Texts on this page have been partially machine translated from German.

Energy Storage and Hydrogen

The central topic for our future energy supply system will be energy storage and hydrogen. Only if the electricity generated can be intelligently stored, converted and transported will the energy transition be successful. With its innovative storage concepts and hydrogen economy projects, the SIJ is already making an important contribution to a reliable energy supply.

Completed projects


Building-integrated thermal storage for load management of power grids with a high share of renewable energy sources

Project duration: September 2013 - June 2017

As the energy transition progresses, electricity grids are increasingly penetrated by fluctuating renewable energy sources. This creates an urgent need for the provision of cost-effective electricity storage or corresponding load management options.

Within the framework of this project, the Solar Institute Jülich at FH Aachen University of Applied Sciences, together with its research partners Viessmann, DuPont de Nemours, RWTH Aachen University and Infrawest, is investigating the option of energy storage using buildings heated with heat pumps and equipped with thermal storage capability as an interface between the electricity and heating markets. In this context, the energy storage capability is to be significantly increased with integrated latent heat storage materials. Successful implementation requires the inclusion of the following aspects: Low-temperature heat source adaptation, predictive control and building-side load management, thermal comfort, required and allowed temperature levels. It is determined how electricity purchase prices must be adjusted to the oversupply or undersupply so that refinancing of the additional investments is achieved.

If the project is successfully completed, a system will be available to the market with which, on the one hand, a high negative control capacity (approx. 5 GW for 1 million enclosures) can be activated in a decentralised manner and, on the other hand, a passive storage capacity of several 100 GWh can be provided to balance out fluctuations in renewable energy sources.

Project funding: Federal Ministry of Education and Research

Project partner(s):

  • Du Pont
  • Infrawest
  • RWTH Aachen
  • Viessmann


High Temperatures Heat Exchange and Storage

Duration: 01.10.2010 - 31.12.2016

The idea of using sand as a storage medium for thermal energy is the basis of this project. The resistance at high temperatures, the high availability and the low material prices make sand an excellent storage material.The aim of the project is the development of a process to transfer heat from up to 700°C hot air into sand.

In cooperation with DLR, the properties of various sands and bulk materials were tested in laboratory experiments to determine their suitability as heat transfer media and as heat storage materials. Based on this, a test facility for direct heat transfer from air to sand was designed and built. This will be used to investigate the behavior of the sand during operation.

This heat exchanger is to be used to realize bulk heat storage in solar power plants. A further application is conceivable in industrial processes for exhaust air heat recovery.



Indirectly solar-heated reformer for the production of methanol

Project Duration: 01.12.2016 - 31.12.2019

In the "Indiref" project, a process of indirect solar-heated reforming for the production of methanol from carbon dioxide and natural gas is further developed. The conventional production of synthesis gas, which is the starting product for many chemical products such as methanol, causes significant carbon dioxide emissions. When concentrated solar irradiance is used, emissions can be greatly reduced. Recycling carbon dioxide in the process further reduces emissions. In this way, the use of solar energy can be expanded into the chemical industry.

The focus is on the development of the reforming reactor and a modified solar receiver for this application, which can be technically implemented and tested under solar conditions. In order to achieve maximum efficiency and cost efficiency of the overall system, a process simulation model will be set up simultaneously and validated against the test results. On this basis, a virtual upscaling of the process takes place in order to evaluate the technical-economic potential for a market launch.

So far, the solar-heated reforming reactor has been developed for the production of synthesis gas. With the help of CFD simulations, the SIJ achieved particularly effective heat transfer and synthesis gas production for the bayonet tube reactor concept developed, on the basis of which a test reactor was designed. Within the framework of the project, the experimental setup was assembled in the Synlight facility (DLR's artificial sun) in Jülich, where tests with artificial solar irradiance will subsequently be carried out. A process simulation of the solar-heated reforming system was modelled and simulated on an industrial scale using Dymola software.

Project Partners:

  • German Aerospace Centre e. V.
  • Hilger GmbH
  • Hille & Müller GmbH

Sponsored by:

  • Ministry for Economic Affairs, Innovation, Digitalisation and Energy of the State of North Rhine-Westphalia using ERDF funds.


Cross-process heat management in production facilities - using the example of UPM's paper mill in Hürth, Germany

Project duration: 01.09.2011 - 30.06.2015

The aim of the project is a comprehensive increase in the energy efficiency of the paper mill. The necessary novel technology is to be exemplary for the entire paper industry and other production sectors. To achieve this goal, an innovative heat-water storage system patented by UPM will be integrated into the existing large-scale plant. This is intended to recover the amount of heat not previously used in the production process comprehensively and, if necessary, decoupled in time. In addition to saving energy, considerable savings in fresh water and waste water can be expected. In addition, the waste water temperature can be significantly reduced. The project thus combines environmental protection with an increase in the competitiveness of the production facility.

The Solar Institute Jülich of the FH Aachen University of Applied Sciences is carrying out the scientific analysis and optimisation calculations and is supporting the partners UPM, Pöyry and Wallstein.

Funded by:

  • European Union
  • Ministry for Climate Protection, Environment, Agriculture, Nature Conservation and Consumer Protection of the State of North Rhine-Westphalia

Project partners:inside:

  • The Biofore Company
  • Wallstein


Electricity storage in high-temperature thermal storage power plants

Project duration 01.01.2019 - 30.09.2021

How can security of supply be guaranteed even without coal-fired power plants? What will happen to the power plants after the coal phase-out? How can the phase-out be designed in a socially acceptable way? StoreToPower can make a significant contribution to solving these problems.

In the project, the conversion of a coal-fired power plant into a thermal storage power plant is planned. A heat storage power plant is an extended thermal power plant in which a heat storage system is connected in parallel to the classic steam generator. The heat storage system uses electricity in low-price phases to store electrical energy in the form of sensible heat by means of an electric heater. Molten salt or a solid material heated via hot air can be used as the heat storage material. When electricity prices are high, the heat can be converted back into electricity using the existing infrastructure (steam cycle with turbine, condenser, generator and cooling system). This concept helps to use volatile electricity (increasingly so in the future as renewables continue to expand) to provide controllable and secure power. In the long term, coal firing could be completely replaced by storage. The goal is to develop and demonstrate CO2-free/low-carbon thermal storage power plants that enable 100% security of supply with minimal CO2 emissions for the energy transition.

For the first time worldwide, such a concept is to be tested in the StoreToPower project at an RWE AG power plant. At the Solar Institute Jülich (SIJ), the project is a direct successor to the I-TESS study from 2017, which was also funded by the Ministry for Economic Affairs, Innovation, Digitalisation and Energy of the State of North Rhine-Westphalia. The SIJ's task in the current project is to develop reference concepts for the expansion/conversion of coal-fired power plants with combined heat and power through high-temperature heat storage and their techno-economic assessment. In addition, a life cycle analysis (LCA) of the heat storage system and dynamic simulations for the electric heater are carried out. For the economic consideration, a demand analysis for heat storage power plants in the European interconnected grid and an estimation of the market potential for heat storage power plants coupled to district heating grids will be carried out. The NOWUM Energy Institute of the FH Aachen University of Applied Sciences is creating future market potentials using various stochastic models and calculating the economic return taking into account various electricity price development scenarios using hourly price forward curves for the following three decades. The findings are incorporated into the planning of a pilot plant.


Power-to-Heat Technologies with Salt Storage for Use in Industry and PV CSP Hybrid Power Plants

Project Start: May 2018

The industrial sector accounts for about 30 % of the final energy demand of the Federal Republic of Germany. Of this, around two thirds is used for the generation of process heat, whereby large amounts of waste heat are usually generated. The waste heat is typically generated at a temperature level that is below the temperature required for the respective processes. The SWS project is therefore investigating a high-temperature heat pump in combination with a molten salt heat storage system. By means of the heat pump, waste heat is brought to a temperature of more than 500 °C and stored in the heat storage tank. Depending on the connected consumer, the storage tank is discharged as required.

In addition to a high-temperature heat pump, a commercial resistance heater is being explored as a further power-to-heat technology (P2H). This can also be used to charge a thermal storage unit. During time periods with a large supply of renewable electricity and the resulting surplus, negative electricity prices are regularly observed at the electricity exchange. With help of the technologies studied, this surplus electricity can be used and, as a result, it can make an additional contribution to grid stability. Furthermore, the implementation of P2H technologies in CSP power plants (Concentrating Solar Power) is being investigated. This is of particular interest for the location of North Rhine-Westphalia, as industrial companies located here have a high market share in the production of CSP components and also offer services in this area. Beyond that, the design of these two P2H technologies in an innovative concept for use as a PV-CSP power plant is being examined. Here, low-cost PV electricity will be partially stored in high-temperature heat storage tanks (Carnot battery) for use during times without solar irradiance and will thus be offered as required.

So far, a market analysis of the process heat demand for various suitable industrial sectors has been carried out for the location of NRW. The SIJ has identified and evaluated existing energy-intensive process heat producers and consumers in North Rhine-Westphalia and has made contact with a number of process heat-intensive companies.
Moreover, dynamic simulations of different power-to-heat systems in combination with a molten salt heat storage system for different power classes, working fluids and coupling concepts have already been carried out and partially validated using the Dymola® software.

Project Partners:

  • TSK Flagsol
  • German Aerospace Centre e. V.

Sponsored by:

  • Ministry for Economic Affairs, Innovation, Digitalisation and Energy of the State of North Rhine-Westphalia using ERDF funds.

TESS 2.0

Thermal electricity storage

Project duration 01.10.2017 - 31.10.2021

The storage of high-temperature heat with subsequent conversion to electricity in steam power processes is known from solar thermal power plants. In these applications, the high-temperature heat is collected by concentrating solar collectors. The idea with thermal electricity storage is to load the storage unit using a power-to-heat concept from surplus electricity from the grid instead of solar energy. The multiTESS (multifunctionalthermalelectricity storage) storage concept is being developed by the Solar Institute Jülich for a decentralised and flexible electricityand heat supply. In contrast to the conventional power-to-heat approach, the heat in the thermal electricity storage system of multiTESS is stored as high-temperature heat at up to 1000 °C and can thus be partially converted back into electricity in a thermal power process. The multifunctionality of multiTESS is based on the flexible choice of heat source and sink (cf. Figure 1). Electric heating or waste heat can be used as heat sources. In addition to electricity, heat can also be provided at different temperature levels during storage.

In the TESS 2.0 project, the utilisation chain Power-to-Power&Heat of the multiTESS concept is mapped for the first time in the form of a pilot plant (cf. Figure 2). The project, which is funded by the BMWi, benefits from the expertise of the industrial partners Dürr Systems AG, Kraftanlagen München GmbH and Otto Junker GmbH. The focus is on the generation and process control of 1000 °C hot air, the storage of the high-temperature heat, as well as the integration of reverse power generation and heat extraction. For the generation of the high-temperature heat, the project partner Otto Junker GmbH has developed an innovative heating concept (state of the art: 750 °C). The conceptual design and the construction of the ceramic storage tank, which is also new, were carried out by Dürr System AG. The detailed planning of the system concept was largely realised by Kraftanlagen München GmbH. The Solar Institute Jülich is the idea generator and initiator of the project, acts as project coordinator, provides support in the concept planning and carries out the scientific investigations after completion of the enclosure.

During the tests, the operating behaviour of the individual components will be investigated and their process control optimised in the overall system. The aim of the project is to realise an innovative and primary energy-saving overall system from the combination of the individual components.

More information can be found here: More


Evaluation of the Dispatchability of a Parabolic Trough Collector System with Concrete Storage

Link to the EDITOR homepage: EDITOR

Project Duration: 01.10.2015 to 30.09.2018

The objective of EDITOR is to demonstrate and verify the base load capability and performance of a solar thermal system designed for continuous operation. During the project duration, a system consisting of a medium-sized parabolic trough collector, concrete heat storage tank and boiler will be installed in Cyprus. The system will produce saturated steam and feed it into the steam system of a beverage producer.

The parabolic trough collector uses an innovative vacuum receiver to heat a novel, environmentally friendly thermal oil to a temperature above 400 degrees Celsius. An innovative new concrete heat storage system stores the extracted heat to use it for the production of saturated steam in times without (sufficient) direct sunlight.

In the project, both the technical activities of installation, start-up operations and running of the system, as well as commercial aspects, such as feasibility in terms of upscaling, identification of future customers and the accompanying communication process with the potential market, will be implemented.

Project Partners:

  • protarget AG
  • Cyprus University of Technology
  • CADE Soluciones de Ingeniería, S. L.
  • German Aerospace Centre e. V.


Quasi-closed heliostat field control of a multi-chamber reactor for solar hydrogen production

Project Start: October 2018

The project aims to realise a fully automated control of the process temperature in a solar-chemical multi-chamber reactor by means of the heliostat field. For this purpose, an innovative, novel, quasi-closed control concept (H2Loop) is being developed.

An innovative model-based optimisation tool makes it possible to predictively calculate and optimise the target point strategies for a multi-chamber reactor. The second innovative step is the integration of an online calibration procedure into the heliostat field control software. The real-time capable communication network represents the third innovation in the heliostat field, while the fourth innovation concerns the heliostat itself. To this end, the design of the heliostat is optimised for the use of the network. In addition, individual, automated canting is made possible.

These innovations as a whole enable the automated control of the multi-chamber reactor and, independently of each other, make a significant contribution to increasing performance and reducing costs in solar tower plants, leading to improved cost efficiency of solar hydrogen production.

The SIJ has investigated and improved various existing calibration procedures as well as developed new ones. One calibration procedure was selected and will be tested on a larger scale in the further course of the project.

Project Partners:

  • Hilger GmbH
  • Heliokon GmbH
  • German Aerospace Centre e. V.

Sponsored by:

  • European Union - Investing in our Future European Regional Development Fund
  • State Government North Rhine-Westphalia - Ministry of Economic Affairs, Innovation, Digitalisation and Energy of the State of North Rhine-Westphalia
  • EFRE.NRW - Investition in Wachstum und Beschäftigung (Investment in Growth and Employment)


Integration of thermal electricity storage in existing power plant sites

Project duration: 01.10.2015 - 31.12.2016

The conversion of the German electricity system to renewable, fluctuating forms of generation will pose major challenges for the various players in the coming decades. The I-TESS project analyses the extent to which thermal storage systems can contribute to the demand-oriented provision of electricity and heat and to the stabilisation of the electricity grid. In addition to the use of old power plant sites for the construction of new types of thermal electricity storage power plants, the integration of thermal storage in existing coal-fired power plants also plays a decisive role. The latter should drastically increase the flexibility of today's coal-fired power plants and thus make a decisive contribution to demand-oriented electricity production. In addition to technical issues, another focus of the project is on estimating the investment costs and the economic chances of success.

More detailed information can be found in the project flyer. Please click here.


Meander-shaped tubular reactor for biological methanation as chemical storage for providing flexibility options in power grids

Funding period: 01.11.2019 - 31.10.2022

The planned increase in electricity generation from renewable energies, such as wind turbines and photovoltaic enclosures, with a simultaneous decline in conventional power plant capacities poses a major challenge for electricity grid stability and energy supply security. Energy supply security can only be ensured through the use of demand-responsive storage technologies as well as other accompanying measures.

The focal points of NOWUM's work in the project:

Bio-Power-to-Gas is a type of energy storage that uses microbes to convert hydrogen - produced by electrolysis in the event of an electricity surplus - into natural gas-equivalent methane, which can be fed into the existing natural gas grid almost without restriction. The aim of the project is the construction and test operation of a new type of reactor design as a meander-shaped tubular reactor. This can significantly minimise both the energy required for operation and the system costs compared to conventional reactors. In addition, a flexible design allows integration into existing building facades, for example. In the project, the use of this structurally flexible and thus decentralisable technology is being tested in real operation for the first time.

The focal points of the SIJ's work in the project:

The effect of the reactor on the overarching sector-coupled energy system and its stabilisation potential with a focus on the electricity grid will be determined in a model for the Jülich region. All relevant system components are modelled for this purpose and validated using the test operation data. Expansion scenarios for future load and generation profiles are developed taking into account the expansion of renewable energies, sector coupling and changed energy requirements (e.g. increased use of e-mobility), so that future operating scenarios can be simulated for selected grid areas. Potentials for transferability to other grid areas and with regard to scalability are derived.


Increasing the Cost Efficiency, the Utilisation Rate as well as the Flexibility and Operating Time of the Storage System in the Solar Tower Jülich

Project Start: 01.07.2010 - 31.12.2013

With the solar thermal experimental power plant Jülich (SVJ), the first power plant of this type in the world was built in Germany. This project aims to improve the utilisation of storage technology and, as a result, reduce the operating costs of the power plant. The focus of this project is to use new numerical simulation tools to increase the economic efficiency, degree of utilisation, flexibility and operating time of the storage system. The optimisations should result in an innovative storage system concept that is ideally suited for use in solar tower power plants.

Project Partners:

  •     KBA-MetalPrint GmbH | KBA
  •     Kraftanlagen München GmbH | KAM


Development and Qualification of Solar Receivers Based on Transparent Ceramics for Solar Process Engineering Processes

Project Start: March 2018

Nowadays, high-temperature heat from concentrating solar thermal systems is used commercially for the production of electricity, but it is also suitable for substituting fossil energy sources in process engineering. Especially in the chemical industry, there is great potential for the use of solar energy.

In the TRAKSOL project, a receiver concept is being developed for the application of concentrating solar technology in chemical processes. The focus is on the investigation and qualification of the transparent ceramic Perlucor® - developed by CeramTec - with regard to its suitability for concentrating solar technology. Due to the possibility of directly heating the working fluids, the use of this ceramic offers the promise of higher degrees of efficiency. Given its high resistance, the ceramic can be used for a wide range of processes.

The evaporation of sulphuric acid at about 400 °C was considered as an exemplary process. The evaporation of the sulphuric acid is the most energy-intensive part of the two-stage sulphuric acid hybrid process (HyS), in which water is split using thermal energy and hydrogen is produced. Conventional hydrogen production processes cause high CO2 emissions. The use of solar energy can greatly reduce these emissions.

The objective of the project was adapted to the results of corrosion tests and the property profile of the ceramics:  The focus of the development is now on developing a high-temperature particle receiver. The extremely hard and temperature-resistant ceramic enables direct irradiation of the particles. After heating, the thermal energy of the particles can be stored and used for steam cycle processes to generate electricity or for continuous chemical processes, such as that of sulphuric acid evaporation.

Project Partners:

  • CeramTec-ETEC GmbH
  • German Aerospace Centre e. V.
  • Hilger GmbH

Sponsored by:

  • European Union - Investing in our Future European Regional Development Fund.
  • Government of North Rhine-Westphalia - Ministry of Economic Affairs, Innovation, Digitalisation and Energy of the State of North Rhine-Westphalia
  • EFRE.NRW - Investment in Growth and Employment