Tesis por compendio / [ES] Uno de los mayores retos para el mercado de bombas de calor geotérmicas es el alto coste asociado a la perforación de los intercambiadores de calor geotérmicos. Conseguir unos intercambiadores de calor geotérmicos más eficientes reduciría dicho coste, ya que sería necesaria una menor longitud de intercambiador para obtener las mismas temperaturas de trabajo en él (misma eficiencia de la bomba de calor). La eficiencia térmica de un intercambiador de calor geotérmico está caracterizada por su resistencia térmica. Dicha resistencia térmica depende de una serie de elementos entre los que se encuentran: propiedades y caudal del fluido que recorre el intercambiador de calor, diámetro de la perforación geotérmica, geometría y materiales de la tubería del intercambiador de calor y las propiedades del material de relleno de la perforación (grouting). Cuanto mayor sea la resistencia térmica del intercambiador de calor, menor será el calor transferido entre el fluido caloportador y el terreno, traduciéndose en una necesidad mayor de longitud de intercambiador enterrado. Por lo tanto, es necesario una reducción de este parámetro al mínimo posible. En consecuencia, el objetivo principal de esta tesis doctoral consiste en, a partir de un modelo analítico comprensivo de cuantificación del impacto de los parámetros anteriores, realizar un estudio detallado para analizar su influencia combinada en la resistencia térmica del intercambiador geotérmico, pero también examinando dicho efecto en otros planos, como costes económicos de ejecución del intercambiador y de explotación (consumo eléctrico de la bomba de calor y costes de bombeo asociados). / [CA] Un dels majors reptes per al mercat de bombes de calor geotèrmiques és l'alt cost associat a la perforació dels bescanviadors de calor geotèrmics. Aconseguir uns bescanviadors de calor geotèrmics més eficients reduiria aquest cost, ja que seria necessària una menor longitud de bescanviador per a obtenir les mateixes temperatures de treball en ell (mateixa eficiència de la bomba de calor). L'eficiència tèrmica d'un bescanviador de calor geotèrmic està caracteritzada per la seva resistència tèrmica. Aquesta resistència tèrmica depèn d'una sèrie d'elements entre els quals es troben: propietats i cabal del fluid que recorre el bescanviador de calor, diàmetre de la perforació geotèrmica, geometria i materials de la canonada del bescanviador de calor i les propietats del material de farciment de la perforació (grouting). Com més gran sigui la resistència tèrmica del bescanviador de calor, menor serà la calor transferida entre el fluid termòfor i el terreny, traduint-se en una necessitat major de longitud de bescanviador enterrat. Per tant, és necessari una reducció d'aquest paràmetre al mínim possible. En conseqüència, l'objectiu principal d'aquesta Tesi Doctoral consisteix en, a partir d'un model analític comprensiu de quantificació de l'impacte dels paràmetres anteriors, realitzar un estudi detallat per a analitzar la seva influència combinada en la resistència tèrmica del bescanviador geotèrmic, però també examinant aquest efecte en altres plans, com a costos econòmics d'execució del bescanviador i d'explotació (consum elèctric de la bomba de calor i costos de bombament). / [EN] One of the biggest challenges for the ground source heat pump market is the high cost associated with drilling geothermal borehole heat exchangers. Achieving more efficient geothermal heat exchangers would reduce this cost, since a shorter exchanger length would be required to obtain the same working temperatures in it (same efficiency of the heat pump). The thermal efficiency of a geothermal heat exchanger is characterized by its borehole thermal resistance. This borehole thermal resistance depends on a number of parameters, mainly: properties and flow rate of the working fluid that flows through the borehole heat exchanger, diameter of the geothermal borehole, geometry and materials of the heat exchanger pipe and the properties of the borehole grouting material. The higher thermal resistance of the heat exchanger, the less heat is transferred between the heat carrier fluid and the ground, resulting in an increased requirement for the length of the buried heat exchanger. Consequently, it is essential to reduce this parameter to the minimum possible. Therefore, the main objective of this Ph. Doctoral Thesis is to carry out, based on a comprehensive analytical model of quantification of the impact of the above mentioned parameters, a detailed study to analyze their combined influence on the thermal resistance of the geothermal borehole, but also exploring this effect in other less researched areas, such as economic costs of running the exchanger and operating it (electricity consumption of the heat pump and associated pumping costs). / This research has received funding from the European Union’s Horizon 2020 Research and Innovation program under grant agreement No [657982], [727583] and [792355]. / Badenes Badenes, B. (2020). Optimización teórico-experimental de sondas de calor para intercambio geotérmico (SGE) según condiciones hidrogeológicas, características geométricas y propiedades de sus materiales [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/160477 / Compendio

This report travels through multiple disciplines to seek innovative and sustainable energy solutions for wastewater treatment plants. The first subject is a report about increased global temperatures and an over-exploitation of natural resources that threatens ecosystems worldwide. The situation is urgent where the current trend is a 2°C increase of global temperatures already in 2040. Furthermore, the energy-land nexus becomes increasingly apparent where the world is going from a dependence on easily accessible fossil resources to renewables limited by land allocation. A direction of the required transition is suggested where all actors of the society must contribute to quickly construct a new carbon-neutral resource and energy system. Wastewater treatment is as required today as it is in the future, but it may move towards a more emphasized role where resource management and energy recovery will be increasingly important. This report is a master’s thesis in energy engineering with an ambition to provide some clues, with a focus on energy, to how wastewater treatment plants can be successfully integrated within the future society. A background check is conducted in the cross section between science, society, politics and wastewater treatment. Above this, a layer of technological insights is applied, from where accessible energy pathways can be identified and evaluated. A not so distant step for wastewater treatment plants would be to absorb surplus renewable electricity and store it in chemical storage mediums, since biogas is already commonly produced and many times also refined to vehicle fuel. Such extra steps could be excellent ways of improving the integration of wastewater treatment plants into the society. New and innovative electric grid-connected energy storage technologies are required when large synchronous electric generators are being replaced by ‘smaller’ wind turbines and solar cells which are intermittent (variable) by nature. A transition of the society requires energy storages, balancing of electric grids, waste-resource utilization, energy efficiency measures etcetera… This interdisciplinary approach aims to identify relevant energy technologies for wastewater treatment plants that could represent decisive steps towards sustainability.

<p>With rising temperatures, urbanization, population growth, improving economic wellbeing, decarbonization and electrification efforts, the demand for space cooling and heating equipment is continuously increasing around the world. To counteract the effect of rising demand for air conditioners and heat pumps on total energy consumption, peak electricity demand, and emissions, it is crucial to promote the development and market penetration of energy-efficient systems. Establishing minimum energy performance standards (MEPS), energy labeling and utility programs are some of the effective and tested methods for achieving this goal. The technical basis for these energy efficiency standards is a testing and rating procedure for estimating equipment seasonal performance from laboratory tests. Although the current rating procedures provide standardized metrics to compare different equipment performances, they fail to appropriately characterize the field representative performance of systems by not considering the effects of: 1) test unit embedded controls, thermostat, and realistic interactions with the building load and dynamics; 2) different climate zones and building types; and 3) and other integrated accessories for improving energy efficiency such as economizer for rooftop units (RTUs). Therefore, current approaches for performance ratings neither incentives the development and implementation of improved system and control designs nor consumers with a metric that represents the advanced systems' actual energy savings. To address this, a load-based testing methodology that enables dynamic performance evaluation of equipment with its integrated controls, thermostat, and other accessories was recently proposed. The test methodology is based on the concept of emulating the response of a representative building conditioned by the test unit in a test lab using a virtual building model. </p> <p>In this work, the proposed load-based testing methodology was further extended, evaluated, and validated for residential heat pumps to integrate it into next-generation energy efficiency testing and rating procedures and to serve as a tool for engineers to develop and validate improved control algorithms in a laboratory setting. Further, a load-based testing method for evaluating the dynamic performance of RTUs with integrated economizers was also developed and demonstrated.</p> <p>A load-based testing approach previously developed for residential cooling equipment is extended for heat pump heating-mode and demonstrated for a variable-speed system. The heat pump's typical dynamic behaviors are captured along with controller imperfections that aren't reflected in current testing approaches. Further, a comprehensive comparison was performed between the proposed load-based testing approach to the current steady-state testing approach in the U.S., AHRI 210/240, based on performance evaluation of three residential variable-speed heat pumps to understand the differences and their significance for the next-generation rating procedure. For cooling mode, steady-state testing estimates higher seasonal performance, but for heating mode, the steady-state testing approach estimates higher seasonal performance for warmer climates and is comparable for colder climates. The load-based testing methodology was validated by comparing the laboratory performance of a heat pump to that of a residential building in a controlled environment. The virtual building modeling approach for building loads and thermal dynamics effectively captured these characteristics of the house. The heat pump's cycling rate response with run-time fraction, which represents the unit's overall dynamic response, matched well between lab load-based tests and house tests. The test unit's COP difference for cooling and heating tests was within 3% between the two facilities, except for 9% in 95°F and 6% in 104°F cooling dry-coil test intervals. To evaluate the applicability of the developed load-based testing methodology as next-generation rating standards, its repeatability and reproducibility were assessed based on multiple heat pump round-robin tests conducted in two labs. Overall, reasonable to good repeatability was observed in load-based test results in both labs, however, poor reproducibility was observed except for one heat pump heating mode results. A root cause analysis of the observed differences along with recommendations for a next-generation rating approach are presented. This work aided in the development of a CSA (Canadian Standards Association) standard EXP07:19 and its subsequent revision for equipment rating based on load-based testing.</p> <p>The application of the load-based testing methodology as a tool for the development and evaluation of a residential heat pump controller design was demonstrated. Further, a load-based testing methodology was developed and demonstrated for the dynamic performance evaluation of RTUs with integrated economizers in a test laboratory setting. Recommendations for future work to further develop and improve the repeatability, reproducibility, and representativeness of the load-based testing and rating approach for residential and commercial air conditioners and heat pumps are summarized at the end of the dissertation. </p>