As part of the "Electrolysis made in Baden-Württemberg" project, the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) has developed an alkaline pressurised electrolyser with an output of 1 MW together with 40 companies. The dosing pump for the demonstrator was supplied by Lewa GmbH from Leonberg. The diaphragm dosing pump, called "ecoFlow", supplies what is necessary for hydrogen production in order to maximise the efficiency of the electrolysis process.
The "ecoFlow" diaphragm dosing pump from the Stuttgart-based company supplies the electrolyser with the water required for hydrogen production. The pump feeds in exactly the amount of process water that the system consumes during electrolysis.
To do this, the delivery volume must be adjusted in real time to the actual consumption conditions. Otherwise, the dosing process would have a negative effect on the system's control loops. Dosing is therefore carried out using two-point control.
The company used the ecoflow LDC1 M910S, which has a hydraulic output of 0.2 kW, for this purpose. Due to the hydrogen produced during the process, it is equipped with an explosion-proof motor. In accordance with the requirements of the application, it pumps water at up to 30 °C at a flow rate of 130 l/h against 40 bar in the electrolysis system demonstrator.
Special requirements for electrolyser pumps
"This type of pump enables the precise adjustment of a defined amount of water in a wide control range," says Frank Baumgart, laboratory manager in the Renewable Energy Sources and Processes (REG) department at ZSW. This is important for the system demonstrator, as electrolysis stacks with different lengths and performance classes have to be tested here.
As such systems are designed to operate for up to 20 years, all system components must have a long service life and be easy to maintain and repair. Due to possible points of contact with the potassium hydroxide solution in the electrolysis stack, the parts of the ecoflow unit must also be highly resistant to chemicals.
This is why the components in contact with the product are made of stainless steel, which is also resistant to caustic potash solution. The head of the pump has a robust PTFE sandwich diaphragm. Thanks to its permanent monitoring, there can be no leakage-related interruptions even when the electrolyser is in continuous use.
