24 | Kieran Claffey — Senior Research Engineer, Southern Company

<p><strong>🏭 For the electric utilities, what is the </strong><strong>most important </strong><strong>metric for energy storage technology? What is the rule of 17%? What is dunkelflaute?!</strong> For answers, we turn to Kieran Claffey of Southern Company in discussion with BioZen's CEO Nate Kirchhofer. To add some weight to Kieran's opinion, consider that as of 2021, Southern Company is the second largest utility company in the US, serving 9 million gas and electric customers in 6 states and delivering electricity to 120,000 square miles of territory.The Department of Energy targets a $0.05/kWh levelized cost of storage (LCOS) as a key performance parameter for energy storage technology. Kieran emphasizes that utilities instead employ a comprehensive approach considering approximately 30 parameters, including geographic flexibility, energy density, power density, and lots more. The most important? Reliability, and CapEx.Kieran highlights the utilities' need for safe and cost-effective 10-hour duration batteries, which is (and will likely continue to be) <strong>beyond lithium-ion's capabilities</strong>, even though Li-ion will serve mobile applications and durations &lt;6 h.</p><p>This insight is possible because Kieran is a subject matter expert in energy storage at Southern Company: his experience ranges from startups making microwatt (1e-6 W) solid lithium batteries, to now where he considers gigawatt (1e9 W) projects, all within the context of regulations like <a href="https://www.nfpa.org/codes-and-standards/nfpa-855-standard-development/855" target="_blank" rel="ugc noopener noreferrer">NFPA 855</a>. This enabled him to publish a peer-reviewed manuscript recently, entitiled "<a href="https://doi.org/10.1002/prs.12491" target="_blank" rel="ugc noopener noreferrer">Hazards of lithium-ion battery energy storage systems (BESS), mitigation strategies, minimum requirements, and best practices</a>." In that paper the authors emphasize the importance of proper spacing to prevent battery fires, and dispels myths about the frequency of Li-ion battery explosion events: the probability is about 1 in 1400 (at worst), making these systems at least an order of magntude safer than the common claim of "1 in 100 fail."</p><p>We get a few predictions about the future energy storage mix: that Li-ion and sodium-ion will dominate short-duration storage (0-6 hours), while thermal energy storage and flow batteries may be suitable for medium durations (6-12 hours). For lo