 2,000 units of lithium-ion rechargeable batteries, and a 20ft-long container unit, in which two power conditioners are installed. Power conditioners are used for direct current (DC)/alternating current (AC) conversion and their input/output control. Each container unit can be moved by container trailers. The system has the capacity to store 408 kWh (kilowatt hour) of power and is designed to have a system efficiency of 90%.

The power storage system is capable of providing electricity for some 100 households for three to eight hours. By using multiple units of the system, power output can be increased to the level of several tens of thousands of kilowatts.

The system installed for verification testing in Nagasaki is currently being adjusted towards an in-plant electric-load leveling test. Testing will be conducted envisaging such cases as short-cycle conditioning to level fluctuations of electricity generated, including power produced by wind power and solar cells, and medium- and long-cycle conditioning for a period of several hours. It will also test the system for a micro-grid application to enable a stable supply of electricity by storing power from renewable energy, for the use in the areas where connections to regular power transmission/distribution grids are difficult.

The research and development activities of large-capacity energy storage systems are advanced mainly in countries and regions that depend largely on renewable energy, such as wind power and solar energy, which are vulnerable to fluctuations in weather conditions. Where a substantial portion of the entire power supply relies on such sources, instability in power generation has been a challenge to solve. The verification testing of the energy storage system using high power density lithium-ion rechargeable batteries is actively being conducted in the US and Europe as a promising technology. The mobile container-type ESS is especially advantageous due to its variety of applicable usages, including its ability to power sources for large-scale outdoor events, construction sites and mobile power charge stations for electric vehicles, in addition to power supply stabilization and serving as an emergency-use power source.

MHI has positioned energy and environment related businesses as one of the company’s focused segments in the 21st Century. By aggressively proposing container-type ESS with lithium-ion rechargeable battery for a variety of applications, the company will further contribute to the establishment of energy-saving society.