Offshore Wind Farms: Profiting from Feed-in Curtailment

TVS News AI, editorially supervised, presents Offshore Wind Farms: Profiting from Feed-in Curtailment.

Offshore wind farms are set to stabilize the grid

The Veja Mate wind farm lies around 95 kilometers northwest of Borkum, consists of 67 turbines, and normally generates electricity. According to its marketer, it is now the first offshore wind farm to be pre-qualified for the balancing energy market — that is, for the mechanism that compensates for fluctuations between power generation and consumption. According to its own statements, the energy supplier Vattenfall is for the first time marketing balancing energy out at sea.

What balancing reserve is — and who has supplied it so far

Balancing reserve kicks in when the grid briefly needs more electricity or less is being generated. Pre-committed capacities step in, keep frequency and voltage stable, and are paid for doing so. So far, this role has been filled mainly by pumped-storage hydroelectric plants, gas-fired power plants, and battery storage. According to figures from the Federal Network Agency (Bundesnetzagentur), wind power's contribution to this balancing reserve is vanishingly small. If the grid operators and utilities have their way, that could soon change.

Trianel and Vattenfall are the first to move

Alongside Vattenfall with Veja Mate, the municipal utility consortium Trianel is pushing ahead: in August it became known that Trianel had the Borkum I wind farm pre-qualified for the balancing energy market — marketing there had already begun in July, according to the company. Both parks fall under the responsibility of transmission system operator Tennet for the North Sea, which confirms the trend: "We are seeing growing interest from wind farm operators in the balancing reserve market." This explicitly applies to the offshore sector as well. According to its own statements, 50Hertz, responsible for northeastern Germany and the Baltic Sea, also has several offshore wind farms in the so-called pre-qualification phase — that is, undergoing review to determine whether they meet the technical requirements. A spokesperson: "Interest in participating in the balancing capacity market is growing."

How it works technically — and why standing still can bring in money

What the offshore wind farms can primarily offer is negative balancing capacity: on call, they reduce their feed-in. In practice, according to 50Hertz, it works like this: when revenues on the power exchange are small, it can pay for operators to forgo feeding in — the turbines are turned out of the wind, and the standstill is marketed as negative balancing capacity on the balancing energy market. The Fraunhofer Institute for Energy Economics and Energy System Technology (IEE) sees this as a trend: "The current pre-qualifications indicate that offshore wind farms are being tapped more strongly as a flexibility option for the balancing energy market."

It gets harder with positive balancing capacity — that is, more power on call: according to Fraunhofer IEE, this would require "turbines being curtailed preventively in order to hold back capacity for a potential call-off" — an avoidable curtailment of renewable energy that is usually not cost-competitive.

Batteries would be more efficient — but are stuck on grid connection

In principle, offshore participation strengthens the balancing reserve market. From the systems engineers' perspective, however, expanding battery storage would be even more efficient. Its problem lies elsewhere: "It's becoming harder for project developers to get connected to the grid," says Fraunhofer IEE. It is precisely this connection hurdle that opens a window for offshore wind farms — provided they pass pre-qualification and can actually place their flexible output on the market on a regular basis.