Energy Storage, Renewable Energy, Smart Grid, Transmission

Choose Wisely

Issue 9 and Volume 21.

Why the Right Battery-Storage Chemistry is Important

By George Brendahl, EnerSys

Many utilities view the implementation of energy storage as an important way to help meet current and future energy needs. Consider the following when choosing a system for your operation.

As utilities face the converging stresses of increased demand, aging infrastructure and greater reliance on renewable energy, their ability to access scalable power has never been more critical. Peak electricity demand in the U.S. has exceeded transmission growth nearly 25 percent every year since 1982, according to the U.S. Department of Energy. In addition, the U.S. Energy Information Administration states that 51 percent of all generating capacity (530 GW) is at least 30 years old.

Utility operators-already among the top users of electrochemical battery storage systems-increasingly understand the benefits of energy storage and the key role it will play moving forward. Energy storage offers not only greater reliability and control in the face of the aging electrical infrastructure, preventing service interruptions and downtime, it also allows utilities to reduce costs by simplifying wind, solar and other intermittent renewables integration into the power mix; by helping postpone or avoid expansions or upgrades; and by hastening retirement of outdated facilities. In addition, it can allow for distributed service, placing the energy source closer to the equipment and loads that will use it. The Energy Storage Association claims that energy storage “accelerates the decarbonization of the electricity grid as it improves efficiency, stabilizes market prices for electricity and ensures a higher security of energy supply.”

While batteries are the key component of energy storage systems, choosing the right type-lead acid or the increasingly popular lithium-ion-involves operational, environmental and other considerations.

Operational variables

Some forecasters assume that newer technologies will drive energy-storage growth. The Electric Power Research Institute (EPRI) holds, however, that “no single storage system can meet all the application needs of the power grid, and a wide variety of technology options are being proposed for utility-scale uses.” The key is to match the application with the right storage solution, a process that should begin with a review of the following operational needs:

Use: A utility first must determine how it plans to use and incorporate energy storage-to generate power, store energy or both. This is done by first identifying the performance needs of the system; for example, value at risk support, frequency regulation, renewable integration, ramping and smoothing, etc. The ability to positively affect these performance profiles will lead to an increase in grid reliability, improved power quality or easier renewable energy integration or all three. Capacity and reaction time also must be defined.

Cycle Life: While some storage applications require long cycle life, this feature can be cost overkill if it is not a critical need. Lithium-ion batteries, for example, offer more than twice the cycle life of lead acid batteries. This choice might be cost-efficient only for applications where size, weight and required cycle life justify it.

Energy Density: As with cycle life, energy density is attractive, but comes at a premium and should be considered only when space is limited. Again, lead acid batteries, though less energy-dense, may deliver the necessary performance of both power and energy, at greater savings than high-density solutions.

Monitoring and Safety: In most energy storage systems, the amount of stored energy can equal the amount of potential risk undertaken. The more energy stored in the device, the more that can be released in a failure. Even a seemingly isolated electrical short can be a major concern. A short not only damages the immediate cell, but also can generate heat that spreads to surrounding cells. For this reason, utilities must understand how to avoid potential failures through the use of effective controls and monitoring devices. While some systems monitor strings, for example, individual cell monitoring is more effective at detecting spikes and identifying trends.

Reliability: Lead acid, in use for more than 100 years, has a far longer track record in both safety and reliability than any other rechargeable battery technology available to date. While both lead acid and lithium-ion technologies are theoretically capable of overheating, the likelihood and consequences of such an event can be higher for lithium-ion because of the high amount of energy it stores in a small volume.

Cost vs. Performance: Lead acid battery systems cost less ($ per kWh) than the initial cost of the more energy-dense lithium-ion. However, an equal capacity of lead acid units is heavier and bulkier, and therefore can be slightly more expensive to ship and install. Regarding performance, lithium-ion has significantly higher cycle life than lead acid in deep-discharge applications. This disparity increases as ambient temperatures rise. And, while the cycle life of each chemistry can be increased by limiting the depth of discharge (DoD), discharge rate and temperature, lead acid is generally more sensitive to each of these factors. If space allows, however, lead acid offers a compelling, cost-saving alternative.

Enclosure: Though often the final piece of the energy-storage system, the enclosure should be as robust as the budget will allow. Outdoor installations should include a watertight, sealed enclosure mounted on a thick concrete pad with a grounding structure. Direct current (DC) ground-fault monitoring and protection should be added. Other considerations can include built-in fire suppression, spill containment, gas detection and climate control systems.

Environmental Variables

The environmental impact of battery construction, use and disposal is significant, and must be considered when choosing an energy-storage system. According to Black & Veatch’s “The 2013 Strategic Directions in the U.S. Electric Industry Report,” most utility leaders rank environmental issues a top concern. They understand that battery life cycle must be viewed from “cradle-to-grave,” starting with the mining of raw materials, through disposal and recycling to the re-use of raw materials.

Disposal/Recycling: Because the battery owner is liable for the unit’s post-use disposition, all disposal and recycling efforts must be checked and verified. A battery dumped in a landfill or shipped to a scrap dealer that does not handle it properly could have a significant financial or legal impact or both on the battery’s most recent owner.

Integrating DC Chemistry

Choosing the appropriate DC chemistry requires as much, if not more, due diligence than specifying the alternating current (AC) electronics. A systems integrator can help build a customized solution, including the battery-storage system and related support elements. Ideally, utilities should partner with an experienced DC integrator or DC supplier who offers a range of storage chemistries and can recommend an ideal match.

DC suppliers with expertise in both AC and DC technologies may be best suited to offer a truly integrated solution. Be wary, however, of integrators who approach energy storage from the AC perspective only, leaving the DC chemistry decision up to the customer. Lastly, with so many new vendors flooding the market, look for a partner with a firm financial history to ensure long-term security of supply.

Conclusion

Today’s utilities are balancing “just-in-time” energy demands while coping with an aging infrastructure and budget limitations. Renewable energy helps fill gaps, but presents challenges due to its intermittent nature. Energy storage provides a convenient and practical solution. Choosing the right system and partner, however, is critical. The key is understanding the application requirements.

Some new energy storage solutions may offer sleek packaging and greater energy density, but today’s utility leaders must not overlook familiar technologies, which can still deliver proven, cost-effective results.

George Brendahl is marketing manager, nuclear and utility, for EnerSys. The company offers stored energy solutions for industrial applications, and manufactures and distributes reserve power and motive power batteries, chargers, power equipment and other equipment.

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They understand that battery life cycle must be viewed from “cradle-to-grave,” starting with the mining of raw materials, through disposal and recycling to the re-use of raw materials.

Disposal/Recycling: Because the battery owner is liable for the unit’s post-use disposition, all disposal and recycling efforts must be checked and verified. A battery dumped in a landfill or shipped to a scrap dealer that does not handle it properly could have a significant financial or legal impact or both on the battery’s most recent owner.

Integrating DC Chemistry

Choosing the appropriate DC chemistry requires as much, if not more, due diligence than specifying the alternating current (AC) electronics. A systems integrator can help build a customized solution, including the battery-storage system and related support elements. Ideally, utilities should partner with an experienced DC integrator or DC supplier who offers a range of storage chemistries and can recommend an ideal match.

DC suppliers with expertise in both AC and DC technologies may be best suited to offer a truly integrated solution. Be wary, however, of integrators who approach energy storage from the AC perspective only, leaving the DC chemistry decision up to the customer. Lastly, with so many new vendors flooding the market, look for a partner with a firm financial history to ensure long-term security of supply.

Conclusion

Today’s utilities are balancing “just-in-time” energy demands while coping with an aging infrastructure and budget limitations. Renewable energy helps fill gaps, but presents challenges due to its intermittent nature. Energy storage provides a convenient and practical solution. Choosing the right system and partner, however, is critical. The key is understanding the application requirements.

Some new energy storage solutions may offer sleek packaging and greater energy density, but today’s utility leaders must not overlook familiar technologies, which can still deliver proven, cost-effective results.