• Energy Research
• French National Research Agency (AN... close
• 2017 close

The CNRS / Université de Pau et des Pays de l'Adour, in collaboration with the world's leading producer of organic solar cells, OPVIUS GmbH, and local politicians and artisans in the Vic-Montaner region, has recently demonstrated that it is possible to produce large-scale (1.5 x 0.7 m) organic solar panels (OSPs), that are lightweight (10.2 kg) and have robust polycarbonate encapsulation. The project attracted a great deal of attention in the press (google Baylère, Hiorns, Vic-Montaner, Sud-Ouest for example) and in local communities. Importantly, unlike perovskite-based devices, these panels are non-toxic and fully recyclable. They are installed with minimal effort on public buildings for on-site use of generated electricity, even in restricted zones areas due to their colour adaptability. This is an important step in the industrialization of OSPs. Silicon solar cells should be placed directly facing the sun to give their maximum efficiency, otherwise they lose up to 50% of their power output depending on the angle of the sun. This is not the case for OSPs. They work at all angles, just as well. This opens up a vast area that is available on the walls of private and public buildings. For example, lightweight and ergonomic, our polycarbonate panels are easy to install. It should also be noted that local laws (in France imposed by Bâtiments de France) restrict the implantation of silicon cells in villages. However, we have already negotiated with them locally to ensure that OSPs are now accepted within 500 m of sacred and culturally important buildings. These two elements open up a large market for OSPs in France. However, the daily power of the OSPs is still less than that of silicon cells. Therefore, we will build a project to close the efficiency gap between the power produced by silicon cells and OSPs. This project will be called "Increasing the efficiency of large-scale photovoltaic panels" (ELEVATE). It will aim to improve the efficiency of OSPs so that they are equivalent to Si-based panels on vertical walls. To achieve this objective, ELEVATE will need to bring together the key, highest quality teams from across Europe working in the following fields: i) macromolecular chemistry, ii) physics of devices and modules, ii) polymer processing, iv) physical characterization, and v) modelling that will deliver: new materials; new module architectures; new film processing techniques; depth characterization of materials; and predicting the best macromolecules and understanding their behaviour. ELEVATE will call on the world-leading OSP manufacturers, OPVIUS, and will integrate the leading manufacturers of semi-conducting materials. To solve the challenge of high-performance OSPs, we will rely on the leading academics in each relevant area from across Europe. While France has exceptional talents, ELEVATE would not be possible at a national level alone due to the extremely diverse and cross-science level of industrial and academic expertise required. To build ELEVATE will be a project in itself. For this reason, this project, called INFO was developed to finance project construction meetings, determine working groups, decide on milestones and deliverables, and take into account the needs of public interactions. Given the high public profile of the project ELEVATE, particular attention will be given to fostering open scientific activities with scientific communities, the general public and schools throughout the world.

The BAGETE project will focus on the development of nanostructurated metal oxide electrodes for their use as photo-anodes for hydrogen production by Photo-ElectroChemical (PEC) water splitting. This project fits in the frame of the Challenge 2 “Clean, safe and effective energy” for the Young Scientist competition. Solar energy is an attractive renewable energy source with low environmental impact. However, it remains a challenge to produce a continuous flow of usable energy from sunlight, due to the diffuse and fluctuating nature of the solar irradiation. Therefore this project aims at developing new materials that can directly convert solar energy into energetic chemical species, also called “solar fuels”, which can be stored and distributed on demand. The PEC approach combines, in a single structure, a light absorbing material (usually a semiconductor), and a catalytic part for the redox reactions. The principle of PEC cell has been confirmed for production of H2 and O2 by water splitting at the laboratory scale. However among all the different materials and architectures tested, none is totally satisfying yet. This is due to the fact that it is difficult to combine high solar-to-chemical energy conversion efficiency with stability of the semiconducting material toward photo-corrosion. The project will use titanium dioxide as a starting material. TiO2 is known for its good stability for photo-electrochemical applications. However its performances are largely limited by its wide bandgap that only allows absorption of UV light. Therefore in order to improve its performances, this work will focus on developing novel synthesis methods that can modify the morphology and the electronic structure of TiO2. The first objective will be to synthesize 1D aligned TiO2 nanostructures which will improve the photo-generated charge transport. Then, a large part of the project will be devoted to the development of original co-alloyed TiO2 structures. This approach aims to introduce large atomic percentage of cationic and anionic species in substitution of Ti4+ and O2- in the TiO2 lattice. This insertion should be stoichiometric to achieve a balance of the charge between anions and cations. By an appropriate selection of anions/cations pairs, we can modify the electronic band structure of TiO2, with the aim to reduce its bandgap for a better solar light absorption. Furthermore, thanks to the charge balance, the co-alloying approach will provide a more stable crystalline structure with fewer defects than the classical mono-doping approaches. This last point is important to preserve a high mobility of charge carriers and avoid their recombination. Cationic species insertion will be achieved simultaneously with the TiO2 nanotubes growth by an original in-situ method while the anion insertion will be achieved by adapted thermal treatments. Specific characterization methods will be developed to explore the properties of the co-alloyed materials, especially their crystalline structure (TEM with cartography, XRD) and electronic properties (photoluminescence, impedance spectroscopy). Ultimately, the knowledge we will gain on co-alloying method will be used to synthesize TiO2-NTs photo-electrodes with variable co-alloying elements concentrations, in order to absorb photon with different energies gradually in the thickness of the film. We expect these original structures will provide a better light absorption with efficient transport of charge carriers. To further improve the PEC properties of the co-alloyed TiO2 photo-electrodes, we will deposit catalytic nanoparticles on their surface to enhance the charge transfer and the overall efficiency of the reaction. Finally, the modified TiO2 nanostructures will be tested in PEC experiments in different conditions (such as irradiation, electrolyte pH) to identify the best approaches and modifications to reach stable and highly efficient solar-to-chemical energy conversion.

This project deals with the exploration of the possibility to use control theory tools for the design of vibrational piezoelectric energy harvesters (vPEH) devoted to supply tracking devices in migratory birds. The proposed explored techniques, radically different and scientifically novel relative to existing design methods of vPEH, will provide four major advantages: i) giving methodological designs, ii) pushing the actual limitation on power density, iii) introducing robustness for the harvested energy over a frequency variation of the ambient vibrations, iv) and permitting the substantial increase of their autonomy. The impact of the resulting vPEH to birds tracking are evident: volume and weight radically small allowing to equip more species of birds while than the actual possibility, devices autonomy extremely high (calculated for the bird entire life), and safety and harmlessness for the equipped animal thanks to the reduced sizes and weights.

Solar energy conversion and storage by Concentrated Solar Power (CSP) technologies receive an increasing attention because the integrated thermal energy storage (TES) system enhances the reliability, the dispatchability (production of electricity on demand) and reduces the operational cost of CSP plants (increase of annual capacity factor). Currently available options of TES system for CSP applications mainly include two-tank storage and single tank thermocline. Two-tank storage is the most common design and widely used in which hot and cold fluids are located into two separate tanks. In single-tank thermocline storage, both hot and cold fluids are stored within the same tank, but separated by a temperature gradient (stratification) during different operating periods. It is a more cost competitive (about 35% cheaper compared to two-tank storage) and efficient option: space compactness, reduced thermal loss, use of cheap solid materials as fillers and no extra heat exchanger needed between hot and cold tanks. However, no industrial-scale prototype was built and tested in the world since about 30 years. The main scientific barriers include: (1) lack of detailed data obtained by independent research organization; (2) reduced controllability of the temperature stratification which may be strongly disturbed by maldistribution of the injected inlet fluid flow; (3) non-optimized packing configurations of solid fillers. How to overcome the flow maldistribution problem is actually one major challenge. In fact, the improper design of fluid distributor/collector may cause the flow non-uniformity, local turbulence and recirculation. The mixing of hot and cold fluids and the disturbance of the temperature stratification (increase of the thermocline thickness) will reduce the energy efficiency of the system and the storage capacity. The general objective of this project is to design and develop a single tank thermocline technology with high energy efficiency and storage capacity by thermal stratification and optimized packing configurations, as a TES system for CSP plants. In fact, this innovative technology is not limited to CSP applications but can be applied in the TES sector in general. The major novelties of the proposal include: (1) systematic studies from the design tools, the modeling, local experiments to the prototypes testing and scaling up guidelines. All these steps were never performed before with the purpose of developing a validated model that can be applied to thermocline tank scaling-up; (2) optimized baffled fluid distributor/collectors to solve the flow maldistribution problem, which was rarely tackled before. The energy efficiency improvement and the storage capacity enhancement by maintaining the undisturbed temperature stratification in the thermocline will be highlighted; (3) use of recycling materials as fillers to reduce the material cost (by a factor of 5 to 10), an idea developed in the framework of a previous ANR project SOLSTOCK, but has never been demonstrated at pilot scale (>100 kWth). The proposal is thus ambitious. It presents a research of multi-scale nature from the fundamentals (3D modeling, fluid management) via a lab-scale experiments for hydrodynamic study and fluid/solid interactions, to the field testing of pilot-scale prototypes with different heat transfer fluids and global performance evaluation/optimization of the TES system. Finally it includes steps towards the system integration optimization, the scaling-up issue and the commercialization of the thermocline technology for CSP plants. The project will be realized in collaboration between two academic partners (LTEN-CNRS and PROMES-CNRS) and two industrial partners (Eco-Tech Ceram and ADF PROCESS INDUSTRIES). The consortium presents excellent and complementary experience and expertise. The strategies and methods for operating the project are well established to ensure its good progression.

Pc2TES aims at developing a new kind of materials with high potential for cost-effective compact thermal energy storage (TES) at high temperature. The proposal is based on a ground-breaking idea which consists in using chemical compounds formed during peritectic transitions. The term peritectic refers to reactions in which a liquid phase (L) reacts with at least one solid phase (a) to form a new solid phase (ß). The reaction is reversible and takes place at constant temperature. The formed phase (a) is either a solid solution of one of the components, an allotropic phase of one of the components, or a new stoichiometric compound. In such materials, the thermal energy will be stored by two consecutive processes: a melting/solidification process and a liquid-solid chemical reaction. On cooling (discharge process), the pro-peritectic phase ß(s) starts to nucleate once the liquid phase reaches the liquidus temperature, and then it grows until the peritectic temperature is reached. At this point, the liquid phase reacts with ß(s) to form a(s). On heating (charging process), the solid a(s) decomposes at the peritectic temperature into a liquid phase and the solid ß (s). Then, the solid ß(s) melts. As far as we know, this idea has never been proposed before and no team in the world is exploring it. It follows the recent preliminary research conducted by partner 1 (I2M) and might lead to a TES technology with higher performances and lower cost than those currently used or investigated. The proposal will focused on the 300-600°C temperature range, which allows covering a wide spectrum of significant and challenging applications. Compared to the state-of-the-art in TES at high temperature, the main expected advantages of using peritectic compounds are as follows: Compact TES. The effective energy density provided by the liquid-solid reaction leading to the peritectic compound lies within the interval 200-400 kWh/m3 in many cases, whereas it can be as high as 400-650 kWh/m3 when the energy associated to the melting/solidification of the pro-peritectic solid is added. These values are comparable (even higher) to those of gas-solid reactions under investigation in the world and make peritectics attractive for large-scale TES applications. Simple TES technology. Contrary to gas-solid reactions in which chemical reactants have to be separated, the liquid phase and the solid phases involved in peritectic formation separate and recombine by themselves. Moreover, the storage material works at atmospheric pressure both in charge and in discharge. As a result, simple storage concepts, like one-single tank with storage material in bulk and embedded heat exchanger, will apply. Cost-effective TES solutions. The investment cost (as well as those of operation and maintenance) will be therefore much lower than that of the technologies based on solid/gas reactions. Moreover, as the expected volumetric energy density is much higher than that of currently used phase-change materials, the investment cost should be lower than that of latent heat storage technologies and probably close to that of the cheapest sensible heat storage systems. To summarize, the perictectic compounds could lead to TES solutions gathering the advantages of the technologies currently used or investigated while avoiding their respective drawbacks.