Still large reserves in the electricity grid for integration of renewables

The electricity grid itself still offers extensive leverage to accelerate the expansion of renewable energies. Experts from the Energy Technology Society (ETG) in the VDE electrical engineering association point this out in a study published in August. In it, they make recommendations on how reserves can be used for grid congestion management by temporarily increasing the utilization of resources in the existing electricity grid. This would allow the lines and key grid components to be quickly adapted to the integration of solar and wind power without jeopardizing the security of supply.

The number of electricity generators is currently growing, particularly via balcony power plants. Grid expansion has not been able to keep pace with this development in recent years. The authors write that there is increasingly more electricity supply than demand in some places. Wind turbines have to be switched off. Large photovoltaic and wind farms could not be connected to the grid due to a lack of capacity. In addition, there are bottlenecks in grid operation, which require the grid operators to intervene at short notice.

As the expansion is bumpy and is likely to take many more years, the ETG has examined the higher utilization of operating resources in the energy transition grid and their actual physical load capacity in more detail. It limited itself to components that are particularly important for the transmission of electricity. In order to rule out overloading with unacceptable risks for the technology, the experts said they only looked at the potential for "permissible higher utilization within the material limits".

Additional load capacity of up to 60 percent

As a result, the team calculated a higher current carrying capacity of up to 60 percent for cables and up to 50 percent for transformers. Conductor cables can therefore withstand up to 58 percent more stress if they are set to weather-dependent overhead line operation. The current carrying capacity is dynamically calculated from weather data and transferred to the control technology. According to the analysis, the additional load capacity for switchgear is 15 percent, which can be achieved through improved cooling or digital monitoring with sensors.

However, the authors point out that for such measures to be used across the board, the interplay between technical regulation, the actual physical possibilities and legal restrictions resulting from liability risks would have to be improved across all disciplines. They say: "An overly safety-oriented approach by manufacturers and operators to these issues can inhibit innovation." While norms and standards clearly illustrate the cyclical load capacity of transformers, for example, there are no corresponding limit values for switchgear. It would make sense to create a manual for the entire electricity transmission chain.

Avoiding the shutdown of generation plants

Greater "flexibility on the demand side" in electricity consumption is also seen as an approach to integrating renewables into the grid, solving the problem of insufficient electricity generation during hours with little sun and wind, balancing supply and demand and using the electricity infrastructure efficiently. According to the report, e-cars serving as storage could significantly reduce the financial burden on consumers in a flexibly designed system. With Redispatch 2.0, the distribution system operators often limit themselves to power generation to prevent overloads. There are currently proposals that would enable "remote control of loads by the grid operators". For example, the Federal Network Agency should be able to throttle the charging of e-vehicles for "peak smoothing".

"Switching off generation plants should always be the last resort," emphasizes Maik Koch from Magdeburg-Stendal University of Applied Sciences as head of the ETG working group. "We therefore suggest tackling the problem technically." With the practical approaches supplied "for modern operational management", the aim is to encourage operators and planners to implement them. With comparatively simple means, millions of tons of CO2 could ultimately be saved.

(nen)