More efficient use of grid connection points for renewable energy plants

12.04.2024 – Grid connection points for renewable energy plants are a rare commodity. Many project developers wait a long time for this. The distance to the grid connection point is often very long and therefore expensive. Once a plant is connected, however, it only uses part of the existing capacities, because each connected system must be able to feed in 100 percent of its output at all times. This is what the law provides. However, wind and photovoltaic systems do not always generate 100 percent of the theoretically possible amount of electricity. On average, photovoltaic systems use only 13 percent of the capacity of their grid connection point over the year, wind turbines 33 percent.

This analysis comes from a joint study by the German Renewable Energy Association (BEE) together with the Fraunhofer Institute for Energy Economics and Energy System Technology (IEE). The organisers have received overwhelming support for the study from the energy industry, companies and associations, as Matthias Stark, Head of Renewable Energy Systems at BEE, emphasised at the presentation of the study.

The study makes suggestions for the more efficient use of network connection points. This would not only allow the expansion of renewables to take place more quickly, but grid operators would also have advantages.

The BEE's proposal envisages connecting several renewable energy plants, storage facilities and sector coupling plants together at a grid connection point in the future. More power is connected than the point can actually transport. This is referred to as a superstructure. Together with the study, a web application was developed that can simulate the optimal superstructure for specific projects.

In various scenarios, different types of superstructures are considered – on the one hand in terms of quantity (overbuilding of 150 percent or 250 percent), on the other hand a wind- or PV-dominated superstructure. It shows that the utilization of grid connection capacities can be increased many times over in some cases, on average over Germany to up to 53 percent. There would even be enough capacity available to connect back-up power plants, such as flexible biogas plants or hydroelectric power plants, to the grid connection point.

Dealing with surplus electricity that cannot be fed into the grid

However, with the development, there are also periods in which not all the electricity generated can be fed into the grid. The resulting RE surpluses could be used for sector coupling, for example for heat supply or in an electrolysis plant. However, they could also be stored and fed in later or curtailed if there are no possibilities for use on site.

Benefits for all stakeholders

For the energy transition, the development means one of the greatest possible accelerations with regard to the implementation of grid connections, as existing structures such as cable trays, transformers and substations of the existing connection can be used. For project developers, the overbuilding means faster project implementation and thus considerable cost savings. Controllable, flexible decentralised generation plants (including bioenergy) can be better integrated into the power grid.

For the financing banks, a more stable, faster and more cost-effective implementation of projects can have a positive impact on risk assessment. For the grid operators, the overbuilding approach enables a variety of advantages. In this way, the assets used (including transformers or substations, lines) can be used much better. The "cutting off" of the RE surpluses leads to simplified grid operation management, as feed-in peaks are taken out. With the additional use of storage to shift the RE surpluses, not only can the utilization of the assets be significantly increased, but a more stable and steady feed-in framework can be enabled at the NVP level. Removing the feed-in peaks also reduces redispatch volumes and thus also their costs.

Legal implementation relatively easy

The necessary legal adjustments were also considered. Only minimal adjustments to two paragraphs in the EEG could make the presented proposals legally effective.

Simone Peter, President of the BEE, appeals to the federal government to implement the joint use and overbuilding of grid connection points before the end of this year. "200 stakeholders from the entire energy industry support the BEE's proposals. This shows how urgent the need for action is and how great the benefits are for everyone involved." Pf