Energy Storage

High-performance aqueous calcium-ion battery

Image: RPI

Researchers from Rensselaer Polytechnic Institute in the United States have developed a special class of materials for bulky calcium ions, providing pathways for their facile insertion into battery electrodes.

From pv magazine

Against a backdrop of soaring prices and predicted shortfalls of lithium-ion battery materials, the search for inexpensive, abundant, safe, and sustainable battery chemistries has never been more critical. Calcium has been considered in batteries, but the larger size and higher charge density of its ions, relative to lithium, have posed challenges for their insertion into electrode materials.

Now, researchers from Rensselaer Polytechnic Institute in the United States have reported progress in addressing this issue and unlocking the potential of high-performing calcium-ion batteries.

“The calcium ion is divalent, and hence one ion insertion will deliver two electrons per ion during battery operation,” said Nikhil Koratkar, the John A. Clark and Edward T. Crossan Professor of Engineering at Rensselaer. “This allows for a highly efficient battery with reduced mass and volume of calcium ions.”

However, the larger size and higher charge density of calcium ions relative to lithium impairs diffusion kinetics and cyclic stability, he added. The team has overcome this problem by developing oxide structures containing big open spaces (heptagonal and hexagonal channels). In their work, an aqueous calcium-ion battery is demonstrated using orthorhombic and trigonal polymorphs of molybdenum vanadium oxide (MoVO) as a host for calcium ions.

The researchers have demonstrated that calcium ions can be rapidly inserted and extracted from the material, with these tunnels acting as “conduits” for reversible and fast ion transport. The findings indicate that MoVO provides one of the best performances reported to date for the storage of calcium ions.

Specifically, for trigonal MoVO, a specific capacity of ∼203 mAh g−1 was obtained at 0.2C and at a 100 times faster rate of 20C, an ∼60 mAh g−1 capacity was achieved. The open-tunnel trigonal and orthorhombic polymorphs also promoted cyclic stability and reversibility. These findings were recently published in Proceedings of the National Academy of Sciences (PNAS).

“Calcium-ion batteries might one day, in the not-so-distant future, replace lithium-ion technology as the battery chemistry of choice that powers our society,” says Koratkar. “This work can lead of a new class of high-performing calcium-based batteries that use earth abundant and safe materials and are therefore affordable and sustainable. Such batteries could find widespread use in portable and consumer electronics, electric vehicles, as well as grid and renewable energy storage.”


Compressed air storage vs. lead-acid batteries

The experimental setup at the campus of the University of Sharjah. Image: University of Sharjah

Researchers in the United Arab Emirates have compared the performance of compressed air storage and lead-acid batteries in terms of energy stored per cubic meter, costs, and payback period. They found the former has a considerably lower Capex and a payback time of only two years.

From pv magazine

Scientists from the University of Sharjah in the United Arab Emirates have compared the storage potential of compressed air energy storage (CAES) systems and conventional lead-acid batteries in an experimental setup and have found that CAES offers a series of operational advantages over electrochemical systems. “Our CAES concept is applicable to all locations as it just needs tanks buried underground,” the research’s corresponding author, Abdul Hai Alami, told pv magazine. “but it would really shine in hot climates.”

In the study “Experimental evaluation of compressed air energy storage as a potential replacement of electrochemical batteries,” which was recently published in the Journal of Energy Storage, the UAE group described the experimental setup as a unit combining a CAES system operating as an AC generator that is connected to various loads through an electrical panel. Its performance was compared to that of a 12 V, 70 Ah battery provided by US-based Incoe Corporation, which was connected via a 600 W inverter through an inversion circuit to the same load.

The CAES system consists of an air motor connected to a 3-phase, permanent magnet AC generator supplying 380 V and 5 A. The connection was made either directly or through a 1:2 or 1:4 speed-up gearboxes to compare the discharge time and output energy quality. The system also had a rudimentary heat exchanger – a pipe loop in a water bath – to control air temperature, which affects air density significantly, resulting in better system efficiency. The scientists tested two different motor sizes of 5 hp and 9 hp, respectively.

The performance of both storage technologies was measured in terms of energy stored per cubic meter, costs, and payback period. “In order to assess system performance, three loads are operated, a 6 W fan, 100 W lamp, and a 250 W drill,” the scientists explained. “A No-load condition was also performed to determine the full capacity of the system and compare it with theoretical calculations in terms of voltage and time of discharge.”

The researchers also installed electrical cabinets to receive load cables from the generator in order to investigate the suitability of the CAES system for industrial applications. “These include Industry-standard sockets for single phase and three phases with two different colors, protect against inadvertent electric shocks, provide earth leakage protection and finally the coated panel provides protection against environmental elements,” they emphasized.

The academics explained that the quality of the energy generated by the generator’s air motor, which is in turn activated by the kinetic energy coming from the storage air cylinders of the CAES system, is provided by maintaining operation at the rated rotational speed of the generator in order to satisfy the minimum output voltage and operational frequency that will eventually be supplied to the end-users.

According to their calculations, the theoretical maximum output power of the CAES system, at 12 bar pressure, should be 0.048 kW and its theoretical roundtrip efficiency was estimated at 86.6 %. The experimental maximum output power of the system, however, was 27% lower at 0.035 kW and its experimental roundtrip efficiency was around 60%. The battery was found to ensure continuous operation of around 50 minutes, after which the power supplied to the inverter proved to be insufficient and the loads were immediately unpowered.

“The main factors to enhance roundtrip efficiency are the larger air storage volumes to ensure consistent pressure input to the air motors, better thermal management of air temperature, connecting more than one tank to the system and operating them in series or in tandem and finally having an air motor/generator as a single unit to overcome mechanical losses,” Alami further explained. “Simulation and control of system operation allowing input pressure variation to follow demand is another important factor in enhancing operation and scale up.”

In their cost comparison, the researchers considered an 840 kWh/3.5 kW CAES setup and a 1400 kWh lead Acid battery connected to a 3.5 kW battery inverter. The cost of the second setup was estimated at $130,307 and that of the CAES system at $23,780.

“As a rough estimate, breakeven point with a battery storage system can be achieved within 3–5 years depending on charge-discharge cycles required from the battery and no including the price for battery cabinet, air conditioning and the costs of the cooling load,” they highlighted, noting that if the CAES capacity is solely a function of the storage tanks capacity and space available for them, the above-ground footprint of the system is minimal and comparable with a battery enclosure connected to an air conditioning split unit. “The payback period, in this case, would be around 1–2 years,” they said.

The research team is currently considering how to bring the proposed storage technology closer to commercial production. “The system is intrinsically compatible with off-grid solar farms, charging the tanks with high-pressure 100 bar air compressors with a capacity of around 30 kW,” Alami said. “With tanks available and amenable to underground burial, the main technical issues of the system are clear and manageable for such installations. Also, the system can power EV chargers in off-grid locations.”


Storage for load shifting viable in several Brazilian states

Image: pv magazine, Eckhart Gouras

Greener says that battery storage could help large electricity consumers in Brazil to cope with sharp differences between peak tariffs and off-peak tariffs.

From pv magazine

Batteries are already competitive for consumer energy storage in behind-the-meter applications in several Brazilian states. Marcio Takata, the director of consulting company Greener, Marcio Takata, described this market opportunity during the Greener Business Summit earlier this month in Sao Paulo, Brazil.

He presented a case study involving an industrial consumer in the area of ​​Cosern, in the state of Rio Grande do Norte. The difference between the tariff at peak hours and the off-peak tariff is BRL 3.004 ($0.55)/MWh.

According to Greener, such consumers could reduce their annual bills from approximately BRL 273,600 to BRL 173,600. They would achieve 36% savings on the energy tariff by installing a lithium-ion battery with a capacity of 0.6 MW/2.5 MWh.

In the simulation, the consumer would have a reduction of BRL 123,800 in the peak tariff, from BRL 173,400 to BRL 49,600, and an increase of BRL 21,800 in the off-peak tariff, from BRL 103,200 to BRL 124,000. The net savings with storage would therefore be BRL 102,000.

The investment, for a useful life of 15 years, was estimated at BRL 11 million, with an operating cost of BRL 55,000 per year. There is a need for reinvestment in the tenth year of the asset, consisting of 15% of capex, or BRL 1.65 million. The tariff adjustment for the period was 6% per year.

The difference between peak and off-peak tariffs is crucial to the viability of battery storage to manage the load. According to the Greener survey, this difference can range from BRL 354/MWh in the CEA concession area, in the state of Amapá, to BRL 3,971/MWh, in the Equatorial concession area, in the state of Pará. In addition to the distributors in Pará and Rio Grande do Norte, other distributors such as Coelba (BA), Enel RJ and EMS (MS) have peak and off-peak rates with differences above BRL 3,000/MWh.

Battery storage is seen as a way to diversify for companies that already operate in the solar sector. Sao Paulo-based Brasol, for example, is expected to invest in its first storage projects this year.


The real value of energy storage

A rechargeable battery bank. Image: Jelson25, Wikimedia Commons

An international research team has developed a new way to evaluate the economic value of energy storage technologies. They went beyond pure cost assumptions to consider the benefits that such technologies could bring to energy systems.

From pv magazine

An international research team has developed a new approach to energy storage technologies that does not exclusively consider costs, as it also considers their interaction with energy systems.

The scientists said their “market potential method” can be used to simultaneously analyze multiple energy storage systems. “We show that current cost metrics can be misleading for technology design decisions,” they said. “A narrow cost focus on designing energy storage is not enough.”

The researchers stressed the importance of discovering the “hidden values” of storage technologies. They said network or peak plant deferral, or reduced solar and wind power plant curtailments, are hidden variables that are often neglected in storage cost analysis.

They apply their method in two phases. It initially focuses on a market potential indicator (MPI) and then defines market potential criteria to support design decisions.

“The MPI is not a new metric,” the scientists said. “It is a result of energy system models that analyze scenarios in future energy systems and describes the total quantity of a particular storage technology in a cost minimized electricity system.”

The scientists used the new approach to look at how different hydrogen storage technologies could be adopted across several European markets. They found that technologies with high or low levelized costs of storage (LCOS) could have good market potential.

“Not always a technology with the lowest investment or LCOS is most valuable,” they said. “It can also be the more expensive technology that can lead to a cheaper future electricity system.”

They described their findings in “Beyond cost reduction: improving the value of energy storage in electricity systems,” which was recently published in Carbon Neutrality. The research group includes scientists from the University of Edinburgh, Technische Universität Berlin, and the Netherlands Organization for Applied Scientific Research (TNO).

The team said the “market potential method” could help to identify potential growth markets, assess future cost reductions, and reduce the structural uncertainty of linear programming energy system models.

“The results suggest looking beyond the pure cost reduction paradigm and focus on developing technologies with suitable value approaches that can lead to cheaper electricity systems in future,” they said.

Author: Emiliano Bellini

Water-based zinc-ion battery for stationary energy storage

Residential energy storage. Image: Salient Energy

Salient Energy developed the water-based zinc-ion battery to have the same power, performance, and footprint as lithium-ion systems without the safety risk.

From pv magazine USA

Lithium-ion batteries dominate the market for electric vehicles and home energy storage due to lower cost, higher performance, and lower weight compared some alternatives, but the main challenges are safety and sourcing of materials. The safety risk of lithium ion is thermal instability, a condition that can lead to a thermal runaway.

Over the past several years lithium-ion batteries have been known to explode in laptops, cell phones, and to cause fires in large energy-storage facilities. Sourcing of the battery materials, which include lithium, cobalt, nickel, and graphite, is also a challenge as the materials often come from conflict-prone areas like the Congo. These challenges have led some manufacturers to seek alternatives. pv magazine USA spoke with Ryan Brown, CEO and co-founder of Salient Energy, a manufacturer of zinc-ion batteries, and he explained that Salient’s mission is to develop a battery that mimics the performance of lithium-ion while using abundant materials that come from conflict-free areas, and that do not pose a safety risk.

Brown acknowledged that lithium-ion is the best at energy for the weight and that manufacturers have done well to reduce cost, but safety remains an issue. He said, for example, recent fires in Tesla vehicles are caused by thermal runaway in lithium-ion batteries. “When used in home energy systems, safety is also a top priority,” Brown said.

Zinc-ion batteries are a non-flammable option, due to their water-based chemistry, Brown noted. He said that the zinc-ion energy storage systems have the same power, performance, and footprint as lithium-ion systems, “so they are a true alternative to lithium-ion.”

One advantage to zinc-based batteries is that they can be manufactured on the same lines as lithium-ion, which keeps manufacturing costs low. As far as safety goes, “safety is the killer advantage,” said Brown. “What we’ve done is we’ve made a zinc battery that works the same way lithium ion works. We have zinc reacting on both sides, so we don’t have to store the reactant in electrolyte.”

Target market

The main application market that Salient is targeting is stationary energy storage. “Residential yes, but ultimately we want to be in the shipping containers.” With the main advantage being safety, Brown sees the zinc-ion battery as a viable alternative for batteries that need to be placed indoors, such as in apartment buildings. “A city is not place to put energy storage outdoors, and with California mandating that apartments must have energy storage, zinc-ion is a safe solution.”

To demonstrate the safety of zinc-ion batteries as a residential energy storage solution, Salient Energy is partnering with Horton World Solutions (HWS) a sustainable homebuilder that is installing the batteries in 200K homes that it is constructing in the Dallas Fort Worth area as well as across the Sunbelt. Construction on these homes will be underway by Q4 of 2022.

Domestic supply chain

Salient’s batteries are made up of a zinc, a pH-neutral zinc sulphate electrolyte, and a manganese oxide-based cathode, all of which are abundant are mined and processed in North America, allowing Salient to source materials from a domestic supply chain. While Salient is based in Nova Scotia, in early 2022 the company opened an office in Oakland, Calif. A team of 7 engineers based in Oakland are currently focused on developing and improving Salient’s residential battery systems, the same system used in the HWS demonstration.

For now, Salient is manufacturing batteries at its Dartmouth, Nova Scotia facility at a small scale of around 100 batteries per month, but the company is in the process of ramping up production at this facility to the pilot scale (1000s of batteries per month) to support pilot projects in the residential space.

Author: Anna Fischer

Powering EV charging stations with agrivoltaics

Image: wikimedia commons

US researchers find that placing agrivoltaic installations along highways to power EV charging stations can reduce both carbon emissions and range anxiety.

From pv magazine USA

A research team from Oregon State studied the potential of agricultural land to generate solar electricity to power electric vehicles along the state’s highways. They found that agrivoltaic systems placed in adjacent proximity to the highway can be useful in rural areas, which is also where electric charging stations are most needed.

The study, recently published in Scientific Reports, looked at how agrivoltaic technology can be used to improve EV charging infrastructure to reduce range anxiety, which is the worry about making it to the next charging point.  In their analysis, the team envisioned a scenario that had the highest traffic demand and the lowest photovoltaic generation, and the results showed that agrivoltaics could play a role in charging station infrastructure development.

In the study, a total of 231 rural highway access points were identified that had sufficient land area to service EV charging stations with energy generated by agrivoltaic installations. These areas are indicated with black circles Figure 1.

Model results with distribution and quantity of highway access points serviceable by agrivoltaic systems, highway access points not serviceable by agrivoltaic systems, land supply available, and the portion of land supply needed to meet electricity demand at serviceable highway access points. Image: Oregon State University, scientific reports, Creative Commons License CC BY 4.0

The team discovered that to meet the conservative estimate of EV charging station demand at 86% of highway access points through Oregon, 12,000 acres (18.75 square miles) of land would be required. Of the 231 highway access points identified for agrivoltaics, 220 (95%) have a distance between them that is less than 17 miles. The researchers looked at earlier research conducted in Croatia that indicated that people have less range anxiety if charging stations are less than 3.1 miles apart. And other research shows that gas stations tend to be 2.5 to 18 miles apart. The Oregon State team used this range as a basis in their scenario.

Based on the number of vehicles registered in the state of Oregon and how much carbon they emit each year, the team estimated that the potential for carbon reduction through agrivoltaic-powered EV charging stations is about 3.1 million tons or the equivalent to 673,915 vehicles removed from the road each year, if their approach were fully implemented.

Overall the Oregon researchers showed that servicing rural EV charging stations with agrivoltaics next to the highway is feasible, requiring only 3% of total land supply to power 86% of rural highway access points throughout the state.

As rural areas often lack the grid infrastructure to support charging stations, agrivoltaics enable the shift in energy production to the point of use. Oregon currently has 670 EV charging stations, and the researchers’ scenario adds another 231 charge points located in close enough proximity to reduce or eliminate range anxiety. Additionally, the team estimates that implementation of this approach could reduce annual carbon emissions from passenger vehicle use in Oregon by 21%.

Author: Anne Fischer

Harvard, Cambridge scientists improve durabiliy of redox flow batteries with anthraquinone

Anthraquinone (C14H8O) is an aromatic organic compound. Image: Ben Mills and Jynto, Wikimedia Commons

A research team has used a molecule known as 2,6-dihydroxy-anthraquinone (DHAQ) to improve the durability of organic aqueous redox flow batteries. They claim the molecule enables a net lifetime that is 17 times longer than past research has shown.

From pv magazine

Scientists from the University of Cambridge and Harvard University claim to have considerably increased the duration of organic aqueous redox flow batteries. They used a molecule known as 2,6-dihydroxy-anthraquinone (DHAQ) – or more simply, anthraquinone – to avoid the decomposition of chemically unstable redox-active species, which is the main factor affecting the storage capacity of these storage devices.

“Organic aqueous redox flow batteries promise to significantly lower the costs of electricity storage from intermittent energy sources, but the instability of the organic molecules has hindered their commercialization,” said researcher Michael Aziz. “Now, we have a truly practical solution to extend the lifetime of these molecules, which is an enormous step to making these batteries competitive.”

DHAQ decomposes slowly over time, regardless of how many times battery cycles have been performed. When it is in contact with the air, after a cycle, this molecule absorbs oxygen and turns back into its original status. For this reason, the researchers refer to the molecule as a “zombie quinone,” as it is kind of returning to life after being dead.

“But regularly exposing a battery’s electrolyte to air isn’t exactly practical, as it drives the two sides of the battery out of balance – both sides of the battery can no longer be fully charged at the same time,” they said.

Through nuclear magnetic resonance (NMR), the academics discovered that the battery’s active materials can be recomposed via deep discharge. This occurs in a battery when it has been discharged at its full capacity.

“Usually, in running batteries, you want to avoid draining the battery completely because it tends to degrade its components,” said researcher Yan Jing. “But we’ve found that this extreme discharge where we actually reverse the polarity can recompose these molecules – which was a surprise.”

They said redox flow batteries developed via this approach could offer a net lifetime that is 17 times longer than previous research has shown.

“Getting to a single-digit percentage of loss per year is really enabling for widespread commercialization because it’s not a major financial burden to top off your tanks by a few percent each year,” said Aziz, adding that the proposed approach was applied with success to a range of organic molecules.

They described their findings in “In situ electrochemical recomposition of decomposed redox-active species in aqueous organic flow batteries,” which was recently published in Nature Chemistry.

“Now, utilizing 2,6-dihydroxy-anthraquinone (DHAQ) without further structural modification, we demonstrate that the regeneration of the original molecule after decomposition represents a viable route to achieve low-cost, long-lifetime aqueous organic redox flow batteries,” they said.

Author: Emiliano Bellini

China’s massive hydro energy storage goals may be getting bigger

China has been eyeing a major pumped hydro build-out since at least last year. Image: Pixabay

From Bloomberg

BEIJING (BLOOMBERG) – China’s biggest dam builder says the country is launching an even-larger-than-expected campaign to build hydro energy storage to complement renewable power.

The nation will start construction on more than 200 pumped hydro stations with a combined capacity of 270GW by 2025, Mr Ding Yanzhang, chairman of Power Construction Corp of China, the country’s largest builder of such projects, said in a Monday (June 13) commentary in the Communist Party-run People’s Daily.

That’s more than the capacity of all the power plants in Japan, and would be enough to meet about 23 per cent of China’s peak demand.

It would also be a massive increase from what China proposed just three months ago in its 14th five-year plan for energy development, when officials said the country wanted to have 62GW of pumped hydro in operation and another 60GW under construction by 2025.

PowerChina did not immediately respond to an e-mail seeking comment, and the National Energy Administration (NEA) did not answer calls to its Beijing office.

Hydro storage technology dates back more than a century.

Water is pumped into an uphill reservoir using electricity when demand is low, and then generates power when needed by letting gravity carry the water downhill through turbines.

It can be paired with China’s rapidly growing fleet of solar panels and wind turbines to generate electricity when the sun isn’t shining and breezes aren’t blowing.

China has been eyeing a major pumped hydro build-out since at least last year. In August, a draft NEA document identified the potential for 680GW of pumped hydro in the country, and mooted a possible goal of starting construction of 180 gigawatts by 2025.

The final version of the plan released in September toned down the scale, but still called for 120GW of capacity operating by 2030.

The entire world had 158GW of hydro storage at the end of 2019. China is also ramping up plans to deploy newer forms of energy storage such as batteries, with the country’s largest grid saying it hopes to have 100GW of such capacity available by 2030.

Storing renewables with high-rise elevators

Image: Federal University of Espírito Santo, Energy, Creative Commons License CC BY 4.0

Lift Energy Storage Technology is a proposed long-term storage solution that relies on elevators to bring solid masses to the tops of buildings in charging mode. It then lowers the same mass to produce electricity in discharge mode.

From pv magazine

An international research team has developed a gravitational energy storage technology for weekly cycles in high-rise buildings in urban environments.

Lift Energy Storage Technology (LEST) is a proposed long-term storage solution. It relies on the use of elevators in buildings to lift solid masses in charging mode. It lowers the same mass to produce electricity in discharge mode.

“Energy is stored as potential energy by elevating storage containers with an existing lift in the building from the lower storage site to the upper storage site,” the scientists said. “Electricity is then generated by lowering the storage containers from the upper to the lower storage site.”

The proposed system could detect the position of containers and optimize available storage capacity in the upper and lower storage sites through dedicated software. Building owners could choose to only operate the system during periods of low elevator demand, in order to minimize its impact on building occupants. The elevators can run at different speeds, depending on storage requirements.

“When the lifts are not being used, such as during the night, the autonomous trailers can fill the lift with containers and the lift can be used to provide ancillary services to the power grid by lifting and descending the mass continuously on grid requirements,” the academics said.

Autonomous trailer and storage container. Image: Federal University of Espírito Santo, Energy, Creative Commons License CC BY 4.0

The economic viability of the system depends on the cost of the storage space. If this is low, the scientists said that a mixture of sand and water could be a feasible solution. The number of storage containers depends on a building’s ceiling-bearing capacity.

The researchers assumed that the elevators have regenerative braking capabilities and that the cost of renting the containers’ storage space in the upper and lower sites would be zero.

“The only cost requirements are the containers, the material selected to increase the mass of the containers, and the autonomous trailers,” they said.

Considering an average height difference between the upper and lower reservoirs of 100 meters, the cost of installed capacity energy storage cost was found to be approximately $62/kWh.

“The cost of LEST with an average height difference of 300 meters is $21/kWh, whereas an average height difference of 50 meters costs $128/kWh. This is half of the cost of storing energy with batteries.”

The technical lifetime of the system is estimated between 20 and 30 years and its capacity will be strictly dependent on the number of existing lifts.

“The higher the height difference between the lower and upper storage sites, the lower the cost of the project,” the research team said.

The noted a multi-elevator lift developed by German industrial conglomerate Thyssenkrupp that only uses magnetic force to move the lifts, as an ideal solution for the LEST system.

“This allows the lift to move vertically, horizontally and diagonally, and it is particularly interesting for high-rise buildings because several lifts can travel up or down at the same time in the same shaft,” they said.

The scientists presented the gravitational tech in “Lift Energy Storage Technology: A solution for decentralized urban energy storage,” which was recently published in Energy. The research team includes academics from Austria’s International Institute for Applied Systems Analysis (IIASA), the Federal University of Espírito Santo in Brazil, the Wrocław University of Science and Technology in Poland, and the Hamburg University of Applied Sciences in Germany.

“LEST systems are particularly interesting in buildings with rope-free elevators, and they can also provide tuned mass damper services on the top of very high buildings,” they said. “LEST systems are particularly interesting during the night when most lifts are not being used, as the autonomous trailers can continue to fill the lifts with containers to provide ancillary services to the power grid.” 

Author: Emiliano Bellini

Long-duration storage solution based on saltwater

Image: Imperial College London

Developed by Dutch start-up AquaBattery, the storage technology is claimed to independently amend power and energy capacity. The battery system utilizes three storage tanks, one with fresh water, one with concentrated salt water and one with diluted salt water, and also relies on membrane stacks.

From pv magazine

Dutch start-up AquaBattery has been awarded €2.5 million in funding from the European Innovation Council’s (EIC) Accelerator to develop its long-duration energy storage technology based on saltwater.

The company’s patented storage technology uses just saltwater as the storage medium and is described as a flow battery that is able to independently amend power (kW) and energy (kWh) capacity. The proposed solution is also said to be low-cost, highly scalable and sustainable, as it uses only water and table salt, with its storage capacity being expandable by just adding water reservoirs or using larger tanks.

The battery system utilizes three storage tanks, one with fresh water, one with concentrated salt water and one with diluted salt water, and also relies on membrane stacks. During the charging phase, the diluted salt water is split into concentrated salt water and fresh water in the membrane stack and stored separately. The separation is achieved through electrodialysis (ED), which is a separation process in which charged membranes and electrical potential differences are used to separate ionic species from an aqueous solution and other uncharged components.

A pilot project developed by AquaBattery. Image: Imperial College London

In the discharging phase, the two streams are combined and the resulting energy is converted to electricity with the help of the membrane stack through reverse electrodialysis (RED), which is a technology to generate electricity from the salinity difference between two solutions, for example, seawater and river water.

“AquaBattery’s solution could provide virtually unlimited storage capacity from eight hours up to days, weeks or even seasonally,” reads a statement from the Imperial College London, with which the Dutch start-up is cooperating. “The fund will provide around €2.5 million in grant funding to AquaBattery, with options for direct equity investment of up to €15 million depending on their needs. The grant will enable the team to speed up R&D and product development and bring forward commercialization of AquaBattery to 2025 or earlier.”

Author: Emiliano Bellini