Deutsche Version  ACT
Physical Storage
Elektrolysis 12.4.2017

Development goal: Low specific energy consumption of the plant

Hydrogen production in the megawatt-scale

In the P2G electrolysis project, researchers worked on developing and testing an optimised H2 generation plant prototype based on alkaline electrolysis technology in the 300 kWel class. Based on the currently available AEL technology, it is intended to exploit the development potential technically necessary for the entire plant and prepare the upscaling to the lower megawatt class.

Project status Project completed
Typical system size Output 6-10 MW / > 20 MW
Efficiency AC/VNH2 68 % / ca. 75 %
Efficiency AC/VNCH4 < 54 % / ca. 60 %
Service life of the system 1-10 Cycles/Day
Response time when preparing the energy <1 h at starting from the cold state, <1 min at startup from a warm state
Example application areas Hydrogen generation in dynamic mode for all hydrogen storage and applications
Project duration November 2012 until February 2017

The future energy system in Germany shall ensure sustainable and continuous power supply from renewable resources. With a system with 100%-RE full supply, long-term storage capacity of about 20 TWhel is necessary because many of Renewable Energies (RE) are only available with highly dynamically fluctuations.  Chemical fuels such as hydrogen or methane (SNG: Substitute Natural Gas) are the most suitable forms for this long-term storage. For SNG production, ZSW in cooperation with the SolarFuel GmbH and the Fraunhofer IWES has developed the Power-to-Gas concept (P2G).

  • View of a 0.5 m² pressurized electrolysis block &copy; ZSW
  • Development goal: Low specific energy consumption of the plant &copy; ZSW
  • Modular plant concept of the P2G electrolysis &copy; ZSW

Development potentials

The project "P2G-electrolysis" mainly aims on the development and testing of an optimized H2 production plant prototype. The system shall be based on alkaline electrolysis technology in 300kWel scale. Starting on the basis of existing AEL technology, the new system shall make use of the whole range of technically available development potentials. The upscaling  into the lower megawatt class shall be prepared. Furthermore, based on an analysis of the cost structure and value chain, innovative engineering and manufacturing concepts shall be developed.

For further commercialization and dissemination of technology, improving system efficiency and reducing system costs are essential key facts. A key component is the hydrogen production plant, represented within this project by already commercially available alkaline electrolysis (AEL). Hydrogen production has considerable influence on the efficiency and the cost of storage and offers the highest cost reduction potential.

In principal, H2-generation systems are commercially available, nowadays. But existing systems are not optimized to the RE typical dynamic or intermittent operation. Technologically and cost wise, the AEL has principal significant improvement and cost reduction potentials to be used. But so far, existing AELs and AEL installations occupy  only high-priced niche markets for constant operation.

Starting points und development strategy

The joint project is based on three main starting points to create a new technical development stage of the dynamic and intermittent production of hydrogen:

  • technical development of major core systems based on new concepts (electrolysis block, electrolyte-core system, rectifier system, thermal power delivery, plant safety and product gas analysis system),
  • development of a scalable and modularized overall system concept,
  • further development of the subsystems following functional, manufacturing and cost aspects.


The project sees itself as a cooperative project with the participation of the Scientific Institute Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) / Stuttgart and the two SMEs SolarFuel GmbH (SolarFuel) / Stuttgart and Enertrag HyTec GmbH (Enertrag HyTec) / Dauerthal.
The assembly of the prototypical electrolysis system shall take place within the new "power-to-gas" system environment of ZSW in Stuttgart which is available since mid of 2012. The prototype system will be operated and tested over a period of nine months during the project time period as a minimum. A complete laboratory infrastructure for system and subsystem testing is available with ZSW. The main test objective is to demonstrate the correctness of pre-defined specifications in the real hydrogen-generating operation.

Economic viability

Upon successful completion of the project, a 300 kWel hydrogen generation system with its peripheral subsystems has been optimized for dynamic operation and has been tested. Simultaneously, there have been all other preparatory measures for upscaling of electrolysis technology in the energy industry relevant MWe power range. In particular, within the frame of the project, the basic measures for a later, cost-effective mass production have been taken.

Within the short time period of 3 to 5 years after project start, the commercial use of new and more efficient subsystems such as the rectifier system, control components, monitoring and operating subsystems and stable electrode coatings with high efficiency is estimated. Also, the presentation of a new production-capable block approach up to about 2 megawatts is foreseen for this time period.For the medium-term period of 5 to 7 years is the availability of new modularized power plant concepts in the range 2 - 5 megawatts with an optimized, stable energy consumption and commercial competitiveness in the energy sector is planned. In the long term range of 7 to 10 years the provision of a modular system concept for fully automatic operation in the power range up to approximately 20 megawatts in series-prodution quality is seen.

Supported by: The Federal Government on the basis of a decision by the German Bundestag


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  • Andreas Brinner
    Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)
Other Addresses


Research funding

The information system EnArgus provides information on research funding, including on this project (German only).