The present master thesis was done during the spring of 2018. A cottage located in Vifors is studied with regard to its heating requirements. At the time of the study, the house could not be inhabited the whole year because there was no tap hot water available and the space heating demand was covered by electricity. Thus, an alternative heating supply is required to be developed. As a strategic prerequisite, the solution should be achieved considering both solar thermal collectors and a heat pump.First, the characteristics of the building were collected/determined in order to obtain the total heating demand per month and hence annually. Parameters such as the U-values, roof orientation, room dimensions, ventilation rates and internal gains were required to configure the building model in the software IDA ICE 4.8. In addition, the amount of tap hot water required per year was determined as 17 m3 per year. Cold water at 5 °C had to be heated until 55 °C to obtain the tap hot water.Once the heating requirements were known, the most suitable solution was to use a combi system (solar thermal collectors and a heat pump). Solar energy could fulfil the demand in the summer and the heat pump provided energy in the winter. For a commercial model of the flat solar thermal collector (Vitosol 100-F) the solar system was sized according to the heating demand in the summer time. The maximum energy that could be obtained from the solar collectors in summer was calculated, the rest of the demand had to be fulfilled by a heat pump, model WPL-18 E.The achieved solution is compounded by the heat pump and 3 solar thermal collectors with a surface of 2.33 m2 each. The solar energy obtained is 1 843 kWh per year, which covers 9 % of the total annual heating demand (20 098 kWh). However, the 98 % of the heating demand during the summertime comes from the solar collectors. The investment cost is 113 900 SEK and the payback period is estimated in 8 years.

Solar thermal collectors at high latitudes have been studied, with emphasis on concentrating collectors. A novel design of concentrating collector, the Maximum Reflector Collector (MaReCo), especially designed for high latitudes, has been investigated optically and thermally. The MaReCo is an asymmetrical compound parabolic concentrator with a bi-facial absorber. The collector can be adapted to various installation conditions, for example stand-alone, roof- or wall mounted. MaReCo prototypes have been built and outdoor-tested. The evaluation showed that all types work as expected and that the highest annually delivered energy output, 340 kWh/m2, is found for the roof MaReCo. A study of the heat-losses from the stand-alone MaReCo lead to the conclusion that teflon transparent insulation should be placed around the absorber, which decreases the U-value by about 30%. A method was developed to theoretically study the projected radiation distribution incident on the MaReCo bi-facial absorber. The study showed that the geometry of the collectors could be improved by slight changes in the acceptance intervals. It also indicated that the MaReCo design concept could be used also at mid-European latitudes if the geometry is changed. A novel method was used to perform outdoor measurements of the distribution of concentrated light on the absorber and then to calculate the annually collected zero-loss energy, Ea,corr, together with the annual optical efficiency factor. A study using this method indicated that the absorber should be mounted along the 20º optical axis instead of along the 65º optical axis, which leads to an increase of about 20% in Ea,corr. The same absorber mounting is suggested from heat loss measurements. The Ea,corr at 20º absorber mounting angle can be increased by 5% if the absorber fin thickness is changed from 0.5 to 1 mm and by 13% if two 71.5 mm wide fins are used instead of one that is 143 mm wide. If the Ea,corr for the standard stand-alone MaReCo with 143 mm wide absorber mounted at 65º is compared to that of a collector with a 71.5 mm wide absorber mounted at 20º, the theoretical increase is 38%.

The main task of the master project is to design a new energy efficient municipal house in Drnholec. The building has two above-ground floors and partial basement. It has a two-part flat roof. One part is green, the other has the bituminous roofing. The basement contains storage spaces and a boiler room. The ground floor contains an entrance hall, toilets, restaurant, a kitchen with storage and a hall with elevated stage. The first floor contains two club rooms, toilets and a room for the air conditioning system. The vertical load-bearing structures are designed from ceramic walls. Internal walls are designed from ceramic blocks. The horizontal load-bearing structures are designed from the pre-stressed Spiroll panels. The building envelope is insulated with mineral wool. The second part of the master project focuses on designing HVAC, lighting and sewage (including stormwater storage basin). The building utilizes an automatic biomass boiler as the main heating energy source. The summer domestic water heating is supported by photovoltaics. The third part of the master project assesses and compares heating of water by photovoltaics and solar thermal collectors. The project was carried out in the AutoCAD, DEKSOFT, Excel and Word.

Η ηλιακή ενέργεια αποτελεί μια από τις κύριες Ανανεώσιμες Πηγές Ενέργειας (ΑΠΕ). Μπορεί να αξιοποιηθεί είτε μετατρεπόμενη σε ηλεκτρισμό είτε σε θερμότητα. Για τη μετατροπή της σε ηλεκτρισμό η κύρια τεχνολογία που χρησιμοποιείται είναι η τεχνολογία των φωτοβολταϊκών. Αντίστοιχα, για την μετατροπή της σε θερμότητα χρησιμοποιούνται ευρέως οι τεχνολογίες των επίπεδων θερμικών ηλιακών συλλεκτών και των θερμικών συλλεκτών σωλήνων κενού. Βασικό ζητούμενο και στις δύο περιπτώσεις αποτελεί η μεγιστοποίηση της αποδοτικότητας τους. Μια από τις μεθόδους που μπορεί να χρησιμοποιηθεί για την αύξηση της αποδοτικότητας μιας ηλιακής συσκευής είναι η χρήση ενισχυτικών ανακλαστήρων. Επίσης, στις συνήθεις τεχνολογίες φωτοβολταϊκών που εφαρμόζονται σήμερα, η μείωση της θερμοκρασίας λειτουργίας τους βελτιώνει την απόδοση τους. Η διπλωματική ερευνητική εργασία που ακολουθεί περιλαμβάνει τη συγκριτική μελέτη φωτοβολταϊκών διατάξεων, επίπεδων θερμικών συλλεκτών και συλλεκτών σωλήνων κενού. Μελετήθηκαν συστήματα φωτοβολταϊκών με τη χρήση διαφόρων μεθόδων ψύξης, ενεργητικών και παθητικών. Επίσης μελετήθηκε η αύξηση της αποδιδόμενης ηλεκτρικής ενέργειας των φωτοβολταϊκών με χρήση ενισχυτικών ανακλαστήρων (ημικατοπτρικός ανακλαστήρας, ανακλαστήρας αλουμινίου (ματ), λευκός ανακλαστήρας). Υλοποιήθηκαν συνδυαστικά συστήματα με ταυτόχρονη ψύξη και χρήση ενισχυτικού ανακλαστήρα και μελετήθηκε η συμπεριφορά τους. Ακόμα, μελετήθηκε η αύξηση της αποδιδόμενης θερμικής ενέργειας επίπεδου ηλιακού θερμικού συλλέκτη με προσθήκη ενισχυτικών ανακλαστήρων (καθρέπτης, ανακλαστήρας αλουμινίου και λευκός ανακλαστήρας). Τέλος, κατασκευάστηκε διάταξη θερμικού συλλέκτη σωλήνα κενού με επίπεδη ανακλαστική επιφάνεια. Πραγματοποιήθηκαν πειράματα με την προσθήκη ενισχυτικών ανακλαστήρων (ημικατοπτρικός ανακλαστήρας, ανακλαστήρας αλουμινίου και λευκός ανακλαστήρας) και μελετήθηκε η αύξηση της θερμικής απόδοσης του συλλέκτη. Με βάση τα αποτελέσματα των πειραμάτων, εξάγονται αντίστοιχα συμπεράσματα και παρατίθενται προτάσεις σχετικά με τις διατάξεις αυτές. / Solar energy is one of the main Renewable Energy Sources (RES). It can be utilized by being transformed into electricity or heat. The main technology used to transform solar energy into electricity is photovoltaics. Respectively, flat plate solar thermal collectors and evacuated tube solar thermal collectors are the technologies mostly used to transform solar energy into usable heat. One of the main concerns on both cases, is the maximization of their performance. The use of booster reflectors is one of the methods that can be implemented in order to increase the performance of a solar device. Also, a method to increase the performance of the main photovoltaic technologies used at the moment, is to cool them. The following diploma – research thesis includes the comparative study of photovoltaic systems, flat plate solar thermal collectors and evacuated tube solar thermal collectors. Photovoltaic systems with the use of various cooling methods, active and passive, were studied. The increase of the photovoltaic electrical output using booster reflectors (semi specular, aluminum reflector and white reflector) was also studied. Combined systems were implemented, with simultaneous cooling and usage of booster reflector, and their behavior was observed. In addition, the increase of the thermal output of a flat plate collector by using booster reflectors (mirror, aluminum reflector and white reflector) was studied. Finally, an evacuated tube solar thermal collector system with an embedded reflective surface was implemented. Experiments were carried out with the addition of booster reflectors (semi specular, aluminum reflector and white reflector) and the increase of the collector’s thermal output was measured. Based on the experimental results, conclusions and suggestions are made about these systems.

As energy prices keep increasing, energy efficiency measures have come to the spotlight, especially in the residential sector. In this context, energy audits appear as powerful tools in order to assess the energy use and cost of energy of a dwelling, and identify possible energy saving measures that increase the energy efficiency and reduce costs. This work performs an energy audit of a single-family house (SFH) built in the 1970s which uses district heating, located in Gävle, Sweden. An empirical and quantitavive approach is followed, where energy data from the bills of 2022 together with on-site ventilation measurements is combined as a way to determine the energy inflows and outflows of the dwelling. Results concluded that the ventilation needs to be improved as a way to meet the Swedish building regulations. In addition, the energetic situation could be improved by means of the installation of solar photovoltaic (PV) modules to cover part of the electricity demand and solar thermal collectors to cover part of the domestic hot water demand. These measures would decrease the costs of the energy bills 4689 SEK/year at the time they would provide a source of renewable energy. The replacement of windows was also studied, concluding the payoff time to be excessively long to be accepted.

Οι ανανεώσιμες πηγές ενέργειας (ΑΠΕ), όπως η ηλιακή και αιολική ενέργεια μπορούν να προσφέρουν εναλλακτικούς τρόπους παραγωγής ενέργειας. Κάθε μορφή ΑΠΕ έχει τις δικές της ιδιομορφίες και μπορούν να εφαρμοστούν είτε σε μεγάλες εγκαταστάσεις παραγωγής ηλεκτρικής και θερμικής ενέργειας είτε σε μικρότερες μονάδες όπως στα κτίρια. Ενδιαφέρον παρουσιάζει η συνδυασμένη αξιοποίηση των παραπάνω ενεργειακών πηγών, ιδίως για την κάλυψη των ηλεκτρικών και θερμικών αναγκών των κτιρίων. Αντικείμενο της διπλωματικής αυτής εργασίας είναι η μελέτη ενός συστήματος αποτελούμενο από μικρή ανεμογεννήτρια, φωτοβολταϊκά πλαίσια και θερμικό ηλιακό συλλέκτη. Αρχικά γίνεται αναφορά στα επιμέρους συστήματα ΑΠΕ από τα οποία αποτελείται η εγκατάσταση. Στη συνέχεια, αναλύονται τα μετεωρολογικά δεδομένα της περιοχής και ακολουθεί η ενεργειακή μελέτη της συμπεριφοράς του υβριδικού συστήματος. Το κύριο θέμα που εξετάζεται είναι η παροχή ηλεκτρικής ενέργειας για θέρμανση του νερού σε περιπτώσεις που υπάρχει πλεόνασμα ηλεκτρικής ενέργειας. Επίσης αναλύεται η προοπτική συνδυασμού υβριδικών/φωτοβολταϊκών συλλεκτών με Α/Γ. Τέλος παρατίθενται τα συμπεράσματα και οι εκτιμήσεις σχετικά με τη συμπεριφορά του υβριδικού συστήματος στις μεταβολές της ταχύτητας του ανέμου και της ηλιακής ακτινοβολίας σε ημερήσια και ετήσια βάση. / The renewable energy sources (RES) like solar and wind energy can offer an alternative solution to produce power. Each form of RES, has its own specifications and they can applied in big installations of production electric and thermal energy or in smaller units as the buildings. This thesis investigates the performance of a system consist of a small wind turbine, solar photovoltaic modules and solar thermal collector. In the beginning, the design and components of installation is presented. Then, the measured data are used to analyzed the meteorological condition of test site and evaluate the performance of the hybrid system. The main concept, regarding the energy use of electrical to heat water in case that there is surplus of it, is presented. Finally conclusions and considerations about the behavior of hybrid system from the daily and yearly variation of wind speed and solar radiation are included.

The solar hot water storage tank is off great importance in the solar collector array. It allows transformed energy accumulation thus deals with the inconsistency between supply and demand. The suitable design of the storage tank can improve system efficiency. The storage capacity represents the balance between the amount of stored hot water and the tank's heat losses. The design of the storage capacity is based on three hypotheses. The coverage of hot water demand by solar energy, the ratio between storage capacity and solar thermal collector area and the prediction that the storage capacity corresponds to one- to twofold hot water demand. The purpose of this thesis is to share an understanding of the solar storage tanks design and to improve the design through numerical simulation, experimentations and general calculations. It also focuses on the confirmation of the used hypotheses and determination of the best way to design the solar storage tank for general practice and further potential discussions. The simulation model has three variables – the storage capacity, collector area and the number of occupants. The intent is to find the interdependence of these three variables. The purpose of the simulations is to modify the design of the solar tank based on the mutual influence of studied parameters. The modifications are performed based on the users' needs.