Part II of a two-part series on the development of electric energy storage. Part I addressed the storage we need. Here, we look at the technologies and the political challenges they face.
There are now four classes of electric storage technology products — mechanical, magnetic, thermal and electrochemical — but only one sub-class is deployed in a more than minimal way.
Typifying mechanical storage is the pumping of water uphill and its later release to drive a turbine. Superconductors store energy in magnetic fields. Thermal storage uses heat. Electrochemical storage uses reactions in devices like batteries and fuel cells to store and release energy.
As the first article in this series argued, storage is an essential component of a low-carbon economy, but it is mostly not ready for commercialization. The following snapshots focus on the technology with the largest current application, mechanical storage, and the technology with the most near-term promise, electrochemical storage.
"The market for utility scale storage will grow from $329 million in 2008 to approximately $4.1 billion in 10 years. While pumped hydro and CAES [compressed air energy storage] should persist as options and gobble up large amounts of dollars for a small number of projects, advanced Li-ion batteries will be the volume leader and the one technology with a clear and possibly astronomical growth trajectory." —Clint Wheelock, Managing Director, Pike Research
Water and air can be mechanically pumped into storage areas. As needed, they can be released in ways that use their kinetic force to drive electricity-making turbines. A third mechanical storage technology, fly wheels, makes a related use of mechanical inertia.
Pumped Hydro: Nearly all of the energy storage in use today consists of pumped hydro. Its capacity equals 3% of global electricity generation. Being one of the storage technologies that delivers, very quickly, small amounts of power, it is used primarily to support power performance. There are nearly 40 operational U.S. facilities. However, there are few suitable unused reservoirs remaining near (as they must be) points of energy generation or of energy usage.
Compressed Air: Worldwide, there are only two operational Compressed Air Energy Storage (CAES) facilities. They work by pumping air into salt rock caverns, using off-peak priced energy; and then as needed releasing this air at high demand periods to drive turbines. When built two decades ago, they cost too much and delivered too little to make CAES a mainstream tool. However, the value proposition is getting better as CAES technology improves and as the cost of bulk and dispatchable energy rises. Wind farms may find CAES, in fact peaker plant technology, to be an effective complement that evens out wind's intermittence.
Flywheels: A flywheel storage system is essentially a rotating, magnetically levitated cylinder connected to a motor. It is established technology that, with enough investment, can be made better and more cheaply. It already has low life cycle costs and is nontoxic, sturdy, and capable of many recharges. Flywheels can support both grid performance (small, quick burst of energy) and grid efficiency (slower, longer-lasting discharges of energy). Large storage capabilities can perhaps be achieved through flywheel farms.
"... present electrochemical systems are too costly to penetrate major new markets, still higher performance is required, and environmentally acceptable materials are preferred. These limitations can be overcome only by major advances in new materials whose constituent elements must be available in large quantities in nature; nanomaterials appear to have a key role to play .... Transformational changes in both battery and capacitor science and technology will be required to allow higher and faster energy storage at the lower cost and longer lifetime necessary for major market enlargement." —M. Stanley Whittingham, 2008 Materials Research Society Energy Issue
Effective, cheap electrochemical storage — batteries and other portable devices that densely store energy — is the Holy Grail but also may be the Achilles Heel of an effective clean energy ecosystem. Without it there won't be storage at the edge, and so, no PHEVs, or measurably useful distributed wind or solar, or community energy systems. Yet this is technology at the margins of knowledge (as are also, to be fair, thin film solar and carbon capture and storage). While large investments must be made across the clean energy ecosystem — such as in testing smart grid deployments — electrochemical storage investments must first be in good old R&D.
A building-size nickel-cadmium battery — already an outdated technology — has since 2003 provided city-wide energy storage for Fairbanks, Alaska, which has severe winters and doesn't have the protection of being on a regional electric grid.
Sodium Sulfer Batteries: This technology, developed and manufactured in Japan and used in 200 international projects, delivers six hours of stored energy. It can support grid efficiency with peak shaving and arbitrage (storing when cheap, releasing when expensive). It can support grid performance by smoothing out the intermittences of renewable resources.
Flow Batteries: Flow batteries, rather than storing electrochemical energy, flows charged chemicals into storage tanks, and then back into the battery as needed. With this technique it can expand its size by adding tanks; the technology also has promise with small form factors. Research on next generation flow batteries is aimed at driving down costs.
Lithium-Ion Batteries: This technology has many permutations and, in a small form, now dominates consumer electronics. It is widely seen as the one technology capable of scaling, for both grid and distributed storage, through 2030 — the period during which mitigation activists say we must launch the clean energy economy. So it may be the technology we need most to work on. It is highly efficient relative to other batteries. Yet it is unproven except for small devices, and it lacks the durability, safety, low cost, and performance levels in very large combinations that grid and vehicle storage need. Researchers are working to improve this set of battery technologies by means of viruses, nanostructures, nanomaterials, novel lithium-based materials, and other materials innovations.
Beyond Batteries: With the realization of the global importance and economic potential of portable storage, R&D is under way to find revolutionary technology. Magnetic supercapacitors anticipate very high power and high efficiency storage that would degrade very slowly. Others technologies, including hydrogen fuel cells and artificial photosynthesis, look to make fuel from sun or wind and water (efforts attracting some of the world's most prestigious scientists and scientific universities). Still others look to such methods as using self-assembling benign viruses to form themselves into working storage devices.
THE STORAGE ADVOCACY WE NEED
The essential role of scalable electric energy storage (EES) technology in climate change mitigation makes it useful to examine how citizens can support its development.
BARRIERS TO EES DEVELOPMENT
Several barriers have slowed and may continue to slow the development and scaling of EES. As noted above, 20 years old CAES is operational in only two places worldwide; sodium sulfur batteries, developed 20 years ago in Japan, are still manufactured only there; and electrochemical storage and even more game-changing technologies are in their infancy. Contributing to this slowness is the high cost, based in part on false pricing signals, of integrating new EES; regulatory obstacles; and a resistance to change by utilities.
"To count the progressive energy utilities in the U.S., you need both hands but not your toes." —Matthew Nordan, President, Lux Research
False Cost Comparisons: EES technologies aren't cost competitive with spinning reserves, peaker plants, and other high CO2 solutions. While EES costs must decrease significantly, the comparison fails to note that high CO2 solutions don't include a social cost of CO2. Once they do, the R&D costs and the large scale demonstration project costs of EES will seem less burdensome and less risky.
System Obstacles: Storage doesn't fit logically in a century-old grid infrastructure that separates generation, transmission and distribution, as it works across these layers. So it is unclear which investment and cost- recovery methods apply. Nor are there procedures for enabling EES at infrastructure levels. And neither is there regulatory support, because regulators haven't addressed EES in systematic or even ad hoc ways. So it's orphaned for now within a very legalized environment.
"Depending upon the principal application of the energy storage technology and the contributing institution, energy storage can be seen as a generation, transmission, distribution, or end-user resource. When the energy storage technology is connected to the grid either at a substation or in conjunction with a generation resource, the labeling and identification of it as one asset class or another inevitably gets entangled with cost allocation (and revenue accrual) issues." —Bottling Electricity, the DOE Electricity Advisory Committee, December 2008
Utility Resistance: The absence of regulatory guidance regarding EES, and the absence of a price on carbon, both deter utilities from making investments. They are generally prohibited by regulators from making major investments in which they aren't sure they can recover costs. They are far likelier to invest in a peaking plant or in new distribution infrastructure, because the cost recovery is understood. This complication only enforces their traditional aversion to change (proven by an exception, AEP, a large Midwestern investor-owned utility that is running multiple experiments with sodium sulfur batteries).
"We recognize that, today, energy storage is more expensive than most conventional solutions. The difference is the premium we will gladly pay to insure a better future for our business." —Ali Nourai, Manager, Distributed Energy Resources AEP
Given the importance of EES, its early development stage, and the barriers it faces, advocacy should focus on reforming regulations, pricing carbon, and ensuring ongoing RD&D funding. (The following distills policy options presented in May 2009 by The Pew Center on Climate Change).
Regulatory Reform: Certain specific reforms could help to integrate EES within the fifty state and three federal regulatory frameworks. Generation, transmission and distribution companies can be permitted to own EES capacity. EES can be factored into transmission planning, and made entitled to transmission incentives. Real-time pricing can be established, as having consumers pay the actual, very high costs of peak electricity would lead them to supporter EES investments. And EES can be allowed to compete in the performance markets (called Ancillary Electric Services) with spinning reserves and other high-CO2 solutions.
Carbon Pricing: Quoting Pew: "A price on carbon, such as would exist under a greenhouse gas cap-and-trade program, would raise the cost of electricity produced from fossil fuels. ... This would, in turn, increase the value of the services provided by EES in situations where EES could store relatively inexpensive low-carbon electricity to displace carbon-intensive power."
Funding Support: For mitigation advocates, the key metric is that, after essentially nil funding support for EES RD&D during the Bush administration, the 2009 stimulus package pumps in $1.7 billion in matching funds. The allocations go to battery farms in support of grid performance and renewable integration, CAES, local storage for grid support, electric drive vehicle manufacturing, and demonstrations of new technologies. Much of it goes to the "demonstration" side of the RD&D equation, as demonstrations are expensive and as utilities have largely refused to pay for them. Utilities and the other industry participants must also make the investments necessary to claim the matching grants.
It is important to remember that this is a one time, three year investment. If it finally represents an appropriate funding level, a policy question arises of whether this multi-billion dollar public support will be needed every year for several decades.