29 Dec 2015, 00:00

Loop flows: Why is wind power from northern Germany putting east European grids under pressure?

Germany is producing ever-more green power. But grid development hasn’t kept up with the expansion of renewables, meaning excess electricity is spilling over into neighbouring countries and causing headaches for east European grid regulators.

What are loop flows?

Electricity current takes the path of least resistance. When power is produced in one place to supply a consumer elsewhere, it should mainly flow along the most direct power lines between the two. But if the route is congested it will take a detour through other parts of the grid – looping around the blockage. This can result in the current ending up in unexpected places and even flowing through the grids of neighbouring countries.

Is Germany’s renewable power production causing them?

The amount of renewable power generated is not planned but fluctuates with the weather. A storm can mean a huge and sudden supply of green power from wind farms in north Germany. Not all electricity can be consumed regionally so the grid has to transport it in other regions.

At the same time, the abundance of electricity pushes prices down in the common German-Austrian trading zone. Demand rises, with industrial consumers making the most of the low prices. Exports increase too, as international traders buy Germany’s and Austria’s cheap power, making maximum use of their import capacities.

This means huge volumes of power need to be transported from north to south, both through Germany and on via Austria. But gird connections along this route have nowhere near enough capacity, so the power takes a detour, spilling over into the power grids of neighbouring countries.

What does this mean for Germany’s eastern neighbours?

Hungary, Poland, the Czech Republic and Slovakia complain loop flows from the German grid put the security of their power supply at risk and prevent the international power market from functioning properly.

At times, the amount of power being traded between Germany and Austria is twice what the connections between their two grids can handle, meaning half overflows into the Czech and Polish grid systems, and even on to neighbouring countries.

The excess power means interconnectors on the borders between different national grid systems become congested, preventing electricity being traded internationally. The Agency for the Cooperation of Energy Regulators (ACER) has estimated that loop flows from Germany cost the Polish and Czech economies 25 million euros a year in lost revenues from power trading.

The Polish grid operator, PSE, says they also contributed to a “brown out” in the summer of 2015 – meaning that its grid operator had to limit supply to industrial consumers – because it was unable import extra power when production at Polish hydropower plants fell because of a heat wave.

What are possible solutions?

  • Splitting the Austrian-German market zone

In a report published in September 2015, ACER recommended limiting the amount of power traded between Austria and Germany to the capacity of connections between the two countries. This would effectively be the end of the common power market between the two countries. The German grid regulator, the Bundesnetzagentur (Federal Network Agency), is already working on the assumption that this will happen in the coming years. But Austria – which would lose out on cheap renewable power from Germany – is strongly opposed to the plan.

  • Splitting the German grid

An alternative way of preventing too much wind power from the north of Germany flowing south would be to split the German grid in two. This would not only ease congestion at the connections between the German and Austria grids, but also take the strain of the severely restricted capacity of Germany’s north-south grid connections. But this would also mean higher power prices in south Germany, and is therefore politically unlikely.

  • Phase shifters

In the meantime, Poland, the Czech Republic and the East German grid operator are already taking action to control the loop flows by installing phase shifters on both sides of the border with Germany. These act as turnpikes on the electrical current by raising electrical resistance to divert power elsewhere. The first, on the Polish border, is to start operating before the end of 2015. Three more are scheduled for completion by 2017.  Phase shifters on Germany’s western borders are already in place, which is one reason the loop flows from Germany haven’t been as serious a problem for countries like France and the Netherlands.

  • Increasing grid capacity

Experts say a major part of the solution must be grid development in both Germany and Poland. More capacity is needed to ease the strain on the internal German grid and allow for more power to be traded internationally. But this takes time and although high on the political agenda in Germany, has been fraught with delays and controversy, as south Germans resist the construction of power lines across the landscape and close to residential areas.

One important connection between east and south Germany is scheduled for partial completion in early 2016. But there is no agreement on the route for large grid connections from north to south. Two new connections between the German and Austrian grids will not be completed until well after 2020, according to the German Federal Network Agency.

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