PtX is short for Power-to-X, which is a process to convert electricity into another form of energy (X). It is one of the technical solutions that contribute to the green transition by storing renewable energy and equalising the balance between energy consumption and energy production.

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Power-to-X (PtX, also abbreviated P2X) is a collective term that describes the process of converting electrical energy into another form of energy. Power-to-X comes in many varieties, but one of the most described and used methods in the efforts to store green energy is conversion to hydrogen by splitting water to hydrogen and oxygen.

Power-to-X is the way to a greener future

Power-to-X is a solution that can contribute to phasing out black energy from fossil fuels such as oil, coal and natural gas, and which is one of the technical conversion paths for storing green energy. Extraction of green energy comes, among other things, from renewable energy sources such as wind turbines and solar cells, which depend on the weather to produce electricity.

It has popularly been said that the consequence is that we have too little power for the demand from industry and households when the wind does not blow and the sun does not shine. On the other hand, we often have too much power than we can manage to consume when the wind turbines rotate at high wind speeds and when the solar cells are heated by the sun’s rays.

Storage of renewable energy is ensured with Power-to-X

In order to make us less dependent on weather conditions, we therefore need a way to store the green power. The storage can help to even out the balance between production and demand, so that excess green energy from renewable energy sources is not lost. This can be done, for example, with Power-to-X, where one of the methods used is to apply electricity to water molecules. The method is called electrolysis.

Hans Buch helps customer with instrumentation for PtX application

There are a number of challenges for construction, operation and maintenance that ensure the best possible uptime of a Power-to-X plant. Hans Buch provided technical sparring and delivered instrumentation in the form of humidity and temperature meters, as well as dew point meters for the customer’s PtX application.

Read more: “Customer case: Instrumentation for PtX application“

What is electrolysis?

Electrolysis is a way of separating a substance using electricity. By applying direct current (DC) to a container with liquid in it, two energy charges are brought into contact with the liquid. These energy charges are referred to as a plus and a minus connection, which is also called a positive and negative connection. The positive connection (+) is called a cathode, while the negative connection is called an anode (-).

There are various technological methods for carrying out an electrolysis, such as Alkaline, PEM (Proton Exchange Membrane) and Solid Oxide Electrolysis, as well as variants that combine or take as a starting point the mentioned technologies.

Positively and negatively charged ions determine the separation in electrolysis

Thus, ions in the form of atoms and molecules will be attracted to either the cathode or the anode when exposed to current. It depends on whether the atom or molecule has taken up or given up electrons. If electrons have been released, the atom or molecule will be a positively charged ion (cation ion), while an atom or molecule that has taken up electrons will be a negatively charged ion (an ion).

Electrolysis splits water and separates hydrogen and oxygen

Electrolysis is increasingly used to store energy. By using power from renewable energy sources, a storage of the energy is ensured, which could otherwise be lost. A widespread method is to split water (H2O) into hydrogen (H2, hydrogen) and oxygen (O, oxygen -> O2). By applying electricity to the water molecule, the oxygen will seek the anode (-), while the hydrogen will seek the cathode (+). In this way, hydrogen can be captured for storage.

What forms of Power-to-X (PtX) are there?

Power-to-X is also popularly called Power-to-Everything. This knowledge article focuses on the conversion of green electricity produced from, for example, wind turbines and solar cells into hydrogen, but Power-to-X covers a wider range of end products, which can be other than pure hydrogen – for example methanol or ammonia.

In a chemical process where hydrogen is combined with, for example, CO2, different forms of energy can be created that can be suitable for fuel (so-called electrofuels) for heavy-duty transport on the roads, for ships, and for airplanes. The list below provides a larger selection of technologies with PtX-related abbreviations:

• PtX: Power-to-X (Power to Everything, also abbreviated P2X)
• PtG: Power-to-Gas (also abbreviated P2G)
• PtS: Power-to-Syngas (also abbreviated P2S)
• PtL: Power-to-Liquid (also abbreviated P2L)
• PtH: Power-to-Heat (also abbreviated P2H)
• PtF: Power-to-Fuel (also abbreviated P2F)
• PtC: Power-to-Chemicals (also abbreviated P2C)

Sources

• DTU – The Technical University of Denmark: “Power-to-X – from green energy to green fuel”:
  https://baeredygtighed.dtu.dk/en/teknologi/power-to-x
• AAU – Aalborg University: “Power-to-X Technology: Overview, possibilities and challenges” (2022, Simon Araya, Samuel; Cui, Xiaoti; Li, Na; Liso, Vincenzo; Sahlin, Simon Lennart)
  https://vbn.aau.dk/files/514146100/PtX_Report.pdf
• The Danish Energy Agency: “Hvad er Power-to-X?” (“What is Power-to-X?”):
  https://ens.dk/ansvarsomraader/power-x-og-groen-brint/hvad-er-power-x
• Rambøll: “Power-to-X: paving the way for a greener future”
  https://www.ramboll.com/net-zero-explorers/power-to-x-explained
• Brintbranchen: “Om brint” (“About hydrogen”):
  https://brintbranchen.dk/om-brint-2/