Energy Storage
 
 
 
 
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Anyone who believes that exponential growth can go on forever in a finite world is either a madman or an economist.    
 
Kenneth E. Boulding 
      
Energy Storage General 
 
Technology page of the Electricty Storage Association - A brief discussion of the status of various electricity storage technologies. 
 
Compressed Air Energy Storage 
 
Energy Storage and Power Corporation low cost CAES design - This is a low cost CAES design which inject the stored air into an existing natural gas turbine with up to 65% of the generated power being provided by the compressed air. This storage and conversion method is the cheapest as long a natural gas remains at current prices. (Viewed 11/30/2006) 
 
Energy Storage and Power Corporation Paper CAES design incuding storage in underground pipes for wind/biogas combined system - This paper give more details on the use of compressed air with natural gas turbines to improve the over all system efficiency. It includes an economic analysis of the use of compresses air with land fill gas generation systems. (Viewd 11/26/2006)  
 
PSEG Global and Energy Storage and Power Coporation joint venture to market 2'nd generation CAES technology - Energy Storage and Power Corporation, headed by Dr. Michael Nakhamkin, designed and built the McIntosh, Alabama 110MW CAES plant sixteen years ago. They have contiued to do research and development work on CAES but have not built any additional plants. Now they have formed a joint venture with the power company PSEG global to market second generation CAES designs. (Viewed 01/08/2009) 
 
TVA Presentation on Pumped Hydro and CAES Energy Storage - A high level presentation on energy storage systems for utility scale electricty generation systems. The claim made in this paper and the one just above that over 80% of the U.S. has suitable geologic locations for CASE sytem is interesting, but no supporting data is provided. (Viewed 11/30/2006) 
 
European Wind Energy Conference paper on adiabatic CAES  - CAES systems which require natural gas turbines for extraction of the stored energy cannot support wind or solar only generation systems. A European group is exploring the possibility of the heat of compression from a CASES system which, if combined with the stored air, could run turbines without the need of a combustible gas such a methane. (Viewed 11/30/2006) 
 
Hybrid Compressed Air / Supercapacitor Storage System - Another compressed air storage system which does not require which does not require a combustible gas for re-extraction of the stored energy. (Viewed 11/30/2006) 
 
Active Power Thermal & Compressed Air Storage (TACAS) - An interesting compressed air storage system for uninteruptible power supplies (UPS). This system is not appropriate for distributed generation energy storage. However, this is a real product which is currently being sold as an alternative to lead acid batteries in certain niche applications. (Viewed 11/30/2006) 
 
Modeling of Wind Energy / Compressed Air Power System Without Electricity Generation - An interesting paper by Chinese researcher looking into the possibllity of using compressed air from wind turbines as a primary energy source to run pneumatic machinery. This idea may seem rather quaint to a culture which has grown accustomed to a 24/7 electricity from the grid, but in a post fossil fuel world many alternatives to our 'normal' way of doing things may have to be considered. (Viewed 11/30/2006) 
 
 
Pumped Hydro Storage 
 
ESA description of pumped hydro storage - This brief description of pumped hydro storage includes a list of all world will facilities with output >= 1000MW. (Viewed 11/30/2006) 
 
 
Electrochemical Batteries 
 
 
NGK Insulators, Ltd. NAS Batteries for Load Leveling Applications - These batteries appear to be the most commercially advanced alternative chemistry batteries. NGK claims to have installed 130 systems in Japan with the largest being an 8MW /58MWh system. A 30MW / 216MWh system for a wind farm is in the planning stage. They claim triple the energy density and triple the lifetime of lead acid batteries. Their energy efficiency is only 65%. At U.S. $2500/kW these batteries are fairly expensive (wind turbine cost are about U.S. $1000/kW) but there is hope that the costs will come down as the production volumes go up. 
 
Professor Maria Skyllas-Kazacos introduction to the vanadium redox flow battery - An introduction to an exciting new type of battery by the inventor. The estimated capital cost per kWhr of storage ($150) is 25% to 30% larger than for lead acid batteries. However, the abilitity to undergo deep discharge as well as the ability to be charged and discharged very rapidly may allow the cost per kWhr delivered in a renewable energy application to be far lower than lead-acid batteries. Furthermore these batteries have potentiallly a very long life (up to 20 years) and are more environmentally friendly than lead acid batteries. (Viewed 11/30/2006) 
 
SEI Tech Paper on the Development of a Vanandium Redox Flow Battery Storage System - A paper by a Japanese firm on the development of a vanadium redox flow battery storage system for load leveling applications. 
 
HIL Tech Developments Limited application note on Vanadium Redox Flow batteries - An engineering consutancy firm's application note on the potential use of Vanadium redox flow batteries in industrial storage applicaltions in the range of 20kWh to 500kWh. This is a storage niche currently occupied by lead acid batteries. (Viewed 11/30/2006) 
 
 
 
 
 
 
Flywheel Batteries 
 
Active Power flywheelbattery for power conditioning applications - Flywheels made out of advance materials (carbon fiber composites or fused silica) can achieved higher storage densities than chemical batteries. However, high costs and high losses of stored energy make them inappropriate for long term storage applications. Some enthusiactic inventors are hoping to overcome these limits, but their are no signs that they have done so yet. In the mean time flywheel batteries have found a niche in short time period power quality applications such as uninterruptible power supplies (UPS). This paper describes in a clear fashion the development of flywheel energy storage systems and their strengths and weaknesses. Active Power seems to be the only company with signficant sales in this technology. (Viewed 11/30/2006) 
 
Pentadyne carbon composite flywheel batteries - Pentadyne claims that their product rotates at a top speed of 54,000rpm and has an energy storage efficiency of 99.8%. Their product appears to be commercially mature with an signficant number of installation in UPS systems. (Viewed  06/20/2007) 
 
Beacon Bower Flywheel battery systems - Beacon Power flywheels are made out of carbon/fiberglass composites and spin at over twice the RPM of Active Power's steel flywheels. However, Beacon products have not yet come to market . (Viewed 11/30/2006) 
 
Flybrid carbon composite flywheels for hybrid cars - This product is not an electrical battery. Energy is received (during brakin) and delivered via a mechanical transmission. Flybrid claim to attain a maximum rotational speed of 64,500RPM. (Viewed 12/03/2009 
 
Williams Hybrid Power magnetically loaded carbon composite flywheel for hybrid vehicles - Williams incoroporte the permanent magnets of the generator/motor directly into the flywheel vial magnetic particles. They claim that this methodolgy leads to lighter weight and greater safety in the event of flywheel failure. (Viewed 12/03/2009) 
 
Ricardo Kinergy carbon composite flywheel hybrid vehicles - Yet another company building flyweel energy storage systems for hybrid vehicles. Is this a trend? (Viewed 12/03/2009) 
 
 
 
Thermal Storage 
 
EERE Thermal Storage Overview for Solar Trough Systems - This paper discusses various technologies for storage of thermal energy for use in solar trough electricity generating systems. The technology closest to commercial applications seems to be liquid nitrate salts. (Viewed 11/30/2006) 
 
Underground Thermal Storage for Space Heating in Germany - This paper review various underground solar heat storage for districti heating which have been implemented in Germany. They conclude that the cost energy delivered from such systems is about three times the current cost of fossil fuel heating. (viewed 01/24/2009) 
 
Chemical Energy Storage 
 
Wind/Battery/Hydrogen Sytem to Improve Electricity Storage Economics - An ecnomic analysis of hybrid battery/hydrogen production energy storage systems for wind turbines. The idea is that because electoryzers are expensive, installing enough capacity to convert a wind turbine's maximum output into hydrogen is very expensive. So in this scheme, up to a certain level of electric output from the turbine/wind farm all the electrical energy is converted into hydrogen for sale in some appropriate market. Above that level of output, the extra electrical energy is either dumped into the grid (if the grid can absorb it) or stored in batteries. The authors claim that such a hybrid system can improve the economics a wind energy system with storage. (Viewed 11/30/2006) 
 
NREL Estimate of the Costs of Hydrogen Production Via Electrolysis - Estimates of hydrogen prodution costs with current electrolyzer technology. (Viewed 11/30/2006)  
 
Toshiba Proposal for Using Renewable Hdyogen/Methanol for Electricity Generation - A scheme to produce dispatchable electric power from wind or other intermittent renewable energy sources. (Viewed 11/30/2006) 
 
Sandia Labs Advanced Internal Combustion Engine For Hydrogen, Biogas, Ammonia and Other Renewable Fuels - Hydrogen and ammonia are possible form of chemical energy storage for intermittent renewable energy sources. This paper describe an alternative to fuel cells for reconverting the store energy into electric power.  (Viewed 11/30/2006) 
 
GE Development Work on Lost Cost Electrolyzer to Produce Hydrogen from Water - If hydrogen or other chemicals derive from hydrogen d are going to be used to store electric energy economically then electrolyzer capital costs need to be reduced. Here is a potential technology for such cost reduction. (Viewed 11/30/2006)  
 
Norsk Hydro experiment showing that H2 with 10% Nitrogen can be used in standard combined cycle gas turbine without performance or reliability degradation - Since hydrogen can be used to run conbined cycle gas turbines, fuel cells are not needed for stationary electrical generation applications using hydrogen. (Viewed 11/30/2006) 
 
Solar Hydrogen Energy Corporation press release on thermal catalytic production of hydrogen - Research on convering sunlight into hydrogen with out using electric current as an intermmediary. (Viewed 11/30/2006) 
 
Japan Science and Technology Agency reasearch project on photocatalytic hydrogen production using GaN - More research on converting sunlight into hydrogen without the need to first create electrical current. (Viewed 11/30/2006) 
 
Solar Carbothermic Reduction of ZnO - Another method of storing solar energy in the form of chemical potential energy without prior conversion into electricity. (Viewed 11/30/2006) 
 
Amminex solid state ammonia storage system - Ammonia (NH3) is an attractive chemical energy storage substance because it does not contain any carbon. In order to liquify ammonia it has to be stored at high pressure (8 bar). Since ammonia gas is quite toxic any leak in such a storage tank would be extremely dangerous. Ammniex has developed a solid state storage system based on a low cost magnesim cloride salt. If a way could be found to prouduce low cost hydrogen from renewable resources (a big "if" I admit) then ammonia synthesis via the Haber-Bosch process could make ammmonia into a transportable fuel.  (Viewed 04/24/2008) 
 
Carbon monoxide can be reacted with water to produce hydrogen via the water/gas shift reacton (CO + H2O ==> H2 +CO2). Therefore splitting CO2 to produce CO and oxygen is a possible route to producing hydrogen and hydrogen based fuels. The following links are related to efforts at CO2 splitting. 
 
 
 
 
Los Alamos scientists develop solar process for high temperature direct thermal splitting of CO2 - (Viewed 01/07/2009) Since the Los Alamos licensed their CO2 splitting technology to a private company (Subdrop Fules) they removed most of the information about their process from the web. This annoucement contains minimal information about the process other than that it uses high termperature solar energy. The reference below describes some earlier research on this same subject and probably gives some idea of techniques used by the Los Alamos group. (Viewed 01/07/2009) 
 
CO production via direct thermal splitting of CO2  - An iteresting 1986 paper on splitting CO2 in to CO and oxygen and then separating them by use of a semipermiable membrane. The authors conclude that direct thermal splitting of CO2 to produce CO is can achieve much higher efficiencies at a given temperature than the direct thermal splitting of water to produce hydrogen. This paper may give some insight into how the CO2 splitting process developed by the Los Alalmos group referrred to above. (Viewed 01/07/2009) 
 
Super Capacitors 
 
MIT research on carbon nanotube capacitors - A news article on carbon nano-tube based capacitors which may be able to acheive energy densities comparable to chemical batteries and potential lifetimes of 100,000 plus cycles. Don't hold your breath waiting for them to enter the market, however. Carbon nano-tube manufacturing is still an expensive research and development activity (Viewed 11/30/2006) 
The real science of political economy, which has yet to be distinguished from the bastard science, as medicine from witchcraft, and astronomy from astrology, is that which teaches nations to desire and labor for the things that lead to life; and which teaches them to scorn and destroy the things which lead to destruction. 
 
John Ruskin
 
 
 
 
Roger Brown 
Rogerkb@theworldisfinite.com