Energy boost for Renewables

Projects, International, Research |

An interview with Prof. Hartmut Spliethoff, Chair of Energy Systems at the Department of Energy and Process Engineering at the TUM School of Engineering and Design and coordinator of the Future Laboratory for Green Hydrogen, on the energy supply of the future.

Prof. Hartmut Spliethoff
Image: Fabian Vogl/TUM

Russia's war against Ukraine has revealed Germany's energy dependence and caused prices for electricity, petrol and heating to rise sharply. The political discussion about an oil and gas embargo against Russia is in full swing, alternative energy sources are being sought. What is possible from a technical point of view? What potential can be exploited in the short to medium term and what obstacles stand in the way of the changeover?

Interview: Cornelia Freund

ED: To begin with, three news items of the last few days: It is 40 degrees warmer in Antarctica and about 30 degrees warmer in the Arctic than normal at this time of the year. Emissions in Germany are up by 4.5 percent in 2021 ­­– the second year of the Covid-19 pandemic. Politicians are discussing an embargo on fossil energies from Russia and are declaring the early warning stage of the gas emergency plan. What impact do you see in these developments?

Hartmut Spliethoff: The increasingly obvious consequences of global warming require a rapid transformation towards a fully renewable energy supply. The needed time horizon is 10 to 20 years.

A loss of Russian natural gas from one day to the next would have a significant impact on the economy and can hardly be compensated for. It is certainly not enough to heat ones home a little less. The various measures to compensate for this require one to several years and can lead to higher greenhouse gas emissions.  

The Bayernstudie has prospectively examined the expansion of renewable energies until 2040. What can be implemented by whom in the short to medium term to secure the energy supply and promote a shift away from fossil energy sources? What alternatives are there to Russian natural gas?

If supplies of natural gas from Russia were to be cut off, we would not be able to compensate for the shortfall in the short term by increasing and expanding renewable energies. However, the good news is that this can be achieved in the medium to long term. With the Bayernstudie 2021, we had examined what a renewable energy supply in Bavaria could look like by 2040 under certain assumptions. In order to achieve a completely renewable energy supply, wind power and photovoltaics in particular must be expanded enormously.

On the assumption that Russian natural gas would disappear, there are various measures to compensate for this. Obviously, one is to reduce consumption; for private households, this means saving natural gas by turning down the heating. The experience shows that higher energy prices have a direct impact on consumer behavior. In this case, one must try to obtain natural gas from European neighbors or from other sources.

Currently, Germany lacks the infrastructure for importing liquefied gas. Hence, as far as possible, capacities of neighboring countries would have to be used to transport the natural gas to us via pipelines. However, it should also be borne in mind that liquefaction requires ten percent of the energy of natural gas, as well as being more expensive and thus causing higher CO2 emissions. About 20 percent of natural gas is currently used in electricity generation and could be replaced by other energy sources. In the long term, this must be done by expanding renewable energies, but in the short term the only option is to use coal and nuclear power instead of natural gas to generate electricity. Yet coal-fired power generation will lead to higher CO2 emissions.

Are we seeing a comeback of nuclear power?

In Germany, three nuclear power plants are still in operation and are scheduled to be taken off the grid at the end of the year. Continuing to operate nuclear power reduces future natural gas consumption and therefore makes sense, but it does not reduce current natural gas consumption. Extending the lifetime of nuclear power plants does not change the goal of phasing out nuclear power. After all, no one in Germany is talking about building new reactors because they are far too expensive. From a private economic point of view, new nuclear power plants are no longer profitable; renewable energies are cheaper. On the international level, it can be observed that many countries are relying on nuclear power in the future; even Japan is operating nuclear power plants.

Then, for a continued operation, many questions arise that the operators have to answer, e.g., whether highly qualified personnel and fuel elements are available. What is being touched here is a consensus in Germany that was reached after many years. If natural gas extraction from Russia were to stop tomorrow, the coal-fired power plants would certainly be reactivated. As for nuclear power plants, it is questionable to what extent politicians dare to address this issue.

Do coal and nuclear as substitutes for gas also serve for heat?

In the case of private consumers, heating cannot be directly replaced by coal or nuclear power. Although this would be possible via electricity, this would also not be possible in the short term due to the necessary installation of electric heaters or heat pumps. The future technology is electrically powered heat pumps in combination with renewable electricity.

For industrial purposes, natural gas is used as a basic material or for process heat. In this case, a conversion to other energy sources is even more demanding and not possible in the short term; such a change would require a lead time of several years. If Russian natural gas disappears, things will become difficult, and I share Mr. Habeck's opinion that this will have serious consequences. Just giving up a little bit of comfort is not enough, so every little thing will have to be taken care of.

The Bayernstudie assumes that energy consumption will be halved. Electricity, heat, mobility: What potential do you see in saving energy?

A 50 percent reduction is ambitious, but overall I see great potential in increasing efficiency, in that we can significantly reduce consumption, in industry as well as in the private sector, for example through thermal insulation. However, this too is a long-term measure because the building stock cannot be renovated overnight. In the case of heat, this study assumed that consumption would be cut in half. With regard to mobility, we assumed the same mileage in the Bavaria Study as today; the transition to electric mobility will lead to a reduction in consumption due to the more efficient electric motors. Nevertheless, electricity consumption will not be reduced, because it is the key to efficiency. For example, whenever regulation is used for better control, more electricity is needed. Heat pumps are the technology of the future to generate heat efficiently from renewable electricity. Also, there is electromobility. If you look at studies from five years ago, it was always assumed that consumption of electricity should also be reduced by 20 to 30 percent, however this is not realistic.

Overall, savings are an absolute must. Yet these alone will not be enough. We have to expand renewable energies. In the Bayernstudie, we assumed challenging targets: a significant reduction in energy consumption, a massive expansion of renewable energies, greater storage capacities. As for industry, it needs renewable energy sources, either electricity, hydrogen, or biomass, but even these are only available to a limited extent.

Grey, blue, turquoise, green: Which importance will hydrogen have in the future?

For the future, the focus is on green hydrogen as a renewable energy. As a secondary energy, hydrogen is the same as electricity. If it is produced from renewable sources, there will be conversion losses. Electrolysis has an efficiency of 60 to 70 percent, and then maybe it is possible to convert hydrogen into another energy carrier that can be better used, for example synthetic gas or fuel for aviation. Therefore, the chain via hydrogen ultimately requires much more renewable energy than it would if a direct use of electricity is possible.

Looking forward, we will have a system of renewable energies in Germany: Wind and photovoltaics dominate, however, hydropower, biomass and geothermal energy will also play a certain role. At certain times, the energy quantities are not available, and that is when we need storage such as batteries or hydrogen as a chemical energy carrier. Synthetic gas or liquid fuel can be produced from hydrogen and can be transported and used more easily.

In terms of sustainability, grey hydrogen from fossil fuels is not viable. To some extent, blue or turquoise hydrogen offers a transitional solution. It is produced from fossil energy sources, whereby the CO2 is either separated in gaseous form or as solid carbon. This can certainly help to quickly find the way to a hydrogen system.

In Germany, programmes are underway to demonstrate electrolysis for hydrogen production on a large scale. The primary development goal is to reduce the cost of electrolysis, and to create infrastructures. For transport, it is a matter of building or upgrading networks. There is also a need for adaptation of equipment, e.g., gas turbines. The steady expansion of green hydrogen takes time. It will not be done in five years.

Not only should one solution be propagated, but various solutions should be approached in all technologies. The triangle of energy supply objectives - consisting of environmental compatibility, security of supply and economic efficiency - must once again take center stage. The goal of security of supply has been disregarded in recent years because only natural gas was used as a bridging solution. In retrospect, this was obviously a mistake, because we have become heavily dependent.

How can the fluctuations of the weather-dependent energy sources wind and sun be balanced out in a decentralized manner?

Biomass, hydropower, geothermal energy: they are valuable energy sources because they can be planned and used at any time and serve as a balance, the potential in Germany, however, is limited. The highest potentials are attributed to the sun and wind, which must be massively expanded. To balance out the fluctuating wind and solar power, we need storage facilities. Battery storage is excellent for balancing day and night in conjunction with photovoltaics, while hydrogen or synthetic energy sources make sense for balancing over the year.

Furthermore, one can discuss what quantities of renewable energy to import in the future. Of course, we don't want to become as dependent as we are today. But it may well make sense for Germany to generate electricity in other countries - Southern Europe, North Africa, Australia - by using photovoltaic or solar thermal power plants, convert it into hydrogen and other fuels and import it here. A share of imports makes sense because other countries have more favorable framework conditions with regard to solar energy; it costs only half as much to generate solar power there. The hope is that in the future it will be possible to provide hydrogen more cheaply than the price spikes we are seeing on the energy markets right now. However, we will not return to the old oil or natural gas prices.

What innovative technical solutions can research find? 

The current situation is giving energy research a tailwind, and this energy push is definitely positive. A higher price for energy sources also creates new opportunities. Today, it is not yet possible to produce diesel fuel from solar energy for one euro, but in the medium to long term it will be possible for 1.50 to 2 euros - i.e., below the price of diesel at the filling station today. In the long term, it is assumed that the price level of hydrogen can be reduced to six to seven cents per kilowatt hour. This is where we need more research and demonstration in order to achieve these price reductions.

Currently, the chair is developing a concept to efficiently convert biogas into electricity with a high degree of efficiency in a high-temperature fuel cell. The goal is to operate this electrochemical fuel cell reversibly, i.e., in times of electricity surplus we convert the electricity into natural gas and can store this natural gas, and in times of electricity shortage the cell converts the natural gas back into electricity. We are aiming for a high efficiency of 70 to 75 percent in both directions, where otherwise only 60 percent is achieved. For this purpose, a spin-off company is currently being set up to further develop and market this technology.

In addition to high-temperature fuel cells, our chair is researching other products that can be produced from hydrogen, e.g., synthetic natural gas, methanol, or fuel for aviation. At TUM, we bring together scientists researching in this field through platforms such as TUM.Hydrogen and Power-to-X. The Future Hydrogen Laboratory was recently added to investigate reversible, electrochemical fuel cells, biological hydrogen production and biomass as an energy source - an international project to develop research further. Another example is the CleanTecCampus project, in which a sustainable concept was developed at the TUM campus in Garching to reduce energy consumption in the buildings, for example through photovoltaics on roof surfaces, yet there is also a lot that can be done in terms of district heating through efficient heat pumps.

Is there greater acceptance and willingness to change in politics, industry and among consumers? 

People are no longer aware of how necessary an independent energy supply is, and that energy is the driver for all activity, including the economy. People are aware that electricity comes out of the socket, but they are not interested enough in how it is provided. For this, we have to create acceptance.


Personal details

The research of Prof. Hartmut Spliethoff focuses on the development and optimization of central and decentralized energy conversion systems and plants. Through a combination of theory and experimentation, he explores ways to improve the efficiency and flexibility of thermal power plants, convert solid fossil fuels and biomass, capture carbon dioxide and improve the efficiency of low temperature heat conversion. 

After studying mechanical engineering at the Universities of Kaiserslautern and Stuttgart, Prof. Spliethoff did his doctorate (1992) and lecturer qualification (1999) in Stuttgart. Prior to his appointment as full professor at TUM, he was professor and Chair of Energy Technology at Delft University of Technology, the Netherlands, until 2004. He is Scientific Director of Department 1 of the Bavarian Center for Applied Energy Research (ZAE). 



Profile of Prof. Hartmut Spliethoff:

Research projects at the Chair:

Bayernstudie 2021:

Network for Hydrogen and Power-to-X: TUM.Hydrogen und Power-to-X

Future lab hydrogen: Redefine H2E Hydrogen Economy

Energy system optimisation at Campus Garching of TUM: CleanTechCampus Garching