By Chuck Ross
Source:, April 2020

Electrical contractors might be seeing more customers interested in adding battery-based energy storage systems to their homes and businesses, especially in California, Hawaii and Arizona, where incentives are available to pair batteries with rooftop solar panels as a way to reduce demand from the grid. While these batteries might seem to be commodity products, systems can differ in ways that matter for safety and performance.

Even those ECs not working in areas with incentives can see interest grow. Overall, the residential market is helping to drive storage industry growth. Homeowners installed almost 40 megawatts of new battery-based storage capacity in the United States in just the third quarter of 2019, according to analysts at the energy research firm Wood Mackenzie. This group anticipates 20% of residential solar systems installed this year will be paired with battery systems.

Lithium-ion batteries have been the go-to option for electric vehicles (EVs) and stationary storage systems since both markets began to grow over the last decade. The vast majority of these have been powered by chemistries using the heavy metal cobalt. The material helps increase batteries’ energy density—the amount of energy they can store and discharge—but it comes with some serious trade-offs. Cobalt is expensive, and it’s primarily mined from the Democratic Republic of the Congo, often using child labor. As a result of both factors, and fire-related safety concerns, battery developers are looking at new ways to make products cobalt-free.

Lithium-iron phosphate (LFP) is the most advanced of the cobalt-free approaches. It’s already in use in the Eco and Ecolinx home energy-storage systems sold by Sonnen, a German company that’s become one of the top U.S. suppliers. SimpliPhi Power, Oxnard, Calif., has adapted LFP for use in commercial and utility-scale projects.

LFP batteries aren’t as energy-dense as traditional cobalt-based units, so they take longer to charge and discharge. This is less as important with stationary batteries than for those used in EVs. Earlier storage systems were used in high-discharge, rapid-response applications to help balance grid irregularities, but today’s products are generally recharged by solar panels in daylight hours and then discharged at a steady rate as a backup resource or to help reduce peak demand. This profile is well-suited to LFP chemistry. As an added bonus, LFP batteries are less volatile than those using cobalt, so they’re much less likely to experience the “thermal runaway” that has led to some well-publicized battery fires.

Within the next several years, an even more stable and long-lasting technology, sometimes called “lithium glass,” could be coming to market. It was invented, in part, by John Goodenough, who won a 2019 Nobel Prize in chemistry for his work developing the original li-ion battery and LFP designs. Goodenough, 97, and research partner Maria Helena Braga recently licensed their design to the Canadian electric utility Hydro-Quebec, which also helped commercialize LFP batteries.

While most batteries today use some form of liquid as the electrolyte through which ions flow between their cathodes and anodes, this design uses a type of glass. This solid-state approach promises to meet some holy grail goals for stationary and EV batteries with the ability to recharge in minutes, perform well in hot and cold weather, and pose no flammability risks. Hydro-Quebec plans to have the technology ready for licensing by commercial manufacturers within two years.

Zinc-air is another newer, cobalt-free battery technology being targeted toward larger commercial, industrial and utility applications. NantEnergy, Scottsdale, Ariz., has used its zinc-air batteries to help drive electrification efforts in remote villages and islands around the world. The company recently began marketing its products in the United States. The technology behaves more like fuel cells than traditional batteries. During charging, electricity from solar panels or the grid converts zinc oxide to metallic zinc and releases oxygen into the atmosphere in the process. To discharge, the devices reverse that reaction by exposing the metallic zinc to atmospheric oxygen, which releases electrons as a result.

NantEnergy says its battery costs have dropped below $100 per kilowatt-hour (kWh), compared to $156 per kilowatt-hour for traditional li-ion units, according to 2019 figures from Bloomberg New Energy Finance. The company also offers systems that pair zinc-air batteries with traditional li-ion units. Like LFP batteries, zinc-air devices are best suited for long charge and discharge cycles. Pairing them with li-ion can create systems that provide grid stabilization and peak-shaving/backup services, which could be especially helpful in micro-grid applications.

These developments illustrate a continued confidence in battery-based storage’s ability to help balance intermittent solar supplies. Residential solar and storage are expected to grow significantly in the future, and battery installation could soon be adding more power to electrical contractors’ bottom lines.