Renewable Energy Research Network

Wind energy plant is reflected in a photovoltaics module.
(© Alberto Masnovo -

In the Renewable Energy Research Network, experts from industry, universities, research institutes and politics exchange ideas on the use of renewable energy sources. They pass on suggestions for setting priorities in renewable energy research to the Federal Ministry for Economic Affairs and Climate Action and provide concrete implementation ideas for topics or funding concepts.

The members of the network develop research roadmaps, position and strategy papers and inform the public about progress and innovations in the field of renewable energy. With the topics of wind energy and photovoltaics, the technologies that supply the largest share of electricity from renewable energy sources within Germany are initially represented in the network.

Current studies show that the coordinated use of photovoltaics and wind energy is very well suited to provide energy in a reliable, economically viable and environmentally friendly manner. Grid fluctuations, caused by the varying local solar radiation and wind speed are mitigated by combining the two technologies. This is why these complementary sustainable ways of generating energy are viewed as the cornerstones of the transformation of the German energy sector (Energiewende).

In the research network, members work on subject-specific topics, but there are also interdisciplinary topics and events: for example on Industry 4.0, digitization, and system services. They are funded by the Federal Ministry for Economic Affairs and Climate Action (BMWK) to accompany the transfer from science to market maturity.

Photovoltaics research field

In the field of photovoltaics research, the renewable energy network pursues two priorities: improving the integration of photovoltaics in energy systems and further reducing electricity generation costs.

The aim of the research activities is to create the technological basis for innovations relating to

1) further increasing module efficiencies, mainly through tandem concepts and
2) the expansion of possible applications and markets for photovoltaics in integrated solutions for the utilization of already sealed surfaces and for the electrification of the heating and mobility sectors through new materials, concepts and technologies.

All tandem solutions contain at least one thin-film cell. Thin-film technology has advantages in terms of energy and resource consumption with comparable levels of efficiency and in terms of manageable, more resilient supply chains. Existing technologies must also be developed in the direction of energy-efficient production. When it comes to equipment (thin-film processes) for alternative concepts and materials (perovskites, CIGS, CdTe, OPV, III/V), companies in Germany continue to have a unique selling point that must be strategically supported.

Tandem concepts based on crystalline silicon and on compound semiconductors made of copper indium gallium selenide/sulphide (CIGS) as so-called bottom cells in combination with top cells made of perovskites or CIGS as well as multilayer solar cells made of so-called (III/V) semiconductors (e.g. GaAs, GaInP) are the most technologically advanced. The thin-film technologies that are used as top cells in tandem still have considerable potential for improvement - depending on the material system in terms of long-term stability, scaling, production costs and industrial efficiency. They must be flanked by intensive research and development and then industrially qualified. Furthermore, highly efficient thin-film solar cells on cost-effective, lightweight and flexible films are being developed and new (in)organic materials and components are being qualified.

In the future, new markets and applications will emerge that use other functionalities in addition to pure electricity generation: Facades of buildings, open field systems that are also used for agricultural purposes, PV integrated into means of transport or the self-sufficient supply of mobile electronics and sensor technology for Industry 4.0. These new markets require specialized solutions and technologies. The applications offer the possibility of using already sealed surfaces to generate electricity, thus reducing the consumption of natural resources and offering new opportunities for the electrification of the heating and mobility sectors locally at the point of electricity generation.

Prof. Dr. Michael Powalla
Website: Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)

Prof. Dr. Rutger Schlatmann
Website: Helmholtz-Zentrum Berlin

Dr. Thomas Dalibor
Website: AVANCIS,

Photovoltaics based on crystalline silicon (Si) modules is the world's dominant photovoltaic technology. Further major steps in increasing efficiency and reducing costs are possible and could give the European photovoltaic industry a technological edge in international competition. This opportunity is offered in particular by innovative new technological developments. These include new production processes for Si ingot and Si wafers with greatly reduced material consumption. In addition to production processes with increased throughput, the focus is also on material quality. In addition, even more efficient cell technologies with efficiencies of over 25 percent are to be developed, which will enable the highly productive processing of Si wafers. Research into all-side passivating contact schemes and Si tandem solar cells, which can make better use of the solar spectrum, is particularly promising. All new wafer and cell technologies require adapted module technology that must be compatible with the new materials and cell contacts. New connection technologies, the possible cost-saving integration of additional functions such as integrated inverters or displays, an increased service life of the modules and application-adapted modules, for example for building-integrated photovoltaics (BIPV), can further reduce costs and open up new markets. Increasing the energy yield of PV modules is a key lever for reducing the levelized cost of electricity. Innovative technical solutions for resource-conserving photovoltaic production along the value chain with an increasingly closed-loop economy serve sustainability and social acceptance. Good cooperation between the key players from materials, solar cell and module production, mechanical engineering and research institutions is the guarantee for successful photovoltaic production research.

Prof. Dr.-Ing habil. Rolf Brendel
Website: Institut für Solarenergieforschung in Hameln (ISFH)

PD Dr.-Ing. Ralf Preu
Website: Fraunhofer ISE

Dr. Radovan Kopecek
Website: ISC Konstanz

Andreas Waltinger
Website: Meyer Burger

Dr. Peter Fath
Website: RCT Solutions

Photovoltaics is an essential building block for the economically cost-effective realization of the energy transition. Although only around a third of the cost of a kilowatt hour generated depends on the investment, the cost of PV is often equated with the cost of building the system and the follow-up costs are ignored. However, significant expenses are incurred over the life cycle of the investment. Significant contributions are risk assessment (= financing costs), quality costs and operational management.

There is a lack of fundamental understanding of how production processes, material selection and quality assurance strategies, including operational management, influence the LCoE. Minimum production costs and maximum efficiency are no guarantee of low electricity generation costs. One example was a previously unknown defect in a premium backsheet that halved the service life of the modules and thus more than doubled the LCoE. There is a lack of understanding of materials and tests to minimize such risks. The current approach is cost-minimized empiricism, which can lead to economic damage. Such problems can recur with the extremely fast innovation cycles, the growing heterogeneity of products and rapidly changing material combinations. The failure mechanisms are by no means limited to the solar modules – plugs, inverters and other components are also important.

The Performance working group evaluates technologies on the basis of the LCoE over the service life of the system and not on the basis of the output efficiency that is common today. Topics that lead to a significant reduction in LCoE include fault prediction and testing (development of relevant test cycles specifically for new technologies), risk prediction, calculation of quality costs over the life cycle, digitalization of operational management including question-specific applications of AI.

Prof. Dr. Ralph Gottschalg
Website: Fraunhofer CSP

Dr. Claudia Buerhop-Lutz

Dr. Björn Müller

Dr. Andreas Dietrich

The massive expansion of photovoltaics (PV) requires precise integration. How can PV modules be accommodated on land that is already in use and how does PV electricity fit into the changing energy system? By integrating PV into the shells of buildings, vehicles and traffic routes and incorporating it into agricultural and water areas, large areas that are already in use can be opened up for solar power generation. Integrated PV solves land use conflicts and creates synergy effects, for example in terms of climate resilience or material efficiency. The diverse synergy potentials need to be researched and application-specific PV technologies developed.

Future photovoltaic power plants will have to make a greater contribution to stabilizing the electricity grid. They will have to take over functions that were previously provided by conventional power plants. This is why the system technology, i.e. all the components that make up a PV system, must be constantly developed further. It makes photovoltaics efficient and usable – for example, by offering grid-stabilizing system services or ensuring an optimal balance between electricity production and consumption.

The aim of research funding for PV system technology is to achieve the transition from PV systems, which in the past were only designed for grid feed-in, to PV systems that are optimally integrated into local and higher-level system solutions. In addition, the aim is to achieve a significant reduction in costs and an improvement in operating efficiency in order to maintain the international competitiveness of German manufacturers and solution providers and to ensure a cost-effective power supply.

In addition to pure PV systems, complex, resilient system solutions with PV combisystems and sector coupling are increasingly coming to the fore. They are characterized by the fact that local consumption is increased in consumer-oriented systems with battery systems or controllable consumers, for example heat pumps and charging stations, and optimal market and grid integration for energy exchange with the interconnected grid is made possible. Large solar power plant solutions help to build up the interconnected grid or increase economic efficiency as a combined power plant with wind and electrolysis.

Dr. Oliver Fuehrer
Website: SMA Solar Technology AG

Dr. Philipp Strauss
Website: Fraunhofer IEE

Harry Wirth
Website: Fraunhofer ISE

The following topics are of central importance to the Photovoltaics Sustainability Working Group.

Recycling and "easy-to-recycle" product design play an important role. Previous and future module generations (tandem, perovskite, etc.) and special applications, such as vehicle integrated photovoltaics (VIPV) or building integrated photovoltaics (BIPV), must be taken into account.

The repair and re-use of photovoltaic modules is also relevant, with regulations regarding product, disposal and recycling guidelines being a key issue for these areas.

In addition, standardization and building standards are important aspects that remove obstacles – for example, overhead glazing, standardized mounting systems for façades, etc.

Environmental aspects and questions of acceptance are also included in the working group. The materials used, the impact on land and biotopes or the dual use of land are key parameters here.

Finally, the sustainable expansion of photovoltaics is a concern of the working group and thus the regulation of the energy market, remuneration structures, standardization of grid inquiries and registration procedures with grid operators as well as securing financing.

The aim is to bring together stakeholders on the aforementioned topics and bring them into an exchange, to formulate R&D questions and to form expert groups for the discussion of solutions from research projects. Last but not least, the derivation of economic industrial processes (higher technology readiness level) must be the subject of funded projects.

Dr. Jann Binder
Website: Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg

Prof. Dr. Peter Dold
Website: Fraunhofer IWKS

Wind energy research field

In the field of wind energy, the stakeholders primarily pursue the aim of providing electric power from wind turbines at even lower cost and in a more reliable manner. This means increasing the yield from power plants and guaranteeing secure operation.

Besides the location, power plant technology is decisive for electricity generation costs. Reducing these costs is the overarching aim of funding in this area. The decisive factors are the efficiency of energy conversion, the manufacturing costs of all components and the overall system as well as the associated operating costs over the entire life cycle of the wind turbines. This makes a holistic plant design particularly important: already in the design phase, the costs of manufacturing, operating, dismantling and recycling should be considered, as well as how the plants or wind farms can be integrated in the electricity grid.

At the same time, the technical challenges facing the individual components and the overall plant increase continuously: rotor blades are becoming larger and larger, the sites to be developed are becoming more challenging and the requirements for system behaviour are more diverse. The focus is on large-scale components such as rotor blades and drive trains, which need to match the increased requirements both in terms of their material properties and their dimensioning. This topic is complemented by the increased modularization and the establishment of standards in many steps of the value chain. Finally, the development of systemic approaches in the field of high-performance electronics as well as grid integration contribute to the ability to counter the increasing variety of requirements and the rising loads.

Prof. Dr. Jan Wenske
Website: Fraunhofer-Institute for Wind Energy Systems IWES

Jens Demtröder
Website: Vestas Deutschland GmbH

In order to further reduce the costs of wind energy and optimally integrate it into the energy system, wind turbines and farms must be operated intelligently and flexibly. This also requires advanced control strategies for complex sites that provide accurate forecasts of the expected feed-in. Thanks to these improved prediction models, wind farms will be integrated reliably in electricity grids and controlled in hybrid power plant clusters in the future. New and improved sensors will provide a multitude of data whose management and analysis (big data) offer a variety of approaches for optimization. Thanks to improved evaluation of the measurement data, power plants and wind farms will be evaluated more precisely in the future. Preventive maintenance or repairs will thus be implemented in order to avoid downtimes or to reschedule these to weak wind phases.

The more electric power is fed into the grid by wind turbines, the more important the question of how the electricity produced can be well integrated into the energy system and to what extent wind farms can provide useful services for the system, for example supporting grid re-establishment through their capacity for self-contained starting.

Dr. Jan Teßmer
Website: German Aerospace Center (DLR)

Issues of mechanical load or potential acoustic effects during operation require exact knowledge of the incoming wind and – offshore – of waves and ocean currents. The better the properties of wind as an energy resource are known, the more effectively it can be used. The precise description and prediction of wind conditions is directly linked with the basic difficulties of non-linear and turbulent flow physics. This especially concerns the aerodynamics, aeroelasticity and aeroacoustics of wind turbines and particularly their rotor blades. This is also decisive for the dimensioning of wind farms, since wind turbines alter the wind conditions that reach downstream wind turbines.

Due to the increasing size of current wind turbines, more and more components are reaching the limits of their material properties. New materials, for example to reduce weight or increase reliability, are central to effective and cost-efficient power plant construction. For this reason, the material behaviour of rotor blades, towers, foundational structures and other components must be recorded more accurately. New or improved measuring technology will be required in order to record these material properties and their failure behaviour under load in an optimized and reliable manner.

The sound emitted by wind turbines has a vital impact on the social acceptance of wind energy. This is why research into the principles of noise creation, propagation and perception will be advanced so that noise can be reduced as much as possible and predictions and models of noise can be improved. Improved models will also be able to identify operating conditions that particularly contribute to noise reduction in the future.

Prof. Dr. Joachim Peinke
Website: Universität Oldenburg

For the expansion of wind energy to gain social acceptance, the environmental impact must be reduced to a minimum. Issues of acceptance and interactions with the environment as well as of infrastructure are thus gaining significance. Current debates on the costs and the usefulness of wind farms in the energy system are influencing their further development.

When it comes to onshore wind energy, the public discussion often revolves around issues of influence, integration and interaction with the environment regarding the utilization of land and design of wind farms. This includes distance regulations and landscape integration in particular, as well as topics such as water protection and aviation safety. Noise reduction plays a major role for local residents, as well as warning lights at night. For this reason, cost-effective and reliable technical methods for needs-based lighting will be researched.

A wind turbine’s effects on and interaction with fauna and flora as well as the climate are of central importance for social acceptance. Here, systems will be developed that reduce the negative impact on the environment and fauna. In the case of offshore wind energy, the potential impact on the entire ecological system, for example for marine birds and mammals, must be considered and taken into account during construction and operation of the facilities. Onshore, bird- and bat-friendly operation of turbines must be ensured.

Since more and more wind turbines will reach the end of their life cycles in the future and the material volumes flowing into wind energy are continuously high, issues of dismantling and recycling also have to be clarified. Ideally, the materials for future wind turbine generations will be selected in a manner that will allow them to be recycled easily while maintaining high-quality.

Dr. Michaela Herr
Website: DLR – Wind Energy Research

Dr. Dirk Sudhaus
Website: Onshore Wind Energy Agency

Expert commitee on offshore and onshore wind energy.
(© kasto -

Wind energy expert committee: offshore and onshore

There is an expert committee each for the fields of onshore and offshore wind energy. One focus of the onshore committee is on site analysis in order to increase the yield of individual turbines. In addition, the committee looks at logistical innovations that permit wind turbines to be implemented in challenging terrain. The offshore committee investigates grid integration, logistics and reliability of wind farms as well as innovative design approaches.

Expert committee on offshore wind energy

This committee is mainly concerned with the grid integration and logistics of offshore wind farms, which entail large capacities of electricity to be transported across long distances. Novel grid integration concepts and components are required in this field. The installation and operation of offshore wind farms requires efficient and reliable logistics concepts. In view of the (in)accessibility of the turbines on the high seas, the availability and reliability of the turbines have a special priority.
Another aspect that the expert committee is concerned with are innovative support structures and foundational elements. While monopiles and jackets dominate the wind farms in the North and Baltic Seas, floating foundations are increasingly developed for deep-sea applications in international locations. There is a lot of potential here for alternative solutions.

Dr. Dennis Kruse
Website: Deutsche WindGuard

Prof. Dr. Raimund Rolfes
Website: Institute for Statics and Dynamics

Expert committee on onshore wind energy

Wind turbines on land still dominate the development of wind energy. However, available sites on flat terrain are becoming increasingly rare. Yet there is great potential in hilly and wooded areas for further wind farms, including some with lower average wind speeds. Recent technical developments, such as higher towers, promise the economically viable operation of wind turbines even at these types of locations. However, the wind speed profile can vary greatly in the complex terrain. In addition, the interaction of the wind with the terrain and vegetation leads to increased turbulence. This is why research will be conducted into how the locations of individual turbines within a wind farm can be determined in such a way that the energy yield is maximized without simultaneously exceeding the mechanical design loads of the turbines.

Transport and logistics also present a major challenge when wind turbines are to be set up in mountainous complex or wooded areas. For this reason, the turbine components must be designed to be as transport-friendly as possible. In addition, transport concepts must also be developed for large and heavy components.

Haras Najib
Website: VDMA e. V.

Prof. Dr. Po Wen Cheng
Website: Institute of Aircraft Design

Bioenergy Research Network
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