• Energy Research

The new Basic Document on Energy Saving of the Technical Building Code (CTE-DB-HE) provides the necessary requirements to achieve nearly zero-energy buildings (NZEBs) and promotes the use of renewable energies in the Spanish building sector. In addition, the new CTE-DB-HE, transposition of the Energy Performance of Buildings Directive 2018, introduces specific requirements for the implementation of electric vehicle charging infrastructures in building car parks. The objective of this study is to analyse the energy and environmental impacts of the application of the new CTE-DB-HE in the residential sector. Different multi-family buildings in the most representative cities that meet the requirements for new and renovated buildings and use different heating and domestic hot water systems, as well as photovoltaic solar systems, are studied. The results are compared with those obtained by applying the previous regulations. Compared to the previous NZEBs, the new NZEBs achieve reductions by at least 46% in non-renewable primary energy consumption and 13% in total primary energy consumption. In addition, the changes introduced are shown to have helped prompt significant progress in the achievement of a highly energy-efficient and decarbonized building stock, achieving a reduction by at least 19% by 2050 in the main energy and environmental indicators. © 2023 The Authors

The scarcity of energy and water resources and rising temperatures due to climate change has set the focus on improving the energy efficiency of power plant thermodynamic cycles to adapt to higher heat sink temperatures and use fewer resources for energy production. In this work, a review of power production thermodynamic cycles is presented: from Brayton to Rankine and combined cycles, alongside particular cycles such as Organic Rankine Cycles, Kalina, Goswami or the more recently developed Hygroscopic Cycle. The efficiency of these cycles and their possible improvements are considered, as well as their environmental impact. Costs associated with existing power plants found in the literature have also been included in the study. The main existing facilities for each cycle type are assessed, and the most sustainable options in terms of resource consumption (fuel, water, etc.) and future perspectives to ensure both their energy efficiency and sustainability are identified.

AbstractEnergy saving in existing buildings is of vital importance. In this work, the characterization of housing stock in Spain for energy retrofitting purposes has been performed. The regulations in force when the existing stock was constructed (1980–2007) were considered to model the envelope and thermal systems of single-family and block housing. Building energy consumption and CO2 emissions were estimated for each type of dwelling and location, ranging from 44.2 to 130.6 kWh/(m2·year) (13.6–32 kg CO2/(m2·year)) for multi-family homes, and 85.5 to 213.5 kWh/(m2·year) (17.1–45.2 kg CO2/(m2·year)) for single-family homes. A global picture of the energy performance and emissions for 13 different climate zones was obtained with a total of 504 simulations. Retrofitting of the envelope allowed the reduction of consumption and emissions from 37.7% to 58%, depending on the climate zone. Energy consumption per square meter in block housing was lower than in single-family housing; nevertheless, single-family houses responded more effectively to energy improvement actions. Finally, non-renewable primary energy savings seem a better indicator of the improvement by retrofitting than the energy label. The building models designed in this work may serve as a reference for subsequent research concerning energy retrofitting and energy savings of housing stock.

Stricter emission regulations and variability of fuel prices pose the focus on the optimization of steam turbine based propulsion plants of Liquefied Natural Gas (LNG) ships. The efficiency of such a propulsion plant has been improved in this work by studying the introduction of reheating and preheating stages in the onboard regenerative Rankine cycle. A thermodynamic model of the propulsion plant has been developed from the facility diagrams, being validated afterwards with available experimental data from actual ship operations.

Buildings consume in Spain to 26.1% of final energy, corresponding to 17.5% of the domestic sector and 8.6% of the service sector. These data make us reflect on the energy savings that could be carried out by taking efficient measures in the enclosures of buildings, on the one hand, and systems that provide the energy needed to obtain comfort conditions. Thus the current legislation displays a large number of regulations on the matter: Technical Building Code, Regulation of Thermal Installations in Buildings, etc. The Basic Procedure for Certification of Energy Efficiency in Buildings has came into force recently, making it compulsory to qualify new buildings and / or old that are sold or leased, either as a whole or individually. The energy qualification is obtained as a result of quantifying the demand and the final energy consumption in a building. In this study we perform a series of simulations, using the software CERMA with a typical domestic building, placing it in different climatic zones of the Spanish territory, analyzing the obtained results. The most significant results have been the similarity in energy the energy label certification obtained in all scenarios and the lack of harmony between energy rating scale and energy consumption. The ultimate goal is not only the energy qualification of the building but also to know how we can get an improvement on it. It must be stressed that the study was conducted before the entry into force of the Order FOM/1635/2013 from September 10th 2013, laying updated the Basic Document DB-HE.

La quantification du rayonnement solaire incident sur une surface est une tâche complexe qui nécessite la connaissance des caractéristiques géométriques, géographiques, astronomiques, physiques et météorologiques de l'emplacement. Le but de cet article est d'analyser les processus d'atténuation du rayonnement solaire et de passer en revue les travaux scientifiques dans ce domaine, en particulier les modèles analytiques pour le calcul de l'irradiance solaire, ainsi que d'établir une méthode alternative pour calculer l'ampleur de la transmittance atmosphérique globale. Des modèles analytiques ont été développés depuis 1940 et leur précision et leur complexité se sont améliorées. Jusqu'à présent, le modèle Bird & Hulstrom est le plus complet et le plus précis de tous. Le principal inconvénient de ce modèle est qu'un grand nombre d'équations et de paramètres tels que la température, les heures d'ensoleillement, l'humidité, etc. sont nécessaires. Dans cet article, une nouvelle méthode très rapide et précise est développée pour quantifier les irradiations solaires sur n'importe quel site. L'analyse montre que les paramètres requis ne sont que le type de climat, l'altitude et l'état de l'atmosphère. Cette méthode permet également de quantifier l'influence du degré de turbidité dans les irradiations directes et diffuses. Ces informations sont essentielles pour sélectionner les technologies solaires qui conviennent à chaque endroit. En tant qu'application, la nouvelle méthode a été mise en œuvre et caractérisée au Mexique. L'énergie solaire est une ressource abondante au Mexique, et il existe des études sur le potentiel de l'énergie solaire dans ce pays, mais l'influence des facteurs physiques et météorologiques sur le rayonnement solaire n'a pas été liée. Dans cette étude, les informations météorologiques de 74 stations météorologiques situées dans différents climats du pays ont été utilisées pour déterminer les paramètres requis. Les résultats ont été validés avec des données expérimentales disponibles pour différents sites. Cuantificar la radiación solar incidente sobre una superficie es una tarea compleja que requiere el conocimiento de las características geométricas, geográficas, astronómicas, físicas y meteorológicas de la ubicación. El objetivo de este trabajo es analizar los procesos de atenuación de la radiación solar y revisar los trabajos científicos en este campo, específicamente los modelos analíticos para el cálculo de la irradiancia solar, así como establecer un método alternativo para calcular la magnitud de la transmitancia atmosférica global. Los modelos analíticos se han desarrollado desde 1940 y han ido mejorando en precisión y complejidad. Hasta ahora, el modelo Bird & Hulstrom es el más completo y preciso de todos. La principal desventaja de este modelo es que se requiere un gran número de ecuaciones y parámetros como temperatura, horas de sol, humedad, etc. En este documento, se desarrolla un nuevo método muy rápido y preciso para cuantificar las irradiancias solares en cualquier sitio. El análisis muestra que los parámetros requeridos son solo el tipo de clima, la altitud y el estado de la atmósfera. Este método también permite cuantificar la influencia del grado de turbidez tanto en irradiaciones directas como difusas. Esa información es esencial para seleccionar qué tecnologías solares son adecuadas en cada lugar. Como aplicación, el nuevo método ha sido implementado y caracterizado en México. La energía solar es un recurso abundante en México, y existen algunos estudios sobre el potencial de energía solar en ese país, pero no se ha relacionado la influencia de factores físicos y meteorológicos en la radiación solar. En este estudio se utilizó la información meteorológica de 74 estaciones meteorológicas ubicadas en diferentes climas del país para determinar los parámetros requeridos. Los resultados se han validado con datos experimentales disponibles para diferentes ubicaciones. Quantifying incident solar radiation on a surface is a complex task that requires the knowledge of geometric, geographical, astronomical, physical and meteorological characteristics of the location. The aim of this paper is to analyze the attenuation processes of the solar radiation and to review the scientific works in this field, specifically the analytical models for solar irradiance calculation, as well as to establish an alternative method to compute the magnitude of the overall atmospheric transmittance. Analytical models have been developed since 1940 and they have been improving in precision and complexity. Up until now, the Bird & Hulstrom model is the most complete and accurate of them all. The main disadvantage of this model is that a great number of equations and parameters such as temperature, sunshine hours, humidity, etc. are required. In this paper, a very fast and accurate new method is developed to quantify solar irradiances at any site. The analysis shows that the parameters required are only the type of climate, altitude and state of the atmosphere. This method also allows to quantify the influence of the turbidity degree in both direct and diffuse irradiances. That information is essential to select which solar technologies are suitable in each place. As an application, the new method has been implemented and characterized in Mexico. Solar energy is an abundant resource in Mexico, and there are some studies about the solar energy potential in that country, but the influence of physical and meteorological factors on the solar radiation have not been related. In this study, the meteorological information of 74 weather stations located in different climates of the country were used to determine the parameters required. The results have been validated with experimental data available for different locations. يعد القياس الكمي للإشعاع الشمسي الساقط على السطح مهمة معقدة تتطلب معرفة الخصائص الهندسية والجغرافية والفلكية والفيزيائية والأرصاد الجوية للموقع. الهدف من هذه الورقة هو تحليل عمليات توهين الإشعاع الشمسي ومراجعة الأعمال العلمية في هذا المجال، وتحديدًا النماذج التحليلية لحساب الإشعاع الشمسي، وكذلك إنشاء طريقة بديلة لحساب حجم النفاذية الجوية الإجمالية. تم تطوير النماذج التحليلية منذ عام 1940 وتحسنت من حيث الدقة والتعقيد. حتى الآن، يعد نموذج Bird & Hulstrom الأكثر اكتمالًا ودقة من بينها جميعًا. العيب الرئيسي لهذا النموذج هو أن هناك حاجة إلى عدد كبير من المعادلات والمعلمات مثل درجة الحرارة وساعات أشعة الشمس والرطوبة وما إلى ذلك. في هذه الورقة، تم تطوير طريقة جديدة سريعة ودقيقة للغاية لقياس الإشعاع الشمسي في أي موقع. يوضح التحليل أن المعلمات المطلوبة هي فقط نوع المناخ والارتفاع وحالة الغلاف الجوي. تسمح هذه الطريقة أيضًا بتحديد تأثير درجة التعكر في كل من الإشعاعات المباشرة والمنتشرة. هذه المعلومات ضرورية لاختيار تقنيات الطاقة الشمسية المناسبة في كل مكان. كتطبيق، تم تنفيذ الطريقة الجديدة وتميزها في المكسيك. الطاقة الشمسية مورد وفير في المكسيك، وهناك بعض الدراسات حول إمكانات الطاقة الشمسية في ذلك البلد، لكن تأثير العوامل الفيزيائية والأرصاد الجوية على الإشعاع الشمسي لم يكن مرتبطًا. في هذه الدراسة، تم استخدام معلومات الأرصاد الجوية لـ 74 محطة أرصاد جوية تقع في مناخات مختلفة من البلاد لتحديد المعلمات المطلوبة. تم التحقق من صحة النتائج من خلال البيانات التجريبية المتاحة لمواقع مختلفة.

Abstract Tidal energy has significant potential yet to be developed. One of the key areas of the research lines being developed is the ability to perform accurate computational models in order to make a full appraisal of kinetic energy potential in different areas through tide movements. So far, due to the limitations of computational resources and the extension of the geographical domains, existing models have manly used simplifications such as low resolution mesh sizes and velocity profile approximations in the vertical dimension. The investigation put forward includes a high resolution two dimensional equivalent model of the zone studied using a longitudinal section with depth and length dimensions, as well as a simulation methodology to study the velocity field in different sections. The model can be used in cases of channels of high width compared to the depth. With such data, kinetic power and energy of tidal currents can be predicted. Both, model and methodology have been applied and validated to the specific case of the estuary of Aviles port, thereby obtaining a new perspective in the hydrodynamic study as well as a tidal current energy potential assessment.