Energy Storage

Energy storage and heat storage are key to the energy transition.

They help balance fluctuations in electricity generation from renewables like solar and wind power. Surplus energy is stored and made available when needed – vital for a stable and sustainable energy supply.

There are many technologies for storing electricity and heat, each differing in efficiency, storage duration, flexibility, and cost. RWE has already built many battery storage projects and is also researching new storage technologies for a sustainable energy market – so electricity is always available when we need it.

Innovative electricity storage technologies

Many new concepts for electricity storage are now being developed to support the energy transition – from stationary mechanical storage systems to transportable chemical long-term storage systems.

We test and evaluate these technologies for their technical and economic potential and work actively to develop them further.

A construction site with many white containers in the foreground, power pylons and an industrial building in the background.

Diagram illustrating four methods of heat storage: solids, liquids, gases, and phase change materials.

Innovative heat storage technologies

Heat storage systems working above 300 °C could play an important role in renewable and efficient energy supply. Integrating them into thermal power stations increases flexibility and benefits both the electricity and heat markets.

That’s why we analyse different solutions for thermal energy storage for many applications.

Optimisation of energy systems

Intelligent linking of renewable and conventional generation can make energy systems more secure, but it is often complex. Combining short-term and long-term storage types challenges current calculation methods.

Modern computer-based optimisation allows us to design even complex energy systems efficiently – including planning, operation, and analysis of the economic performance of storage facilities.

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Further information

StoreToPower project

In the StoreToPower project, the German Aerospace Centre (DLR), RWE Power, and Aachen University of Applied Sciences explored how a heat storage unit could be added to an existing lignite-fired power plant in the Rhenish lignite area. The project also included the design of a pilot plant to test a high-temperature heat storage module at a large lignite plant.

Although the technology was not economically viable at this site, the experience gained provides valuable knowledge for future storage projects elsewhere.

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Compressed air energy storage (CAES)
Compressed air storage systems can store large amounts of energy for hours or even days, similar to pumped storage power plants.

How they work:

During charging, electricity compresses air. The heat produced is either released (D-CAES) or stored in a heat storage facility (A-CAES).

The cooled, compressed air is stored underground (e.g. in caverns or old mines).

In D-CAES plants, this air is used to burn fuel gas, and the heated gas flow drives a turbine.

In A-CAES plants, the compressed air is reheated using the stored heat, then used to drive a turbine.

The ADELE and ADELE-ING projects designed a 260 MW adiabatic compressed air energy storage (A-CAES) plant in Stassfurt. It was not built at the time because it was not economically viable.

With storage demand rising, we continue to investigate innovative compressed air storage solutions.
Redox flow battery

Redox flow batteries store electricity in liquid electrolytes kept in tanks. During use, the electrolytes are pumped into a cell stack, where they absorb or release energy through redox reactions. Storage duration depends on tank size, and power depends on cell area. This means redox flow batteries can be easily adapted for different needs, including long storage times over 8 hours.

Their advantages are high safety (they are not flammable) and high cycle stability. Current systems, however, still have high costs. New developments using organic electrolytes or solid redox flow batteries could improve this. We are monitoring developments and testing a pilot plant to gain first practical experience for possible commercial use.

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Venite R&D project

Molten salts are already used to store heat at 560 °C in large tanks. Higher storage temperatures could improve efficiency and capacity, but further research is needed. The main challenge is chemical reactions between the molten salt and gases at temperatures above 560 °C, which lead to decomposition and more corrosion.

This project aims to find a suitable gas system with coordinated components so that molten salts can be operated continuously over 600 °C. RWE’s R&D team is an associated partner in this project.

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R&D project HIT (Hydrogen Iron Transport)

The HIT project studies iron as a solid chemical energy carrier for large-scale hydrogen transport. Green hydrogen reduces iron ore, which is then transported over long distances. At the destination, iron is oxidised to recover hydrogen.

This could be a cost-effective alternative to current processes, but is still at an early stage.

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TIC02-logo-hit

The project aims to develop the first technical and economic principles. It analyses the whole process chain – from chemical reactions to plant design – and includes life cycle and economic assessments.

This funded project is a collaboration between Italy (in the Mediterranean region) and Germany (in central Europe).
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