The energy sector is currently in a state of change as conventional energy sources are questioned by the need of new clean and sustainable energy sources to satisfy the global energy demand in the long term. Renewable energies respond to this increasing demand and solar energy is an advanced example of them. Photovoltaic modules are experiencing a steady reduction in their production costs. It is needed that this trend continues and, along with it, their propagation and expansion in the market continues. One way of reducing production costs is by using inexpensive light concentrators to increase the output of the costly photovoltaic cell. In this respect, the Solarus AB hybrid PV/T collector has been designed based on this principle. This collector is a CPC (Compound Parabolic Collector) and belongs to the MaReCo (Maximum Reflector Collector) family. The aim of this thesis is to deeply investigate this technology in two main areas. Firstly, the collector will be tested both electrically and thermally in order to evaluate its performance. To do so, a solar test rig has been built and connected at the building Hall 45 of Högskolan i Gävle, Gävle, Sweden. The second main area of investigation of this thesis is to determine the optimal price for the Solarus AB hybrid PV/T collector in order to be competitive in the solar energy market. This study will be based in the current market prices of photovoltaic and thermal collectors. Regarding the electrical performance of the collector, the results obtained show that the front side of the receiver produces more electricity throughout the day than the reflector side. This has guided Solarus AB to decide to change the design of its receiver to improve its performance. With the current design, it has been obtained a peak power at STC of 220W. In relation with the thermal part, the heat losses of the collector have been estimated obtaining a U value of 6,8W/(m2*K), a thermal optical beam efficiency of 63,5% and a total optical beam efficiency of 74,5%. The price market study of photovoltaic and thermal collector has shown that 2m2 of the Solarus AB hybrid PV/T collector produces approximately the same annual electricity and heat as 1,1m2 of a photovoltaic module with an efficiency of 15,5% and a flat plate collector of 0,85m2 of aperture area. According to the market study, its cost is equivalent to 190€ for the PV module and 220€ for the flat plate collector. This means that the price of the Solarus AB hybrid PV/T collector should be lower than 410€.

Despite the share of renewable energies worldwide is increasing, which can help in reducing the CO2 emissions, their unpredictability has become a problem due to the mismatch between generation and demand. Among the different alternatives to solve this problem, energy storage is a very interesting solution. Depending on the aim of the storage, there are two types: intra‑day or seasonal. The former corresponds normally to a highly efficient and high‑cost storage, such as the Li‑ion; whilst the latter is a low efficient and low‑cost storage. An example of this second type of storage is the power‑to‑heat‑to‑power storage, whose efficiency is mainly determined by the heat‑to‑power converter, and it can be increased if the waste heat produced in the converter is reused in a combined heat and power system.Given that the residential sector represents a large amount of the global energy use (both electricity and heat), this study has considered a power‑to‑heat‑to‑power storage in a fully electrified residential building with a PV installation in order to increase self‑consumption and reduce the cost. Both the heating, electricity and cooling demand are supplied by the system.As this storage technology is currently under an early stage of development, this project aims to understand the main challenges for this storage and the advantages over a very well settled technology, such as the Li-ion. In order to achieve this objective, a model has been created in Matlab. A parametric study has been conducted in which optimum sizing of the components for several scenarios have been considered, as a means to identify the most important parameters that could hinder the feasibility of the power‑to‑heat‑to‑power storage system.From the optimization it was concluded that the scenarios with a thermally driven heat pump for cooling, resulted in larger installations leading to higher cost due to the low coefficient of performance. Regarding the other scenarios which consider an electrical heat pump for cooling, this technology can surpass the Li-ion performance for heat‑to‑power efficiencies over 20 %. In these cases, the feasibility is clearly hindered by the cost per energy capacity, which must be below 5 €/kWh and could be achieved with silicon; and the cost per power capacity that must be around 300 €/kW. An example of a heat‑to‑power converter could be the TPV technology which is a solid‑state converter, whose efficiency is currently around 30 % and is expected to reduce its cost up to 300 €/kW. In smaller systems, in which the stand‑by heat losses have more impact over the system’s feasibility due to the larger surface to volume ratio, it is imperative to reduce these heat losses, as well as reduce the cost per energy and power capacities. In addition, it is remarkable that there is no significant improvement when increasing the heat‑to‑power efficiencies over certain values. To finish, as this technology increases its feasibility when implemented in large systems, further studies should be done in the industrial and tertiary sector.

Main purpose of the thesis is to create proposal of the photovoltaic hybrid system for commercial building in accordance with applicable rules for energy savings program. The introductory part of the thesis describes the rules regarding the photovoltaic system parts. The next part of the thesis describes the available technical solution for realization of the photovoltaic system design and the possibilities of electric energy accumulation in these systems and how to deal with power overflows using the power flow controller and what is the negative impacts on the distribution network when switching the connected load. In the next part the design of the PV system is carried out according to the valid assumptions described in the theoretical part of the thesis. Verification of power flow controller and measurement results in UEEN laboratories. The last part of the thesis is an evaluation of the economic part of the proposed system.

La limite théorique de rendement des cellules photovoltaïques simple-jonction est de l’ordre de 33% d’après le modèle de Shockley-Queisser, ce qui reste éloigné de la limite de Carnot, prédisant une limite maximale de conversion énergie solaire → électricité de 93%. L’écart important entre ces deux limites découle des pertes intrinsèques, essentiellement liées à la conversion inefficace du spectre solaire et à la disparité entre les angles solides d’absorption et d’émission. Pour surmonter ces pertes et se rapprocher de la limite de Carnot, trois stratégies sont envisagées dans cette thèse : les cellules multi-jonction àconcentration, la combinaison de la concentration et de la restriction angulaire et les systèmes hybrides PV/CSP. Chacune de ces stratégies est limitée par des mécanismes qui dégradent leur performance.L’objectif de cette thèse est donc de comprendre dans quelle mesure les différents mécanismes limitants sont susceptibles d’affecter les performances des différentes stratégies étudiées, et d’optimiser l’architecture des cellules dans le but d’accroitre leur efficacité de conversion. Dans ce but, un modèle détaillé de cellule solaire tenant compte des principaux mécanismes limitant a été développé. Un outil d’optimisation par algorithme génétique a également été mis au point, afin d’explorer l’espace des différents paramètres étudiés pour identifier les conditions d’opération optimales. Nous démontrons l’importance majeure que revêt l’adaptation des propriétés optoélectroniques des matériaux utilisés aux conditions opératoires, que ce soit dans le cas des cellules solaires à concentration endurant des pertes résistives significatives, ou encore dans le cas de cellules solaires fonctionnant à des niveaux de températures très supérieurs à l’ambiante. Enfin, nous avons déterminé l’effet des principaux facteurs limitant que constituent les pertes résistives et les recombinaisons non-radiatives sur les cellules solairessimultanément soumises au flux solaire concentré et à la restriction angulaire du rayonnement émis. / The maximum efficiency limit attainable with a single-junction PV cell is ~ 33% according to the detailed balance formalism (also known as Shockley-Queisser model), which remains far from the Carnot limit, predicting a solar to electricity efficiency upper value of 93%. The large gap between both limits is due to intrinsic loss mechanisms, including the inefficient conversion of the solar spectrum and the large discrepancy between the solid angles of absorption and emission. To overcome these losses and get closer to the Carnot limit, three different strategies are considered in this thesis: concentrated multi-junction solarcells, the combination of solar concentration and angular confinement, and hybrid PV/CSP systems. Each strategy is inherently limited by several loss mechanisms that degrade their performances. The objective of this thesis is, hence, to better understand the extent to which these strategies are likely to be penalized by these losses, and to tailor the cell properties toward maximizing their efficiencies. To address these questions, a detailed-balance model of PV cell accounting for the main loss mechanisms was developed. A genetic-algorithm optimization tool was also implemented, aiming at exploring the parameter space and identifying the optimal operation conditions. We demonstrate the uttermost importance of tailoring the electronic properties of the materials used with both multi-junction solar cells undergoing significant series resistance losses, and PV cells operating at temperature levels exceeding ambient temperature. We also investigate the extent to which series resistances losses and non-radiative recombination are likely to affect the ability of PV cells simultaneously submitted to concentrated sunlight and angular restriction of the light emitted by band-to-band recombination.