The wide acceptance of renewable energy resources and their introduction into both utility and distributed generation mixes is mandating the development of new kinds of energy storage for a variety of reasons, the least of which is to smooth out generation delivery.
Energy storage can also reduce the amount of new generation and transmission capacity that would otherwise need to be built. It can help to relieve uncertainty in the power market by providing a scheduled resource, thereby helping consumers to avoid high prices, it can increase reliability and security and create new choices and opportunities for both consumers and investors.
Anaheim PUD Takes the Lead
“The goal is to build a super-stable utility grid,” says Edward Murdock, the New Product Development Specialist for the Anaheim Public Utilities Department (PUD). He was talking about Anaheim’s two-year pilot project testing the 50-kW lithium ion energy storage system manufactured by iCel Systems Inc. It has been operating since last June. Two solar photovoltaic (PV) systems totaling 75 kW will feed power into the energy storage system, and during peak electricity usage periods the storage system will discharge the power into the grid. Both solar arrays are located near the energy storage system in a park where a 28-kW solar PV array was installed on a roof with an undulating architectural design that shades picnic tables. A second nearby 47-kW array is ground mounted.
|Photo: Beacon Power Corp.
Beacon Power assembly supervisor, George King, lowering the one-ton carbon-fiber flywheel rotor into its housing.
|Photo: Beacon Power Corp.
Two megawatts of flywheel energy storage installed adjacent to Beacon’s Tyngsboro, MA, headquarters
Murdock explains the grid is not growing for several reasons, including resistance from neighborhoods. Anaheim, CA, is tapping into renewable sources, it is rewarding conservation, and it is already offering incentives to commercial and industrial customers to turn on generators or shut off loads during peak periods. The utility would also like to offer incentives to customers who install solar systems to also install energy storage systems, including residential customers. Customers would be encouraged to dispatch stored energy when called upon by the utility.
During the pilot phase, the utility will be evaluating the dollar value of the $100,000 energy storage system in terms of the savings it brings to the utility. It will experiment with peak shaving, load shifting, and firming up power as it adds wind resources to its generation mix.
During the weekdays when electrical usage is at its peak at 7 pm, the stored energy is sent to the grid to supply additional power and flatten the peak loads. Energy is replaced in the batteries at night when power costs are at their lowest. On weekends, the load profile peaks during the day, so power is fed into the grid earlier.
Anaheim PUD is applying for grants, including federal Department of Energy stimulus money, to fund three combination solar/energy storage projects and a single energy storage unit. With enough energy storage systems connected to the grid, the utility would have a critical load supply serving as standby, Murdock says. The utility now has 100 customers sending power to the grid, and 28 new projects are in customers’ planning stages.
UCSD’s Microgrid Integrates Energy Storage
The University of California San Diego (UCSD) has fast become the very model of a microgrid community living with little need for utility power. The university, with 54,000 students, faculty and staff, is served by an onsite 42-MW peak load system that generates 80% of the electricity the campus depends on. Not satisfied, the university will add a 2.8-MW fuel cell paired with a 2.8-MW advanced energy storage system, sometime in 2010.
UCSD’s microgrid operates on 26 MW of cogeneration, 1 MW of solar PV, and 60 generating sets totaling 32 MW, all in parallel with San Diego Gas & Electric’s distribution network. Its 3.8-million-gallon chilled water storage system for cooling shifts about 14% of its load off-peak.
Last July, UCSD was awarded $11 million in incentives, from the California Public Utilities Commission, to install the fuel cell and energy storage system. FuelCell Energy will supply the fuel cell system that will operate on methane gas originating from the Point Loma Wastewater Treatment Plant in San Diego and delivered by BioFuels Energy of Encinitas, CA.
According to Byron Washom, director of strategic energy initiatives at UCSD, a solicitation for proposals to supply the energy storage system was released in September, with responses due in 60 days. Acknowledging that different energy storage technologies have different capabilities, Washom says he is looking for a system that will have at least 12 MWh of energy discharge capacity. He was expecting proposals from many of the companies reviewed below.
EPRI Sees Energy Storage As Fertile Ground
Dan Rastler, with Electric Power Research Institute (EPRI) in Palo Alto, CA, believes energy storage is part of the evolution to a smart grid. As technical leader for the energy storage and distributed generation program at EPRI, he has kept an eye on development of technologies at a growing number of companies. Furthermore, he feels microgrid deployment in industrial parks and small cities, such as UCSD and Anaheim, will further the advancement to smart grids.
|Photo: Anaheim Public Utilities District
Chaz Haba, chairman and CEO of iCEL, briefing Anaheim PUD executives on the 50-kW energy storage system his company installed
|Photo: Anaheim Public Utilities District
The ICEL energy storage system at Anaheim Public Utilities District. A series of stacked 1.5-kW energy storage packs make up the 50-kW system.
|Photo: Anaheim Public Utilities District
Anaheim PUD’s two solar arrays. In the background to the right is the mounted solar system. In the background on the left is the small building that houses the ICEL energy storage system.
Rastler says the combination of combined heat and power and energy storage play into low-cost energy solutions in combination with utility power. Energy storage will be integral to controlling the increasing cost of wholesale power, the cost of natural gas, and the cost of renewables, he says.
There are quite a few technology choices that will depend on the application and the need for energy storage, Rastler says. Some technologies are best suited to providing backup power that requires infrequent supplies of energy. Other technologies are suited to storing large amounts of energy that can be dispatched at high peak grid loads. Still other technologies are optimal for firming up solar and wind power.
In the commercial and industrial arena, energy storage could fit into energy management portfolios for peak shaving, reliability, and power quality. But the system will need to provide two to four hours of storage to provide value, Rastler says. If a large industrial building is fitted with solar PV panels, for example, an energy storage system might provide the ability to time-shift power purchases—from peak to off-peak periods. “We’re working on making [energy storage] more connective to grids. This is fertile ground now,” says Rastler.
Distributed storage could be a win-win between a utility and its customers if they can be used to support the customers’ need for backup power, he says. The utility could partner with a customer who would dispatch its stored power during peak periods, as Anaheim PUD is thinking about. A new tariff would become very important in this instance that would allow the customer to make a business case to pencil out the cost for an expensive energy storage system.
Rastler says the California Public Utilities Commission has established incentives for energy storage as part of its Self Generation Incentive Program. End-use customers can get up to $2 per watt for installing either of two eligible storage systems at a planned fuel cell site or at a wind facility.
Right now, the type of energy storage systems that utilities could use for grid support are very expensive. Rastler says the hypothesis EPRI is testing is that the vehicle market for energy storage will drive costs down. In other words, is there a high value stationary market that will compliment the vehicle market?
In a 2008 article in Electric Perspectives, Rastler lays out costs for commercial energy storage. Large compressed air energy storage, 100 MW to 200 MW in size, was, by far, the cheapest at $1 to $2 per kilowatt-hour. Lead acid batteries were $330 to $480 per kilowatt-hour for 10 MW. Flow battery costs were estimated at $280 to $450 per kilowatt-hour, also for 10 MW. The cost for a 10-MW flywheel was estimated to cost $1,340 to $1,570 per kilowatt-hour.
Energy Storage Technologies
Pumped-Hydro Storage has been used by utilities for decades to pump water uphill at night into a reservoir when the cost of power is low, and then to release the water during peak periods to generate electricity. This option is typically not available to commercial or industrial users and is heavily dependent on the appropriate geography.
Thermal Energy Storage technologies have been around for a couple of decades and are widely used by institutions, such as colleges, local governments, and, perhaps, some commercial and industrial buildings. Water or refrigerant is chilled or iced at night by chillers operating when the cost of power is low, and then used during the day to supplement cooling loads to reduce air-conditioning operating costs and peak demand charges. Another type, molten salt thermal systems, is in the developmental stage and is designed for steam production. This type of system could theoretically extend the ability of solar and wind resources to continue operating past peak periods.
A new thermal storage technology introduced by ICE Energy is particularly attractive in distributed generation applications. The company’s Ice Bear freezes water at night in an insulated storage tank and cools during the day by circulating chilled refrigerant from that tank to a conventional air conditioning system during the day, thereby, eliminating the need to run the energy-intensive compressor during peak daytime hours.
In a pilot project, Redding, CA’s electric utility recently purchased 50 Ice Bear units to distribute to small business customers throughout the city. The cities of Victorville, CA, and Anaheim have also installed Ice Bear units, as described in the November/December 2008 issue of Distributed Energy, “Managing the Peaks with Business Smarts.”
Compressed Air Storage systems use off-peak power to pressurize air into an underground reservoir like a salt cavern, abandoned hard rock mine, or aquifer. This air is then released during peak daytime hours to power a turbine/generator for power production. The pressurized air substitutes for the more expensive gas turbine-produced power to compress the air for combustion.
Two plants currently exist: a 290-MW unit in Huntorf, Germany, built in 1978, and a 110-MW unit built in McIntosh, AL, in 1991. Several more are under development. Because the technology is dependent on certain geologic structures and location and their large size, this type of storage system would not be a useful application for distributed generation.
Flywheels—a popular technology for use as uninterruptible power supplies for short ride-through duration in the eight- to 12-second range for frequency regulation. A flywheel energy storage system accelerates a rotor up to a very high rate of speed and maintains energy in the system as inertial energy. The flywheel releases the energy by reversing the process and using the motor as a generator. New technology promises energy supplies in the range of 20 seconds.
Beacon Power advertises its flywheel technology as having the capability, among other things, to stabilize distributed generation systems by improving a cogeneration system’s ability to follow fast-changing loads. Beacon’s “Smart Energy 25” flywheel technology that can deliver 25 kWh each in multiple integrated systems, has the ability to buffer the fluctuations in solar PV systems when cloud cover can come and go, dropping and then increasing power output within seconds.
Battery Technologies Are Proliferating
New battery technologies are entering the marketplace rapidly and range from new lead acid battery technologies to small flow battery systems and lithium ion systems. Spurred on by the vehicle battery market, companies have quickly picked up on stationary battery storage applications as a supplementary market.
|Photo: Beacon Power Corp.
The first 1-MW flywheel energy storage system connected to the ISO New England grid since November 2008 and providing frequency regulation services from Beacon Power headquarters
Lead acid batteries have traditionally been used for energy storage, but, according to Rastler, they cannot do deep recycling. The introduction of carbon fiber and woven materials has potential, he says, and field applications will begin in 2010.
Discover Energy produces non-hazardous sealed lead acid batteries with absorbed glass mat or AGM construction. The fiberglass mat is only 95% saturated with sulfuric acid—there is no excess liquid, and the thicker plate walls do not degrade. The batteries are designed for electric vehicles, such as golf carts, floor machines, recreational vehicles, and boats, and as an energy backup to cable distribution parts.
Discover Energy has developed off-grid applications that are maintenance-free, and ideal for remote workstations and solar and wind installations, according to Lehann Wallace, vice president of marketing. If used for backup power, the lifetime of the sealed or dry lead acid battery is seven to 10 years. If discharged daily, lifetime is shorter, she says.
Regenerative fuel cells or flow-cell batteries use a reversible electrochemical reaction between two salt solutions or electrolytes. One design features zinc bromide or sodium bromide as the electrolytes.
ZBB Energy Corp. produces a regenerative fuel cell based on zinc bromide technology, which is proprietary and patented. Each cell or module can be combined in a series of modules to increase power. The ZESS 50 holds 50 kWh that would roughly power a home for two days and includes three cell stacks, each containing 60 cells. The ZESS 500 fully charges in 4.5 hours and has continuous power of 250 kW, sustainable for two hours, with 200% peaking capability or, by slowing down the discharge amount, over three to four hours.
Christopher Kuhl, lead sales application engineer at ZBB, says his company has chosen a market niche to discharge quickly in two hours. He says the industry is fragmenting according to packaging of the power electronics. As the market becomes more specialized, this packaging becomes more complex. “Our new installations have more sophisticated inverter systems that allow multiple onsite renewable and potential emergency generators to be on the same DC [Direct Current] bus,” he says. “The system manages automated flow either to the load or to the grid, and in and out of storage.”
Vanadium Redox Flow Battery (VRB). In another regenerative fuel cell design, this converts energy stored in different ionic forms of vanadium into electrical energy.
The VRB has a range of utility applications. According to Rastler’s writing in the Electric Perspectives article referred to earlier, the VRB is most suited for utility-scale power systems in the 100-kW to 10-MW range, in applications having long discharge durations including peak shaving, spinning reserve, and wind farm stabilization and dispatch, due to its relative mechanical complexity and economies of scale.
Tim Hennessy is president of Prudent Energy, headquartered in Beijing, China, with offices in Vancouver, Canada, and Portland, OR. The company manufactures a small 5-kW system and larger systems up to 4 MW. They are modular and scalable.
Prudent’s 4-MW energy storage system is installed at the Tomamae Wind Farm in Japan, while its small systems are installed at the South Carolina Air National Guard and two other locations overseas.
Lithium Ion Batteries Get Bigger
Rastler says lithium ion batteries haven’t been available for very long, although they’ve been available in consumer electronics for 10 to 12 years. Their lightness and high-energy density have made them attractive in the transportation sector, and companies are looking for synergistic applications in stationary markets, he says. The companies reviewed below can testify to that. In addition to the companies discussed below, EnerDel, Compact Power, and Xtreme Power also offer battery storage systems.
GreenSmith Energy manufactures stationary energy storage systems using lithium iron phosphate, or LFP, batteries from China, a variant of the traditional lithium ion technology. It has focused initially on a 20-kWh unit, according to Rod Smith, a cofounder and CEO. The company also looked at other types of batteries and identified disadvantages for the type of energy storage system it wanted to build. Smith says the LFP batteries are much more stable and reliable and are commercially available. They are rated at 3,000 cycles and can be cycled daily for over eight years.
Smith says GreenSmith is working on containerized energy storage units to be deployed at solar PV farms. This application is different from wind, because individual PV panels have small output. Panels can be aggregated and married with the storage size needed, forming clusters throughout the solar field. On the other hand, an energy storage unit at a 1.5-MW wind tower will have to be large enough to catch one burst of wind at a time, he explains.
Another application Smith foresees is the distribution by utilities of 50-kW energy storage units at the neighborhood level throughout an area. He says 200 50-kW units would total 1 MW of distributed power, solving what he believes is not a peaking problem, but one of distribution of electricity.
Energy storage will increase the value of solar by 50%, if the two technologies are partnered, Smith predicts, and solar’s economic value becomes greater as you get closer to the meter. Furthermore, energy storage adds value when avoiding peak power purchases on the open market.
Smith agrees with EPRI’s Rastler, that energy storage is a natural partner to the smart grid. Its built-in electronic intelligence will be able to interact with the grid to provide frequency regulation, for example. There are very good market opportunities for energy storage, he says.
BYD Company Limited is headquartered in the city of Shenzhen in China and, according to Patrick Duan, BYD America Corp’s regional manager for North America, the company has developed a new iron phosphate battery for both energy storage and electric vehicles.
Duan says the energy density is a bit lower than the traditional lithium ion battery that contains about 30% cobalt. He explains that cobalt in the lithium ion battery can explode if overcharged or is in high temperatures, but the iron phosphate battery has very little cobalt and will not explode. He considers the iron phosphate battery the most advanced in the industry and is now in mass production in BYD’s factory.
BYD built a 2-MW demonstration energy storage system in a 40-foot mobile container for PacifiCorp, in Portland. It also has a 1-MW stationary demonstration storage project in its factory in Shenzhen, that is connected to the grid, and a 200-kW storage unit in a 40-foot container, that features four-hour discharge, as well as a 600-kW 40-foot storage container for 1.5-hour discharge.
iCel Systems Inc., headquartered in Van Nuys, CA, manufactures lithium ion energy storage packs ranging from a 1.5-kW system for backup power in a residence, to a 50-kW system that can be stacked up to 1 MW for a utility application. It uses lithium ion batteries manufactured by Panasonic.
A small “green house” sitting next to iCel’s Van Nuys headquarters demonstrates what is possible in a residence. It has inputs for a grid connection; it has 14 solar panels on the roof and 10 iCel packs on its back porch. This PV/energy storage system provides power to operate the LED lights, air-conditioning, and refrigerator, and has reduced the house’s energy use by 80%.
Steven Meixner, executive director of business development at iCel, says, “It’s what we do with the electronics that differentiates our cells from others.” He explains the electronics prevent the lithium ion cells from overcharging and overheating.
iCel’s 50-kW energy storage pack is installed at Anaheim PUD’s pilot project. Operating since June, it contains a pack of 50 lithium ion batteries with a parallel architecture and physically integrated circuitry. It can simultaneously charge and discharge energy and provides 50 kWh of energy storage.
Ryan Wartena, iCel’s chief technology officer and designer of the system, says the prototype three-phase system operates at 24 volts DC and 480 volts alternating current (AC), and is fully integrated with the distribution grid. An integrated energy management system monitors and dispatches the stored energy to the grid when needed. The system can determine when to take in or discharge electricity, either on AC or DC power, whichever is required.
Wartena describes the energy storage system and its inverter/converter and communication technology as an integral part of the grid. Smart grid technology will help integrate all this, he says. “It really changes the model of the utility.”