Glossary of energy terms

Energy transition describes the transition from the non-sustainable use of fossil energy sources like nuclear power to renewable sources for a sustainable energy supply.

Renewable energies are energies from supply sources that are almost inexhaustible on a human time scale or that regenerate relatively quickly. These energy resources are available to us in a sustainable manner, particularly hydropower, wind energy, solar energy, geothermal energy and tidal energy. Another source of renewable energy is potential energy sourced from biomass like wood or organic waste.

The demand for electricity is characterised by highs and lows over any 24-hour day. The laws of physics, however, require that grid voltage and grid frequency should always be at the same level, meaning that the exact amount of electricity consumed at a given moment must be fed into the grid. In the event of an imbalance in the system, inadmissible grid loads, damage to electrical devices, power outages or even a blackout may occur.

A blackout is a complete breakdown of large-scale electricity supply grids, caused by the sudden unexpected failure of a major power station, damage to a transmission line, a short circuit or grid overload due to an imbalance of production and consumption.

After a blackout without stable external voltage being supplied, the grid needs to be restored. This is a very complicated technical process that requires ready-to-operate power stations that have "black start" capability. This means that they can cover their own electricity demand even in the absence of a functioning public grid and can therefore start autonomously. Also, these power stations need to be able to operate as "islands". This in turn means that they can regulate the grid frequency to 50.0 Hz, can withstand load fluctuations, in particular large step changes in load, and can provide sufficient energy reserves. After building such a grid of island plants, "ordinary" power stations and consumers can then be re-connected gradually until normal conditions are restored.