Deutsche Version  ACT
Physical Storage
ENABEL: PEM electrolyser 12.4.2017

The future at a glance
© GP Joule

Power gap filler in the megawatt class

In the project "Stromlückenfüller" Researchers investigate a

power-to-gas-to-power concept. The aim is to buffer excess solar and

wind power in the form of hydrogen. For the conversion, the researchers

are developing a PEM electrolyzer stack for a rated input power of one

megawatt. The electrolyzer combines with a hydrogen storage and biogas

technology giving an efficient storage system.

Project status Near completion
Typical system size Energy 500 - 4000 MWh
Typical system sizeOutput 0,2 - 1,0 MW
Volumetric energy density 3 Wh/l
Gravimetric energy density 33.000 Wh/kg
Efficiency AC/VN H2 70 %
Project duration July 2013 until July 2017

The power gap filler as energy storage enables a time delay of the provision of electric power and so compensates the deviation of supply and demand. The goal of the project, launched by the project partners GP Joule, H-TEC SYSTEMS and North Tec, is to develop PEM-pressure electrolysis stacks suitable for mass production and the associated pressure electrolyzer. The electricity is sourced from renewable energy and the pressure electrolyzer is connected to an existing biogas plant. An adequate operational concept for the power gap filler is developed simultaneously. The project inclusive the testing phase is to be completed by 2016.

  • Schematic drawing Power Gap Filler © GP Joule
  • From initial idea to reality © GP Joule
  • Power Gap Filler - The name speaks for itself © GP Joule
  • Construction plan electrolysis © H-Tec Systems
  • Schematic drawing PEM-cell © H-Tec Systems
  • The future at a glance © GP Joule

In a subsequent phase, the periphery of the electrolyzer is projected. It includes for example a biogas plant, the plant control system or the integration of a hydrogen storage. All components together result in the combined cycle power plant. Simultaneously to the technical development the operational concept of the overall system is designed. There are various possibilities of power procurement and power marketing that will be analysed for the project. By the end of 2015, the development of the combined cycle power plant and the operational concept is to be completed. With the end of another milestone the power gap filler will then be tested in 2016.

The primary goal of the power gap filler project is the development of a megawatt-PEM stack (proton electrolyte membrane). Inside the stack, the PEM electrolysis takes place where water is decomposed into oxygen and hydrogen. Hydrogen is considered as an important energy carrier. Oxygen can also be used both, materially and energetically. The fed water serves contemporary as a cooling medium since it is not entirely split by the stack. The cooling water and water from hydrogen-drying is returned to the process water cycle und again fed to the stack. The waste heat of the process can be utilized in local district heating networks. A use of toxic or otherwise hazardous equipment is not required.

PEM electrolysis holds potential

The technology of the PEM electrolysis as a core element of the power-to-gas-to-power concept holds immense potential as a medium and long-term energy storage of the future. The principle of electrolysis is known since many years. The application of this as an energy store is new and bears challenges. The PEM electrolysis has the great advantage, in comparison to other types of electrolysis, that it responds immediately to changes in load, uses no hazardous or toxic resources, can be operated with pressure and is capable of cold starts - these are good prerequisites for an efficient energy storage! A high optimization potential is seen in the mechanical and electrochemical durability. They are the key to improve the feasabilty, too.

Project status

The project „power gap filler“ is in the stage of stack development. Its objective is to develop stacks which have an input power of up to one megawatt. With a slight time lag, the periphery of the stack is completed in parallel. Together they form the electrolyzer.


The consortium coordinator of the project, GP Joule, is project manager, planner, general contractor and operator of wind mills, photovoltaic ground-mounted systems and biogas combined heat and power plants (biogas CHP) and designs the operational concept of the combined cycle power plant with the Megawatt electrolyser and the existing biogas plant as the central unit. The focus lies on the economic power procurement and marketing as well as the study of the legal framework. In addition, the company is responsible for the test operation of the finalized plant at the end of the project.

The company H-TEC is a manufacturer of PEM electrolysers and PEM fuel cells. It developes hydrogen technology for schools, vocational schools and universities since 1997 and PEM electrolysers with power in the kW range since 1999. Therefore it is responsible for developing and building the 1 MW PEM stacks of the project.

North Tec operates primarily as a "problem solver" in the devision of biogas systems. Core business are special solutions in all areas of the plant and its affiliated areas. North Tec develops, plans and implements customer-specific, taylor made biogas plants. Therefore North Tec takes over the development of the combined cycle power plant with the electrolysis unit as well as the existing biogas plant and a hydrogen storage. Furthermore North Tec is responsible for building a prototype at the headquarter of GP Joule in Reußenköge.

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


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Research funding

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