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Release: March 9, 2004
The Tokyo Electric Power Company, Incorporated
NGK Insulators Ltd.

Outline of NAS Battery

1. Efforts for and achievements of development

During the 1980s, the development of energy-storage technology for load leveling was advanced in order to meet the increasing peak energy demand. NAS Battery (sodium-sulfur battery for energy storage) development was prompted with high expectations in the area of practical applications. Due to its high energy density, high efficiency, and long operating life, the NAS Battery is suitable for load leveling of electrical power. It also functions as a large-scale secondary battery for backup power supply in cases of an instantaneous voltage drop or power outages caused by lightning and other accidents.
Since 1984, TEPCO and NGK have advanced the development of the related technologies, ensuring durability and safety. Demonstration facilities (cumulative sum of 30,000 kW) have been installed at TEPCO's substations. After extensive feasibility tests and demonstrations, they have achieved the world's first practical applications of NAS Batteries.
Besides installation of the NAS Batteries facilities at substations, TEPCO has been distributing the Batteries directly to customers since 2001. TEPCO's advancements have attracted major clients, such as supermarkets, which demand load leveling and semiconductor-related entities that require high-quality electricity. To date, the company has made installations at 18 sites, with Battery capacity totals of approximately 13,500 kW.
In 2003, NGK constructed a plant focused on full-scale production (annual output of 60,000 kW) and sales, based on NGK's past achievements.
Through our efforts to commercialize the NAS Batteries, TEPCO and NGK will continue to supply efficient and high-quality services, such as load leveling of electricity and the securing of high-quality electricity.

2.Outline of NAS Battery

So far, NGK has invested a total of ¥10 billion in 3 major overseas plants

1) What is the NAS Battery?

• The NAS Battery consists of sodium (Na) at negative electrode, sulfur (S) at positive electrode, and Beta alumina ceramics as the sodium-ion-conductive solid electrolyte. The Battery operates at high-temperature, charging/discharging at temperatures in the range of 300 degrees Celsius.

2) Features of NAS Battery

• High energy density, high efficiency, and long-term durability.
  - An energy density three times higher than lead batteries, requiring smaller installation space.
  - A high charge-discharge efficiency and no self-discharge allow efficient power storage.
  - Long-term durability, capable of full charge/discharge for 2,500 times.
  - A "no emissions" clean battery using a completely sealed cell structure

3) Benefits of Introduction

• Lowering electricity costs
  Adopting a selective tariff, such as the "electrical energy by seasons and hours", electricity costs are lowered by applying less expensive night-time electricity and the reduction of contract demand.
• A more reliable power supply
  The NAS Battery acts as an emergency power supply, including protection from an instantaneous voltage drop occurs.
  - Prevents instantaneous voltage drop (IVD).
  Using a high-speed switch for essential services preserves communication function and prevents damage of data and automation based products.
  - Functions as emergency power supply
  No liquid fuel stock and no onerous inspection and maintenance are needed, such as are necessary for emergency power generators.
• Environmentally friendly
  The NAS system uses no fuel, thus, producing no air pollutants such as NOx, SOx, soot, particulate matter, etc.

3.Partnership for development

• The Tokyo Electric Power Company, Incorporated
  < Determination of development goals and specification, Implementation of tests, Evaluation of results>
  - Address: 1-3, Uchisaiwai-cho 1-chome, Chiyoda-ku, Tokyo, Japan
  - President: Tsunehisa Katsumata
• NGK Insulators, Ltd.
  < Development of single cells and module batteries based on development specifications, Production and sales>
  - Address: 2-56 Suda-cho, Mizuho-ku, Nagoya, Japan
  - President: Shun Matsushita

4.Typical NAS Battery facilities at TEPCO customer sites

Name of clients	Facility capacity (kW)	Features
(1)Fujitsu Akiruno Technology Center [Place of semiconductor business/ Akiruno, Tokyo](First distribution by TEPCO)	1,000	For load leveling 3,000 kVA IVD protection function included
(2) Tokyo Dome City LaQua [Amusement facilities with hot springs/ Bunkyo-ku, Tokyo]	1,000	For load leveling Emergency power supply function included
(3) Ito Yokado, Oyama Store [Retail store/ Oyama, Tochigi]	750	For load leveling

5.NAS Battery facilities installed at TEPCO substations (for load leveling, currently in operation)

Installation location	Facility capacity (kW)	Date of operation start
(1) Chichibu Substation [Chichibu, Saitama]	1,000	June, 2002
(2) Matsuo Substation [Matsuo-machi, Sanbu-gun, Chiba]	2,000	February, 2004
(3) Kamiyama Substation [Tamatsukuri-machi, Namekata-gun, Ibaraki]	2,000	March, 2004