Battolyser Systems, a Dutch cleantech startup founded in 2021, develops an integrated battery and electrolyser system known as the battolyser. The battolyser is charged when there is a surplus of renewable electricity. When the battery is full, the surplus of energy produces hydrogen and oxygen for energy storage. It can maximize the wind and solar energy captured.
Challenges: energy storage
The unpredictability and intermittent nature of renewable energy sources such as wind and solar is one of their greatest obstacles. For example, solar energy can produce an excess of electricity during the day and summer, but the supply decreases at night and during the winter.
Conventional batteries, such as those based on lithium, can store energy in the short-term, but when they’re fully charged they must release any excess or they will overheat and degrade. The green hydrogen production from water electrolysis powered by renewable energy may enable long-term energy storage in fuels and feedstock via chemical processes such as the Sabatier (methane from H₂ and CO₂), Haber-Bosch (ammonia synthesis from clean H₂ and N₂), and Fischer- Tropsch (alkanes from CO/CO₂ and H₂) process.
Thereby, the storage infrastructure should provide for these different requirements throughout the year and support the ‘storage merit order’ of first efficient battery storage, followed by less efficient fuel production, storage, and conversion. Alkaline electrolysers coupled with batteries are prevalent in the hydrogen-producing industry and can perform this function.
Battolyser Systems Technology
Battolyser Systems developed a low-cost, durable battolyser that integrates the functions of rechargeable battery and alkaline electrolyser. The battolyser provides electricity storage capacity, which is charged when there is a surplus of renewable electricity and discharged when there is an electricity deficiency. When the battery reaches its maximum capacity, hydrogen is produced from the excess electricity that exceeds the battery’s capacity. This makes the battolyser flexible with respect to energy insertion.
Battolyser Systems battolyser
Below is an image of a battolyser system and a diagram of the battolyser stack, which is composed of numerous cells.
The right corner of the above figure depicts the top view of a battolyser cell. The electron storage electrode is a single, continuous electrode, whereas the gas evolution electrode is a plurality of spatially separated electrodes in functional contact with different parts of the electron storage electrode. Each gas evolution electrode is surrounded by a separation space to prevent short-circuiting with the electron storage electrode.
A cross section of the above battolyser cell, which is composed of four bipolar plates, as depicted in the figure below (left), reveals the internal arrangements of the electrodes.
Two bipolar plates are stacked on each other to provide an interdigitation of the gas evolution electrode and electron storage electrode. A plate sealing connects the two bipolar plates stacked together. The electrical connections to the top and bottom bipolar plates control the voltage difference (or current flow) between the two electrodes.
The bipolar plate has openings on both the top and bottom. The top opening adds and/or removes a gas, while the bottom opening adds and/or removes electrolytes. Before charging and/or discharging, the battolyser cell has no electrolyte.
The figure above (right) depicts a magnified view of the battolyser cell. The bipolar plate has an isolator to prevent direct contact with the electrolyte. The gas evolution electrode is a hollow electrode. It is surrounded by a separator that separates hydrogen and oxygen gas while allowing water and OH⁻ ions to flow between the electrodes. A hydrophobic coating on the interior of the hollow gas evolution electrode directs the gas evolved at the electrode.
The porous (or mesh) gas evolution electrode is composed of nickel-, stainless steel-, titanium-, or platinum-based materials. The electron storage electrode is composed of iron-based materials. The gas evolution electrode’s electrochemical storage capacity is less than 5% of the electron storage electrode’s electrochemical storage capacity.
The working mechanism of the battolyser
The diagram below depicts the control of the voltage difference (or current flow) between a battolyser cell’s gas evolution electrode and electron storage electrode. Line L₁ represents the measured voltage between the electrodes while charging/discharging with a controlled current flow.
During a first time period τ₁ and a third time period τ₃, a charging current was imposed between the electrodes of the battolyser cell. As shown in the figure below, Fe(OH)₂ transfers to Fe at the electron storage electrode, while Ni(OH)₂ transfers to NiOOH at the gas evolution electrode.
When fully charged, the formed Fe and NiOOH electrodes become more active as efficient hydrogen and oxygen evolution reaction catalysts. As depicted in the figure below, the overcharging results in O₂ evolution at the gas evolution electrode (Fe) and H₂ evolution at the electron storage electrode (NiOOH).
During a second time period τ₂ and a fourth time period τ₄, a discharging current was imposed between the electrodes. As depicted in the figure below, Fe transfers to Fe(OH)₂ at the electron storage electrode, while NiOOH transfers to Ni(OH)₂ at the gas evolution electrode.
When fully discharged, as depicted in the figure below, the formed Ni(OH)₂ electrode becomes more active as efficient H₂ evolution at the gas evolution electrode. Approximately no O₂ is produced.
During τ₁ and τ₃, the production ratio of O₂ and H₂ is approximately 7.5:1. During τ₂ and τ₄, approximately no O₂ is produced. The ratio of H₂ produced in τ₁ and τ₃ versus τ₂ and τ₄ is approximately 6.5:1.
Battolyser Systems Patent
- US20220074059A1 Electrolytic cell for h2 generation
- US11552352B2 Hybrid battery and electrolyser
Battolyser Systems Products
Early in 2021, Battolyser Systems installed the first 15kW/15kWh Battolyser for electricity storage and hydrogen production at the Magnum power station in Eemshaven in the Netherlands. They intend to scale up to 10 Megawatt installations at industrial partners, solar parks and locations where large amounts of electricity from offshore wind farms are arriving on shore. Ultimately, they will install gigawatt-scale battolyser systems.
The following figure shows the modeling performance of a 10 Megawatt Battolyser.
- Electricity market prices are average, battolyser is charging and produces H₂;
- Electricity market prices are high, battolyser is discharging and makes money on electricity market;
- Electricity market prices are low, battolyser is charging and produces H₂ at negative cost;
- Electricity market prices are high for more than an hour, battolyser is empty and sits idle;
- In the Dutch 2020 market context, the Battolyser would produce H₂ most of the time (80%).
Battolyser Systems Funding
Battolyser Systems has raised a total of €40M in funding over 2 rounds. Their latest funding was raised on Oct 11, 2023 from a Debt Financing round.
Battolyser Systems Investors
Battolyser Systems is funded by the European Investment Bank.
Battolyser Systems Founder
Fokko Mulder is Co-Founder.
Battolyser Systems CEO
Mattijs Slee is CEO.
Battolyser Systems Board Member and Advisor
Boudewijn Tans is a Board Member.
Kees Koolen is a Advisor.