EESAT five years on

Five years ago, 150 delegates interested in electrical energy storage met for a conference in Chester, UK, to discuss and promote energy storage applications and technologies. In a little over five years, four conferences in the EESAT series have been held, and EESAT 2003 (27-29 October) was as well attended as the first. In those five years technologies have moved from demonstration to reality.

Ultra-capacitors are now more widely understood and are being used in many applications. Interest in flywheels has been maintained, with several manufacturers running successful businesses. The battery industry has seen the growth of large and small installations. The recently commissioned 27 MW nickel cadmium battery of the Golden Valley Electric Association in Alaska is a showpiece for both ABB and SAFT. NGK Insulators Ltd continues to demonstrate the reliability of its sodium sulphur battery with good progress at the AEP site in Ohio and several multi MW projects with TEPCO in Japan. Sumitomo Electric Industries continues to hold the record for the largest flow battery installation, with VRB Power and ZBB both making good progress. The traditional lead acid industry continues to supply thousands of smaller scale storage facilities around the world. Compressed air, once only spoken about in dark rooms at night is now being actively promoted and new technologies, such as the lithium ion battery have emerged, with the promise of low cost, lightweight and high power batteries for all. The absence of discussion about superconductivity as a storage medium suggests that some have fallen by the wayside. There was also a noticeable lack of news about the large flow battery installations that were underway in the UK and the USA. The conference was held about two months before Regenesys announced its withdrawal from flow battery development and great care was taken in what was said.

But it is not just the technology that counts –it is the applications that add commercial realism to the topic. And the applications need to be seen in the context of commercial reality. One target for applications in the 21st century is to combine storage with renewable sources of energy. Solar and wind power immediately come to mind.

Carl Johan Rydh is attempting to quantify the future for energy and seeing whether we will survive. It will be tough. Based at the University of Kalmar in Sweden, he has looked at the energy payback of photovoltaic devices. The urban legend is that the manufacture of a PV panel consumed more energy than the panel would ever generate in its lifetime. We have made some progress, and now most PV panels have an energy payback in the range 1 to 5 years. He his taking his research one step further by examining the energy payback of a combined photovoltaic and battery system. Putting a lead acid battery with a PV panel pushed the energy payback out to somewhere in the 10 - 19 year period. Clearly, there are many approximations in his analysis, but his thoughts set the conference going and elevated the discussion to the higher level where we should properly consider what energy storage is going to achieve in the world.

A little known battery project, in the middle of Idaho, provides another reference point. Tom Hund of Sandia National Laboratories has been monitoring a 1.44 MWh lead acid battery at the USAF Electronic Warfare site at Grasmere. With 50 miles between the site and the nearest distribution pole, electricity is a key resource. The USAF use two 210 kW diesels to generate about 1000 kWh each day for the small site’s operating requirements. By adding the lead acid battery and some PV panels, fuel consumption has dropped dramatically, and the on site electricity costs have fallen from $0.82/kWh to less than $0.30/kWh. The PV provides a relatively stable power source for several hours each day, and the demand can be modulated by the battery, so reducing diesel starts and part load running. Now if everyone could save half their energy costs by using a battery, the energy storage enthusiasts would be much happier! But the underlying message can be picked up and extrapolated from this simple off grid renewable hybrid system through to much larger networks.

The theme of storage and emissions was picked up by Paul Denholm of the University of Wisconsin, who considered the overall environmental burden of power plants and an associated storage unit, such as battery or CAES unit. Assuming there is no excess renewable generation at present in the USA, the marginal plant on the system is coal, which produces about 975 kg CO2/MWh. Linking a conventional CAES plant to the system, would increase emissions to 1018 kg CO2/MWh (because of the fuel switching characteristics of the CAES device). Pumped hydro pushes the CO2 burden higher, up to 1340 kg/MWh. New power plants in the USA must meet the NSPS (New Source Performance Requirements), but these are not retrospective. So storage, which is off site, would not trigger an NSPS review, but on site storage may do so.

Now the debate about storage becomes more interesting. Applications for storage have always fallen into two broad groups, those looking at power quality and reliability issues, where fast response is needed to ensure maintenance of a high quality power supply, and the group called “energy management” where the principal object is to move energy from one part of the day to the next. This has been the role of pumped storage, and has been the target of the CAES developers. Battery developers have made good progress in this area, with many projects working at relatively small scale often in conjunction with small-scale renewable projects. Making the jump from small scale to “utility scale” (a power rating of sufficient size that it affects the operation of a utility’s system) is taking the industry some time, but the change is now taking place.

Mark Kuntz of Regenesys Technologies gave a new perspective on uncovering value in industrial applications of storage. He saw value through rearranging an industrial customer’s demand profile, reducing the spikes to a more level profile and enabling the utility to offer an improved tariff. Working on the customer side of the meter gives a

clear indication of value, where the value reflects the lower costs of the generating plant as it no longer has to respond to a highly variable load.

There were a few comments about the delays in the construction of the two large scale Regenesys installations but Mark’s presentation turns out to have been the swansong for Regenesys, as it has withdrawn from electricity storage development. The announcement by TVA at the end of 2003 that the development work had ceased marks a sad time in the development of energy storage. Innogy (the parent company of Regenesys) has decided to cease funding the necessary further development work. It is not clear what will happen to the partially completed flow battery installations.

The US Department of Energy has taken an enlightened view in supporting a number of projects in remote areas of the USA where renewable energy, energy storage and perhaps a diesel generator are used in combination – the hybrid system. ILZRO,

the International Lead Zinc Research Organisation has been a strong supporter of hybrid systems for remote areas and their work in developing power supplies for two villages in Peru should be noted, both for their technical aspects and for the humanitarian support that they provide. Again, the use of storage reduces the fuel demand of diesel generation by a substantial margin.

Remote area hybrid systems provide good examples of how storage can be used to maximum effect. The store provides the means of modulating the demand and the supply, so that maximum use is made of the renewable power source (which is the least environmentally disruptive) and optimum use is made of the fuel-powered generation. Fuel savings have been significant. Diesels can be run at optimum load and constant power output, thereby reducing fuel and maintenance costs. Frequency and stability on these mini systems is controlled with benefits for the operators and consumers alike.

CAES developers are now considering how their projects would fit in alongside other generating plant on the system, or in other words the portfolio benefits have again been recognised for their significance. This point was ably made by Steven Lefton. Steven’s insight into the true cost of operating power plant and his enthusiasm for working with power plant operators to help them identify least cost strategies provoked strong discussion. It gave a new impetus to energy storage developers, who seemingly in an instant had a new value stream to develop. The hypothesis is that running a power plant at any point other than its optimum setting incurs extra costs, in fuel and maintenance, and even varying the load to start or stop the plant, or to load follow, incurs cost. Steven quoted typical costs of between $6000 and $32000 for each hot start. The message was taken on board very quickly, but without supporting data from power plant operators, storage developers will continue to find it difficult to present a winning argument to their customers, in all but the simplest of cases.

The simple cases are being examined in detail, with computer models such as Hybsim, being developed by Lumas Kendrick of Sentech, Inc, a Washington DC based consulting company. Their model allows a village community to calculate its energy costs using a combination of wind, solar, diesel and battery power. Such models need to be expanded to include the whole system, for without looking at the overall system cost, we cannot find the overall total benefit of storage. Looking afresh at the dynamics of each system is certain to reveal some interesting results, and we need to look at both sides of the meter. Urenco’s flywheel systems are selling like hot cakes to operators of metro systems and light rail, as they are able to absorb and output power to meet the second by second requirements of electric traction.

Delegates, including Robert Schainker of EPRI, were quick to point out that the restructuring of the power industry into separate generation, transmission and distribution companies limits the opportunities for storage owners and operators to access and control all the value streams – including the potentially very valuable ancillary services. It seems that the regulatory and structural issues of grid operation are as much as a challenge as improving the technical performance of the storage technologies. In this context, the opening comments of Terry Winter of the Californian ISO were very relevant. Terry is a keen supporter of energy storage and he was happy to tell anecdotes about the pumped storage resources of California. The Helms pumped storage plant provides his system with a much-needed resource of 100 MW for up to 10 hours. He would like more storage, if he could get it. Obviously, such storage should be cost competitive. And, of course, everyone agreed.