Battery storage announcements have been coming out more frequently this year, with commitments from utilities to build large-scale storage projects in Florida, California, and even Texas. The attributes of storage add value to a more flexible grid, but what’s behind this technology that is important to understand in order to safely and efficiently operate these assets?

Today, Li-ion cells are mass produced and billions of units are used around the globe in multiple daily applications. Li-ion battery storage systems involve the assembly of cells into a mobility pack or stationary storage rack or container. Each storage system is made of thousands of cells interconnected and managed with electronics all packaged into modules that efficiently store and deliver energy.

Small cracks occurring in the cell or connections may lead to short-circuits that can cause a rise in temperature and make the cell thermally unstable. The high heat of a failing cell may also propagate to adjoining cells. Statistically, because of this, the risk of a thermal runaway event is not nil as it may be assumed. We have seen plenty of examples in recent years of fires or explosions in airplanes, cars, electronics, and energy storage assets.

The risk of self-igniting events can be a concern to asset owners and project developers. Also, the cost of mitigation strategies (insurance, installation of fire suppression equipment or cooling, for example) is not always considered as a component of the energy storage system but rather as a balance of plant cost. It is important that selected storage systems comply with the UL Safety Standards addressing the specific technology used.

Li-ion storage systems need air conditioning equipment for optimal operation. Operating the A/C requires drawing energy from the battery which may otherwise be used for revenue generation. O&M practices need to account for the maintenance of the A/C, a critical component of the system.

Large number of Li-ion cells are produced in big automated facilities—many of dubious quality that may not meet the strict UL standards. In a way, this is reminiscent of what happened in the early days of solar PV development when low quality modules were dumped in the market at below production cost.

This brings yet another risk consideration related to the performance of the cells, the expected life of the product, and the honoring of the warranty by the manufacturer.
In addition to the above, engineers need considering that Li-ion cells degrade and their capacity or ability to store energy does not remain constant throughout their life. As a result, storage ‘augmentation’ needs to be considered with incremental addition of storage during the project lifetime to meet capacity availability commitments. The additional capital cost and associated operational expense may not always be considered as part of the business plan.

In the late 2000s, when solar manufacturing shifted to China, the balance between price and quality did not have the same potentially catastrophic risk projects involving battery storage. In today’s climate, there is a similar race to the bottom for storage, making it even more important to find the right companies with the experience and proven technology to lower risk in the investments over the lifetime of the project.

Emily Easley is principal at ERE Strategies. Adrian Tylim is a renewable energy expert with Blue Solutions.

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