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Power-to-Gas: Innovative method for storing green electricity

Power-to-Gas is one of the so-called Power-to-X technologies, in which excess electricity is converted into other forms of energy. With power-to-gas, electricity is converted into hydrogen or synthetic methane by electrolysis.

The power-to-gas principle is more relevant than ever because the energy revolution is in full swing. More and more electricity is being sourced from renewable sources and power-to-gas is the storage solution that is urgently needed to fully utilize green electricity efficiently.

This is how power-to-gas works

Power-to-Gas is the central coupling element between the electricity and gas infrastructure and a special type of energy storage.

Excess green electricity is converted into hydrogen by electrolysis using water and stored in this form as so-called additional gas in existing gas infrastructures. It can then be used as a gas, for example for heating, cooking or mobility, but it can also be converted back into electricity.

Alternatively, the resulting hydrogen can also be methanized, i.e. converted into synthetic methane by adding CO2. Hydrogen can only be partially fed into existing gas infrastructures as an additional gas, while synthetic methane is a so-called replacement gas. It can be fed in unlimited amounts. The CO2 required for this can be taken from biogas plants, for example, where CO2 is produced that is not used.

Power-to-Gas as a central element of the energy transition

Green electricity can be produced in huge quantities. Wind power, solar power and water power is not consumed and is available in infinite measure. The only problem is the unreliable availability. Above all, solar radiation and wind power sometimes generate electricity in excess, but then at other times not at all.

The power-to-gas principle solves the problem because it allows the energy generated but not used to be stored in the form of methane or hydrogen. The higher the share of renewable energies in the power supply, the more important power-to-gas becomes.

The expansion of power-to-gas plants is in progress. There are already numerous locations for power to gas plants in Germany. So much that it is already possible today to store around 200 terawatt hours of energy in underground gas storage tanks, according to the estimate of the German Technical and Scientific Association for Gas and Water DVGW e.V.

Disadvantages of power-to-gas technology

As important as power-to-gas may be for the energy transition, the technology is not free from disadvantages. On the one hand, power-to-gas is still associated with very high costs, which significantly exceed the prices for fossil natural gas. The most optimistic projections of when power-to-gas will become competitive are around 2030, with some projections putting the technology's economics a full decade later.

The further the energy transition progresses, the cheaper renewable energies and electrolysis systems become, the easier it will be to reduce the costs for power-to-gas. But one thing should not happen: that conventional electricity is used to make a power-to-gas system more economical. Because the systems are more economical the better they are utilized. The surplus electricity from renewable energies is sometimes not enough and could then be supplemented with conventional electricity. But that would mean that power-to-gas would lose its status as an important element of the energy transition.

However, the costs are not the only problem, because power-to-gas is also associated with high efficiency losses. Because when hydrogen is methanized, it has to be heated to several hundred degrees Celsius. As a result, energy is lost. In concrete terms, only about a third would remain of the electricity that is made into hydrogen with the help of water, methanized and later converted back into electricity. However, the efficiency losses can be cushioned by using the waste heat that is produced during methanation, for example.