Choosing the right battery storage solution

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Davion M. Hill Davion M. Hill
Principal Engineer
Energy storage
Variable renewable energy sources like wind and solar need energy storage to help balance production and demand. Battery-based systems are fast emerging as an ideal solution, but with big differences between batteries; how can manufacturers provide performance assurance and how do project developers choose the right storage solution?

Variable renewable energy sources like wind and solar need energy storage to help balance production and demand. Battery-based systems are fast emerging as an ideal solution, but with big differences between batteries; how do project developers choose the right one? Manufacturer warranties give an indication of lifetime and performance. However, given the scale of their investment, project stakeholders need more detailed, independently validated performance data to make an informed choice.

In DNV GL’s Energy Transition Outlook, we predict that annual energy storage usage could reach 50 terawatt-hours by 2050. This global energy storage fleet will be used primarily for renewables integration and grid management, in a world where renewables will represent 80 percent of our electricity generation.

Large scale adoption of battery chemistries in the automotive sector mean battery energy storage provides a cost effective and readily available solution for managing variable renewables. As a result, manufacturers are developing a range of battery storage solutions to address this fast-growing market. But this presents a challenge for project developers and investors, who need to have confidence that the storage solution they choose will meet their specific needs.

In particular, they need to be sure their chosen system will perform reliably and have a predictable life expectancy. As the economic viability of entire projects is based on these factors, buyers want more reassurance than just the word of the manufacturer. They want independent validation of battery performance. And as performance can differ significantly for different battery configurations, detailed performance data is crucial to the decision-making process.

Why does battery performance vary so much?
Even though they are based on the same technology, similar lithium-ion batteries can still perform very differently. This is partly due to different manufacturing processes but is mostly because they each have their own unique formulation of chemistry additives. Also, to meet specific market demands, manufacturers engineer their batteries to have particular characteristics, perhaps focusing on high temperature resistance or a better cell charge rate (C-rate), for example. This is evidenced by the rich field of patents filed in Li-ion chemistries since the early 2000’s.

Each battery system also performs best in a particular state of charge (SOC) range or window. Keeping the battery within this window can extend its operating life. But, if the average SOC condition is not within this window, this could adversely affect the reliability of the battery. For instance, a battery that degrades at a faster rate at high SOC would not be a good choice for an infrequent peak-shaving function, where it would typically be sitting at high states of charge. A battery that performs well at high SOC may be a better fit for this particular application.

Batteries can also be designed for specific environments where there could be high or low ambient temperatures. As cell temperatures is critical to a battery’s lifetime, inadequate or too much cooling will shorten its life. In short, no two batteries are exactly alike, even if they are generically described as the same chemistry.

Performance data accelerates the decision-making process
Clearly, having access to detailed performance data on different batteries’ capabilities would be a significant asset to project developers and their lenders. Not only is this information invaluable in choosing the best-fit solution, it can also help mitigate the high financial risk by verifying manufacturers’ warranties and guarantees.

Built on test data compiled over several years, DNV GL’s Battery Performance Scorecard provides a level playing field to show stakeholders how batteries from different manufacturers compare across a range of key performance indicators including SOC conditions, C-rate (a measurement of power) and temperature. This enables project developers to compare the performance characteristics of different batteries and choose the best match for their specific system design.

Closing more deals
Deployments in the solar industry accelerated when a contractual mechanism was standardized (the power purchase agreement, or PPA) and the data to support warranties became widely distributed and accepted. The financial community expects the same of energy storage.

DNV GL saw the gap in lifetime and degradation data for batteries, and developed the Battery Performance Scorecard to provide more confident independent engineering reports on energy storage projects, thereby enabling their financing. The Scorecard helps project developers choose the best solution for their systems and provides independent validation of the system performance and manufacturer warranties. This makes the decision-making process easier and quicker.

Battery manufacturers can also benefit from having their products in the Scorecard. It provides developers with assurance on the performance of their systems. It can even bring them new business by providing instant validation of their solutions against other manufacturers products. Since the Battery Performance Scorecard was published, independent engineering reviews can be performed faster, and DNV GL has received many requests from developers for more information about the storage systems covered in the Scorecard. In the end, more closed deals will lead to more growth in the renewables and energy storage markets.

If you have a battery solution that you would like to have validated for inclusion in the 2019 edition of the Battery Performance Scorecard, please contact us.