The duck curves are a visual description of the production pattern of solar cells, where production and consumption of electricity are out of phase. Now system operators such as Svenska kraftnät are forced to warn of the problems with wind and solar energy, as the so-called duck curves only get worse and worse.
– The examples show that it only gets worse and worse over time,” says electrical systems expert Paul-Frederik Bach to the Näringslivet newspaper.
If the balance between production and consumption of electricity is not precisely maintained – the benchmark is between 49.9 and 50.1 hertz – disturbances in the system can occur. Negative electricity prices are a signal that something is not right, and according to Energiföretagen, such 400 hours occurred in 2023, which corresponds to as much as five percent of the time.
Negative electricity prices, which mean that supply does not meet demand, increase the more weather-dependent power there is in the system.
– Negative electricity prices are not good for anyone because it means that all producers have to pay to get rid of their electricity, which also discourages future investments in electricity production, says Magnus Thorstensson, responsible for the raw power market at Energiföretagen, to Tidningen Näringslivet.
The system operator can then call on a producer to shut down production or tell a consumer to consume more electricity, and then activates misplaced up- and down-regulation bids on the market.
But sometimes the capacity in the regulation power market is not enough. According to Tidningen Näringslivet, it happened recently when Svenska kraftnät and Energinet issued serious warnings to the players in the electricity market. A week or so earlier, all deregulation bids in Denmark had ended. Concretely, this meant that Denmark could not take care of all the electricity it produced, but delivered the surplus to Sweden. In the worst case, the system operators can intervene and shut down electricity production – if the collapse of the entire system threatens.
Then there is the problem of duck curves – the name is a description of what a sitting duck looks like. The production pattern of solar cells does not follow consumption at all – it is lower in the morning when people turn on their devices and falls rapidly in the afternoon or evening when the sun goes down. This becomes a challenge for the power system operators, who have to ramp up and down other generation sources to meet demand
Experts who have followed developments in solar cell-rich California, where the concept of duck curves was first coined, have been able to see that the problem is only getting bigger and bigger the more solar cells are put into operation.
In Sweden, the use of solar cells is marginal, but in southern Sweden the phenomenon is imported from other countries, not least Germany and Denmark.
For TN, Pontus De Maré, operations manager at Svenska kraftnät, confirms that duck curves occur and that they are becoming increasingly difficult to manage with more weather-dependent power.
