What is power-to-X?
Power-to-X is a term for technologies taking surplus renewable electricity from wind, solar or water and convert it into other energy carriers to be able to store the energy for later use and absorb energy fluctuations.
The first step of the power-to-X process is to convert the renewable power into hydrogen (H2) by electrolysis. Hydrogen, the smallest molecule we know, does not emit CO2 when burnt. It can be used immediately, or it can be stored in pressurized tanks and retrieved when supply is low.
Use of hydrogen
There are several different ways of utilisation: Feeding hydrogen into the gas network, displacing some of the CO2 containing natural gas (power-to-gas), or through a methanation process with CO2 converting the hydrogen into methane (power-to-methane). The methane can be injected into the natural gas network replacing the fossil natural gas (power-to-gas). The CO2 source for the methanation process could be biogas produced from biowaste in biogas plants or wastewater plants. Other concepts include production of methanol or ammonia to be used in fuel cells in cars and ships, or synthetic fuels to be used in conventional car and jet engines (power-to-liquids). This is all achieved through synthesis that involves hydrogen and a CO2 source that could, again, come from the process of converting waste into biogas.
The “green hydrogen” generated from renewable energies can also be used in fuel refining (hydrogenation) in conventional refineries or as a basic chemical in many different industries (power-to-chemicals, power-to-plastics). Finally, the stored hydrogen can also be converted back into electricity via fuel cells when needed (power-to-power).
Testing hydrogen in natural gas network
AVK visited a small, closed natural gas network in Denmark. With pressures ranging from 3 to 65 bar, they perform tests with up to 15% hydrogen.
Flow limitors are used to secure the network in case of a pipe burst. AVK UK and AVK Donkin are supplying flow limitors to a test network with 100% hydrogen.