The climate change that we as the world's population − and here especially in the industrialized nations − are driving with our hunger for energy, mobility, consumption, global networking, will primarily harm ourselves and our future generations … These are the challenges against which we must measure our work, and we at Fraunhofer ISC want to make essential contributions to their solution.
Since the 1980s, society has become increasingly aware of the need for an energy turnaround. The transition from the use of finite resources to renewable energies is also accompanied by the necessary increase in efficiency of solar energy converters. Even silicon solar cells having the highest efficiencies currently available offer clear advantages, but also face physical limitations.
On the one hand, highly efficient silicon-based solar cells deliver cost-effective electricity and consume less surface area and materials than simple photovoltaic cells. On the other hand, their efficiency cannot be increased at will. For this reason, it is important that a future-oriented research approach focuses on the combination of several materials. The lead project “MaNiTU” therefore emphasizes the development of multi-junction solar cells by concentrating on research into absorbent materials.
The starting point of the lead project is perovskite solar cell technology, which has seen its efficiency increase from 3.8 % to 24.2 % over the past ten years. This technology promises not only potential for increasing efficiency, but also minimal production costs and simple manufacturing processes.
Due to their physical properties, the class of perovskite materials is also suitable for use in multi-junction structures based on silicon solar cells. Multi-junction solar cells of this type are particularly interesting because they can achieve efficiencies of over 35 %.
However, the EU RoHS Directive which restricts the use of toxic or critical materials, renders the use of perovskites problematic. This is because, in the manufacture of solar cells, the class of perovskite materials currently is dependent on lead, a material classified as critical.
Annual photovoltaic installations are expected to increase to more than 1 TWp worldwide in the next five to ten years. Consequently, the elimination of toxic as well as critical materials from the manufacture of solar modules is becoming increasingly important. The use of perovskites without the addition of lead is not yet possible. In the lead project “MaNiTU”, six Fraunhofer institutes are working together on the development of new lead-free absorbent layers as well as contact and passivation layers.
These layers are based on well-known perovskite absorbent materials that do not contain any critical or toxic substances thanks to state-of-the-art methods of materials science. With the combination of lead-free perovskite technology and silicon technology, perovskite solar cells can be deposited directly on silicon solar cells. The individual solar cells use different parts of the solar spectrum particularly efficiently, so that the overall efficiency is increased. As a result, the same solar cell area ultimately produces more electricity.
With its expertise in wet-chemical material synthesis and electrode applications, Fraunhofer ISC plays a key role in the “MaNiTU” lead project. In combination with its expertise, the multi-junction approach will advance solar cell research in Germany and provide an innovative edge that is also economically interesting.
© Fraunhofer ISE
Large parts of European industry, including the European automotive industry, are increasingly dependent on imported lithium-ion cells. The European Green Deal and various supporting measures aim at exploiting the employment, growth and investment potential of batteries. The objective is to create a competitive “battery” value chain in Europe – not least to make battery technologies more environmentally friendly and “greener”.
Lithium-ion batteries require a number of special functional materials in addition to lithium for their performance, some of which, i.e., conductive additives, sound rather unspectacular. In fact, conductive additives such as conductive carbon black or carbon nanotubes are crucial building blocks for the performance and environmental compatibility of lithium-ion batteries, and they are essential for achieving fast charge and discharge rates. In the rapidly growing battery market, raw materials account for the majority of costs in production. Carbon, specifically conductive carbon black in this case, is usually produced with high energy and process material input.
The “HiQ-CARB” joint project, coordinated by Fraunhofer ISC, aims at providing new carbons with superior performance and a low carbon footprint for future “greener” batteries in Europe.
The “HiQ-CARB” approach to “green” carbon additives is to combine thin carbon nanotubes and acetylene black, which score high in conductivity and low in CO2 emissions during production. In combination, they form a nearly ideal conductive network within the battery electrode. This contributes significantly to improving the environmental balance, e.g., by
reducing the carbon footprint of material production. In addition, the standard carbon nanotubes (CNTs) that have already been commercialized are being replaced by new, much thinner CNTs. This allows to reduce the amount of carbon materials for the same or even better battery performance and leads to improved resource efficiency. Moreover, this is the only CNT material in the world made from a renewable bioethanol feedstock.
In addition, a life cycle analysis will be carried out as part of the project to assess the sustainability of the production process.
On the one hand, the “HiQ-CARB” project team relies on high-profile companies such as ARKEMA or ORION for the production of advanced additives and Customcells for battery cell production. On the other hand, well-known R&D partners such as the Fraunhofer Institute for Silicate Research ISC, Aalto University and the University of Bordeaux are involved in the scientific part of evaluating and testing the new material combinations themselves and the battery cells produced from them. The project is funded by the European Union through EIT RawMaterials.
The project is funded by the European Union through EIT RawMaterials.
The DeCaBo (DeCarbonization of Buildings and Operation) project was launched as part of the Fraunhofer-Gesellschaft‘s self-financed innovation program. With a duration of just five months, the project investigated solutions for four relevant technology areas that support the Fraunhofer-Gesellschaft‘s goal of being climate-neutral by 2030: low-CO2 building products, planning and operation of buildings as well as recycling of building materials.
The broad know-how of 16 Fraunhofer Institutes was incorporated into the various issues.
With the aim of developing methods and tools for the transformation of the Fraunhofer-Gesellschaft towards climate-neutral operation, performance models for renovation roadmaps and potentials for renewable energy sources were identified. For the digitization of building operation to increase energy performance, a roadmap was drawn up for the nationwide introduction of intelligent building monitoring and initial innovative financing models were also developed for the public sector.
But we also wanted to find new solutions for the production, use and efficient recycling of building materials because the development of new building materials and methods can make an important contribution to reducing CO2 emissions. In addition to methods and processes for new building products, such as insulating materials made from recycled rotor blades and renewable raw materials or hybrid wood-concrete building components, the project also successfully tackled restoration render and new technologies and materials for composite heat insulation systems. In this context, Fraunhofer ISC played a key role in the development of joining technologies in glass technology using inductively fusible glass solders for energy-saving vacuum heat-absorbing glazing, which enable rapid and energy-saving gas-tight bonding of the glass panes.
The key to success here was the bonding of special magnetic particles (MagSilica®) with low-melting glass.
More environmentally friendly alternatives for PVC frame profiles and sealing compounds based on renewable raw materials in combination with rPET/rHDPE recyclates were also tested. Fraunhofer ISC contributed know-how and material for long-term temperature and UV protection of the novel extrusion materials with its ORMOCER® coatings. ORMOCER® know-how was also used to improve natural-fiber-reinforced geopolymers, which have a significantly better carbon balance than
concrete with steel reinforcement.
In addition to purely mineral construction waste - as shown in the picture - there are now a number of composite construction materials with a complex mineral-organic-metallic material mix. One of the tasks of the DeCaBo project is to separate such composite systems as well and easily as possible. © Fraunhofer (graphic), Pixabay (photo)
When building materials are recycled, the separation of the different material components poses a key challenge. Within the scope of the project, processes for the application of thermal separation methods to adhesives were successfully refined.
Here, too, specially adapted MagSilica® particles from the ISC were used, which can be readily dispersed in resin systems. This enabled inductive processes to be successfully used for the simple separation of bonded joints of composite heat insulation systems and precast concrete parts.
With the DeCaBo project, a number of interesting and creative solution approaches were conceived and tested that can greatly contribute to the CO2-saving construction and operation of buildings. What initially generated ideas for the Fraunhofer-Gesellschaft itself will also be able to provide important impetus for the construction industry in the future for the further development of building materials and methods to reduce the high CO2 emissions from this sector.
MagSilica®: registered trademark of Evonik
The EU Horizon 2020 funding program aims at supporting the transformation process of energy-intensive manufacturing industries towards carbon neutrality in 2050. The SPIRE joint project “FORGE” addresses four essential challenges in the four key technologies of cement, steel, aluminum and ceramic production: H2 embrittlement, corrosion, abrasion as well as mechanical and thermal damage.
Equipment currently used in energy-intensive industries is susceptible to corrosion and erosion, as well as brittle fracture and cracking caused by the gas atmosphere and thermal stress during furnace operation. Increasing the production efficiency and service life of plant components is essential for more environmentally friendly cement, steel, aluminum and ceramics production, also in view of plants with reduced CO2 emissions planned for the future. The EU-funded “FORGE” project aims at developing new cost-effective coating solutions specifically for the protection of particularly vulnerable plant components. The focus here is on novel compositionally complex materials, which in theory promise outstanding mechanical, chemical and thermal stability due to their special composition. FORGE will explore this new material range of compositionally complex alloys (CCA) and compositionally complex ceramics (CCC).
Within the scope of the “FORGE” project, the Fraunhofer Center for High Temperature Lightweight Materials and Design HTL is responsible for the development of novel coatings to reduce thermal and corrosive degradation of refractory material in tunnel furnaces. The focus is on ceramic coatings based on CCC with complex, entropy-stabilized compositions. These compositions will be developed by combining methods dealing with machine learning, artificial intelligence and computational chemistry, as well as by thermodynamic considerations and high-throughput experiments.
The project will use the new CCA and CCC high-performance coatings in particularly vulnerable process steps such as carbon capture and waste heat recovery, as well as directly in the furnaces to combat the degradation forces that occur there. As a result of the FORGE project, it is expected that the operating life of the vulnerable components in the addressed industries can be considerably increased, leading to a significant minimization of costs as well as CO2 emissions.
In the field of aviation, weight reduction and energy efficiency are at the top of the list of requirements – also for new materials and components. Ceramic matrix composites (CMC) offer significant advantages for use in aircraft gas turbines: CMC components are only one-third as dense as conventional metal components, so they contribute to a significant reduction in weight. They can also be used at temperatures up to 300 K higher. In the hot section of gas turbines, CMC components therefore enable more efficient and complete combustion, save fuel and thus reduce CO2 emissions. Oxide ceramic matrix composites (O-CMC) also naturally ensure high oxidation resistance and a low tendency to corrosion in the combustion atmosphere, thus increasing the service life of the components.
Since the beginning of 2021, the Fraunhofer Center HTL has been working within the scope of the “AirfOx” project, funded by the Bavarian aerospace program BayLu25, to develop a process that can be automated and technologies with which near-net-shape engine blades for aircraft gas turbines (airfoils) can be integrally manufactured from oxide ceramic fibers in series production.
By using multiscale simulation and CAD programs for load-oriented fiber design, an airfoil will be used as an example to demonstrate how a complex 3D preform can be developed in CMC manufacturing. Innovative weaving techniques are being used to develop a new manufacturing method for three-dimensional fabric preforms made of ceramic reinforcing fibers for CMC components with cover surfaces of different lengths, while at the same time allowing support structures in the form of webs to be woven in. Locally occurring stress peaks, which are detected during modeling, can also be taken into account as early as in the fabric design phase. The transfer of textile 3D weaving techniques to ceramic fibers is a particular challenge due to their brittleness. With the special manufacturing technology, the textile-ceramic 3D preforms are produced in one piece close to the final contour. This ensures high resource efficiency in the manufacturing process.
In the project, a digitization concept for the production of the preform is being developed in order to continuously record and evaluate the production data, which are essential for the component properties, during the weaving implementation of the textile semifinished product. The aim is to set up a data management system as a preparatory measure for certifications to ensure the traceability of all process parameters, thus facilitating subsequent aviation approval.
The textile semifinished product is converted into a CMC component in four steps, with the special process for infiltration being used for the first time for this type of 3D preform. Focal points are the development of the technology for the infiltration process and the ability of the process to be automated.
CMC airfoils can significantly contribute to reducing fuel consumption and lowering CO2 emissions. “AirfOx” will make a significant contribution here towards series production and is intended to pave the way for establishing the new resource-efficient technology for producing complex 3D fiber prefoms for CMCs, which can then also be used for other CMC types, e.g., SiC/ SiC-CMC.
© Fraunhofer Application Center Textile Fiber Ceramics/Fraunhofer Center HTL
Fraunhofer Institute for Silicate Research ISC