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[en] Under the current macro-economic trends, the so far abundant support system for renewables (mainly in the form of feed-in-tariffs and quota systems) has been drastically modified. In many EU countries, companies are trying to find alternative ways to secure financing for their renewable energy projects. Therefore, new ways of attracting private capital for the realisation of green energy goals have to replace the old schemes. Some new forms of financing are coming together with the EU Cohesion Policy 2014-2020 (project guarantees, packaging of small project for micro-financing schemes at the regional level, preferential loan instead of subsidies etc.). Advanced financial structures are likely to play an increasingly important role in the allocation of risk and reward among different investor classes. The finance and investment gap needs to be filled by the private sector. The challenge is to identify the appropriate policy options and financial tools to attract and scale-up private investments. There are, however, already innovative and promising business and financial models to promote the deployment of RES in the EU. The aim of the EurObserv'ER case studies is to find such examples and describe them so as to put forward the best practices and the replicability of the future promising financing mechanisms. EurObserv'ER will aim at choosing only the most promising ones and try to describe them in order to promote replicability in other geographical areas. The selection criteria for the choice of case studies should ensure (i) diversity across regions and RES, (ii) diversity across finance instruments/mechanisms, (iii) success of approach and its potential to be replicated, (iv) and a wide range of the 'size' of actors/ investors and the resulting RES investments (capacity). The current selection also takes into account the fact that there were already some case studies published in 2014, 2015, 2018 and 2019. These are also available for download on the project web site: www.eurobserv-er.org
[en] In this review work, energy harvesting methods for waste heat with small temperature differences between heat source and sink are discussed. At present, many methods are tried and employed to utilize this type of waste heat. A typical example is found in a conventional power generation system. By utilizing this type of waste heat, additional energy can be produced in regular power generation systems. Up to this point, two energy harvesting methods have been introduced and applied for the use with this type of waste heat. One is a method using an organic Rankine cycle (ORC) while the other is a method using a thermoelectric generation (TEG). An ORC is a Rankine cycle that can be applied to this type of waste heat using organic fluids such as refrigerants as working fluids instead of water used in a typical Ranking cycle. On the other hand, a TEG utilizes Peltier, Seebeck, and Thomson effects caused by the temperature difference between the heat source and sink for energy harvesting. In this work, various aspects associated with the use ORC and TEG for waste heat harvesting with small temperature differences between the heat source and sink.
[en] Highlights: • Bulk Cu2ZnSnSe4 materials are directly produced by combustion synthesis under gas pressure or high gravity. • Simultaneous densification is finished during synthesis to realize one-step preparation of dense samples. • By In-doping the Cu2ZnSn0.9In0.1Se4 sample shows an enhanced ZT of 0.59 at 773 K. Thermoelectric materials are attractive for solar thermal energy conversion and waste heat recovery. The preparation of bulk thermoelectric materials usually involves multi-step processes with considerable time and energy consumption. Here we report an alternative way called combustion synthesis to realize one-step and fast fabrication of bulk Cu2ZnSnSe4 thermoelectric materials. The combustion synthesis was carried out in 2 MPa Ar gas atmosphere or in a high-gravity field in order to reduce the porosity in samples and complete simultaneous densification during synthesis. Nearly full-dense Cu2ZnSnSe4 samples with a porosity of 2ZnSnSe4 materials prepared by other methods. The ZT of the Cu2ZnSnSe4 samples was clearly improved by partial substitution of Sn with In, and reached 0.59 at 773 K for the composition of Cu2ZnSn0.9In0.1Se4. Compared with the conventional melt growth and powder sintering methods, combustion synthesis offers a fast, one-step, and furnace-free way for directly producing bulk Cu2ZnSnSe4 samples, which may open up new possibilities for synthesis and applications of Cu2ZnSnSe4-based thermoelectric materials.
[en] Photothermal conversion is one of the most effective ways of absorbing and utilizing solar energy. The key issues of photothermal conversion are seeking for nanofluids with strong and wide-range sunlight harvesting. In this work, near-infrared (NIR) light absorbed Bi2WO6 is first exploited for solar thermal conversion. However, the photothermal conversion efficiency is low owing to its insufficient NIR-light absorption. After coating Au nanoparticles on Bi2WO6 nanosheets, the localized surface plasmon resonance effect of Au nanoparticles enable Bi2WO6 show strong optical absorption. Au/Bi2WO6–H2O nanofluids have higher temperature rise and better photothermal conversion efficiency than Bi2WO6 and the base fluid water. The present work not only explore a new way for improving the photothermal conversion efficiency of NIR-light nanofluids, but also help design and prepare novel broad-band sunlight absorption nanofluids.
[en] In regions of hot and dry climate, as in part of the north, northeast and central-west regions of Brazil, intense solar radiation in buildings increases the consumption of electrical energy with air conditioning, especially in buildings with low thermal resistance fences. Although in Brazil the energy matrix uses mainly renewable sources, the impacts of the implantation of the plants are not negligible. Bioclimatic architecture offers passive solutions for thermal comfort in buildings with low investment, low maintenance and good thermal efficiency. In this context, a bioclimatic residence was built, applying different compositions of walls to evaluate their thermal properties in a real scenario. This work evaluated the internal and external temperatures of each type of wall composition for one year. Other physical parameters, such as relative humidity, solar irradiance and paint reflectance were also measured and analyzed. Costs and savings were calculated in a brief feasibility study, pointing to thermal insulation with Expanded Polystyrene (EPS) as an affordable solution to the heat problem caused by sunlight and the consumption of electrical energy with air conditioning. (author)
[en] This thesis deals with an experimental and theoretical study of micro-structured silicon surfaces, obtained by processing in SF6/O2 plasma at cryogenic temperatures. Texturing which results from this treatment gives remarkable properties to these surfaces. One of them is the ability to trap and absorb light, resulting in a black color of the surface, hence the name of Black Silicon. This property that we find in the visible and near infrared spectral ranges, is of particular interest for solar energy conversion, both through photovoltaic and photo-thermal means. The study that we conducted, however, covered a much wider spectral range, extending to the Tera-hertz. For this purpose, different spectral characterization techniques have been implemented. Analysis of the results was also done using electromagnetic simulations. Correlations were found between the optical and morphological characteristics of micro-structured surfaces. The analysis of images taken by electron microscopy allowed sketching a theory attempting to explain the mechanism of formation of the microstructures of Black Silicon. Finally, a micro-component has been fabricated towards implementing the first part of this application work. It is a photo-thermal conversion device that incorporates platinum thermo-resistance on a surface of Black Silicon, realized on a thermally insulated Silicon membrane. (author)
[fr]Cette these porte sur une etude experimentale et theorique de surfaces micro-structurees de silicium, obtenues par traitement dans un plasma SF6/O2 a des temperatures cryogeniques. La texturation qui resulte de ce traitement confere a ces surfaces des proprietes remarquables. L'une d'entre elles est la capacite de pieger et absorber la lumiere, qui se traduit par une couleur noire de ces surfaces, d'ou l'appellation Black Silicon. Cette propriete qu'on retrouve dans la gamme spectrale du visible et du proche infra-rouge, presente un interet particulier pour la conversion d'energie solaire, aussi bien par voie photovoltaique que par voie photo-thermique. L'etude que nous avons menee a toutefois porte sur une gamme spectrale plus large, s'etendant jusqu'aux Terahertz. A cet effet, differentes techniques de caracterisation spectrales ont ete mises en oeuvre. L'analyse des resultats a ete effectuee egalement au moyen de simulations electromagnetiques. Des correlations ont ete mises en evidence entre les proprietes optiques et les caracteristiques morphologiques des surfaces microstructurees. L'analyse d'images prises au microscope electronique a permis d'esquisser une theorie pour tenter d'expliquer le mecanisme de formation des microstructures de Black Silicon. Enfin, un microcomposant a ete realise en vue de mettre en oeuvre le premier volet applicatif de ce travail. Il s'agit d'un dispositif de conversion photo-thermique qui incorpore des thermo-resistances en platine sur une surface de Black Silicon realisee sur une membrane thermiquement isolee. (auteur)