Canada has set an ambitious target to be net zero by 2050. Key to achieving this target will be decarbonizing the country’s energy grid.Renewable energy sources will be an important aspect of these plans. But while these energy sources are both cheap and increasingly accessible, a problem they continue to face is variability. After all, the sun doesn’t always shine and the wind doesn’t always blow when power is needed.Canada’s dominant renewable energy source — hydropower, which made up almost 62 per cent of Canada’s total renewable electricity generation in 2022 — is also highly vulnerable to climate change. Low precipitation in 2023 reduced reservoir levels in Canada below average. This led to a 25 per cent drop in electricity exports to the United States. The situation was even worse in British Columbia, where BC Hydro had to import electricity to meet provincial demand.Given these challenges, critical questions arise about whether renewable energy sources will be able to cope with energy demands now and in the future.One way of addressing these issue is by building large-scale energy storage systems. These would be capable of storing excess renewable energy when it’s abundant and deploying it when needed. Storing energyAround 90 per cent of global energy capacity is stored using pumped hydro energy storage systems.This system stores energy by pumping water from a lower level reservoir to a higher one using electric pumps powered by a renewable energy source. To release this stored energy, the reverse process occurs — so the water in the high levels flows down through turbines, generating electricity.Pumped hydro energy storage is currently the most desirable energy storage method. This is because it can have a lifespan of up to 100 years, is highly efficient and very cost-effective.However, a major pitfall of these storage systems is the geographic conditions required for them to work. These systems rely on large amounts of water flowing through different elevations. This incurs a significant cost. There are also environmental concerns, since it needs a large infrastructure to be built.But a type of water-based battery may, in some cases, offer a better way of storing renewable energy for large-scale use — all without requiring as much space and infrastructure as pumped hydro systems. Aqueous redox flow batteries are a type of battery that store energy in external tanks filled with water-based solutions. These solutions are then pumped and cycled through the battery’s electrochemical cell, causing reactions which allow the battery to release and store energy until needed. Aqueous redox flow batteris could help store renewable energy for decades. (Shutterstock) These batteries are able to store and release energy for years. Some companies claim they can last up to 25 years.Alongside their long life, aqueous redox flow batteries are potentially more cost-effective to scale-up compared to other batteries — such as the conventional lithium-ion batteries found in our phones and cars. They’re also a lot safer than conventional batteries, as the water-based electrolytes means there’s no risk of flammability.Aqueous redox flow batteries are highly scalable due to their modular design. Increasing storage capacity can be done by building larger tanks without needing to change the entire system. This makes them useful for both small and large-scale projects — whether that’s powering a single home or an entire community.These batteries have the potential to benefit the energy industry by providing a reliable way of managing fluctuating energy supply. They could also be well-suited for supplying reliable, renewable energy in rural communities and during disaster recovery.The world’s largest aqueous redox flow battery was recently built in China. Assuming an average consumption of one kilowatt-hour per hour per household, this one battery alone would be able to supply electricity to approximately 58,000 homes for 12 hours. Aqueous redox flow batteries can also be used in many other applications. For example, as electric vehicles become more prevalent, this technology could be suitable for supporting EV charging stations. South Korea even announced in 2021 that these batteries would be trialled to enhance EV charging infrastructure.This is particularly relevant in Canada, given plans to have 12.4 million zero-emission vehicles on the road by 2035.Battery limitationsWhile commercial aqueous redox flow batteries have many advantages, their main limitation is cost. Currently, commercial aqueous redox flow batteries rely on expensive and rare materials, such as vanadium. This makes them too costly for widespread adoption. Cheaper, more abundant organic materials (such as anthraquinones) could replace the vanadium in these batteries. But organic materials come with their own challenges. Currently, some cost-effective organic redox flow batteries degrade much faster than versions made with vanadium, which can last for decades.However, current research is making significant progress in improving the stability of organic materials- helping to extend the lifespan of cheap organic redox flow batteries, making them an increasingly viable alternative.Given the current costs of the materials needed to make commercial aqueous redox flow batteries and the short lifespan of cost-effective organic compounds, this technology is not yet fully ready for widespread use. Continued investment in research and development will be crucial. If we can overcome these current challenges and unlock the full potential of aqueous organic redox flow batteries, they could become a key component of the global transition to renewable energy.Nothing to disclose.