Press Information

Ryoju Estate Develops "ene-self" Power Supply System
For Apartment Bldgs., Adopting PV Modules,
Emergency Generator and Lithium-ion Battery
-- Can Alternate as Lifeline Power Source during Electricity Outages --


Tokyo, March 7, 2013 - Ryoju Estate Co., Ltd. a group company of Mitsubishi Heavy Industries, Ltd. (MHI), has developed a secure power supply system for apartment buildings, dubbed "ene-self," which uses three power sources in combination: photovoltaic (PV) power generation modules, an emergency generator and a lithium-ion rechargeable battery. Ryoju Estate will begin full-scale marketing of the system in the Japanese market on March 18. The system can alternately function as a stable emergency power supply source for lifeline equipment such as elevators and water supply pumps in cases of electricity outage due to a natural disaster or other event, while in normal times it helps reduce electricity costs through PV power generation. The company is targeting 40 orders for the system within the first three years, mainly for installation in new or existing apartment and condominium buildings.

In addition to its three power sources, "ene-self" also incorporates a power conditioner (PC) and PC controller. A PC is used to convert electric current generated by PV modules to power usable by home appliances. In general applications, the PC is set to go off as a safety precaution when an outage is detected. For the "ene-self" system, however, Ryoju Estate developed a new PC controller that automatically maintains power to drive the PC, enabling use of PV power as an emergency energy source.

At normal times, during the daytime users can use the power generated by the PV modules either for their own consumption as a way of reducing usage of power supplied by a utility company, or for sale to a utility company. At night, they can take advantage of low nighttime utility rates and use utility power for their everyday needs and for charging of the "ene-self" system's lithium-ion battery.

In case of a utility power outage, the "ene-self" system will supply power for communal use in order to maintain minimum levels of operation of lifeline equipment such as elevators, water supply pumps for toilets and meeting room electricity*1. During daytime, power will be supplied progressively: first by PV; then, when PV power is inadequate, by battery; and lastly, by emergency generator when the situation requires. When PV power generation exceeds consumption, the excess power is stored in the battery for the use at night. At night, power is supplied from both the battery and the emergency generator.

The "ene-self" system automatically controls start/stop of the generator and switching of the power supply systems during outages and power recovery. In addition to using the complete system of three power sources (PV modules, emergency generator and battery), customers can alternately select a combination of PV modules with either generator or battery according to their needs. They can also make use of previously installed PV modules and add the other power sources.

Ryoju Estate's business portfolio has traditionally spanned a broad range of services including the design, construction, marketing and management of office buildings and condominium residences, and in all endeavors the company has focused on energy saving and reduction of environmental burdens. In the wake of the Great East Japan Earthquake, public interest has now also heightened toward power sources for use in times of emergency, systems that make use of renewable energy, etc. In response, Ryoju Estate is now proactively promoting the use of its "ene-self" power supply system not only for residential applications, but also for use at facilities nationwide that have PV installations: for example, convenience stores, hospitals, and schools designated as evacuation centers. In these ways, the company looks to contribute to ensuring the safety and security of any areas that might be impacted by a disaster of major scale.

1.Based on test data, "ene-self" can maintain the power supply to satisfy these needs for a minimum of three days. The test specifications are 5.6 kilowatts (kW) to power two elevators, 3.7kW to drive two water pumps, and approximately 6kW to maintain power to a standard-size meeting room.

Business contact:Ryoju Estate Co., Ltd.

About MHI Group

Mitsubishi Heavy Industries (MHI) Group is one of the world’s leading industrial groups, spanning energy, smart infrastructure, industrial machinery, aerospace and defense. MHI Group combines cutting-edge technology with deep experience to deliver innovative, integrated solutions that help to realize a carbon neutral world, improve the quality of life and ensure a safer world. For more information, please visit or follow our insights and stories on