Investigation of concentrating solar thermal systems in building sector

The objective of this thesis is to investigate the application of Concentrating Solar Thermal (CST) systems of linear parabolic trough type, in the building sector.Firstly, the theoretical background of CST technology is investigated and the available tools for CST systems’ simulation in international level are evaluated. This knowledge is used as a basis for the development of a new computational routine (New Component TRNSYS Type240) in order to simulate the operation of CST systems parabolic trough type in a more realistic and reliable way compared to the current practice.The experimental procedure that was carried out as part of the thesis, was designed and conducted towards to CST parabolic trough collector’s energy efficiency estimation as an outcome of collector’s fluid inlet temperature, pressure and flow rate parameters. The experimental results were used to validate the computational routine by means of comparative valuation. Considering the comparison’s outcome between experimental and simulated results using the New Item TRNSYS Type240, was derived that the model has a very good accuracy in cases where the operating conditions are within the range given in the international standard EN ISO9806. Then, it was examined the CST systems application in buildings, by means of simulated tools. A range of applications, covering geographically and climatically the country and typologically the most common types of buildings and energy requirements that can be met with CST technology, were investigated. Furthermore, a parametric analysis and evaluation of 35 selected CST variables was carried out. The results showed that the use of CST systems can be considered as an energy-efficient solution, providing environmental advantages over conventional technologies. However, further actions are required towards to reduce their costs and improve their competitiveness.Το αντικείμενο της διδακτορικής διατριβής αφορά στη διερεύνηση της εφαρμογής των Συγκεντρωτικών Θερμικών Ηλιακών (ΣΘΗ) συστημάτων, παραβολικού τύπου γραμμικής εστίασης, στον κτιριακό τομέα. Αρχικά, διερευνάται το θεωρητικό τεχνολογικό υπόβαθρο των ΣΘΗ και εν συνεχεία αξιολογούνται τα σχετικά υπολογιστικά εργαλεία προσομοίωσης που είναι διαθέσιμα σε διεθνές επίπεδο. Η γνώση αυτή χρησιμοποιείται ως βάση για την ανάπτυξη της νέας υπολογιστικής ρουτίνας (New Component TRNSYS Type240) για την προσομοίωση της λειτουργίας των ΣΘΗ παραβολικού τύπου με τρόπο πιο ρεαλιστικό και αξιόπιστο σε σχέση με τα ως σήμερα εφαρμοζόμενα. Τα αποτελέσματα της πειραματικής διαδικασίας που διεξήχθη στα πλαίσια της διατριβής, χρησιμοποιήθηκαν για την επικύρωση της υπολογιστικής ρουτίνας μέσω της συγκριτικής αποτίμησής τους. Από τη σύγκριση των υπολογιστικών και πειραματικών αποτελεσμάτων, προκύπτει ότι το μοντέλο έχει μια πολύ καλή ακρίβεια για τις περιπτώσεις όπου οι συνθήκες λειτουργίας είναι εντός του εύρους που προβλέπει το διεθνές πρότυπο ΕΝ ISO9806. Στη συνέχεια, έγινε διερεύνηση της εφαρμογής ΣΘΗ στον κτιριακό τομέα, όπου με προσομοιωτικά εργαλεία εξετάστηκαν μία σειρά από εφαρμογές, καλύπτοντας γεωγραφικά/κλιματικά την χώρα και τυπολογικά τα πλέον διαδομένα είδη κτιρίων και ενεργειακών απαιτήσεων που μπορούν να καλυφθούν με την τεχνολογία των ΣΘΗ. Έγινε παραμετρική ανάλυση και αξιολόγηση 35 προσομοιώσεων επιλεγμένου ΣΘΗ συστήματος. Από τα αποτελέσματα συνάγεται ότι η χρήση των ΣΘΗ είναι ενεργειακά αποδοτική, διαθέτοντας περιβαλλοντικά πλεονεκτήματα έναντι των αντίστοιχων συμβατικών τεχνολογιών. Απαιτούνται, όμως, ακόμη δράσεις για τη μείωση του κόστους τους και τη βελτίωση της ανταγωνιστικότητάς τους

A new TRNSYS component for parabolic trough collector simulation

This study describes and evaluates a new simulation component for parabolic trough collectors (PTCs). The new simulation component is implemented in the TRNSYS software environment by means of new Type that is suitable for integration into the calculation of a whole concentrating solar thermal plant, in order to evaluate the energy production of a PTC. The main advantage of the new Type is that is derived from experimental data available on efficiency Test Reports, according to the current European and International standards, rather than the theoretical approach considered in the existing parabolic trough component of TRNSYS library. The performance of the new Type has been validated with real experimental data obtained from the DISS solar test loop in Plataforma Solar de Almería, Spain. The paper describes the modelling approach, presents the comparison of simulation results with measurements taken at the DISS facility and evaluates the results

Preparation of Phase Change Microcapsules with the Enhanced Photothermal Performance

The performance of solar-thermal conversion systems can be improved by incorporation of encapsulated phase change materials. In this study, for the first time, CrodathermTM 60 as a phase change material (PCM) was successfully encapsulated within polyurea as the shell supporting material. While preparing the slurry samples, graphite nanoplatelet (GNP) sheets were also incorporated to enhance the thermal and photothermal properties of the prepared materials. The morphology and chemical properties of these capsules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrum, respectively. The results show the spherical-like and core-shell structure of capsules with an average diameter size of 3.34 μm. No chemical interaction was observed between the core and the supporting materials. The thermal characteristics of the microencapsulated PCMs (MEPCMs), analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), indicate that the prepared samples with 0.1 weight percentage of GNP possess the latent heat of 95.5 J/g at the phase transition temperature of about 64 °C. Analyzing the rheological properties of the prepared slurry with 16 wt % of MEPCMs proves that the prepared material meet the requirements given by the heat transfer applications. The thermal storage capacity, good thermal stability, and improved photothermal performance of the prepared material make it a potential candidate for using in direct absorption solar thermal applications

Preparation of phase change microcapsules with the enhanced photothermal performance

The performance of solar-thermal conversion systems can be improved by incorporation of encapsulated phase change materials. In this study, for the first time, CrodathermTM 60 as a phase change material (PCM) was successfully encapsulated within polyurea as the shell supporting material. While preparing the slurry samples, graphite nanoplatelet (GNP) sheets were also incorporated to enhance the thermal and photothermal properties of the prepared materials. The morphology and chemical properties of these capsules were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrum, respectively. The results show the spherical-like and core-shell structure of capsules with an average diameter size of 3.34 μm. No chemical interaction was observed between the core and the supporting materials. The thermal characteristics of the microencapsulated PCMs (MEPCMs), analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), indicate that the prepared samples with 0.1 weight percentage of GNP possess the latent heat of 95.5 J/g at the phase transition temperature of about 64 °C. Analyzing the rheological properties of the prepared slurry with 16 wt % of MEPCMs proves that the prepared material meet the requirements given by the heat transfer applications. The thermal storage capacity, good thermal stability, and improved photothermal performance of the prepared material make it a potential candidate for using in direct absorption solar thermal applications

HOTRES: renewable energies in the hotels. An extensive technical tool for the hotel industry

The project HOTRES aimed at the systematic implementation of conditions for future massive applications of the renewable energies in the tourism industry. Under the umbrella of this project five renewable energy technologies were promoted (solar thermal, solar passive, solar PV, biomass and geothermal energy) in parallel in five EU regions (East Attica, Sicily, Alpes-Maritimes, Andalusia and Madeira) by the corresponding agencies and promotion centers following an extensive and intensive work program be composed of six elaboration phases. The purpose of this article is to esteem the results achieved in the technical-economic field of the relevant extensive technical support project in 200 hotels as well as to validate the strategic methodology applied for the promotion of the renewable energy technologies (RETs) through the technical assistance of the hotel SMEs. Finally, by proving the liability and economic viability of RET applications in hotels, the largest European hotel installation with solar thermal is presented within technical and economic details.Renewable energy Tourism Hotel Environment Solar thermal energy Geothermal energy Photovoltaic Biomass Solar passive

Decarbonization of industrial processes: technologies, applications and perspectives of low-temperature solar heat (80-150°C)

Low-temperature (80-150°C) solar collectors guarantee a very high efficiency (up to 60%) in the conversion of solar radiation into useful thermal energy. Moreover, solar thermal technologies are already reliable solutions, relatively cheap and widely available in the market. For that reason, solar collectors operating at low temperatures are among the most important sustainable technologies that can reduce the fossil fuel consumption of industrial processes and their corresponding carbon footprint. Unfortunately, Solar Heat for Industrial Processes (SHIP) is still mostly unused for several reasons, e.g., not easy identification of the appropriate applications (e.g., cleaning processes, drying, desalination) or lack of knowledge of the potential environmental and economic benefit of the use of SHIP technologies. For that reason, this work includes i) an overview of solar technologies for low/medium -temperature SHIP (80-150°C) ii) results obtained on the innovative design of the mirrors used in evacuated receiver tube by means of a variation in the shape of its internal reflector iii) estimation of CO2 saving using a solar field based on evacuated tube collector (ETC). The work also includes a comparison of the standard ETC solar plant with an ETC solar plant embedded with reflectors with innovative shape