When over 150 people from four continents meet and discuss electrical energy storage there is bound to be some heat generated. With that in mind, it was just as well that there was a cool breeze in San Francisco for the third Electrical Energy Storage Applications and Technologies conference, held in April 2002. The previous ones were in Chester, UK in 1998, and Florida in September 2000. This year’s meeting, organised by the US Department of Energy, packed in 39 papers and presentations covering all aspects of energy storage, ensuring a packed hall for most of the events.
Electrical energy storage might be described as the Cinderella of the power industry. Beautiful stuff, but yet to be recognised. The potential beauty of energy storage is its capability to balance supply and demand over short or long time-scales. This should bring technical and commercial benefits to everyone in the industry. Users, such as power companies, and large and small consumers of electricity should have an interest because they could control their costs, and receive more reliable and higher quality power. Inefficient power plants which run for only part of the time could be replaced by more efficient plant operating at higher load factors. Transmission and distribution links could be optimised. These simple messages need to be received by a much wider audience if developers of energy storage devices are going to get their products into the market place.
The governmental view
Governments and regulatory bodies have been somewhat slow to recognise the importance of these issues and one can search through their policy statements and find only a few references to storage. This is strange, given the substantial numbers of storage devices already installed. Enthusiasts point to over 90 GW of pumped hydro energy storage in operation, showing the usefulness of bulk energy storage, and at the other end of the scale there are thousands of smaller devices such as flywheels, batteries, supercapacitors and superconductors. New technologies are under development, such as flow batteries, ultracapacitors and high performance flywheels. It is therefore very timely that conferences such as EESAT provide an overview of the current status of these technologies.
Dr Robert Dixon of the US Department of Energy gave the opening address. He spoke about energy issues now being national issues. The US economy is based on energy, and the system is ageing, with parts over 50 years old. As the economy changes and grows there is a crucial need to update the system. 54 recommendations in President Bush’s energy bill dealt with distributed energy, showing that it was an increasingly important technology. There was an implied link to distributed storage. Robert Dixon said that there was a need to articulate why energy storage was important to the USA. Most of the audience knew that and perhaps were looking for some help in promoting this message. He went on to say that energy storage systems could help meet real issues in power quality and energy storage systems could make “village power” possible in some regions of the world. The challenges facing the energy storage industry are clear. We need:
• better equipment, meaning lower costs and higher reliability;
• greater co-operation between utility and user; and
• common interconnection standards.
One way of getting the storage industry moving might be to use public money on demonstration projects. Terry Surles of the Californian Energy Commission spoke about how the CEC Public Interest in Energy Research programme was supporting energy research, and storage was a part of this. It will be interesting to see if many energy storage projects can get funding from groups such as the CEC in the future.
Storage: theory or practice?
Any discussion on electrical energy storage always leads to the question of economics and commercialisation. Power system planners need real examples of how new forms of storage can be used in order to have confidence to use storage in the networks of the future. The developers meanwhile need to have more sales, in order to gain the economies of manufacture and offer cost competitive products.
Breaking this circle is going to be hard work, and so it fell to Joe Iannucci, of Distributed Utility Associates, to start the conference sessions with his paper on technical and market aspects of innovative storage opportunities. This is provocative stuff, and the delegates loved it for that. He makes the point that efficiency of a storage device does not necessarily drive the economic case for storage. With commercialisation of new technologies in energy storage just around the corner his work demonstrates that a major effort is needed to gain an understanding of exactly how storage can be used in today’s and tomorrow’s power industries. Joe gave some powerful insights into the effects of initial capital cost, reliability and efficiency of storage devices on the overall economics and he is betting his money on the use of storage in transmission and distribution as the most promising application for bulk energy storage. His view was that a comfortable size for storage plants would be 1 MW in distribution and 10 MW or greater to access transmission benefits. It will be interesting to see how Joe’s predictions turn out.
Not many people are prepared to claim real commercial benefits from storage. There are good reasons for this, in particular the obvious point that many power project promoters are reluctant to reveal their commercial knowledge in public. However, without such data it is always going to be hard to present a convincing case.
Henk Kroon of REMU (a Dutch utility company) and Gerard Thijssen of KEMA did present this kind of commercial information, having made a study of the use of flow batteries in the Netherlands. Not only did this highlight the importance of getting the economics right, but also the need to anticipate the regulator.
In order to justify the use of energy storage, most situations demand more than one value stream. This theme was brought out by Bob Taylor of the Tennessee Valley Authority who described a theoretical case study on the use of energy storage with wind power for arbitrage and the importance of combining value streams to demonstrate an economic case for storage.
Obviously wind power and other renewable generation is a high priority area. Best value would currently be in New York State with its high power rates, so Bob postulated that there is a need to move storage plants from one place to another. Mindi Farber de Anda and Ndeye Fall also brought out the importance of location in siting energy storage. Their company, Energetics, had installed a variety of distributed generation options on a site at the University of Maryland. Although financial savings on this site were small, this was because of the incumbent utility’s current tariff structure. With other types of tariffs, monthly savings would triple.
The agenda to save the planet often includes optimistic targets. One target in the USA is to reach 20 per cent penetration of distributed energy. For this to happen, a new way of connecting distributed generation would be needed. Abbas Akhil of Sandia National Laboratories suggested the use of microgrids as a way of addressing commercialisation of storage. These microgrids would combine storage and other distributed resources and improve the control of the local network.
There are a number of storage types and the experts know their way around. For those who didn’t guides to the technologies were given by Susan Schoenung of Latitude 122 West and Tom Key of EPRI. Tom spoke in particular about bridging power systems. He felt that four technologies were appropriate: batteries; flywheels; ultracapacitors; and SMES (superconducting magnetic energy storage systems). This led naturally into presentations by developers and users of these technologies.
The theoretical part of the conference was followed by positive news on real energy storage systems. Achieving a wider penetration for energy storage involves many steps and the first steps are to construct new energy storage plants and publicise their progress.
The world’s most powerful battery
One new such plant under construction is in Alaska. Last year, a contract was let for the construction of a 40 MW battery system near Fairbanks. This will probably be the most powerful battery in the world when it is finished. The plant specification called for 40 MW power for 15 minutes, and the plant must have a warranted lifetime of 20 years. Tim DeVries of the Golden Valley Electricity Association gave the first public presentation on the outcome of the tendering process for this exciting project. Tim talked about the unique position of Alaska as an electrical island, the associated system stability problems and the application of energy storage to improve reliability and performance of the system.
ABB Industrie is the prime contractor and supplier of the power conversion system for this battery. The liquid filled NiCd batteries will be supplied by SAFT. The project started on 30 October last year. Operation is planned for July 2003 and all four battery strings should be complete by December of that year.
Other battery technologies are coming to the fore. At the medium to large scale, flow batteries are making real inroads into the market. Since the last EESAT conference in September 2000, construction of two Regenesys flow battery plants has started. Other flow battery types are making progress. Kenchi Suzuki of Sumitomo described the Vanadium Redox flow battery and its use in mitigating voltage sags. This style of battery is suited for both short term and long term applications. With a response time of 350 microseconds and the capability for a high overload rate of 3 – 5 times rated power for up to 1 second, this is a versatile system.
John Hawkins of Vanteck gave a review of the Vanadium Energy Storage System Field Trial at Stellenbosch University in South Africa. He gave a detailed visual description of the installation and how it was being used.
The review of flow batteries included a joint presentation by Peter Lex of ZBB Inc, accompanied by Thomas Rhae of Detroit Edison and Vince Scaini of SatCon Power. They jointly described the demonstration of a transportable ABESS (advanced battery energy storage system) using the zinc bromine technology. ZBB have built a system, mounted in a specially adapted ISO shipping container. The user can pick it up and move it to where it is needed, so demonstrating the value of storage as either a temporary or a permanent part of the network. Development of this elegant solution is well worth watching.
The most novel technology introduced at the meeting was the cerium based high energy redox battery system reported on by Stephen Clarke of Plurion Systems, Inc. Plurion’s battery uses an electrochemical couple based on cerium, so as to achieve a high power rating. Although development work was at an early stage, Stephen promised an exciting product for utility applications. If the audience was getting confused by the number and types of flow batteries, they could take some comfort from a comparative study by Chris Lotspeich who spoke about the differences between the various systems and praised their benefits.
The battery theme was continued by David Nichols of American Electric Power who described the development of the sodium sulphur (NaS) battery. This is a high temperature battery, which has achieved some impressive technical results. The Japanese utility TEPCO has been collaborating with the manufacturers, NGK, since 1984. With 43 installations greater than 25 kW now operating in Japan and eight units of 2 MW completed since 1996, NaS has achieved a great track record. Its peaking capability of five times rated power is good for power quality improvements and peak shaving. AEP said that the NaS battery has reached commercial reliability status.
Kamibayashi Kazuhito Furuta of TEPCO explained later how the NaS battery performed over time, showing performance charts for 2500 cycles. It should be possible to reach lifetimes of 21000 cycles by making technical improvements to the electrodes. Electrical energy storage is a reality in Japan!
In a section on new battery developments, Jim McDowall of SAFT summarised his outlook for distributed generation and the opportunities for a range of battery techniques. He talked about lithium ion batteries using organic electrolytes to produce high voltage outputs and very high over-discharge potential. With shallow depth of discharge they would have a very long cycle life.
Ultra caps: the spark for the future
SAFT was also very interested in supercapacitors as they were similar in construction to batteries and no doubt SAFT has some exciting development work going on in their labs.
Supercapacitors could be one the key technologies of the future. At present, the efficiency of capacitors is thought to be unsatisfactory and their energy density is low. Michio Okamura of Okamura Labs summarised his developments in supercapacitors (aka ultracapacitors). These included a 150 farad capacitor the size of a D cell, and operating with 84 per cent AC-AC efficiency.
Alfred Rufer of the Ecole Polytechnique Fédérale de Lausanne gave further examples of supercapacitor development. He wanted to use them as a means of rapidly recharging electric buses at intermediate stops along their route, so avoiding long recharging periods.
Dale Bradshaw of the Tennessee Valley Authority talked about transmission issues and their importance in the power grid. Dale has been an enthusiast for energy storage for many years, and he wants to use ultracapacitors to support transmission flows. “Ultra caps” can be air-cooled and have the advantage of no moving parts. A new proprietary form under development uses grated diamond tips as dielectrics, so increasing switching frequencies and reducing high voltage loss. Dale’s colleague, Mike Ingram felt that the breakeven point between choosing a supercap instead of a lead acid battery was around 15 seconds discharge period. All this means that we should expect to hear more of supercapacitors in the near future.
Flywheels: still spinning
Many people are familiar with flywheels as a relatively simple form of energy storage but are unaware that thousands of systems are being installed worldwide. The basic concept is being refined and improved. Scott Richey of Active Power described a second-generation flywheel with a power rating of 250 kW to 2 MW. They have delivered over 400 units. Piller GmbH is producing a 600 MJ parallelled flywheel generator to support a pulsed energy tokamak device for nuclear research. Pentadyne Power has built twelve beta systems comprising a 120 kW, 20 second, 2 MJ flywheel and a Capstone microturbine. Rob Wagner described NASA’s work in flywheels and Arthur Day of Boeing spoke about non-contact magnetic suspensions. Boeing are developing flywheels for aerospace, but expect them to have earthly applications as well. Their target is a 45 kWh machine. Donald Bender spoke about Trinity’s 250 kW flywheel and Rob Hebner of the University of Texas at Austin suggested using magnetic nano particles in flywheels to improve performance.
Matt Lazarewicz of Beacon Power Corporation suggested that there was a complementarity between flywheels and batteries. They currently produce a flywheel rated at 250 kW for 89 seconds. Their target is a flywheel rated at 250 kW for 25 seconds, which would drop to 50 kW over 200 seconds. Such a device would have applications in power quality and reliability applications, again demonstrating the versatility of energy storage.
Steps in developing new and improved forms of storage are going on almost everywhere. There were many papers on aspects of power electronics and their applicability to energy storage. Companies such as Satcon and Airak are using advanced power electronics to develop better power conversion systems. These form an important part of almost every energy storage device. Money spent on development in these areas today is going to bring rewards later.
Compressed air: a new plant
A blast of fresh air in the storage industry came from Septimus van der Linden of Alstom. With some humorous opening lines he grabbed attention by describing bagpipes as an early form of compressed air storage. Sep updated us on the operating regime of the Huntorf plant, near Hamburg, which was now operated by E.On. This 290 MW plant is used to provide peaking power and ancillary services to the network demonstrating the usefulness and economic viability of storage.
Alstom was now proposing to use decoupled compressors, driven by motor drives, run independently from the turbines, and optimised for the compressed air energy storage application. This is a change in the way that compressed air plants are designed.
Alstom is involved with the large compressed air energy storage project at Norton in Ohio, where they air is to be stored in a disused mine. The size of the 2700 MW plant, split into 300 MW modules, each with a 15000 MWh storage inventory, took many people’s breath away.
The future
Phil Symons, the Chairman of the Electricity Storage Association, gave his views on the value of energy storage in the closing address. He built upon many speakers’ views that transmission and distribution was an important area, as was the integration of renewables.
He said that there is value to be obtained from using electrical energy storage. The challenge is there, the technologies are ready, all it will take is just a few more steps and there will be a more widespread use of storage on the power networks of the world.
Sceptics may say that this message has been pushed out for years. Similar themes exist with other technologies such as fuel cells, and microturbines.
In the novel, the thirty-nine steps is a code for a mysterious group of infiltrators. This conference shows that electricity storage is no longer a mystery, but a growing and exciting technology. Governments and energy regulators need to include storage on their agendas for future regulation. Support for distributed resources and environmentally clean technologies such as fuel cells, renewables and combined heat and power should also include storage technologies. Power markets should have open access for large and small storage operators to buy and sell ancillary services such as frequency response and reserves as well as energy and power. Potential users of storage need to understand their value streams and be prepared to use storage in some novel instances where value is going to be high.
There are good demonstrations of both old and new storage technologies in action, in North America, Europe, Africa and Asia. Developments in technologies such as batteries, flywheels, supercapacitors and compressed air are pulling the energy storage bus to the top of the hill. The commercialisation process just needs to give it one more push to get it over the summit.
Or, to return to my earlier Cinderella metaphor, developments in technologies such as batteries, flywheels, supercapacitors and compressed air have got electrical energy storage to the ball. The dancing has begun, but the commercialisation process needs a little more help from Prince Charming before we can say that everyone recognises its beauty, value and potential applications.
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