Flow batteries can turn intermittent wind power from a utility manager's headache to a green and reliable energy source
|NAS (Sodium Sulfur) Flow Battery|
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2. Types of Batteries [Added Zinc Air Batteries]
4. Business Case
7. Next Steps
- Utilities typically use batteries to provide an uninterruptible supply of electricity to power substation switchgear and to start backup power systems. However, there is an interest to go beyond these applications by performing load leveling and peak shaving with battery systems that can store and dispatch power over a period of many hours. Batteries also increase power quality and reliability for residential, commercial, and industrial customers by providing backup and ride-through during power outages.
- Wind energy is entering the grid at an ever-increasing pace. As penetration levels increase, utilities are adjusting to the variable nature of wind-generated energy. Substantial penetration of such intermittent generation can place considerable, localized stress on the electricity grid in the U.S. Any need to back up these variable generators with conventional fossil-fired generators limits their positive impact on emissions production.
2. Types of Batteries
- Flow Batteries - A flow battery stores and releases energy by means of a reversible electrochemical reaction between two electrolyte solutions. Flow batteries differ from conventional rechargeable batteries mainly because the power and energy ratings of a flow battery are independent of each other. This is made possible by the separation of the electrolyte and the battery stack (or fuel cell stack). Flow batteries can be thought of as a hybrid of a fuel cell and a battery. They operate by flowing a charged electrolyte from one tank to another across a charge/discharge stack and that can operate for decades. Flow battery technology utilizes an active element in a liquid electrolyte that is pumped through a membrane similar to a fuel cell to produce an electrical current. The system’s power rating is determined by the size and number of membranes, and the runtime (hours) is based on the gallons of electrolyte pumped through the membranes. Pumping in one direction produces power from the battery, and reversing the flow charges the system. early prototypes are already in commercial operation, but they need further testing.
There are four leading flow battery technologies:
- Polysulfide Bromide (PSB)
- Vanadium Redox (VRB)
- Zinc Bromine (ZnBr)
- Hydrogen Bromine (H-Br) batteries
|In this VRB Flow battery, pipes and pumps carry the vanadium solution to stacks of proton exchange membranes, which transfer electrical charge and create a current|
The largest lead-acid battery grid energy storage installation is a 10-MW/40-MWh ﬂooded lead-acid system that was built in 1988 in Chino, CA, which is used for load leveling at the Chino substation of Southern California Edison Company. The primary advantage of the lead-acid batteries is their low capital cost and easy availability. The battery demonstrated the value of stored energy in the grid, but its limited cycling capability, along with high maintenance, made its life-cycle cost unacceptable.
Ni-metal batteries were another early electrochemical energy storage technology that was demonstrated for stationary applications. These batteries all share the same cathode (nickel oxyhydroxide in the charged state) but a diﬀerent anode that can be cadmium, zinc, hydrogen, metal-hydride, or iron. A nickelcadmium system was commissioned in 2003 in Fairbanks, Alaska, to provide 27 MW ac power for a short period of time (up to 15 min) until back generation comes online. The Ni-metal batteries are susceptible to overcharge, and their direct current DC-to-DC round-trip eﬃciency is low (<70%, round-trip eﬃciency). For the Ni-cadmium in particular, cadmium is toxic and considered a serious environmental hazard that has to be handled with special disposal means. The use of high-cost metals makes it diﬃcult to meet the cost targets for the stationary market.
- This type of battery exhibits a high energy density, high efficiency of charge/discharge (89—92%), long cycle life, and is fabricated from inexpensive materials. . These chemistries produce battery systems with very high power densities that serve well for storing large amounts of energy.
- Because of the operating temperatures of 300 to 350 °C and the highly corrosive nature of the sodium polysulfide, such cells are primarily suitable for large-scale non-mobile applications. A suggested application is grid energy storage. A 6 MW, 48 MWh system has been installed at Tsunashima, Japan. Several other utilities are considering and implementing such a system. The sodium sulfur battery is a technology widely used in Japanese utilities.
- The NaS battery is currently being deployed in the United States by several large utilities in demonstration projects. One noteworthy leader in applying energy storage to T&D applications is American Electric Power (AEP). AEP is deploying a 5 megawatt NaS battery to solve a transmission issue in southern Texas. AEP has stated a commitment to add 1,000 MW of energy storage to their grid by 2020.
- NaS battery is currently being deployed in the United States by several large utilities in demonstration projects. The NaNiCl battery systems are utilized in Europe primarily for electric bus applications.
Lithium-air batteries might be considered a "generation after next" technology, given the steps that remain between theory and practical application. One big problem is that it's difficult to reverse the reaction that provides power, making recharging a challenge. Some key problems include finding the right catalysts to reverse the chemical reaction at low enough energy levels, as well as advances in nanotechnology to distribute that catalyst close enough to the metals.These more advanced batteries may also require three to four times as much lithium as current batteries, which adds cost.
In July 2011, MIT researchers announced they have found a way to improve the energy density of lithium-air batteries, producing a device that could potentially pack several times more energy per pound than the lithium-ion batteries that now dominate the market for rechargeable devices in everything from cellphones to cars.
The work is a continuation of a project that last year demonstrated improved efficiency in lithium-air batteries through the use of noble-metal-based catalysts. In principle, lithium-air batteries have the potential to pack even more punch for a given weight than lithium-ion batteries because they replace one of the heavy solid electrodes with a porous carbon electrode that stores energy by capturing oxygen from air flowing through the system, combining it with lithium ions to form lithium oxides.
The new work takes this advantage one step further, creating carbon-fiber-based electrodes that are substantially more porous than other carbon electrodes, and can therefore more efficiently store the solid oxidized lithium that fills the pores as the battery discharges.
IBM says we will see battery performance jump tenfold with a lithium air battery. Lithium-air batteries store energy by combining lithium with oxygen. On a theoretical basis, lithium air can store 3,400 watt-hours of energy per liter. Lithium cobalt can store 1,450 watt hours per liter.
Large primary zinc-air cells such as the Thomas A. Edison Industries Carbonaire type were used for railway signaling, remote communication sites, and navigation buoys.These were long-duration, low-rate applications.
The term zinc-air fuel cell usually refers to a zinc-air battery in which zinc metal is added and zinc oxide is removed continuously. Zinc electrolyte paste or pellets are pushed into a chamber, and waste zinc oxide is pumped into a waste tank or bladder inside the fuel tank. Fresh zinc paste or pellets are taken from the fuel tank. The zinc oxide waste is pumped out at a refueling station for recycling. Alternatively, this term may refer to an electrochemical system in which zinc is a co-reactant assisting the reformation of hydrocarbons at the anode of a fuel cell.
Rechargeable zinc-air cells are a difficult design problem since zinc precipitation from the water-based electrolyte must be closely controlled. The problems are dendrite formation, non-uniform zinc dissolution and limited solubility in electrolytes. Electrically reversing the reaction at a bi-functional air cathode, to liberate oxygen from discharge reaction products, is difficult; membranes tested to date have low overall efficiency. Charging voltage is much higher than discharge voltage, producing cycle energy efficiency as low as 50%. Providing charge and discharge functions by separate uni-functional cathodes, increases cell size, weight, and complexity.
A satisfactory electrically recharged system potentially offers low material cost and high specific energy, but none has yet reached the market. Eos Energy Storage of New York has developed the Eos Aurora, a proprietary zinc-air battery that can be used to meet the energy storage needs of utilities, electric vehicles, the military, and major industrial and commercial enterprises. They have acheived the most cycles ever realized by metal-air battery >1000 battery cycles demonstrated to date with no physical degradation and are hoping for a commercial product release in 2013.
- Anode - the electropositive electrode from which electrons are generated to do external work. In a lithium cell, the anode contains lithium, commonly held within graphite in the well-known lithium-ion batteries.
- Cathode - the electronegative electrode to which positive ions migrate inside the cell and electrons migrate through the external electrical circuit.
- Electrode – Anode or Cathode
- Electrolyte - Transfers ions/charge between electrodes during charge and discharge cycles. It allows the flow only of ions and not of electrons. The electrolyte is commonly a liquid solution containing a salt dissolved in a solvent. The electrolyte must be stable in the presence of both electrodes. An ideal electrolyte provides high conductivity over a broad temperature range, is chemically and electrochemically inert at the electrode, and is inherently safe. Too often the electrolyte is the weak link in the energy storage system, limiting both performance and reliability.
- Current Collectors - Allow the transport of electrons to and from the electrodes. They are typically metals and must not react with the electrode materials. Typically, copper is used for the anode and aluminum for the cathode (the lighter weight aluminum reacts with lithium and therefore cannot be used for lithium-based nodes).
4. Business Case
- A Smart Grid is a key enabler in integrating batteries with the goal of peak reduction.
- Large-scale, efficient, electrical energy storage (EES) systems should be able to compensate for intermittent or variable generation and still ensure that electricity is reliably available 24 hours a day without the need for fossil-fueled generation backup.
- Economics of Sodium Sulfur Batteries
- Capital $420-550 per kW
- Variable $350-400 per KWh
- Hours 4
- Total Cost $1850 - 2150 per kW
$kW + (Hours x $/kWh)
|Grid Frequency Regulation Opportunities for Fast Storage Systems - Current method to balance constantly shifting load fluctuation is to vary the frequency and periodically adjust the generation in response to a signal from the ISO|
- Load Shifting - Utility load shifting can reduce T&D congestion, improve asset utilization and defer system upgrades. Time shifting of wind generated energy to meet desired utility criteria.
- Ramp Rate Control - Minimize need for and affect on fossil fueled backup generator operation
- No Fuel Required - Like traditional batteries, but unlike fuel cells, flow batteries are an "electricity in, electricity out" system. There is no external fuel source, such as hydrogen, that is added regularly to recharge the system. Instead, electric energy is supplied to the system at one time, and the system stores that electric energy in electrochemical form until it is needed later. For grid applications, this simpler arrangement avoids the need to create new fuel or distribution systems.
- Common Materials - In addition, unlike fuel cells, flow batteries are not based on rare or valuable materials. Fuel cells typically use platinum or other expensive catalysts to speed the oxidation of their energy carrier. Instead, the material at the heart of a flow battery cell is vanadium, a plentiful, nontoxic metal.
- Cost - Too expensive - To cut costs, battery makers need new sources of raw materials. For example, the cobalt oxide used for cathodes in lithium-ion batteries is expensive and comes from politically unstable regions. Options being explored for cathode material include lithium iron phosphate, lithium manganese oxide spinel, titanium, and aluminum.
Sixty percent of the batteries cost comes from the raw materials and forty percent from the manufacturing process which can have up to sixty steps. If cheaper materials can be secured and the manufacturing process streamlined, real cost savings can be realized.
- Fire Safety - In August 2012. a fire destroyed Xtreme Power's battery storage facility n on the north shore of Oahu, Hawaii, at the 12-turbine, 30-megawatt Kahuku wind farm,. Developed by First Wind, the Kahuku facility is augmented with a 15-megawatt battery from VC-funded Xtreme Power and sells power to the island utility, HECO.
As reported by Hawaii News Now, "Flames destroyed a crucial building, raising questions about Kahuku Wind's future." (Video of the fire fromHawaii News Now is here.)
Firefighters did not enter the building until seven hours after the flames started because of questions regarding the toxicity of the "12,000 batteries." The Honolulu Fire Department said a fire at the same building in April 2011 burned itself out. There was another fire in May of this year, and both fires were attributed to ECI capacitors in inverters from Dynacorp. Xtreme is suing Dynacorp, according to Courthouse News Service.
- Charging - Take too long to charge
- Low Energy Density - While a flow battery using an electrolyte solution doesn't have the same energy density as a fuel cell using hydrogen as an energy carrier, for most grid applications high energy density is not a key design factor. Because of this lower energy density, you won't see a flow battery powering a car on the street, but the price and performance do create the potential for significant grid applications.
- Electric Vehicles vs. Grid Battery Requirements - The electric vehicle application drives most R&D for advanced materials today, but it is also the most demanding application and thus the one that justifies higher costs. In the long term, the best energy storage technologies for utility-scale applications may be different from those used for electric-drive vehicles.
- Approximately $615 million in Recovery Act SmartGrid Demonstration’s FOA’s were released on June 25. Applications are sought in Battery Storage for Utility Load Shifting or for Wind Farm Diurnal Operations and Ramping Control. The system should demonstrate an 8-15 MW / 4-8 hour battery storage system placed in the grid for load shifting or reliability. The system may be centralized or consist of aggregated, distributed units. Applications are also sought for systems in the same power and duration regime, for storage systems operating directly in conjunction with an established wind farm. The storage demonstration facility may have a shorter storage period but correspondingly higher power output if it specifically addresses ramp control.
- A123 - Watertown, MA (Nasdaq: AONE) - Founded in 2001, now one of the world’s leading suppliers of high-power lithium ion batteries. A123Systems’ proprietary Nanophosphate technology is built on nanoscale materials developed at MIT.
The stock market is showing its displeasure with the lithium-ion battery maker, sending its shares to record low prices. The company's stock sank 14 cents, or 14 percent, to 87 cents per share, and has shed more than 90 percent of its value since its 2009 IPO price of $13.50.
A123 Systems may be struggling with the automotive battery business, but it’s making some strides on grid energy storage, announcing several projects in December that show how large-scale lithium-ion batteries can help the power grid. A123 announced an 11-megawatt energy storage project to back up a wind farm that Sempra Energy plans to build on the Hawaiian island of Maui. A123 is also supplying 32 megawatts to AES Energy Storage to provide frequency regulation and wind power smoothing in West Virginia.
As of July, the Waltham, Mass.-based company had grid battery installations and orders that added up to 100 megawatts by the end of 2011, much of it in partnership with AES Energy Storage.
Another project with Massachusetts utility NSTAR is a 2-megawatt pilot that A123 will own and operate to serve ISO New England’s frequency regulation market under the grid operators Alternative Technology Regulation (ATR) pilot program.
A123’s project with Hawaii’s Maui Electric Co. is aimed at supplying a different set of energy storage functions. The battery array will be installed at a substation serving the high-end resort community of Wailea, and will be able to supply 1 megawatt-hour of energy storage, both to reduce peak load by as much as 15 percent and to smooth voltage and improve power quality, said Chris Reynolds, Maui Electric’s operations superintendent.
- Altairnano (Nasdaq: ALTI)- Reno, NV - For the first quarter of 2011, Altairnano reported a 114 percent increase in revenues to $2.6 million, up $1.4 million from the first quarter of 2010. Customer caused delays in first quarter shipments of lithium titanate to Zhuhai YinTong Energy (YTE) and of battery modules to Proterra, our largest customer in the transportation market, negatively impacted revenues. The net loss was $5.9 million, or $0.22 per share, compared to a net loss of $6.1 million, or $0.24 per share, for the first quarter of 2010.
- Amprius - From Stanford - A stealthy battery startup raised $25 million in a round led by Kleiner Perkins, with VantagePoint, IPV, Trident, Google's Eric Schmidt, and Stanford University. The firm is using a silicon nanostructure to replace a carbon anode system in batteries. The CEO, Kang Sun, claims that silicon has "an intrinsic energy density ten times higher than carbon." He called Amprius "late science stage, early engineering stage" and noted that the firm's technology is four times better than current technology. The company started in 2008 with a mission to make anodes and advanced materials that it would sell to established manufacturers.
- Axion Power (AXPW.OB) - New Castle, PA - Developing advanced batteries and an energy storage product based on a patented lead carbon battery PbC Technology™. Conventional lead-acid batteries use negative electrodes made of sponge lead pasted onto a lead grid current collector. In comparison, their technology uses negative electrodes made of microporous activated carbon with very high surface area. The result is a battery-supercapacitor hybrid that uses less lead.
- Cerametec - Salt Lake City, UT - the R&D arm of CoorsTek - Inside Ceramatec's wonder battery is a chunk of solid sodium metal mated to a sulphur compound by a paper-thin ceramic membrane. The membrane conducts ions -- electrically charged particles -- back and forth to generate a current. The company calculates that the battery will cram 20 to 40 kilowatt hours of energy into a package about the size of a refrigerator, and operate below 90 degrees C.
This may not startle you, but it should. The most energy-dense batteries available today are huge bottles of super-hot molten sodium, swirling around at 600 degrees or so. At that temperature the material is highly conductive of electricity but it's both toxic and corrosive. You wouldn't want your kids around one of these. The essence of Ceramatec's breakthrough is that high energy density can be achieved safely at normal temperatures and with solid components, not hot liquid.
Ceramatec says its new generation of battery would deliver a continuous flow of 5 kilowatts of electricity over four hours, with 3,650 daily discharge/recharge cycles over 10 years. With the batteries expected to sell in the neighborhood of $2,000, that translates to less than 3 cents per kilowatt hour over the battery's life. Conventional power from the grid typically costs in the neighborhood of 8 cents per kilowatt hour.
Five kilowatts over four hours -- how much is that? Imagine your trash compactor, food processor, vacuum cleaner, stereo, sewing machine, one surface unit of an electric range and thirty-three 60-watt light bulbs all running nonstop for four hours each day before the house battery runs out. With a projected 3,650 discharge/recharge cycles -- one per day for a decade -- you leave the next-best battery in the dust. Deep-cycling lead/acid batteries like the ones used in RVs are only good for a few hundred cycles, so they're ready for recycling in a year or so.
- Deeya Energy - Fremont, CA - Developed a unique unitized electrode/cell design with significant manufacturing and assembly advantages. Deeya's patent-pending L-Cell technology is the heart of the ESP product family. This flow battery technology offers very large storage capacity, superfast charging and capability of operating in rugged outdoor environment with temperature ranges from -5C to 50C. Deeya is working on energy storage technology for three applications — replacing diesel generators, stockpiling renewable energy, and stabilizing the electric grid — closed a third round of financing in March 2010. The oversubscribed $30 million round brings Deeya’s total venture capital investment since its founding in 2004 to $53 million
- EnerVault - Sunnyvale, CA - EnerVault is currently looking to raise its first round of funding to build a demonstration of the flow battery.
- EOS Energy Storage, New York, NY - Developed the Eos Aurora, a proprietary zinc-air battery that can be used to meet the energy storage needs of utilities, electric vehicles, the military, and major industrial and commercial enterprises.
- Low capital cost: $1000/kW, ($160/kWh which is one fifth the cost of a lithium ion battery system, according to Steve Hellman, president of the company.)
- Low operating cost: no periodic replacement of components (e.g., membranes, cells). Lowest levelized cost/kWh for renewable integration and load shifting applications Cost competitive with incumbent technology: gas-fired turbines used for peaking capacity
- 30 year life, 10,000 full cycles
- Safe, non-toxic, non-flammable electrolyte and materials
- Easily transportable: Aurora 1000 | 6000 constructed in 40 foot ISO shipping container
- Easy to locate: not site constrained like some other energy storage technologies
- Stable and self healing battery operation
- Available in 2013: Currently scaling up battery prototypes for initial manufacturing in 2012 and delivery of MW scale systems to first customers in 2013
The Ionex Energy Storage System is a 1-megawatt-hour unit using large-format prismatic batteries based on lithium iron phosphate (LiFePo4) and capable of producing 1 megawatt or 2 megawatts of continuous AC power from a 40-foot shipping container weighing 35,000 kilograms. The container can be mounted on a concrete pad or on a wheeled trailer.
Using seed money from within MIT, Sadoway and his team invented the liquid metal battery or, more academically, a process called Reversible Ambipolar Electrolysis.
The battery uses molten antimony and molten magnesium separated by an electrolyte. Sadoway claims that the all-liquid configuration is self-assembling and is expected to be scalable at low cost. Furthermore, this technology may have a shot at being cheaper than sodium sulfur (NaS) batteries. This battery is intended for large-scale electrical grid applications.
NGK, the maker of what has long been considered the most bankable electrochemical energy storage solution, sodium sulfur batteries, has had to revise its revenue forecasts due to a "fire incident." Excerpts from a statement by the firm follow:
On September 21, NGK-manufactured NAS batteries for storing electricity owned by The Tokyo Electric Power Company, Incorporated (Head Office: Chiyoda-ku, Tokyo) and installed at the Tsukuba Plant (Joso City, Ibaraki Prefecture) of Mitsubishi Materials Corporation (Head Office: Chiyoda-ku, Tokyo) caught on fire.
At present, the fire authorities are investigating the cause of the fire.
NGK began shipping NAS batteries in 2002 and since then they have been installed in a total of 174 locations in 6 countries around the world, storing 305,000 kilowatts of electricity.
NGK is putting the highest priority on identifying the cause of this incident and looking at measures to prevent a reoccurrence. At the same time, NGK has temporarily halted production of NAS batteries in the meantime. Furthermore, in order to make doubly sure of safety, NGK also asks customers who need to maintain a minimal level of functionality such as using the batteries as an emergency power source and so on, to consult with it on an individual basis about the method of operation.
NGK has requested that customers refrain from using the NGK batteries until the cause of the fire is discovered. NGK has halted production of the energy storage product and reduced its revenue forecasts for the year by about 20 percent.
In July 2010 they received an ARPA-E grant to develop an extremely low cost and long life electrode for their EnergyCells
In July 2011, Primus Power, has generated $11 million in follow-on funding for its grid-scale storage technology—five times more than ARPA-E's $2 million 2010 investment. As Secretary Chu has said about follow-on funding for ARPA-E projects, "This is precisely the innovation leverage that is needed to win the future."
Primus Power has developed a low-cost, distributed storage flow battery made of tanks filled with high energy density electrolytes that are pumped throughout the battery system. This flow battery can store renewable energy such as wind and solar power and then release that energy into the grid during peak load times. Since renewable energy is often variable, the ability to store this electricity to balance grid power is becoming significantly more important as renewables become more prevalent in the United States.
- The VRB Energy Storage System (VRB-ESS) is an electrical energy storage system based on the patented vanadium-based redox regenerative fuel cell that converts chemical energy into electrical energy. Energy is stored chemically in different ionic forms of vanadium in a dilute sulphuric acid electrolyte. The electrolyte is pumped from separate plastic storage tanks into flow cells across a proton exchange membrane (PEM) where one form of electrolyte is electrochemically oxidized and the other is electrochemically reduced.
Seeo has now raised a total of more than $10.6 million for its solid-state battery, which is based on a solid polymer electrolyte that the founders developed at the Lawrence Berkeley National Lab. The material, which Seeo began licensing from the lab in 2007, allows for a more stable battery with higher energy density and none of the flammable liquid electrolytes that present a safety risk in conventional lithium-ion batteries.
- SEI has 16 operational VRB systems in Japan, which include peak shaving, utility and renewable energy storage applications, and has developed a 42-kW cell stack. A 3 MW x 1.5 sec. plus a 1.5 MW x 1 hr system for Tottori Sanyo Electric has been operating since 2001 at a large liquid crystal manufacturing plant as a combination of UPS for voltage sag compensation and a peak shaver to reduce peak load.
- Leonardo Energy - Wind farm with battery storage in Ireland
- Mechanical Engineering - Flow batteries can turn intermittent wind power from a utility manager's headache to a green and reliable energy source
- Seeking Alpha – Energy Storage on the Smart Grid
- Seeking Alpha – John Peterson Blogs
- Electrochemical Energy Storage for Green Grid Zhenguo Yang,* Jianlu Zhang, Michael C. W. Kintner-Meyer, Xiaochuan Lu, Daiwon Choi, John P. Lemmon,and Jun Liu Paciﬁc Northwest National Laboratory, Richland, Washington. Sep 2010