Background

Environmental consequences like the greenhouse effect, burdens from combustion residues or the missing final disposal sites for nuclear waste have led to a change in people’s attitudes in Europe. The wish for clean and sustainable energy and the technological advance have finally initiated the energy transition. It has been strongly advanced by the German energy policy. The renewable energies like wind energy, photovoltaic, biomass and solar thermal energy are expanded, while large power stations are continuously shut down.

The energy transition also significantly affects the heat supply. Today's heating is supplied via oil and gas as well as district heating from large power stations.  Superseding fossil energy sources by renewable energies and shutting down large power plants cause the need for action for the heat supply.

Technical Background

The initial situation is that electricity is generated by large power plants on the highest voltage level. Conventional power plants benefit from the economies of scale. This means the greater the plant is, the more efficient and economical it becomes. The produced electricity is transmitted in the active transmission grids (high and maximum voltage level) and finally led through passive distribution grids (medium and low voltage level) to the consumer. He finds a constant electricity supply, independent of location and time.  This results in a directed current flow from the power plants to the consumer. The power plants produce as much energy as consumed.

Assuming a continuing development, there will be only few large power plants after the energy transition. The power will mainly be generated by renewable and sustainable systems. These do not benefit from economies of scales. Typically they will be installed in the distribution grid nearby the consumers. Future distribution grids have to be adjusted since the generation in this network creates new, unforeseen power flows. This may lead to an inversion of the direction of the current flow up to higher voltage levels. In passive distribution grids violations to technical limits will be the consequence which can lead to system failures and destruction of technical devices and facilities.

Characteristic for renewable energies like photovoltaic, wind and solar thermal energy, is their fluctuating power generation.  The power generation depends on weather conditions, resulting in a volatile power generation. Contrary to large power stations, the power generation from renewable energies cannot be attuned to power demand, causing supply gaps and overproduction.

In the past large power plants did the most of the system control, like the voltage and frequency control. Their shut down results in a steep drop of control options. Without its compensation the system gets instable.

Challenges

For ensuring future security of electrical supply, a balance of production, storage and consumption on the energy level has to be guaranteed.At the system level,  the challenges of energy transport, control and trade must be solved.  This leads to the following challenges of the energy transition:

  • Energy balance between generation, storage and consumption (e.g. network expansion, load control, storage, etc.)
  • Adjustment of the passive distribution grids regarding undirected current flows
  • Compensationo f the loss of control.

The most popular challenge is the energy balance. Topics like wind turbines, pump storage plants and additional high power cables became a part of the medial debates. All three challenges are equally important for the energy transition. The CoSES addresses all these challanges and aims for bringing the rarely discussed issues more into the focus of the political and social discussions.