Power-to-X: The concept of storing, converting and reviving power in different forms

The “Power-to-X” concept covers the activities of taking surplus renewable electricity from wind, solar or water and converting it into other energy carriers (the “X”) to be able to store the energy for later use and absorb energy fluctuations.

The first step in the 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 pressurised tanks and retrieved when supply is low.

There are several different utilisation pathways: 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. The methane can be injected into the natural gas network replacing the fossil natural gas (also Power-to-Gas). The CO₂ source for the methanation process could i.e. 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 generated “green hydrogen” from renewable energies can also be used in fuel refining (hydrogenation) in conventional refineries as well as a basic chemical in many different industries (Power-to-Chemicals, Power-to-Plastics).

Finally, the stored hydrogen can also be concerted back into electricity when required via fuel cells (Power-to-Power).

Where can AVK contribute to the Power-to-X concept?

Many countries are looking at adding hydrogen into the existing gas networks to decarbonise natural gas. Gas at concentrations of up to 20% hydrogen can be transported in the existing natural gas network without the risk of damaging gas installations, distribution infrastructure etc.

Until well into the 20^th century, hydrogen-rich town gas with a hydrogen concentration above 50% was distributed to households in i.e. Germany, the USA and England via gas pipelines. It could be assumed that many of the gas transport networks, distribution lines and storage facilities that were operated in the past are still in use today.

Blending hydrogen into natural gas pipeline networks has also been proposed as a means of delivering pure hydrogen to markets, using separation and purification technologies downstream to extract hydrogen from the natural gas blend close to the point of end use. As a hydrogen delivery method, blending can defray the cost of building dedicated hydrogen pipelines or other costly delivery infrastructure during the early market development phase.

In the UK and in the Nederlands, the possibility of converting the regions’ existing natural gas network (used primarily for municipal heating supply) entirely to hydrogen is being explored.