Combining renewable energies to provide a stable electricity supply

April 1st, 2013 by Fraunhofer Institute for Wind Energy and Energy System Technology

Some German renewable energies - wind, solar and biogas (click image to expand - ©RLLord)

Some German renewable energies – wind, solar and biogas (click image to expand – ©RLLord)

A conglomerate of many smaller power plants can replace traditional power plants.

The Combined Power Plant 2 (Kombikraftwerk2) research project shows how it is possible to provide a stable power supply using renewable energies without an increased risk of a blackout.

Researchers of the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) in Kassel, Germany are introducing the project at the Hanover Trade Fair from 8 April to 12 April 2013.

Dr. Kurt Rohrig, Deputy Director of IWES, said “each source of energy – be it wind, sun or biogas – has its strengths and weaknesses.”

“If we manage to skillfully combine the different characteristics of the regenerative energies, we can ensure the power supply for Germany,” he said.

The combined power plant shows that it is technologically possible to let each individual producer feed their electricity into the grid and have the grid remain stable during this process.

To ensure that this will work, IWES and Siemens Group scientists have developed a software platform as part of the E-Energy Initiative of the German federal government under the motto “Together we are strong”, in which many small power plant operators can act together as a “virtual power plant“.

Since January 2011, the scientists have been testing with very good results such a power plant in the Harz regenerative model region (RegModHarz).

Regenerative Modelregion Harz has linked together via the Internet 25 power plants with a nominal power output of 120 megawatts and, as simulated storage, a pumped storage power plant and electric vehicles.

A central control ensures that the disadvantages of the renewable energies are reduced, as photovoltaic panels and wind turbines do not always provide electricity.

When many small producers work together, the regional differences produced by wind and solar energy can be balanced out by the power grid, or by controllable biogas facilities. In this system, surplus power can be stored or turned into thermal energy.

A powerful network of energy producers can act as a larger entity.

In order for this system to work, the control room takes on two roles simultaneously.

In its function as the “power plant facility manager”, it monitors the facilities that are interconnected within the virtual power plant, and acting as the “pool coordinator”, it simultaneously markets the energy that is produced.

The software of the virtual power plant in the Harz region is being partially adopted for the Combined Power Plant 2 and expanded with grid stabilization functions.

In Germany, on some days of the year the electricity being generated from solar, wind, biomass, hydro and geothermal production already accounts for more than half of the load required.

Kaspar Knorr, project manager of the Combined Power Plant 2 research project at IWES, said “ensuring that the electricity continues to reach the consumer reliably with a voltage of 230 volts and a frequency of 50 Hertz, is a challenge that the regenerative energies will have to meet in the future.”

The renewable energy sources will also have to increasingly make contributions to the ancillary services.

In the current system that is geared towards a few central producers, primarily traditional power plants ensured that these requirements were being met.

In their project, scientists are modeling in detail what the power supply system of the future will look like and how the individual facilities might be distributed across Germany.

They determine the requirements for ancillary services such as frequency and voltage stabilization, black start capability and inertia reserve, so that the renewable electricity will stably reach the consumer.

Kaspar Knor said “due to their decentralized character and innovative developments, renewable energies can contribute to stabilizing the power supply system already today.”

“With the Combined Power Plant 2, we are able to show what changes are in store for our power supply, and we demonstrate how the renewables master this task and how they can ensure the stable supply of electricity in the future,” he said.

The “Kombikraftwerk2” research project examines how a power supply fed only by renewables could work and what kind of ancillary service requirements there will be.

The experts determine possibilities, at the same time, how the plants for renewable energies can provide these ancillary services that are necessary for grid stability.

The solution approaches are tested at real facilities.

The partners of the consortium are: CUBE Engineering GmbH, German Weather Service, ENERCON GmbH, Fraunhofer Institute for Wind Energy and Energy System Technology (IWES), ÖKOBIT GmbH, Leibniz University Hanover Division of Electrical Power Supply, Siemens AG, SMA Solar Technology AG, SolarWorld AG and the Agency for Renewable Energies.

The project is sponsored by the German Federal Ministry for the Environment and follows up the Combined Power Plant 1 project, which began in 2007 and indicated the feasibility of an electrical power supply based solely on renewable energy sources.



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