As renewable energy explodes worldwide and displaces legacy power generation systems, stationary energy storage will be implemented with increasing regularity to allow electrical systems to operate more efficiently with lower prices, fewer emissions and increased reliability. Because of this, the energy storage market is expected to grow from 172MW in 2014 to 12,147MW in 2024, according to Navigant Research. So it is only natural that companies across the globe are scrambling to get their piece of this rapidly growing pie. To date, the vast majority of the entries into the energy storage market have depended on lithium-based battery chemistry, but, the idea that lithium-ion is the technological and economic front-runner in the stationary storage space is a myth that is in dire need of de-bunking.
One size battery does not fit all
Manufacturers of lithium-ion batteries for EVs and handheld electronics would naturally like to apply their technology that was designed with only one application in mind – high energy density – to large-scale energy storage. But just because it is right for your phone, laptop, or hoverboard, it doesn’t mean lithium is the right chemistry for far more demanding, higher energy uses. Lithium-ion’s high energy density is useful for personal electronics where (smaller) size matters, but for stationary storage applications that need to have the ability to handle high power and/or long duration applications multiple times a day, a far more versatile, robust energy storage system is required.
Zinc-iron flow batteries utilise one native platform to perform both energy services (measured in kilowatt hours) which involve longer, steady discharge of the battery at lower power and power services (measured in kilowatts) which is a rapid discharge at higher power. To perform the same functions using lithium-based storage, you’d need two complete systems; one for power, one for energy. This is because one type of lithium cell is used for power applications and a different type of lithium cell is needed for energy services and a single storage system cannot accommodate both. Duration, cycle life, versatility, and overall battery life are areas where the chemistry and design of lithium-ion energy storage systems don’t stack up to zinc-iron battery stacks.
Battery manufacturers list capacity for energy and power, but manufacturers’ specifications generally state that lithium-ion should not be discharged below 20% state of charge (SOC). This means that the available power is actually only around 80% of the initial power rating. A redox flow battery, on the other hand, has access to 100% of its capacity at full state of charge for 20 years.
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