VFlowTech ($13M to develop highly efficient flow battery for long-duration renewable energy storage)

VFlowTech, a cleantech company founded in 2018 in Singapore, develops and manufactures low-cost and efficient modular vanadium redox flow batteries for long-duration energy storage solutions.

Challenges: energy storage

Renewable energy sources, such as solar and wind power, are becoming increasingly prevalent in the global energy mix. However, they are inherently intermittent; they are unavailable when the sun is not shining or the wind is not blowing. This intermittent nature creates a significant challenge for integrating renewable energy into the power grid, as the energy must be stored when it is available and then released when it is needed.

Vanadium redox flow batteries are a promising technology for storing large-scale renewable energy. They are particularly suitable for autonomous energy supply systems in areas with no individual power supply, such as remote farms or mobile radio antennas, as well as for storing energy generated by photovoltaic systems or wind power plants.

Flow batteries are a type of rechargeable battery that stores and releases energy via the movement of electrolytes. The electrolyte is stored outside the battery cells and is pumped through the system during charging and discharging, making them distinct from conventional batteries. This design makes flow batteries an ideal candidate for large-scale energy storage applications due to their scalability advantages over conventional batteries.

One of the most significant advantages of flow batteries is their long lifespan. Typically, they can operate for at least 10,000 charge and discharge cycles, which translates into a lifespan of over 20 years. This durability makes them a very cost-effective option for large-scale energy storage applications.

Additionally, flow batteries have a high level of safety. Unlike conventional batteries, they do not produce heat or gas during operation, which eliminates the risk of thermal runaway or explosion. This feature makes them an attractive option for grid-scale energy storage applications, where safety is a primary concern.

Flow batteries can independently scale the energy storage capacity and power output of the system by merely increasing the volume of stored electrolyte, making this technology highly adaptable to the local conditions of the energy source.

Despite these advantages, flow batteries have a significant drawback in that their typical operating efficiency ranges from 70 to 80%, which reduces the economic benefit of renewable energies. This inefficiency is caused by the need to continuously pump electrolytes through the system, which results in energy losses.

VFlowTech Technology

VFlowTech develops flow battery systems with improved efficiency of up to 85%. The flow battery systems have smart pump and stack management that can improve their efficiencies by 3-5% because some of the pumps can be deactivated under low-load conditions. In addition, the design of primary and auxiliary stacks enables an economic mode to be activated when only the primary stack is required to supply the load, allowing the auxiliary stack to be disconnected and its electrolyte pumps to be deactivated to save power.

The structure of VFlowTech’s flow battery

The diagram below depicts VFlowTech’s flow battery system.

VFlow Tech’s flow battery system (ref. WO2022159037A1).
VFlowTech flow battery system (ref. WO2022159037A1).

The flow battery system comprises electrolyte tanks,  a primary stack, an auxiliary stack, pumps, DC power bus, relays, and a controller.

  • Electrolyte tanks

Electrolyte tanks store a positive electrolyte and a negative electrolyte. The electrolytes in the tanks are pumped through the electrodes of primary and auxiliary stacks and back to the tanks.

  • Electrolyte

The stable electrolyte comprises water and sulfuric acid solvents, 1 – 3 M of vanadium sulfate, a deprotonation inhibitor for [VO₂(H₂O)₃]⁺, and V₂O₅ precipitation inhibitor.

The deprotonation inhibitor for  [VO₂(H₂O)₃]⁺ prevents the chemical reaction:

[VO₂(H₂O)₃]⁺ → 2H⁺ + 2VO(OH)₃ + 2H₂O

The deprotonation inhibitor is less than 0.3 wt% in the electrolyte. It is an inorganic compound, such as NH₄H₂PO₄ and (NH₄)₂HPO₄.

V₂O₅ precipitation inhibitor prevents the condensation of VO(OH)₃:

2VO(OH)₃ → V₂O₅ + + 3H₂O

The precipitation (or condensation) inhibitor is less than 0.5 wt% in the electrolyte. It is an organic compound, such as polyvinylpyrrolidone (PVP) and a water-soluble polyalkylene glycol.

WO2022265579A2 describes the electrolyte of VFlowTech’s flow battery.

  • Primary stack

The primary stack comprises a positive porous electrode and a negative porous electrode separated by a membrane.

The positive electrolyte flows through the positive porous electrode, while the negative electrolyte flows through the negative porous electrode.

Positive and negative porous electrodes are both connected to a DC power bus.

  • Auxiliary stack

The auxiliary stack is identical to the primary stack.

Positive electrolyte is flowed through the positive porous electrode, and negative electrolyte is flowed through the negative porous electrode.

Positive and negative porous electrodes are coupled to a DC power bus via a relay that is activated or deactivated by a controller which monitors the power load on the power bus.

  • DC power bus

The power bus is a direct current bus with positive and negative lines. The positive electrode current collectors are coupled to the positive power bus line. The negative electrode current collectors are coupled to the negative power bus line.

  • Relays

The relays allow the connections between the auxiliary stack and the power bus to be activated or deactivated.

  • Controller

The controller monitors the power load on the power bus and controls the activation of electrolyte pumps and the relays.

The operation of VFlowTech’s flow battery

VFlowTech’s flow battery system has the advantage of a 3-5% efficiency improvement with smart switching between high power mode, economic mode, and silent mode.

When the controller detects that the DC power bus has a higher power demand than a threshold, the flow battery system operates in a high power mode, as shown in the diagram below.

In the high power mode, both the primary and auxiliary stacks are connected to the power bus. The controller activates the both stacks’ pumps to circulate electrolytes through their electrodes.

VFlow Tech’s flow battery system operating in a high power mode (ref. WO2022159037A1).
VFlowTech flow battery system operating in a high power mode (ref. WO2022159037A1).

When the controller detects that the DC power bus has power demand below the threshold of the high power mode, the flow battery system operates in an economic mode, as shown in the diagram below.

VFlow Tech’s flow battery system operating in an economic mode (ref. WO2022159037A1).
VFlowTech flow battery system operating in an economic mode (ref. WO2022159037A1).

In the economic power mode,  the primary stack is connected to the power bus. The controller disconnects the auxiliary stack from the power bus. The controller activates the pumps of the primary stack to circulate electrolytes through the electrodes and deactivates the pumps of the auxiliary stacks to save power.

When the controller detects that the DC power bus has a very low power demand that is less than the threshold of the economic power, the flow battery system operates in the silent mode, as shown in the diagram below.

VFlow Tech’s flow battery system operating in a silent mode (ref. WO2022159037A1).
VFlowTech flow battery system operating in a silent mode (ref. WO2022159037A1).

In the silent power mode,  the primary stack is connected to the power bus. The controller disconnects the auxiliary stack from the power bus and deactivates the pumps of both stacks to save power.

The electrolytes within the primary stack are adequate to support the power load without requiring a constant supply of fresh electrolyte from the electrolyte tanks.

The primary stack pumps may be activated intermittently to refresh the electrolytes within the primary stack when the power demand rises.

VFlowTech Patent

  • WO2022159037A1 Flow battery systems and methods
  • WO2022265579A2 Electrolyte formulation
  • WO2022093117A1 Flow frame for redox flow battery and redox flow battery

VFlowTech Technology Applications

VFlowTech’s vanadium redox flow batteries (VRFBs) have a range of applications primarily in the energy storage sector. These batteries are particularly well-suited for long-duration energy storage, which is critical for integrating renewable energy sources like solar and wind into the power grid. The modular nature of VRFBs allows for scalability, making them adaptable for various uses from residential to utility-scale projects.

  • Renewable energy industries

VFlowTech’s VRFBs are used in power grids and microgrids to manage the variability of renewable energy sources. They can store energy when production exceeds demand and release it when there is a shortfall, thus ensuring a stable energy supply.

  • Residential applications

VFlowTech has commercially deployed 30 kWh and 100 kWh units suitable for residential applications, providing homeowners with a reliable source of backup power and the ability to store excess energy from residential solar panels.

  • Large-scale microgrid applications

The company has completed the production of its MWh system for large-scale microgrid applications. These systems can provide uninterrupted power supply and are particularly useful in remote or rural areas where grid connectivity is unreliable or non-existent.

VFlowTech is involved in rural electrification projects in countries like India and parts of Africa, where their technology is used to store energy from solar and wind sources, providing a reliable power supply to communities with limited or no access to electricity.

VFlowTech Products

PowerCube 5-30

PowerCube 5-30 is ideal for residential storage, telecommunication towers, and solar trackers in remote areas that rely on diesel generators.

The key technical specifications are listed below.

Electrical output:

  • Voltage: 230 VAC;
  • Inverter efficiency: 96%;
  • Frequency: 50 Hz; and
  • Phase: Single phase;

Battery

  • Nominal power 5 kW;
  • Max. Power: 8 kW;
  • Energy capacity: 30 kWh;
  • Backup time: 6 hours at 5 kW load;
  • Cycle: > 10,000;
  • Shelf life: 25 years;
  • Round trip efficiency up to 80% at 100% depth of discharge; and
  • Max. energy efficiency: 85%.

Mechanical data

  • Size (length x width x height): 1.5 m x 1.7 m x 2 m;
  • Installation weight: 1,000 kG;
  • Operation weight: 3,000 kG;
  • Operation up to 55 ºC without active cooling; and
  • Equipped with sensors and smart IoT solutions for 24 x 7 remote monitoring and control;

PowerCube 10-100

PowerCube 10-100 is ideal for commercial and industrial applications, and off-grid applications which rely on diesel generators in many remote and rural areas.

The key technical specifications are listed below.

Electrical output:

  • Voltage: 400 VAC;
  • Inverter efficiency: 96%;
  • Frequency: 50 Hz; and
  • Phase: Three phase (Single phase available);

Battery

  • Nominal power: 10 kW;
  • Max. Power: 15 kW;
  • Energy capacity: 100 kWh;
  • Backup time: 10 hours at 10 kW load;
  • Cycle: > 10,000;
  • Shelf life: 25 years;
  • Round trip efficiency up to 80% at 100% depth of discharge; and
  • Max. energy efficiency: 85%.

Mechanical data

  • Size (length x width x height): 3 m x 2.44 m x 2.66 m;
  • Installation weight: 2,500 kG;
  • Operation weight: 9,000 kG;
  • Operation up to 55 ºC without active cooling; and
  • Equipped with sensors and smart IoT solutions for 24 x 7 remote monitoring and control;

PowerCube 100-500

PowerCube 100-500 is ideal for solar and wind farms that require grid stabilization and power supply and demand balancing as a large industry.

The key technical specifications are listed below.

Electrical output:

  • Voltage: 400 VAC;
  • Inverter efficiency: 96%;
  • Frequency: 50 Hz; and
  • Phase: Three phase;

Battery

  • Nominal power: 100 kW;
  • Max. Power: 130 kW;
  • Energy capacity: 500 kWh;
  • Backup time: 5 hours at 100 kW load;
  • Cycle: > 10,000;
  • Shelf life: 25 years;
  • Round trip efficiency up to 80% at 100% depth of discharge; and
  • Max. energy efficiency: 85%.

Mechanical data

  • Size (length x width x height): 12.2 m x 2.44 m x 2.59 m;
  • Operation up to 55 ºC without active cooling; and
  • Equipped with sensors and smart IoT solutions for 24 x 7 remote monitoring and control.

VFlowTech Funding

VFlow Tech has raised a total of $13M in funding over 3 rounds:

Their latest funding was raised on Feb 7, 2023 from a Series A round.

The funding types of VFlow Tech.
The funding types of VFlowTech.
The cumulative raised funding of VFlow Tech.
The cumulative raised funding of VFlowTech.

VFlowTech Investors

VFlow Tech is funded by 12 investors:

Sing Fuels and Inci are the most recent investors.

The funding rounds by investors of VFlow Tech.
The funding rounds by investors of VFlow Tech.

VFlowTech Founder

Avishek Kumar and Arjun Bhattarai are Co-Founders.

VFlowTech CEO

Avishek Kumar is CEO.

VFlowTech Board Member and Advisor

Avishek Kumar, Arjun Bhattarai, Zeki Şafak Ozan, Doug Parker  Louis Murayama and Michael Gryseels are Board Members.

Ad Ketelaars is Advisor.

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