BC: NAS BATTERY TECHNOLOGY GOES COMMERCIAL
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Due to the development of a high-technology-society, power demand has been increasing year after year.
A big problem under such an environment is the big difference of the electric demand between day and night, and also throughout the seasons.
It is getting difficult to construct power stations and transmission facilities which cover peak power demands not only from the point of construction cost but also conservation of resources. If we succeed to reduce these fluctuations, we can contribute to efficient operation at power stations, decrease of operation cost, and conservation of resources. Our focus has been on a power storage system which applies high energy density and high efficient sodium-sulfur(NAS) batteries.
This system reduces fluctuation by load leveling and peak shaving.
We have jointly developed this "NAS battery" with the Tokyo Electrical Power Company. After extensive testing and demonstration, the prospect of commercial utilization has now been realized. Our NAS battery is expected to play an important role in reducing power demand fluctuation. NAS batteries can function as a power station to charge electric power in the base power source at low demand and discharge it at peak demand. By applying it to a consumer, reduction of an electricity bill and the improvement of electric power quality will be possible.
By applying Beta alumina for its solid electrolyte, the NAS battery is free from secondary reaction due to charge/discharge. In addition, the thermal energy loss caused by internal resistance is used to keep the battery warm. As a result, the NAS battery can obtain high efficiency.
The NAS battery's key technology, Beta alumina solid electrolyte, which NGK developed by making the best use of its ceramic technology, makes the high reliable battery available.
Features of the NAS Battery System
Large capacity by connecting many batteries, several MW system can be easily constructed
Compactness required area for installation is approx. one third of that for a lead acid battery
High efficiency 75% of energy charge/discharge efficiency system efficiency
Long-term durability long-term durability : 15years
assumed specification : 2,500 cycles
Preservation of the enviroment no discharging of any pollution gases, no vibrating, low noise
Principle of the NAS Cell
NAS battery consists of sulfur at positive electrode, sodium at negative electrode as active materials, and Beta alumina of sodium ion conductive ceramic which separates both electrodes.
This hermetically sealed battery is kept at approx. 300 centigrade and is operated under the condition that the active materials at both electrodes are liquid and its electrolyte is solid. At this temperature, since both active materials react smoothly, and internal resistance becomes low enough, NAS battery has an excellent performance. Because of reversible charging and discharging, NAS battery can be continuously used.
Principle of NAS Battery
Approx. 2V voltage generated between positive and negative electrode at about 300 centigrade. If a load is connected to terminals, electric power is discharged through the load. During the discharge, sodium ions converted from sodium in a negative electrode pass through solid electrolyte then reach to sulfur in positive electrode.
The electrons finally flow to outside circuits. The electric power is generated by such current flow.
With the progress of the discharge, sodium polysulfide is formed in positive electrode; on the contrary, sodium in negative electrode will decrease by consumption.
During the charge, the electric power supplied from outside form sodium in negative electrode and sulfur in positive electrode by following the reverse process of the discharge. Because of this, the energy is stored in the battery.
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Safety Design of Single Cell
For the safety application of sodium and sulfur, NAS battery employs a structural design, which builds in a metal insert inside the solid electrolyte tube. If solid electrolyte tube has a breach in the cell, the chemical reaction between sodium and sulfur is retained inside, which can prevent the trouble from extending outside. According to evaluation tests in case of a troubled battery, a troubled system, an irregular operation, and a disaster, a NAS battery has proven its safety for every test.
Compact Design of Module Battery
A module battery contains many single cells in a thermal enclosure which is equipped with an electric heater to raise or maintain temperature. The single cells are densely arranged and connected with metallic bars inside the enclosure. This module battery is a basic unit to consist a system; however, the module itself can be operated as well. To make an enclosure compact, a module battery employs a heat insulating structure, which makes inside the walls of enclosure vacuum. Several safety measures are adopted inside a module battery; therefore, it can be utilized without care.
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AEP to deploy additional NAS large scale batteries on
their grid .... Big growth opportunity here ....
This could be the 'solution' for the intermittancy
issues with solar ( PV and CSP ), wind, tidal etc ..
Also, Sodium ( NA ) and sulfur ( S ) are adundant
materials, so this technology can 'scale' ......
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COLUMBUS, Ohio, Sept. 11 /PRNewswire-FirstCall/ -- American Electric Power (NYSE: AEP - News),
As part of the company's comprehensive effort to integrate new technologies for reliability, renewable energy and energy efficiency to meet customers' future needs, is expanding its use of large-scale battery technology on its electricity grid.
AEP, the only U.S. utility currently using advanced energy storage technology as part of its electricity infrastructure, will be adding stationary sodium sulfur (NAS®) battery technology in its West Virginia and Ohio service territories next year.
The company will also work with wind developers to identify a third location within AEP's 11-state service territory for NAS battery deployment next year, using the storage capability to help offset the intermittent nature of wind generation.
AEP has placed an order for the three new NAS batteries with NGK Insulators Ltd. of Japan, the manufacturer and co-developer, along with the Tokyo Electric Power Co., of the technology. AEP anticipates delivery in spring 2008.
The six megawatts added to AEP's system during this deployment is a step toward the company's goal of having 1,000 megawatts of advanced storage capacity on its system in the next decade.
"We are extremely impressed with both the performance and the potential of this technology after using it in real-world applications and from experience we've gained through our long relationship with NGK," said Michael G. Morris, AEP's chairman, president and chief executive officer. "These new installations will move us a step closer to the full potential of advanced energy storage technologies in areas like reliability improvement, peak-load shaving and the use of stored energy from renewable sources like wind to supplement available generation resources.
"We're first movers on advanced storage among U.S. utilities, a position we've held on a wide number of technologies in our century of existence," Morris said. "Our near-term goal is to have at least 25 megawatts of NAS battery capacity in place by the end of this decade. But this is just a start. Our longer-term goal is to add another 1,000 megawatts of advanced storage technology to our system in the next decade. We will look at the full spectrum of technologies -- flow batteries, pumped hydro, plug-in hybrid vehicles and various other technologies in early stages of development today -- to determine their feasibility and potential for commercial application.
"In our view, advanced storage technologies, like NAS batteries, and other emerging technologies to increase customers' ability to benefit from energy efficiency will play equally important roles in delaying or avoiding costly future investments in new energy delivery or generation infrastructure," Morris said. "I believe other companies will begin deploying storage technologies in the coming years."
AEP plans to add two megawatts of NAS battery capacity near Milton, W.Va., to enhance reliability and allow for continued load growth in that area. AEP will also add two megawatts of NAS battery capacity near Findlay, Ohio, to enhance reliability, provide support for weak sub-transmission systems and avoid equipment overload.
A specific site for the third NAS battery, which is expected to be integrated with wind generation, will be announced in the coming weeks.
The combined cost for the three installations, including associated site preparation, equipment and control systems, will be approximately $27 million.
AEP has identified other potential sites for future deployment of advanced storage technologies.
In 2006, AEP installed the first megawatt-class NAS battery system to be used on a U.S. distribution system. That installation, on a substation near Charleston, W.Va., operated by AEP utility unit Appalachian Power, delayed the need for upgrades to the substation. A similar, but much smaller, NAS-based system installed in 2002 at an AEP office park in Gahanna, Ohio, was the first U.S. demonstration of the NAS technology.
The agreement to purchase additional NAS batteries was reached during an August visit to NGK in Japan by Holly Koeppel, AEP's chief financial officer.
"AEP and NGK have had a very close business relationship for more than five years," Koeppel said. "Our meeting in August generated the agreement for our deployment of additional batteries, but it also provided an opportunity for us to arrange an upcoming meeting with NGK for other Ohio utilities and state officials. Advanced storage technologies like NAS batteries are important to our industry's future. That's why we continue to lead the public policy and technology integration efforts."
The deployment of additional advanced storage capacity is part of a comprehensive AEP initiative focused on preparing the company's 11-state distribution system to meet future needs of customers.
"We're looking at where we need to be in the year 2020 and will be making changes to transition our system to the grid of the future," Morris said. "We have teams of employees examining the current and likely future needs of customers as well as the variety of technologies under development that could meet those needs. We're looking at ways to improve reliability and efficiency of our system as well as ways to reduce consumption, which delays or avoids the need for additional generation.
"Some elements, like additional large-scale storage systems to enhance reliability, advanced metering systems to provide customers with options for reducing energy use and further integration of renewable resources, are among the likely solutions customers will see in the near term," Morris said. "We're also testing distributed energy resources and 'smart grid' or 'self- healing grid' technologies designed to seamlessly separate sections of the distribution grid when problems develop elsewhere, with customers seeing no disruption in power supply or quality in situations where outages would be likely today. But implementation of these technologies is a bit further off."
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