BY JENNIFER EIRICH, JOHN P. GAGGE JR., MICHAEL KULESKY AND STEPHEN L. VECHY, ENERSYS
Traditionally, utilities have generated electricity to meet immediate demand. Today, utilities are challenged to meet increasing demands with an aging infrastructure and a greater reliance on renewable resources. This presents concerns for power quality, service reliability and efficiency.
Energy storage works to address these power concerns, and utilities are relying increasingly on it for cost-effective power grid management. This has opened the floodgates on new technologies as suppliers rush to meet the new demands. Utilities must proceed with caution to find the optimum solution. Choosing the right storage option means understanding the technology, its risks and benefits and the application at hand. In many cases, traditional technologies might offer the most cost-effective solution. As energy demand increases, today’s utility leaders need the right solution and the right partner.
Delivering power over aging, congested lines during peak demand can result in power loss. During the past 20 years, blackouts have increased 124 percent, according to research at the University of Minnesota. Researchers at Lawrence Berkeley National Laboratory estimate power outages cost U.S. electricity users $80 billion a year. Other estimates made by researchers at Sandia National Laboratory on behalf of the Department of Energy are even higher, assessing the lost time, lost commerce and damage to equipment because of interruptions. Because of an increasing dependence on technology, the consequences of power failure will be devastatingly apparent. The U.S. has adapted generation to match peak load, resulting in low capacity factors for the electric power industry because much of the capacity is used infrequently to meet peak demand. The shift in generation resources from fossil fuels to renewable energy will aggravate the low capacity factor because wind power, in particular, often is strongest when electric demand is far from peak, according to the Electricity Advisory Committee’s report “Bottling Electricity: Storage as a Strategic Tool for Managing Variability and Capacity.”
STORAGE IS THE SOLUTION
Electricity Storage Association Executive Director Brad Roberts points to the numerous utility-scale demonstrations in operation across the country in a recent Renewable Energy World article by contributor Robert Crowe, “Energy Storage Industry Grows To Integrate Wind, Solar.”
“We still hear people say storage isn’t ready for primetime, but that isn’t the case,” REW quotes Roberts.
Crowe’s article supports that statement.
“Grid-scale energy storage is gaining momentum as batteries, flywheels and compressed air systems begin proving they can regulate frequency and ancillary services with the same efficiency as “Ëœspinning reserves’ from fossil fuel-fired power plants,” the article states.
A Frost and Sullivan report, “Electricity Storage Technologies: Market Penetration and Roadmapping,” goes further.
It predicts “electric energy storage technologies will be an inseparable part of smart grids and distributed energy generating systems in the future.”
This is coming to bear as electric utilities already are among the largest owners and users of electrochemical battery systems, according to the National Renewable Energy Laboratory.
ENERGY STORAGE BENEFITS
The benefits of energy storage are numerous and diverse. Energy storage augments conventional power generation and provides immediate, ready-to-use power. This practice offers flexibility for management and helps save costs for the utility and its customers by balancing supply and demand while improving response time, power quality, reliability and efficiency.
Energy storage also helps utilities meet federal and state regulations, integrate renewables and lower emissions. In addition, it reduces the need for upgrades and expansion and might lead to the retirement of older generation plants by maximizing existing transmission and distribution, according to an Electricity Advisory Committee report.
MATCHING THE RIGHT SOLUTION TO YOUR APPLICATION
According to a recent Electric Power Research Institute (EPRI) white paper, “Just as T&D systems move electricity over distances to end users, energy storage systems can move electricity through time, providing it when and where it is needed.”
A 2012 Black & Veatch study indicated the industry is moving in this direction; more than 20 percent of utilities are planning to add storage. Current installed energy storage technologies total more than 125 GW worldwide, according to the Electricity Advisory Committee’s report “Energy Storage Activities in the United States Electricity Grid.”
According to the EPRI white paper, however, “No single storage system can meet all of the application needs of the power grid, and a wide variety of storage technology options are being proposed for utility-scale storage uses.”
Pumped hydro and compressed air systems are the most widely used storage systems employed, predominantly for bulk storage, according to data from the Electricity Storage Association (see Figure). Although more expensive per kilowatt than a bulk storage system, a distributed energy system provides more flexibility. With a distributed energy storage network, a utility can focus on specific regions, storing and providing energy for immediate use, such as in heavy commercial or population-dense areas, and allow for more efficient use of renewables.
To choose the right energy storage solution, a utility must develop a clear profile of the application by addressing several key, decision-making factors.
THE FIVE P’s
Performance. The first step is to determine whether the utility needs to generate power, store energy or both. Also, the utility should identify other performance requirements that need to be addressed, such as increasing reliability, improving power quality, integrating renewables or a combination thereof. The utility also needs a firm idea of how much capacity is needed and how quickly it needs to respond to a signal to dispatch or absorb (reaction time).
Period (cycle life). In some applications, long life cycle is critical; in others, it’s costly overkill. Lithium-ion batteries, for example, can offer more than twice the life cycle of a lead acid battery; however, at almost five times the cost, it is only cost-efficient for those applications in which size, weight and longevity make it absolutely necessary.
Three factors impact cycle life and must be considered when choosing the right chemistry:
- Depth of discharge. There is a direct correlation between the depth of discharge and the number of charge and discharge cycles a battery can perform.
- Temperature. Some batteries are less tolerant of cold, heat or both; others operate at higher temperatures and must be insulated against the cold to prevent degradation.
- Charge. Charging methods vary; charge management is key because overcharging can shorten the life cycle.
Peril. Risk management means weighing one’s appetite for risk. With an increase in new technologies come safety risks. Storing energy involves understanding what to do when there is a failure, how to control it and how to avoid the potential catastrophic results. Like water in a pool, the more energy stored in a device, the more that could release in a catastrophic failure. Electrical shorts also generate heat that can spread to surrounding cells. Effective monitoring is critical. Some systems monitor individual cells and others monitor strings of devices. The former is more effective at spotting spikes, identifying trends and avoiding thermal runaway.
Power. High-energy, high-cycling solutions sound impressive, but as industry engineers like to quip, not every application requires a nuclear reactor. Likewise, energy density is attractive, but it comes at a significant premium and is required only when space is limited. For example, in many applications, lead acid batteries might deliver the necessary performance requirements at greater savings than other high-energy storage solutions.
Price. Cost is a key determining factor in storage selection. Utilities might be surprised to find that familiar technologies may be more cost-efficient than newer solutions at addressing energy storage needs.
In addition to the five P’s, maintenance is also a consideration. Maintenance requirements differ based on the type of technology, amount of run time and physical environment. Although some technologies are widely familiar, others require hard-to-find specialists that can result in added cost and downtime.
PUTTING IT ALL TOGETHER
Once the application parameters are determined, the utility is ready to select the best chemistry for the energy storage system. Choosing the appropriate dc chemistry is a science and requires as much, if not more, due diligence than specifying the ac electronics. So, where does one start?
Some utilities partner with a systems integrator to build a customized solution. Be wary of integrators who approach energy storage from an ac perspective only, leaving the dc chemistry decision up to end customers. Although it is acceptable to have a PCS platform, a one-size-fits-all approach to chemistry, battery form factor or both should signal the customer to proceed with caution. Suppliers refer to these integrators as “battery agnostics,” as this demonstrates an overly simplistic view of the dc market.
Ideally, utilities would align themselves with an experienced dc integrator or, better still, a dc supplier who offers a range of storage chemistries and can recommend the ideal match from several choices. Some suppliers, especially those new to the market, specialize in one technology, and other suppliers have an established line of proven storage chemistries and are better suited to make recommendations on the merits of the individual technologies rather than force-fitting a single solution. As new vendors flood the market, it also is important to choose a partner with a firm financial history to ensure long-term security of supply.
To complete the system, many dc suppliers promote a one-stop shop solution that includes the PCS, monitoring system, shelter construction and financing. Some provide a list of recommended vendors. Other dc suppliers have more established relationships with PCS vendors and provide an integrated solution in which they specify the full package and provide expertise in ac and dc technologies. Demonstrations also may be provided, which allow customers to see the system in operation and review real-world data. This offers a reliable, seamless and time-efficient solution.
The key is to choose the right solution and partner for the application at hand. New solutions might offer sleek packaging and greater energy density, but utility leaders must not overlook familiar technologies that still can deliver proven, cost-effective results.
Jennifer Eirich is the utilities marketing manager at EnerSys. She has a bachelor’s degree in chemical engineering from The Pennsylvania State University.
John P. Gagge Jr. is the vice president of reserve power sales and service at EnerSys. He has a bachelor’s degree in mechanical engineering from Widener University.
Michael Kulesky is the director of commercial marketing for telecommunications, utility and new technologies at EnerSys. He has a bachelor’s degree from The Pennsylvania State University and an MBA in global management from the University of Phoenix.
Stephen L. Vechy is the senior director of engineering and quality assurance, Americas at EnerSys. He has a bachelor’s degree in electrical engineering from The Pennsylvania State University and an MBA in management from Lewis University.
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