Technology

Will flow batteries become the mainstream choice for energy storage?

Rows of giant water tanks filled with chemical feedstocks store energy from massive solar and wind farms that power entire cities: a sight that will be very common in the future.

Batteries will power the energy storage, but they won't necessarily all be lithium-ion batteries. Flow batteries have a place in the renewable energy world of the future.

What are flow batteries? They are systems of two connected containers, both containing an electrolyte liquid: one with a positively charged cathode and the other with a negatively charged anode, just like lithium-ion batteries. Electricity is transferred from one electrolyte liquid to the other through the membrane between the two containers.

Flow batteries last longer because the current flow from one cell to another does not degrade the membranes and can be charged like a lithium-ion battery. True flow batteries are also known as redox flow batteries, according to the two reactions they utilize: reduction, the gain of electrons, and oxidation, the loss of electrons from the electrolyte liquid to the electrolyte liquid.

The main problem with redox flow batteries is their reliance on an expensive material called vanadium. But as innovation continues in the battery space, it is only a matter of time before a breakthrough occurs. Scientists at the University of Southern California have developed a flow battery that uses inexpensive, sustainable materials.

The USC team used a solution of iron sulfate and a compound called anthraquinone disulfonic acid, or AQDS for short. Ferric sulfate is a cheap and readily available mining waste. "The solution can be made from any carbon-based feedstock, including carbon dioxide," said study co-author Surya Prakash.

There's nothing better than a battery that uses an electrolyte made from carbon dioxide, especially if it's cheap to manufacture and lasts longer than its lithium-ion competitor. The length of service life is very important. If the world is really going to develop renewable energy, we need long-lasting energy storage systems to provide reliable power. Lithium-ion batteries are not particularly durable. According to the author: The new redox flow battery will have a longer life.

"Until now, there is no economically viable, environmentally friendly, 25-year-sustainable energy storage solution," said the study's lead author Sri Narayan, a professor of chemistry. "Lithium-ion batteries don't last very long, and vanadium-based batteries use expensive, relatively toxic materials that limit large-scale use. Our system will find the best answer to this conundrum. We expect these batteries to be used in residential, commercial and industrial buildings for renewable energy.”

There appears to be a push to develop the fabled second-generation flow batteries in response to growth in renewable power generation capacity and plans for a complete switch to renewables in some economies.

Flow batteries appear to be more readily available for large-scale utility-scale energy storage projects, and these developers are now focusing on inexpensive and abundant materials, such as iron-containing compounds, and environmentally friendly, non-corrosive solutions. It sounds like flow batteries could give us the ultimate goal of renewable energy: reliable, long-term.

There are already predictions that flow batteries may replace lithium-ion battery technology in the future. According to a recent report from business intelligence firm IDTechEx by Energy Storage News, flow batteries have so far had a storage capacity of about 70 MW/250 mWh and are used in medium to large-scale projects. middle. However, the use of flow batteries will continue to grow thanks to the battery's fast response time, scalability, and easier recycling than lithium-ion batteries.

The report confirms previous predictions, this time also reported by Energy Storage News from Navigant. Despite a slow start, flow batteries are gradually replacing lithium-ion batteries as technology advances, the research firm noted. It's about time. Flow battery technology has been around for decades, but large-scale applications have been hampered by the fact that flow batteries must use expensive vanadium.

This is good news because when this pandemic is over and the world is back on track, energy storage will play a huge role globally when we start talking about carbon footprints again. California alone will need up to 1GW of energy storage capacity by 2026 if renewable energy goals are to be met. The low cost, reliability, durability and, very importantly, the recyclability of all components of energy storage will be valued.

According to IDTEchEx, the redox flow battery market, including expensive vanadium batteries, will grow at an annual rate of 30% in the next few years. Mainstream battery technology is likely to be replaced. This is a wake-up call for the changing times for lithium-ion battery developers.