A big tank, a generous amount of water, and abundant table salt. It isn’t the incipit of the ingredients and tools needed to cook a meal for the whole neighborhood, but what’s required to create a safe and efficient battery to store energy from your solar panels. Don’t venture into DIY, though; this Dutch company knows better.
Founded in 2014, AQUABATTERY developed a battery that can store renewable energy in salt water. In this way, power stashing becomes safe – lithium-ion ones can burn if overheated – leveraging cheap, sustainable, and widely available materials such as table salt and water. These advantages guarantee long-term and large-scale energy storage, making this technology suitable for storing renewable energy.
The company opened its new facility in Alphen aan de Rhijn (the Netherlands) to produce the first modules and deliver its first megawatt-scale batteries. Dubbed by the European Innovation Council as “one of Europe’s breakthrough technologies and game-changing innovations,” AQUABATTERY is working on scaling its system. They developed a ten kW power module and aim to upgrade it to 100 and 300 kW in the coming years.
“I feel very excited to make it to this moment,” Jiajun Cen, CEO of the company, states with a sense of pride. “Although our idea is straightforward, the technology behind it is quite complicated, but making it work and economically available were the main challenges on our way.”
Mimicking biological cells
The stationary battery is made of two units: a power module containing membrane stacks and a storage unit made of water tanks. During the charging process, saltwater flows through membranes, separating it into acid and base – each ending in a separate tank – thereby storing energy. When discharging the battery, the two streams are combined and pass through the membrane again, generating renewable electricity.
“Having a salt gradient – the energy created from the difference of salt concentration in two fluids – creates an energy potential difference,“ explains Emil Goosen, founder of AQUABATTERY. The membrane stacks mimic what biological cell membranes do. “The process replicates active salt transfer, which balances water and salt. After doing some sport or drinking a lot, that balance needs to be restored, and some cells pick certain salt ions from the bloodstream,” he clarifies.
Moreover, storage capacity and power are scalable, allowing for long-duration energy storage – between eight and 100 hours. “Increasing the size of the reservoirs and the volume of water increases the storage duration time,” Goosen underlines. “Therefore, we make it flexible for each application and storage time needed, combining our power module with different-sized water tanks,” Cen adds.
Flow batteries
The table salt and water battery falls under the category of flow batteries. A flow battery is one where two liquids, separated by a membrane to enable ion exchange, undergo electrochemical reactions. AQUABATTERY’s system features membrane stacks placed into a 40-ft sea container connected with pipeworks to the water reservoirs. Therefore, it is a good fit for stationary applications – such as storing excess power from solar or wind parks.
“In the plans for Horizon Europe – one of the EU’s major research and innovation funding programs – lithium batteries were mentioned hundreds of times, while flow batteries maybe twice,” states Kees van de Kerk. He’s the president of Flow Batteries Europe. This umbrella organization brings together several flow battery stakeholders in the EU, which campaigned to promote and showcase the potential of these technologies in the past few years.
Amid the many technological options available in the battery field, flow batteries are optimal for two kinds of usage. “High cycle applications – they can be used for thousands of cycles without compromising their performances – and long storage ones are the two sweet spots. Furthermore, stationary storage is becoming more important, and we need money to kick off projects to scale the technology,” he says.
“Brilliant” solution
In Goosen’s opinion, “positive signals” are coming from the EU concerning energy strategies. “I see that the EU is working with many different parties to add more flexibility to an energy system run on renewables.” His only concern is to bring the technology to the market quickly enough.
In making the transition happen, Cen highlights the “intrinsic motivation” of his team and its commitment to sustainability. “What I like the most about their concept is the storage medium. Most flow batteries companies use vanadium – a metal – because it’s stable, but creating a storage system with just salt and water is brilliant,” says van de Kerk.
Efforts
To get to this point, AQUABATTERY has worked for almost a decade. From the very first experiments in a garage box, countless hours of research and experiments have been devoted to the idea. In the new company’s production space, several prototypes provide a tangible timeline of the endeavor.
The first concept was charging and discharging by using fresh and saltwater. The company then shifted to today’s acid-based solution to improve performance and started experimenting with different membrane stacks. In 2017, AQUABATTERY set up its first pilot in the Delft University of Technology’s Green Village. Three years later, the battery took a trip to the island of Pantelleria, Italy, and was tested at a local power plant. This is a radically improved technology, where the power and energy density has improved tenfold. Last year, the system was tested in the Dutch town of Gorinchem’s sewage treatment plant, which uses self-generated renewable electricity from a solar park.
For AQUABATTERY’s founders, the best is yet to come. Driven by the expansion of renewables, they foresee bringing their product to different users. “At first, we target industrial and commercial applications. Companies will be required to have solar panels, so they’ll need long-duration energy storage to manage electricity production and consumption efficiently. Down the line, we envision installing our batteries in solar and wind parks to buffer them,” concludes Cen.
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