In power-to-gas (PtG) projects, electricity is used to produce hydrogen (PtH2) or, by adding another process step, methane (PtCH4). By applying suitable synthesis processes further conversion to liquid fuels is also possible (power-to-liquid, PtL). When the electricity is generated from renewables, the resulting chemical energy carriers (hydrogen, methane, liquids) are virtually emissions-free.

They can be easily and efficiently stored, offering a promising option for long-term energy storage and providing an interconnection between the electricity, gas, and transport sectors (so-called ‘sector coupling’).

Due to the range of possible synthetic energy carriers the term power-to-X (PtX) is also used to denote the conversion processes. Common to all of them is the production of hydrogen from (renewable) electricity via water electrolysis as a first step.

Since 2011, LBST (energy and mobility consultancy Ludwig-Bölkow-Systemtechnik GmbH, www.lbst.de) has pursued the development of PtX and maintains a database, currently including over 180 projects worldwide. While initially only smaller systems for research purposes with electrolysis capacities in the kWe range were in operation, projects at the several- MWe scale have now been implemented and larger plants are in the planning stage. There are currently more than 50 PtX projects in Germany, including both R&D facilities and those operated on a commercial basis.

PtX plants in Germany with more than 50 kW of installed electrolysis capacity either in operation or at the planning stage have been identified by LBST and classified by size and technology characteristics. See graph.

The number of PtX projects has shown a marked increase and 35 plants are expected to be in operation by 2022 in Germany alone. At present, the total installed electrolysis power of German PtX plants is 26 MW, and has more than doubled since 2014. 

The majority of projects in Germany use so-called PEM electrolysers, which have certain operational advantages over the incumbent alkaline electrolysis technology. Projects using high-temperature electrolysis, which is particularly suitable for power-to-liquid (PtL) processes, are mainly planned outside Germany. Noteworthy for the German projects is a growing focus on the generation and use of hydrogen without further processing of it into other energy carriers. This is a result of the increasing application of green hydrogen as, for example, a feedstock in refineries or as a fuel in the transport sector.

TÜV SÜD (www.tuv-sud.com) and LBST operate a joint hydrogen and fuel-cell portal. 

Uniper and E.ON seize the initiative 

Both Uniper and E.ON have recently announced important initiatives in power to gas.

Following addition, during 2018, of a methanation stage to Uniper’s 2 MWe Falkenhagen power-to-gas plant (Brandenburg), March 2019 saw the first feeding of synthetic natural gas – methane – into the gas grid (as part of the STORE&GO international research project).

Up to then, pure hydrogen produced at Falkenhagen had been fed into the grid.

With methanation, the Falkenhagen facility can produce up to 1400 m3 of SNG per day (energy equivalent = about 14500 kWh).

The methanation employs CO2 from a bioethanol plant, with heat generated during the process used by a neighbouring veneer plant.

The plant was realised by Uniper in collaboration with Thyssenkrupp Industrial Solutions, and Karlsruhe Institute of Technology, the process developers.

Meanwhile E.ON, along with German regional energy suppliers,

Avacon, Bayernwerk, E.DIS and HanseWerk, has launched its new “green gas from green power” initiative, aiming to reduce CO2 emissions in the heating, transport and industrial sectors. The initiative participants are hoping to get German government funding for a range of PtG research projects.

For example, Avacon aims to launch a PtG plant in the former Helmstedt lignite mining area consisting of a 10 MW electrolyser and a downstream methanation unit. The CO2 source for methanation would be a nearby thermal waste processing plant operated by Energy from Waste GmbH. Avacon has recently signed a co-operation agreement with Salzgitter Flachstahl and Linde on a project aiming to generate hydrogen in Salzgitter via electrolysis using wind generated electricity, paving the way for greater use of hydrogen in steel production.

E.DIS is hoping to team up with Berlin-based GASAG to create a scalable P2G plant at its Ketzin site.