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Within the framework of HYBUILD, an EU Horizon 2020-funded project, two innovative compact hybrid electrical/thermal storage systems for stand-alone and district connected residential buildings will be developed and tested in three demos located in Spain, France, and Cyprus. One of the innovative systems is aimed to be placed in buildings located in Mediterranean climate regions, where cooling loads are dominant, while the other system is intended for Continental climate regions, where the heating demand is dominant. Each system will include, among others components such as a sorption storage system and domestic hot water tanks, a latent thermal energy storage (LTES) system that will be connected to a heat pump through an innovative heat exchanger made of aluminium and filled with phase change material (PCM). In both cases, the heat pump works with electricity provided by a photovoltaic system that is, at the same time, connected to an electrical storage battery. The aim of using the LTES system is to enhance the use of solar energy, which will be translated into a reduction of the building energy consumption and related costs. This study focuses on the selection of the most suitable PCM to be used in each system. On the one hand, the LTES system of the Mediterranean system will be used to store cold to reduce the cooling demand. Taking into account that, according to the design parameters, the heat pump will require a refrigerant evaporation temperature around 2 ºC, and the building cooling system will require water supply in the range from 7 ºC to 12 ºC, the PCM melting temperature range should be within 0 ºC and 7 ºC. On the other hand, the LTES system of the Continental system will be used to store heat to reduce the domestic hot water (DHW) demand. The LTES will be located at the compressor outlet and will be charged by the hot refrigerant that exits the compressor at temperatures as high as 120 ºC. During the discharge process, the heat stored in the LTES will be supplied to the DHW at a temperature in the range between 50 ºC to 55 ºC. As a consequence, the range for the PCM melting temperature investigated in this case should be between 62 ºC and 68 ºC. Besides the melting temperature, other selection criteria considered include the PCM melting enthalpy and melting range, maximum allowed working temperature, density, thermal conductivity, availability, cost, and compatibility with aluminium. To decide the ideal PCM candidate for each system, a decision matrix was defined and used, by applying a weighted score to the selection criteria items according to their importance. The preliminary results indicate that for the Mediterranean system the best candidate is the commercial savE OM3 PCM, while for the Continental system, another commercial product PureTemp 63 is the most adequate option. This work was partially funded by the Ministerio de Economía y Competitividad de España (ENE2015- 64117-C5-1-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (GREiA 2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. Jaume Gasia would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2018 FI_B2 00100). This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 768824 (HYBUILD)

Les tecnologies d'emmagatzematge d'energia tèrmica (EET) esdevenen cabdals per tal de superar els inconvenients de les energies renovables. Els sistemes basats en aquesta tecnologia han de complir diversos requisits per tal de ser competitius en tots els nivells. D’entre tots els requisits, la present tesi doctoral està emmarcada en l'estudi dels tecnològics, i més concretament, en dos àmbits d'investigació. Per una banda, se centra en l'estudi de les condicions d’operació a càrrega parcial d’un sistema d’EET per calor latent amb l’objectiu d’optimitzar la seva estratègia de funcionament en un rang de temperatura comprès entre els 100 ºC i els 150 ºC. D'altra banda, aquesta tesi doctoral també se centra en l'estudi del concepte de fusió dinàmica en un sistema d’EET per calor latent de baixa temperatura (-10

Within the framework of IEA SHC Task 42 / ECES Annex 29, a simple tool for the economic evaluation of thermal energy storages has been developed and tested on various existing storages. On that account, the storage capacity costs (costs per installed storage capacity) of thermal energy storages have been evaluated via a Top-down and a Bottom-up approach. The Top-down approach follows the assumption that the costs of energy supplied by the storage should not exceed the costs of energy from the market. The maximum acceptable storage capacity costs depend on the interest rate assigned to the capital costs, the intended payback period of the user class (e.g. industry or building), the reference energy costs, and the annual number of storage cycles. The Bottom-up approach focuses on the realised storage capacity costs of existing storages. The economic evaluation via Top-down and Bottom-up approach is a valuable tool to make a rough estimate of the economic viability of an energy storage for a specific application. An important finding is that the annual number of storage cycles has the largest influence on the cost effectiveness. At present and with respect to the investigated storages, seasonal heat storage is only economical via large sensible hot water storages. Contrary, if the annual number of storage cycles is sufficiently high, all thermal energy storage technologies can become competitive.

El presente estudio evalúa experimentalmente el comportamiento de una parafina comercial, con una temperatura de cambio de fase d 58 ºC, como material de almacenamiento de energía térmica en su fase latente, también conocido como material de cambio de fase (PCM, del inglés Phase Change Material) para incrementar la eficiencia energética en sistemas de agua caliente sanitaria (ACS) y recuperación de calor industrial. Para determinar y evaluar posibles cambios en las propiedades químicas y termofísicas, se analiza el material a dos escalas de estudio diferente: escala de laboratorio (≈ 15 mg) y escala de planta piloto (≈100 kg). A escala de laboratorio, se realizan los siguientes análisis: calorimetría diferencial de barrido (DSC, del inglés Differential Scanning Calorimeter), análisis termogravimétrico (TGA, del inglés Thermogravimetric analysis), termociclado y espectroscopia de infrarrojo (IR). A escala de planta piloto, se realizan varios procesos de carga y descarga según en una instalación experimental diseñada y construida en la Universitat de Lleida, con un tanque de almacenamiento térmico basado en el concepto de tubo y carcasa. Se evalúan tres escenarios diferentes, según el caudal másico del fluido caloportador (HTF, del inglés Heat Transfer Fluid): 500 kg/h, 1500 kg/h i 2500 kg/h. Los parámetros estudiados son los tiempos y potencias de carga y descarga, los balances de energía del sistema y eficiencias del proceso. La evaluación en ambas escalas demuestra que la parafina RT-58 es un material adecuado para las aplicaciones propuestas. Los autores quieren agradecer la Generalitat de Catalunya por la mención de calidad al grupo de investigación GREA (2009 SGR 534). El trabajo está parcialmente financiado por el gobierno de España (ENE2011-22722). Esta investigación también ha sido financiada por el European Union's Seventh Framework Programme (FP7/2007-2013) a través de n° PIRSES-GA-2013-610692 (INNOSTORAGE) y No ENER/FP7/295983 (MERITS). Laia Miró quiere agradecer al Gobierno de España su beca de investigación (BES- 2012-051861).Finalmente agradecer a Gerard Peiró, Joan Tarragona y Camila Barreneche por su ayuda en el trabajo.

This research project contains the theoretical and numerical analysis of Lucifer, a new type ofcone-shaped solar collector, analyzing all the work done so far, studying and testing theprototype already made and finally giving a proposal according to the results obtained duringthe realization of this project.Firstly, a brief introduction to renewable energies is done since the design of this collectorshows a strong commitment with the development of the renewable and more concretely thesolar energy. Subsequently, a theoretical study of the light’s nature, as well as in optics, is donein order to on the one hand, explain and demonstrate the assumptions made and on the otherhand, explain all the phenomena that can occur within the solar cone. Finally, a new prototypeis calculated so to improve the design of the previous cone.For the redaction of this thesis some experts in different fields such as optics, physics,renewable energy and chemistry were consulted, being their comments, opinions andguidance an important part of this document.Additionally, as a last step in the research, some tests with a prism produced with the specificcharacteristics of the cone were done so to prove if all the calculations used for its realizationworked or not.To conclude this thesis, all the mistakes and results obtained were exposed and someproduction tips were added so to make easier for future researchers in this field to understandthe main characteristics of the system. Validerat; 20120615 (anonymous)

Aquest treball consta d’un estudi de les resistències en tancs d’emmagatzematge tèrmic de les centrals termosolars, per tal de conèixer i situar-nos en el mercat necessitàvem fer un anàlisis teòric i per tal de aplicar i testejar les resistències en els tancs o les plantes comercials necessitàvem experimentar amb les resistències, es per això que el treball està classificat en dos parts, una part teòrica i una part experimental. En la part teòrica s’ha buscat informació de totes les plantes termosolars del món i s’ha classificat en funció de diversos aspectes que s’han considerat rellevants, com per exemple: estat, localització, tecnologia, sistema d’emmagatzematge..etc. En cada cas s’ha fet un estudi a nivell nacional per comunitats autònomes i un estudi a nivell mundial per continents. En la part experimental s’ha descrit la planta pilot de l’edifici CREA de la UdL. Aquesta planta ens permet extrapolar els resultats obtinguts amb els que es podria obtenir en una planta termosolar comercial. Aquesta, consta d’un sistema de doble tanc que emmagatzema sals foses, un tanc fred i un tanc calent. Els experiments sols s’han realitzat en el fred. S’han testejat tres tipus de resistències: Resistència amb funda metàl·lica, amb funda aletejada i amb contacte directe. S’han pres les dades en les diferents resistències mitjançant sondes. I s’han representat els resultats en gràfics.

The selection of the proper thermal energy storage (TES) material for an application is crucial. On the one hand, these materials should have suitable thermal properties for the operational temperatures range of the systems they are planned to work for, such as thermal stability, high latent heat and high heat capacity. On the other hand, they should be available on the market and at low price. Besides, researchers have to bear in mind the importance of testing TES materials not only at laboratory scale but also at higher scale, since it has been demonstrated that some thermal characteristics are volume-dependant. In the present study, bischofite, a by-product obtained from the non-metallic industry in the North of Chile with desired thermal properties for mid-temperature applications (around 100 C), has been studied. A first analysis was performed in terms of comparing the thermal properties and cost of bischofite with other material previously studied as TES materials in order to evaluate its potential in both latent and sensible phases. Afterwards, a second analysis was experimentally performed in terms of testing bischofite at large-scale (204 kg) in a pilot plant facility. The experimental procedure consisted on several charging processes within two different temperatures ranges: from 50 C to 80 C and from 80 C to 120 C in order to study the behavior of the material in the sensible solid phase and latent phase respectively. The temperature profiles, the power given by the HTF, the energy balance in the storage system and the accumulation energy rate of the bischofite were analyzed. Results of both analysis showed that bischofite has potential as TES material for mid-temperature applications. The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under Grant agreement n PIRSES-GA-2013-610692 (INNOSTORAGE). The work was partially funded by the Spanish government (Project ENE2011-22722). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). The authors would like to acknowledge the collaboration of the company SALMAG. The authors acknowledge to FONDECYT (Grant No 1120422), CONICYT/FONDAP No 15110019, and the Education Ministry of Chile Grant PMI ANT 1201 for the financial support. Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). Andrea Gutierrez would like to thank to the Education Ministry of Chile her doctorate scholarship ANT 1106 and CONICYT/PAI NO 7813110010.

The present paper provides on one hand, a literature review of the different studies available in the scientific literature where the concept of multiple phase change materials (PCM) configuration, also named cascaded or multi-stage, has been presented and on the other hand, an experimental evaluation of the advantages of using the multiple PCM configuration instead of the single PCM configuration in thermal energy storage (TES) systems at pilot plant to fill the gap of experimental and high scales studies on this concept in the literature. Two PCM with melting temperatures in a temperature range of 150 e200 C were selected due to their high value of heat of fusion and compared: d-mannitol and hydroquinone. Three configurations were evaluated: (1) single PCM with hydroquinone, (2) single PCM with dmannitol and (3) multiple PCM with hydroquinone and d-mannitol. A discussion regarding the results on the specific energy stored and effectiveness as well as the evolution of the PCM and heat transfer fluid (HTF) through the time and at different and representative locations of the facility is presented. Results showed that the multiple PCMs configuration introduced an effectiveness enhancement of 19.36% if compared with single PCM configuration as well as a higher uniformity on the HTF temperature difference between the inlet and outlet. The work is partially funded by the Spanish Government (ENE2011-22722 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n PIRSES-GA-2013-610692 (INNOSTORAGE). Laia Miro would like to thank the Spanish Government for her research fellowship (BES-2012-051861).