Industrial sector a more flexible partner in the energy transition

By 2030, renewable energy is to cover 65% of German electricity consumption - more flexible energy consumption by German industry can improve grid stability: Companies are doing research into solutions for this in the five SINTEG showcases.

Industrial sector a more flexible partner in the energy transition© Adobe Stock/romankosolapov

The smelter in TRIMET Aluminium SE's Hamburg aluminium works is a real diva. Even minor fluctuations in temperature can make the massive cell, containing some 15 tonnes of metal and electrolyte, overrun or solidify – at working temperatures of around 970C. The damage would run into hundreds of thousands of euros.

Aluminium has been made according to the same principle for 130 years: fused-salt electrolysis uses electricity to convert aluminium oxide into aluminium. In order to keep the heat balance and the magnetic field stable, the temperature has not been able to fluctuate by more than ten degrees Celsius in the past. The best way to achieve that is a constant inflow of electricity. However, the energy transition is meaning that more and more renewable energy sources are feeding into the electricity grid at fluctuating levels of intensity. This is confronting the electricity grids, in which generation and consumption always need to be balanced, with new challenges. Trimet has developed a process which can help here. The basic idea is that the stability-dependent electrolysis process should be adapted in a way that enables the take-off of electricity to be flexibilised to a certain degree. And since the aluminium smelter is a major consumer, it can contribute towards the stable operation of the grid when the grid operator needs help. Researchers are working in the Power-to-Aluminium project to find out how to do this; the project is part of the North German Energy Transition NEW 4.0.

Industrial processes can respond to renewables-based generation

Like the aluminium smelter in Hamburg, many other industrial firms are facing the challenge of revamping their industrial processes to make them more flexible. In future, they aim to consume electricity when there’s plenty available – because the wind is blowing or the sun is shining – and to scale back their output when not much power is being generated. This will also enable industry to save money, because the price of electricity goes up and down depending on the weather. And the respective electricity price is an important cost factor for energy-intensive companies. This in turn benefits the electricity sector: it needs to make sure that the supply of and demand for electricity are balanced at all times.

For this reason, a large number of companies and partners are working in the SINTEG – Smart energy showcases research programme on solutions for future flexible industrial processes. In five large model regions scalable model solutions are being developed and demonstrated for a secure, economic and environmentally compatible renewables-based energy supply.

How an aluminium smelter keeps its boilers calm.

Controllable heat exchangers on the external walls of the cell could be the key to success in the aluminium smelter. If the furnace is operated using a lot of energy, more heat will be generated inside, which the heat exchangers quickly remove. If less energy is available, the heat exchangers function as insulators. It may sound simple, but it is actually a major technological challenge. There are 270 such cells, and an initial practical trial using ten of them has been very successful so far. If this succeeds on a grand scale, the companies will be able to make an impressive contribution to grid stability: Trimet produces 135,000 tonnes of aluminium a year in Hamburg, accounting for roughly 20% of Hamburg's electricity consumption.

Flexible despite the flight schedule: smart use of energy by Stuttgart Airport

Stuttgart Airport also wants to do its bit. A 78+ tonne Airbus A300 is just coming in to land in the evening twilight. The lights along the runway show it where it needs to go. The lights of the terminal buildings can be seen in the distance. Nothing works without energy here, and it has to be 100% reliable. In fact, the airport uses 50 gigawatt-hours a year, as much electricity as roughly 18,000 households in the region. In order to be equipped for the future with 100% renewable energy, the airport is already playing a pro-active role in the energy transition. It is part of C/sells, a SINTEG model region.

Tests are taking place on the airport site to see how electricity generation and consumption can be dovetailed more flexibly. The airport produces its own environmentally compatible electricity in a block-type thermal power station and photovoltaic installations. This could enable the airport to supply all its needs in future, and even to 'export' electricity – for example, when it doesn’t need much itself but there’s a big fair in the next town about to switch on its lights. And if the electricity it generates isn’t needed straight away, the energy can be converted into heat or cold and held in thermal energy storage units. To this end, major electricity consumers like air-conditioning and refrigeration systems are operated flexibly, enabling renewables to be used to provide the transport hub with a secure supply of electricity. 'We would particularly like to make use of existing technology and integrate it smartly into the electricity grid,' says Miriam Feil, who is responsible for strategic energy policy at Stuttgart Airport. 'For example, electric cars tend to stand around in our car parks for quite a long time. So we can be flexible about when they are charged.'

Energy from the water boiler; paper from wind energy; electricity, heat and mine gas in the mixer

Papier- und Kartonfabrik Varel (PKV) is also taking part in SINTEG, participating in the enera showcase in the north-west of Lower Saxony. Experts here are testing a module which can make use of spikes in the generation of wind power in order to produce steam for paper manufacturing. Clean wind energy is an important element on the road to carbon neutrality.

STEAG, the energy company, is involved in the Designetz showcase, working on a better combination of electricity, heat and mine gas which can be used more flexibly and smartly. This combination is unique in Germany. To do this, STEAG is using the immersion heater principle to operate a boiler in which surplus electricity heats up water which can be converted into storable heat for district heating. Combining this with engines driven by mine gas makes it possible to respond at lightning speed to unforeseen fluctuations in the electricity grid, thus stabilising the grid without people feeling the cold in and around Saarbrücken and Völklingen.

In contrast, Berliner Wasserbetriebe is taking part in the WindNODE showcase, working on demand-side management and sewage works. The idea is that, as sewage works are major electricity consumers, it is particularly handy to integrate renewable energy into them. Berliner Wasserbetriebe, which already uses renewables to supply a lot of the energy it needs, can use analysed electricity consumption patterns to adapt its consumption to the wind and the sun.

A host of further ideas and projects to flexibilise industry can be found at