Energy Storage News

(Note: My main website is now Only the opening parapgraphs of energy storage related articles appear on this site. The links to the full article point to If you want an RSS feed you need to go to the new web site.)

StratoSolar Proposes to Build Floating PV Platforms in the Stratosphere With Built In Energy Storage

I recently stumbled on the website of a company called Stratosolar which is proposing to deploy floating PV platforms 20km above the earth's surface. The platforms would be 300 meters in length (along the direction of wind flow) and would be tethered to the ground by kevlar straps. Power cables which would conduct solar generated electricity to the ground would be attached to the kevlar straps. StratoSolar claims that the maximum wind speed of 50m/s at 20km altitude will allow stable, secure floating platform deployment with only small variation is horizontal position (According to their caclulation a length of 300 meters is required to achieve this stability.). Weights would be added to the tethers as a form of gravity energy storage. At 20Km of altitude each kg of weight would store 54Wh of gravitational potential energy (compare 38wh/kg for lead acid batteries). Excess electricity would be used to elevate the weights into the stratosphere, and the descending weights would be used to generate electricity during during period of low PV electricity production. full article

Jan 8, 2017

Large-scale Industrial Cultivation of Marine Microalgae (ICMM) Proposed as a Way to Provide Food and Fuel in a Post Fossil Fuel World

Green Car Congress recently posted a story about an article in the magazine Oceanographydetailing a proposal to obtain liquid hydrocarbon fuels and protein for animal feed from large-scale industrial cultivation of marine microalgae (ICMM). Analysis indicates that coproduction of food and fuel is needed in order for algal bio-fuels to achieve production costs comparable to liquid fossil fuels. The authors argue that cultivation of marine micro algae is potentially an order of magnitude more productive (presumably per square meter of ocean cultivated) compared to biomass production on land. They further argue that the fact that salt water is used rather than fresh water can help to manage the demand on this important resource. They particularly emphasize the comparison of algal proteins to soy protein, maintaining that not only is the production more efficient but that the algal protein is potentially of higher quality. If ICMM is as efficient as projected then it may be possible to reforest marginally productive agricultural land thus leading to the removal some amount of CO2 from the atmosphere as well as helping to preserve land based bio-diversity. full article

December 19, 2016

Sion Power Develops Lithium Sulfur Batteries

Sion Power has developed a lithium sulfur battery with and energy density of 350Wh/kg, and they claim that a density of 600Wh/hg will be achievable relatively soon. They do not specifically cite a cycle life for this battery but if I attempt to interpret the cycle life information given in this presentation I conclude that Sion Power's Current lithium sulfur battery has a cycle life at full depth of discharge considerably less than 1000 cycles. Cycle life is currently the Achilles heel of lithium sulfur batteries. Unwanted side reaction of the lithium sulfide formed in the sulfur cathode as well as mechanical damage due the the growing and shrinking of the sulfur cathode conspire to limit the cycle life of this battery technology. Like Oxis Energy Sion Power's applications page does not mention the obvious market of consumer electronics, making be suspect that the cost of the batteries is fairly high compare to lithium ion batteries. The high theoretical energy density of lithium sulfur batteries makes them an attractive alternative to lithium ion batteries, but I do not think that this technology is ready for prime time.

First posted on

Aug 16, 2015

Oxis Energy Develops Lithium Sulfur Batteries

Lithium sulfur batteries have a much higher theoretical maximum energy density than lithium ion batteries (3 to 5 time according to this article). To date, however, practical implementation of this battery chemistry have have achieve only a fraction of the theoretical maximum energy density and have relatively short cycle life because of undesirable side reaction of the lithium sulfide formed in the sulfur cathode and because of physical degradation of the cathode due to swelling and shrinking during the charge/discharge cycle. Lots of fundamental research is being done trying to overcome both of these problems, but commercialization still seems to be in the indefinite future. more
August 15, 2015

Lawrence Berkeley Laboratory Scientists Develop Low Temperature Sodium Sulfur Battery

The most widely used battery technology for multi-hour grid energy storage is NGK Insulator's high temperature (300 to 350C) sodium sulfur (NAS) battery. The high operating temperature is required to obtain adequate mobility for the sodium ions through the solid ceramic beta-alumina electrolyte. The largest installation of such batteries is 204MWhr installation supporting a wind farm in Rokkasho Japan. This installation opened operations in 2008. The sodium sulfur chemistry is attractive from a scalability point of view since both sodium and sulfur are earth abundant elements. more

April 3, 2015

Carnot Compression Has Developed a Centrifugal Isothermal Gas Compressor that can Achieve a 200 to 1 Compression Ratio in a Single Stage

As I have mentioned before several different companies are developing near isothermal gas compression systems which inject water vapor into the compression chamber in order to remove heat from the compressed gas. I have recently read about another company called Carnot Compression which has developed an isothermal gas compressor which injects gas into water. The compression fluid is a gas/water emulsion (i.e. a mixture of gas bubbles in water matrix). The emulsion is contained inside a spinning cylindrical chamber where the gas bubbles are compressed as they migrate to the outer surface of the cylinder. The water absorbs the heat generated in the gas by compression which the compression nearly isothermal. Exactly how the gas gets out of the rotating compressor chamber into the pressure vessel is not clear from the limited description given on Carnot's web site. Apparently only gas gets out and not water, since Carnot claims that the compressed gas is very dry and does not require further drying steps as do other varieties of gas compressor. more

Jan 30, 2015

Lithium Ion Capacitors

The most common negative electrode or anode used in lithium ion batteries is made of graphite, the same material used for pencil lead. The electrodes are comparatively cheap, have high roundtrip charging/discharging efficiency, and have very good cycle life. The positive electrode or cathode is substantially more expensive and has a shorter cycle life. A new class of electrochemical storage devices has emerged called lithium ion capacitors. They are not true capacitors because the anode is the same graphite anode used in lithium ion batteries and undergoes a chemical reaction with lithium. However, the cathode is replaced by the same high surface activated carbon used in ultracapacitors. This electrode does not interact chemically with lithium but stores energy in the electric field between two layers of charges. more

December 23, 2014

Current Lithium Ion Battery Prices

Rechargeable Lithium ion batteries have high energy density and high power density as well as pretty good cycle life (>1000 cycles at 100% depth of discharge) and good round trip efficiency. Historically lithium on batteries have been relatively expensive but have found a performance niche in consumer electronics because of the willingness of customers to pay a price premium for long run times. They are now finding a performance niche in battery electric vehicles for the same reason. more

October 4, 2014

Energy Storage on a Mountain Side

I have written before here and here about energy storage in the form of the gravitational potential energy of a solid mass. A now defucnt startup called Mechanical Electric Inc. proposed to store energy in suspended weights in shafts in commercial buildings. I am not surprised the the company is defunct since as I pointed out in my previous posting the low energy density of this storage system and the high value of the interior space of buildings constructed for human use made such a system economically impractical. more

May 16, 2014

Beacon Power Acquires a New Design for Large Composite Flywheel from Hanyang University Professor Ha Sung Kyu

I have written before about the efforts of Beacon Power and Amber Kinetics efforts to develop flywheel energy storage systems for grid frequency regulation. One can argue that Beacon power is the more successful of the two companies since they have already installed a 20MW flywheel plant at Stephentown NY, and are scheduled to open a second 20MW plant at Hazeltown PA within the next few months, while Amber Kinetics has yet to install its first demo system. However, a bankruptcy and acquisition intervened between Beacon Power's first and second plant and it is not clear that they have received any additional orders. more

April 3, 2014

MIT spinoff Ambri is developing liquid metal batteries for statinary electricity storage applications

Dr. Donald Sadoway, as chemistry professor at MIT, is developing a new type of energy storage device called a liquid metal battery for grid storage applications. The conceptual physical form of this battery is the simplest imaginable: In the charged stated it consists of three liquid layers lying on top of one another. One layer is an electropositive metal, one layer is an electrolytic salt, and one is an electronegative metal. The layers remain separate due to the different densities of the three liquids and due to inherent low solubility of the metals in the liquid salt. more

Nov 23, 2013

Researchers at Northwestern University and the Colorado School of Mines Group Seek to Develop Solid Oxide Flow Batteries Which Would Utilize Water and Carbon Dioxide as Energy Storage Media

An electrolyzer is an electrochemical device with two electrodes which acts somewhat like the energy storage phase of a rechargeable battery; When an electric potential is applied between the two electrodes chemical changes occur which produce two chemical species which are capable of reaction with each other to produce energy. That is to say electrical energy is converted in to chemical potential energy. Electrolysis often takes the form of decomposing a compound chemical substance, the most well known of such reactions being the decomposition of water in to molecular hydrogen and oxygen, although many other substance can also be electrolytically decomposed. For example this paper claims that a solid oxide electrochemical cell can be designed to electrolytically decompose carbon dioxide into oxygen and carbon monoxide just as efficiently as water can be decomposed. Another example of great practical importance is the electrolytic production pure aluminum from its oxide Al2O3. more

Jun 29, 2013

Amber Kinetics Develops Steel Wire Flywheels for Grid Frequency Regulation Applications

In my last posting about flywheel energy storage I speculated that since steel flywheels appear to be beating out carbon fiber composite flywheels in UPS (Uninterruptible Power Supply) systems, it might turn out that steel flywheels would be also be a better choice for grid frequency regulation applications. (Frequency regulation, by the way, is actually power regulation. The grid is set up so that mismatches between load and generation manifest themselves as changes in the frequency of the AC current.) A startup company called Amber Kinetics, which originated from a Stanford University Cleantech Entrepreneurship class, is targeting exactly this application with flywheel rims made out of steel wire (See this presentation). more

May 1, 2013

Flywheels For Short Duration High Power Energy Storage Applications

I first read about the possibility of using composites flywheel suspended in a vacuum as high energy storage devices nearly 30 years ago in an article in Physics Today. Since two of the companies (Pentadyne andd Beacon Power) at the forefront of this field have declared bankrupty within the last year and a half, one would have to say the progress in the commercialization of this technology has been glacial. more

March 1, 2013

Sodium ion battery developed at Murdoch University

Drs Manickam Minakshi and Danielle Meyrick at Murdoch University in Australia have developed a water based sodium ion battery. This is another version of the battery technology being developed by Aquion Energy about which I have previously written. The announcement article reveals only a small amount of information about the battery design: more

Aug 18, 2013

Isothermal Compressed Air Energy Storage

A number of industrial processes (e.g. steel production, air separation, oil refining, nitric acid production, ethylene oxide production, etc) which produce high pressure gas at high temperature use expansion turbines to extract energy from the gas either in the form of mechanical work or of electrical current. This fact suggests the idea of using compressed gas as an energy storage medium. Obviously the cost of the expansion turbine itself is not prohibitive or this technology would not be utilized in existing industrial processes. However, other economic consideration enter the equation when one considers the deliberate compression and storage of gas rather than utilizing compressed gas that is the natural product of some other industrial process. Among these considerations are: more

May 13, 2012

EOS plans to manufacture zinc air batteries for large scale stationary storage applications

A company called EOS is planning to manufacture zinc-air batteries for utility scale grid storage applications. Metal-air batteries which make use of oxygen in the atmosphere as one of the electrodes have long been known to have high energy density. Non-rechargeable zinc-air button cells are currently being commercially produced by a number of companies primarily for use in hearing aids. However, producing rechargeable zinc-air batteries has proved difficult. Among the problems with such rechargeable batteries are the formation of dendritric zinc structures on the anode during recharging (The dendrites eventually pierce the separator between the anode and cathode and cause the battery to short circuit.) and the clogging of the gas diffusion electrode by potassium carbonate evolved from the electrolyte solution containing KOH. According the this posting both of these problems have been solved in a laboratory setting by the use of non-aqueous electrolytes. more.

Oct 9, 2011

Aquion Energy to manufacture low temperature sodium carbon batteries for large scale stationary storage applications

A company called Aquion Energy has developed a new type of sodium ion battery which it claims has superior performance and economic characteristics compared to NGK Insulator's molten salt sodium sulfur (NaS) batteries. They are targeting large scale grid storage applications with this technology. more.

Sep 02, 2011

Highview Power to build cryogenic energy storage plants which use liquid air as the energy storage medium

A British company called Highview power is proposing to store electrical energy using liquid air as the storage medium. Electrical energy will be used to run an air liquefaction plant, and at a later time the air will be reheated, expanded, and use to power a turbine/generator. The discharging cycle can use ambient heat, but with higher temperature heat source better round trip efficiency can be obtained. Highview is planning to use waste heat from existing industrial processes in order to obtain better round trip storage efficiency. A prototype of the turbine generator powered by liquid air and waste heat is already in operation delivering power to the grid, but a fully integrated storage system with on site generation of liquid air is not yet operational. more

Jul 15, 2011

Maxwell Ultra Capacitors Store Relatively Small Amounts of Energy but Accept and Deliver it at High Power

Ultra capacitors utilize high surface area carbon particles surrounded by an electrolytic medium to store energy in the electric field created by charged particles residing on the carbon surface. Maxwell Ultracapacitors is a a leading manufacturer of such energy storage devices. Below are some characterics of the BCAP3000 capacitor taken from the K2 series datasheet: more

Jul 3, 2011

GE Plans to Manufacture Molten Salt Sodium Nickel Choride Batteries for Mobile and Stationary Electricity Storage Applications

Some time ago GE announced that it was planning manufacture sodium metal halide batteries for utility scale storage applications. They have now revealed that the metal/halide combination in question is nickel/chlorine, the same as that used in ">FZ Sonicks's Zebra batteries. Some information taken from Durathon Utilility Battery Brochure is listed below: more (June 25,2011)

Jun 25, 2011

FZ Sonick Plans to Manufacture Molten Salt Sodium Nickel Choride Batteries for Mobile and Stationary Electricity Storage Applications

A sister technology to NGK Insulators molten salt sodium sulfur (NaS)batteries is molten salt sodium nickel chloride batteries also called Zebra batteries after the trade name of their sole manufacturer, a Swiss company called MES-DEA. Like NaS batteries zebra batteries have a molten sodium anode separated from the cathode by a tubular solid electrolyte made out of beta-alumina. The cathode is primarily composed of nickel chloride (NiCl2) rather than of sulphur. During the discharge process sodium ions are formed in that anode and migrate through the solid electrolyte into the cathode. The primarily chemical reaction in the cathode is the exchange of Cl between NiCl2 and the sodium ions resulting in the growth of large crystals of NaCl. During discharge this process is reversed and the NaCl crystals decompose and the sodium ions migrate back into the anode. more.

Jun 16, 2011

Natrion Corporation Proposes to Develop a New Type of Sodium Sulfur (NaS) Battery Superior to NGK Insulators Molten Salt Version

I have written previously about NGK Insulator's large format molten salt Sodium Sulfur Batteries which they are selling in the utility scale storage market. Trans Ionics Corporation is developing a new form of Sodium Sulfur (NaS) battery which they claim will have performance characteristics which will allow it to compete in the EV and PHEV markets. Some details about the design of these battery taken from their web site are given below: more

Oct 21, 2010

Elevated Weight Pumped Hydro Storage System

I have written previously about Mechanical Electric Inc.'s plans of developing an energy storage system which employs elevated weights as the energy storage medium. For reasons which I gave in the previous posting I do not think that this system is likely to be economically competitive (Just as an aside I note that the Mechanical Electric web site has vanished, so possibly their plans are no longer extant). Another possibility for such mechanical energy storage is to dig a deep shaft in the ground in which a large weight can move up and down. Excavating such a shaft is likely to be cheaper than erecting a very tall free standing structure. A company call LaunchPoint Technologies Inc. has recently spun off a subsidiary called Gravity Power LLC which is planning to develop such underground energy storage facilities. Their patent portfolio includes purely mechanical system with weights and cables, but the technology they are pushing is a hybrid system employing a large solid weight and water in a new form of underground pumped hydro storage(I have discussed underground pumped hydro previously here). more

Oct 14, 2010

Energy Storage in Elevated Weights

I have written previously about pumped hydro storage which uses the gravitational potential energy difference between two reservoirs at different altitudes to store energy. The same concept of gravitational potential energy as a storage medium could be used with other substances than water. A while back I ran across the web site of a company called Mechanical Electric Inc. which is proposing to build this type of energy storage system. Below are some extracts taken from their web site: more

Aug 2, 2010

Riverbank Power plans to build underground pumped hydro storage facilities

Pumped hydro energy storage uses reversible hydro electric turbines which employ electricity to run backwards and pump water from a low elevation reservoir to a high elevation reservoir. At some later time the water from the high elevation reservoir can be run back through the turbines to produce electricity. The round trip efficiency (i.e. the percentage of the input electrical energy which is recovered during forward operation of the turbines in the range of 70% to 85%. more

Apr 28, 2010

Deeya Energy Iron Chromium Flow Batteries

Deeya Energy is a company planning to manufacture flow batteries for electrical energy storage. As I have written before the promise of flow batteries is very long cycle life because the electrodes are inert and are not degraded by the chemical interactions which are taking place in the liquid electrolytes which flow past the electrodes and past the ion exchange membrane which separates the half cells of the battery. more

Feb 20, 2010

Vanadium Redox Flow Batteries

Vanadium redox flow batteries are a potential low cost (relatively speaking at least) electrical energy storage technology. In flow batteries liquid electrolytes flow past solid electrodes which are separated by an ion exchange membrane which allows one of the charged species to move back and forth between the two electrodes (one direction of movement corresponds to discharge and the other charging). In pure flow batteries it is claimed that the solid electrodes inert and do not directly take part in the chemical reaction taking place in the two half cells, so that they are not consumed or degraded (or at least degraded only very slowly) by the chemical reaction occurring in the liquid electrolytes. For this reason flow batteries can potentially have very long cycle life compared to other kinds of batteries. more

Jan 24, 2010

Zinc Bromine Flow Batteries For Large Scale Stationary Electricity Storage

As I have written previously sodium sulfur (NAS) batteries are currently the leading commercial technology for large scale electrochemical storage of electricity. Another battery type which is being explored for large scale energy storage is zinc bromine flow batteries. Here are some details about three manufacturers of these batteries. more

Dec 27, 2009

Lithium Ion Batteries in the Stationary Storage Market

Lithium ion batteries are the dominant energy storage technology for mobile consumer electronics. In addition recent years have seen a tremendous flurry of activity trying to develop large format lithium ion batteres for the EV and PHEV transportation market. Can lithium batteries also compete in the large scale stationary storage market? Here is some information about four manufacturers who seem to think so. more (November 21, 2009)

Nov 21, 2009

NGK Insulators Manufactures Sodium Sulfur Batteries for Large Scale Grid Energy Storage

Sodium sulfur (NAS) batteries are the only commericially mature, large scale energy storage technology which can be sited at arbitrary locations. Pumped hydro storage is also a mature form of energy storage, but such storage facilities can only be sited where there a suitable geographical location with high and low storage reservoirs. more

Nov 8, 2009, 2010

Lloyd Energy Manfacture High Temperature Thermal Storage Systems Using Graphite Blocks

As I discussed in a previous post, a practical demonstration of molten nitrate salt as a thermal storage medium for concentrated solar power (CSP) has already been achieved. However a variety of different storage media have been proposed. A company called Lloyd Energy Storage has developed a system based on high purity graphite blocks. Some details about this system taken from their web site are given below: more

Nov 1, 2009

Molten Nitrate Salt for Solar Thermal Energy Storage

Concentrating solar power (CSP) systems which use concentrated sunlight to run steam turbines have been receiving a lot of attention in recent years as a potential low cost alternative to photovoltaic cells. Like all solar technologies the power delivery profile of CSP depends on the availability of sunlight. Adding energy storage to such systems increases their power delivery flexibility. Unlike PV cells CSP systems can potentially store thermal energy rather than electrical energy giving them a cost advantage in this area because sensible heat storage has lower cost than electrical storage in batteries. more

Oct 11, 2009

LaunchPoint Technolgies Design for Ring Type Levitated Flywheel

The engineeing design group LaunchPoint Technologies has proposed a design for a hubless magnetically levitated composite flywheel which has the potential to be scaled up to very large sizes. Here are some details from the presentaion called Third Generation Flywheels For High Power Electricity Storage by O.J. Fiske and M.R. Ricci: more

Sep 26, 2009

Flywheels With Low Loss Superconducting Bearings

I stumbled across an article published on line by International Technology Research Institute at Loyola College in Maryland concering reasearch and develoment on low loss superconducting bearing for energy storage flywheels. Some details of this report are presented below the fold. more

Sep 21, 2009

Flybrid Systems Composite Flywheels for Regenerative Braking Energy Storage

A Britsh company called Flybrid Systems is manufacuring carbon composite flywheel systems for regenerative braking systems. (September 20, 2009)

Beacon Composite Flywheels for Requency Regulation

Beacon Power is manufacturing 25kWh composite flywheels for grid frequency regulation services. Whether or not their product can be economically competitive in this market remains to be seen. (September 14, 2009)

Pentadyne High RPM Flywheels

Pentadyne has been manufacturing high RPM flywheels as energy storage devices for UPS system since 2004. Here is some information about their product. (September 13, 2009)

Isentropic Pumped Heat Storage

UK startup Isentropic claims it has developed a new energy storage method that sound too good to be true and therefore probably is. (Sep 13, 2009)

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