Die Siemens-Gasturbine SGT6-5000F / The Siemens gas turbine SGT6-5000F
Flexibility in the energy system
Using options as efficiently as possible
Flexibility in the energy system
Energy storage & sector coupling
Ein Hochspannungsmasten für Strom vor blauem Himmel und Sonnenstrahlen
Flexibility in the energy system
Grids – extension of grids
Banner Luftbild und Nahaufnahme einer Windenergieanlage
Flexibility in the energy system
Variable power generation is growing

Flexibility in the energy system

Wind- and solar-based variable power generation is growing worldwide. System flexibility in the energy system – guaranteed by the following four options – is required in order to optimally integrate these energy sources:

Dispatchable generation
Storage-e and sector coupling
Demand-side integration

Digital technologies and corresponding IT infrastructure ensure networking and thus the best possible use of the four flexibility options mentioned above. Dispatchable generation is currently the most important flexibility option in the energy system.

Dispatchable generation as vital component

Dimensions of flexible power plant operation

Dispatchable thermal power plants and pumped storage power plants are used as generation plants in flexible operation. Flexibility refers to the speed and extent to which these plants can adapt their load to the difference between current demand and feed-in of variable renewable sources. From the technical point of view, flexibility of generation plants comprises three different dimensions:

  • Low minimum load represents the lowest load level at which the plant can be operated stably and without any supporting fuels such as oil.
  • Short start-up time is the period of time required from starting power plant operation up to achieving stable minimum load.
  • High load ramps indicate how quickly a plants´ output can be changed within a certain period of time.

Flexibility parameters of dispatchable generation plants

flexibility kraftwerksparameter ENG (2019-05-22 wes)
* as per emission limits for NOx and CO. ** limited by minimal load for steam turbine. CCGT = Combined Cycle Gas Turbine

Dispatchable generation plants have the following flexibility parameters:

  • – load gradient in load range indicated,
  • – minimum load and
  • – ramp-up time for warm and cold start-up.

The three values shown are: usual value / state of the art / future potential.

Example: The average load gradient of a hard coal-fired plants amounts to 2%/min, the state of the art is 4%/min and the future potential will be 6%/min.


Thermal power plants

Flexibility Toolbox​

The Flexibility Toolbox supports operators of coal-fired power plants in switching from base-load to flexible operation. It contains information on technologies, further training courses and management topics. The Toolbox offers 40 different measures to increase flexibility through retrofits or technical interventions. The measures concentrate on combustion, water-steam cycle, turbine, control technology and auxiliary systems.

The recipe book for the flexibilization of coal fired power plants

This book presents best practices and operating procedures for the flexible operation of coal fired power plants In India. It is based on the review of published international literature, inputs from pilot studies carried out in the Indian power stations (including the test run activities under the auspices of the Indo-German Energy Forum with VGB involvement) and experts’ interviews. It was compiled by Mr. Anjan Sinha, a highly acknowledged Indian expert on this subject who had worked for NTPC for many years. The book was published in October 2020.

Partner steam power plant

The research project “Partner steam power plant for regenerative power generation” investigated how existing power plants can better regulate variable renewable generation in order to facilitate demand-oriented integration of renewables. In the „FLEXI-TES: Making power plants more flexible through thermal energy storage“ project, it will then be investigated how to further improve flexibility of hard coal-fired plants by storing thermal energy in the plant.

VGB Standard

Some VGB Standards provide important information and recommendations for action, especially for flexible power plant operation:

Pumped Storage Power Plants

Hydro power makes a central contribution to flexibilise the energy system

International activities

Advanced Power System Flexibility Campaign

VGB participates in the Advanced-Power-System-Flexibility(PSF)-Kampagnewhich is coordinated by the International Energy Agency (IEA) and which is a continuation of the Advanced-Power-Plant-Flexibility-Kampagne, concluded at the ninth Clean Energy Ministerial (CEM9) in Copenhagen. CEM is a global platform, comprising 24 countries and the European Union, to promote sustainable and clean energy supply.

Indo-German Energy Forum

Flexible coal-fired power plants are an important focus of the Indo-German Energy Forum (DIEF). The DIEF is a format for the exchange between the Indian and German Governments on issues of energy policy. VGB is cooperating in the Task Force Flexibility, which coordinates all activities around flexible operation of thermal power plants with the focus on two reference power plants at the Dadri and Simhadri sites. VGB cooperates with its Indian partner the Excellence Enhancement Centre (EEC).

Hydropower Europe

VGB is cooperating in a Research and Innovation Agenda & Technology Roadmap for hydropower within the scope of the EU Horizon 2020 programme. In HYDROPOWER EUROPE the issue of flexibilisation also plays an important role.