New vanadium-flow battery delivers 250kW of liquid energy storage

New vanadium-flow battery

Imergy Power Systems announced a new, mega-sized version of their vanadium flow battery technology today. The EPS250 series will deliver up to 250kW of power with a 1MWh capacity. We’ve talked about a number of different battery chemistries and designs at ET, from nanobatteries to metal-air, to various lithium-ion approaches, but we’ve not said much about flow batteries — and since this new announcement is a major expansion for the company (their previous battery was a 30kW unit) it’s an opportunity to take a look at the underlying technology.

Feel the flow

A flow battery can be thought of as a type of rechargeable fuel cell. The electrolyte fuel, in this case, is kept in large external tanks that can be pumped through a reactor. One of the characteristics of a flow battery is that the energy storage can be decoupled from the energy output. The size of the reactor determines how much power can be released at once, while the size of the storage tanks determines how much total power can be stored.

This, in turn, makes it theoretically much easier to expand the size of a flow battery installation as compared to a lithium-ion battery. Doubling your battery life is theoretically as simple as doubling the size of the storage tank. Flow batteries can charge and discharge rapidly — refilling the tank with “charged” electrolyte can be as simple as opening a nozzle and pumping in the replacement fluid while the original electrolyte is recharged in a separate container.

There are different types of flow batteries and multiple compatible battery chemistries, but Imergy’s designs all use vanadium for both electroactive elements. The ability to fill both ‘sides’ of the equation is an unusual property of vanadium and it simplifies certain aspects of the reactor design. Vanadium flow batteries are extremely stable — leaving the battery in a discharged state causes no damage, and the battery has an estimated lifespan of 30-50 years and supports thousands to tens of thousands of discharge cycles — far more than lithium-ion can manage.

The disadvantage of flow batteries is that the total energy density of the solution is rather low energy density and the complexity of the storage and pumping mechanisms. Research into improving vanadium’s energy density is underway, a team at the Pacific Northwest National Laboratory has found a way to boost the energy density of vanadium batteries by up to 70% by switching to a different electrolyte formulation.
The long-term market

Much of the debate over the long-term usefulness of battery technology in the US centers around whether or not batteries can be combined with solar and wind power while still matching the cost of our existing natural gas, coal, and nuclear plants. What’s often ignored is that these equations look very different in other parts of the world, particularly in Africa or Indonesia where import costs are high, infrastructure limited (or nonexistent) and natural deposits of fossil fuels are low.

Africa also has enormous renewable energy potential — it receives huge amounts of solar power, its hydropower generating capability is largely untapped, and its geothermal and wave power are both abundant. The East African Rift in particular has high potential as a long-term geothermal power source.

Vanadium flow batteries could potentially augment renewable power in many areas across the continent, and Imergy is focusing its efforts on both the developing and the developed world. The company claims it can deliver power for a levelized cost as low as $300 per kWh, which would put it in competition with lithium-ion costs — including, possibly, in competition with Tesla as that company scales up its own industrial battery efforts.