A solar eclipse and a tornado-spouting winter storm: Nature has already confronted the German electrical grid with special stress tests this year.
Operators had to deal with a radical decline in solar energy and record-breaking amount of wind energy. But even without meteorological extremes, the energy transition is making it more difficult for the operators to maintain stability in the grid.
Thousands of times each year they have to intervene in order to compensate for sudden fluctuations in the electricity supply, and more and more often they employ their means of last resort: taking large consumers of electricity offline.
One of the bulwarks of the grid is the electricity-devouring aluminum industry. During the March 20 solar eclipse alone, aluminum electrolysis operations at producers Trimet, Germany’s largest, and Hydro Aluminium were stopped for seven minutes on four separate occasions.
This happens very quickly: “Within a single second, the supply of electricity for the production facilities can be interrupted,” said Martin Iffert, managing director of Trimet.
The number of large-scale interventions in the grid has increased significantly.
Under the terms of their contract, grid operator Amprion can cut power to Trimet’s facilities in the Ruhr Valley in north Germany if necessary. Switching Trimet’s three plants off saves around 700 megawatts, equivalent to the entire output of a large power plant. The main production facility in Essen alone requires as much electricity as the entire city.
Trimet and Hydro are always factors when grid operators such as Amprion or 50Herz need time to stabilize the network. This is regardless of whether too much or too little electricity is available.
A legal provision regarding the loads that can be switched off has been in force since 2013; it also regulates the accompanying compensation. The agreement is voluntary and is open to all large customers. Car manufacturers and pharmaceutical firms participate along with refineries.
The firms focus on a cost-benefit analysis, according to the Federal Network Agency. “Not every production process can be interrupted at short notice,” it says. But the more rapid the intervention by the network operators, the higher the compensation.
In 2014, grid operators shelled out several hundred million euros for stabilizing the system — paid for by the price of electricity.
Amprion and other operators have at their disposal an entire range of stabilizing measures that on some days are used hundreds of times. But switching off entire industrial sectors is the next-to-last card played before entire regions are turned off — afterwards would come a country-wide blackout.
Up to now, Germany has been spared that tribulation, but the number of large-scale interventions in the grid has increased significantly.
“It has been rising for years,” confirms the Federal Network Agency, which points to the not always reliable electrical output of wind- or solar-energy facilities: “When there is an erratic change, grid operators have to do some juggling to compensate for the sudden drop.”
Hydro is prepared for such eventualities: “We are on board and know that it can impact on us repeatedly.”
Flexible production is our current challenge, so that we can continue to exist as an industry in the era of energy transition. Martin Iffert, Managing director of Trimet
Aluminum companies are ideal targets in the event of severe fluctuations. For example, Trimet and Hydro together heap almost a gigawatt of electrical output onto the grid – but this can be switched off at the flick of a switch.
One gigawatt might not seem like a lot in view of the 85 gigawatts that are the average load of Germany's grid, but it acts as a round-the-clock buffer as aluminum production proceeds apace 365 days a year. Aluminum plants can shut down for up to four hours without any damage to facilities.
This is a blessing for the grid operators: “Because of the increasing share of renewable energy, the volatility of the network's electrical supply has increased significantly in past years,” said Joachim Vanzetta, who is responsible for grid control at Amprion. “The possibility of taking large industrial customers such as the aluminum industry offline for a short while helps us to keep the network stable.”
Energy experts expect that in the future, industrial customers will have to be removed briefly from the grid more often than they are now.
Thus Trimet, whose roots lie in metal trading, has for a good while now been making a virtue out of necessity and intends to expand the business as a buffer for electricity. The family firm is adapting itself to the revamping of the country's energy supply; the integration of fluctuating amounts of electricity is the biggest challenge. “We are working with network operators on models in order to be able to deliver more balance and performance,” said Mr. Iffert.
The main task for Germany's largest producer of aluminum is to increase production flexibility. “That is where our chance lies,” Mr. Iffert added.
One example is the virtual battery. It works like a pumped-storage power station and is currently being tested on 12 of the 360 electrolysis processes at Trimet’s main facility. The idea is to adapt the production of aluminum to the unsteady supply of electricity from sources of renewable energy.
If there is lots of electricity from sun and wind in the network, the factory ratchets up its performance by as much as a quarter. If electricity is scarce, production is accordingly reduced. Restructuring production sounds easy, but up to now it has encountered physical and technological limits.
Trimet's goal is to orient its production more strongly toward the volatile supply of electricity, in spite of the continuing lack of storage technology. And it is enhancing its function as a stabilizing influence on the grid by expanding its capacity as a buffer.
“Flexible production is our current challenge, so that we can continue to exist as an industry in the era of energy transition,” said Mr. Iffert.
Presently Trimet is an aluminum producer with a sideline in electricity trading. “Perhaps the balance will tip the other way someday,” he said.