2023-04-01 publication

Energy system: Electricity for everything

Power-to-X technologies can supply all sectors with energy based on sustainable electricity and with the help of hydrogen. The methods are extremely promising – but they also call for courage and investment to unlock their full potential.

By Markus Strehlitz

VDE dialog - the technology magazine

The future belongs to renewable energies, which are providing the power needed to transition to a world with low emissions. But how will it be possible to use this energy even in fields that need power in a different form? After all, not all applications can be fully electrified. The key will be "power-to-X" processes, which convert electricity to the required energy form – to hydrogen (power-to-gas), liquid fuel (power-to-liquid) or heat (power-to-heat). Hydrogen almost always plays a critical role in these processes. “One advantage is that hydrogen is already being used in many fields and forms the basis for unlocking many sectors that are difficult to electrify,” says Andrea Appel, a project leader in hydrogen development at VDE. And in contrast to fossil fuels, it can be used with low emissions.

The first step in these processes is converting electricity to hydrogen (power-to-gas) via electrolysis. Here, electricity is used to break water down into hydrogen and oxygen. The hydrogen can then also be converted into methane by means of carbon dioxide (CO2). This produces a synthetic natural gas with combustion properties that are almost identical to fossil natural gas. Hydrogen can also serve as a starting point for obtaining liquid base chemicals such as methanol (power-to-liquid). These can then be used as e-fuels, which in turn can replace fossil fuels.

However, the remaining hydrogen that has not been converted can also be used in a wide range of ways. In industrial sectors like steel manufacturing, it can replace coal as the relevant fuel, And in the mobility sector it's also capable of powering everything from trains and ships to aircraft and heavy goods vehicles. In addition, hydrogen can be used to store excess energy, which provides for flexibility in the power grid.

Vehicle-to-grid methods could play a key role in the redistribution of energy. In addition to drawing power from the system, EVs can feed it back into the grid in line with the current needs of infrastructure operators and users.

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Hydrogen is often the most viable solution – both economically and ecologically

There are still several technical obstacles standing in the way, though. According to hydrogen expert Andrea Appel, the automated production of electrolyzers is “not yet guaranteed”. The methods that have been used so far are complicated and too expensive for production on a large scale. With a group of Fraunhofer institutes now working together on this problem, however, it may soon be a thing of the past. They started by developing a reference factory, which is to be used in the coming years to develop and test new methods for producing electrolyzers. The aim is to make large-scale production profitable by reducing the manufacturing costs of water electrolyzers in the gigawatt range by more than 25 percent. The best methods are being modeled virtually in parallel and added to a technological toolkit. This toolkit gives industrial companies a way to project the costs of certain electrolyzer types before planning their production.

Appel points out that it's now generally important to increase the number of electrolyzer projects as quickly and selectively as possible. “We need more and bigger projects so that we can gather practical experience in interacting with other systems,” she says, adding that there are still quite a few points that need to be clarified. For instance, there are the questions of how electrolyzers deal with a flexible mode of operation and how they impact local water consumption.

There are also other technological challenges, such as the transportation of hydrogen. It's not yet clear which parts of the existing gas supply infrastructure can be used for this and converted accordingly. One possible solution would involve converting hydrogen to methane, but adding another conversion step would require more energy – and thus make the overall process less efficient.

One thing is clear: The need for hydrogen is growing. Prof. Martin Wietschel from Fraunhofer ISI assumes that "no-regret" applications are a crucial driver of the demand for hydrogen. These are applications where there are no economically or ecologically viable alternatives to hydrogen. In a related study, Prof. Wietschel examined the hydrogen demand in areas such as industry, transport and energy conversion. The prognosis: Just like the demand, the prices for hydrogen will probably reach a relatively high level in the future. “This applies in particular to the use of materials and energy in certain industrial applications, such as in the steel or basic chemicals sectors,” Prof. Wietschel explains. “The calculations in the study show that the demand here will amount to around 250 terawatt-hours in 2045, which is about 10 percent of the current final energy demand in Germany.”

Due to the limited availability over time, it's natural that prioritizing the use of hydrogen in certain applications by means of the emission-reduction lever continues to come up as a topic of discussion. VDE hydrogen expert Andrea Appel has concerns here, including with regard to the risk that this could hinder the takeoff of the hydrogen market. She fears that if not all potential users are allowed to consume hydrogen, this could have a negative impact on the willingness to invest in the technology.

Heat pumps are popular – but they don’t always pay off

Reluctance to invest is no problem with the most popular power-to-heat applications. The most obvious example is heat pumps, the demand for which has risen dramatically since the beginning of the energy crisis. These appliances are powered by electricity and pump heat from the external air or the ground into a building. They therefore convert electricity into heat, which presents huge potential for saving significant volumes of CO2, even in the heating sector.

Until recently, heat pumps were primarily planned for use in new buildings, but this is another area where the technology continues to move forward. Appliances that provide heat or cooling on a higher temperature level can also be used in existing buildings.

There's one problem in particular, however, as Dr. Sibylle Braungardt explains. Among other areas, she specializes in the development and evaluation of policy measures in the building sector at the Öko-Institut. Dr. Braungardt says that it's often cheaper to continue heating with fossil fuels at the moment, and that heat pumps aren't always worth the price. “The politicians could change that,” she points out, “by reducing the price of electricity, imposing a carbon tax on fossil fuels, abolishing the EEG allocation and subsidizing the purchase of heat pumps.”

In principle, the power-to-heat concept is attractive in more areas than just private use. For example, some municipal utility companies are testing electrode boilers. In this process, any excess power from renewable sources is used to heat water in a boiler. The water is then pumped into a basin and used as storage for the district heating supply.

Using electric cars as mobile storage units for passing on electricity

The field of electromobility also offers further potential for the flexible management of electrical power. Here, one obvious use case involves charging vehicles that are powered by electric batteries. This essentially makes a car a mobile energy storage unit, as well – and that is exactly how it could be used. It's possible to feed electricity from a car battery back into the electricity grid. This type of concept is called vehicle-to-grid (V2G) and could be a significant component in the future energy system. Dennis Schulmeyer, CEO of the startup Lade, explains: “The technology can be implemented very easily and cheaply, it has an enormous impact and the storage units are already available.”

His company provides a complete system for operating and using the relevant infrastructure. According to Lade, the concept is built around a load management system which makes it possible to optimize the performance of charging stations dynamically, individually and virtually in real time based on the current needs of the infrastructure operators and users.

Along with an intelligent load management system of this kind, achieving these aims hinges on an expansion of the available charging infrastructure. This goes hand in hand with Schulmeyer's belief that V2G will only be economically viable with AC (alternating current) charging stations. To unlock the full potential of the technology, parked vehicles would have to use V2G-capable connections to connect to the grid whenever possible. This would require a lot more charging stations.

Other experts are also tinkering with ways to integrate electric vehicles into the power grid. Recently, the transmission network operator Tennet reported that it had succeeded in utilizing electric vehicles as storage capacity in a limited community to balance out “frequency fluctuations in the power grid in the short term”. “The integration of EVs into the electricity grid is an important milestone that will help us respond to future challenges in power availability,” says Tennet COO Tim Meyerjürgens.

Markus Strehlitz is a freelance journalist and editor for VDE dialog.