NEC Corp released a household power storage system using a lithium-ion (Li-ion) rechargeable battery March 29, 2012.
The capacity of the system is 6kWh (minimum charging capacity: 5.53kWh). It is expected to be provided to housing manufacturers, building material trading companies, etc.
Though there is no manufacturer's suggested retail price, the expected retail price of the system is ¥1 to 1.5 million (approx US$12,180-18,270), NEC said. In other word, its price is ¥250,000 or lower per 1kWh. So, it is the most inexpensive power storage system manufactured in Japan.
NEC will start shipment of the power storage system in July 2012, aiming to sell 10,000 units per year. In July 2011, the company released a prototype of a household power storage system using a Li-ion rechargeable battery having the same capacity with a limited number of 100.
The power storage system consists of battery cells, battery control unit, main body storing a power conditioner, "system controller" (which is installed near a distribution panel) and "operation panel" (which is installed in a living room, etc). It uses 48 battery cells, each of which has a capacity of 125Wh and a laminated structure.
The system measures 980 (W) x 1,100 (H) x 310mm (D) and weighs about 160kg. Compared with the prototype released in July 2011 (760 (W) x 880 (H) x 450mm (D), about 200kg), the depth and weight of the new system are 30% smaller and 20% lighter, respectively. NEC reduced thickness and weight without deteriorating heat radiation performance by improving the component layout. Also, by eliminating the need for the cooling fan used for the prototype, noise was reduced.
The new system is mass-produced at NEC's Sagamihara Office. The company will newly build a production line for the battery cell and an assembly line.
By connecting the new power storage system to a distribution panel in a house, it works together with an electricity grid and a photovoltaic (PV) power generation system, enabling to control charging and discharging. It can not only store electricity generated by PV cells but also store midnight power, which is cheaper, and use it during daylight hours. In case of power outage, autonomous operation that collaborates with a PV power generation system begins.
The power storage system can be connected to NEC's data center via the Internet. As a result, it becomes possible for NEC and its partner companies such as housing manufacturers to constantly monitor the temperature and charge/discharge status of the system for safety control and maintenance of the rechargeable battery.