Securely determining residual loads and expanding the grid in accordance with needs

Project state
Graphical representation of wind speed, global radiationand the infeed from wind energy and photovoltaics resolved to the grid node level.
Wind speed (top left), global radiation (top centre) and the infeed from wind energy and photovoltaics resolved to the grid node level (right) as well as the resulting total load curves in relation to the load (bottom left)(right) as well as the resulting total load curves in relation to the load (bottom left) © FhG IWES, Carsten Pape

In the STERN research project under the direction of Dr Carsten Pape, researchers are working on depicting the residual load curve as precisely as possible in order to analyse the future electricity supply system. The term residual load refers to the power demanded minus the simultaneous capacity generated by intermittent renewable energy sources. This remaining part of the electricity requirement needs to be met by controllable power plants and imports.

The steady progression of the German Energiewende (energy transition) to predominantly decentralised and intermittent generation from renewable energies presents the current state of the grids with a decisive hurdle: the grid expansion can only be planned efficiently if there is detailed knowledge of the spatial and temporal behaviour of the residual load. Here the spatially high-resolution residual load time series provide the basis for grid operation simulations that enable the required grid expansion to be determined.

Ahead of the actual grid expansion needs analyses, the primary goal of the project is to further develop models for determining the spatially resolved residual load time series and to improve the data basis so that more robust results can be achieved. It is intended that the models will be adapted and further developed for this purpose in accordance with the requirements of the grid planners. Specific challenges include spatially locating the renewable energy systems planned in the scenarios within the models. Other major challenges include precisely modelling the course of the infeed from wind turbines in complex terrain and determining the local electricity yields. This is because changes in the wind conditions in complex terrain occur on a much smaller scale than are reflected in the resolution for the weather model data. The STERN project can make a significant contribution to the success of the energy transition. In addition, the simulated infeed time series for renewable energy generally provide the basis for energy system studies that benefit from the improved quality in the form of more robust results.

Initial steps at the start of the project

At Fraunhofer IWES, researchers have already developed partial models for modelling the infeed from renewable energies. At the start of the project they are combining these existing partial models to form an integrated model. As one of the first steps, a written survey of stakeholders is aimed at determining the areas with the greatest need for development and greatest potential for improvement with regards to the realistic depiction of residual loads, i.e. where are model improvements most needed from the perspective of the grid planners.

Overview of the project phases

  • Determination of the technical requirements for residual load time series from the perspective of the grid planners

  • Integration of existing partial models

  • Modelling the additionally installed capacity of renewable energies

  • Further development of renewable energy and regionalised electricity demand models

  • Integration of demand side management and CHP

  • Final workshop (project findings with a focus on Germany)

  • Further development of the European simulation

  • Expansion of the demand side management for Europe

  • Economic viability of the remuneration models

Project duration

08/2014 – 07/2017


Dr. Carsten Pape
Project coordinator
Fraunhofer IWES
Königstor 59
34119 Kassel, Germany

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