El método de análisis exergético en los edificios. Su aplicación en la caracterización en régimen dinámico de los cerramientos.

356 p.En la actualidad existe una gran preocupación e interés mundial por reducir el consumo energético y las emisiones de gases contaminantes. El sector de la edificación no es ajeno a esta tendencia, ya que es el responsable del 40% del consumo de energía final y del 50% de las emisiones de CO2 a nivel mundial. Como consecuencia de ello a lo largo de estos últimos años se han ido endureciendo las normativas, tratando de reducir tanto la demanda, como el consumo de energía, al mismo tiempo que trata de incorporar las energías renovables. Estas medidas han logrado pequeños avances, pero es necesario ir más allá. Para ello resulta imprescindible analizar y comprender el comportamiento dinámico de los cerramientos. Hasta hace relativamente poco tiempo esos análisis se basaban únicamente en el concepto de energía primaria y en la primera ley de la termodinámica. Sin embargo, este tipo de planteamientos ha alcanzado sus límites y se ha demostrado que por sí mismo no permite adquirir una total comprensión de los procesos de utilización de la energía. Al igual que ocurre en otros sistemas termodinámicos, en los edificios es necesario realizar un análisis basado en una combinación de la primera y segunda ley de la termodinámica, es decir, basado en la exergía. En el ámbito de las instalaciones esto se ha empezado a realizar. No obstante, no existe una metodología que permita caracterizar exergéticamente los cerramientos en condiciones dinámicas.Es en este contexto donde surge esta tesis, cuyo objetivo principal es la aplicación del método exergético para comprender la inercia térmica de un cerramiento y determinar cuál es la inercia que debe tener un cerramiento, con objeto de lograr el mejor comportamiento térmico de la envolvente de un edificio.Para ello se ha desarrollado un método de cálculo, que partiendo de los resultados obtenidos con un programa de simulación energética de edificios, permite analizar el comportamiento térmico del cerramiento mediante el análisis exergético. Puesto que no existe en la bibliografía ningún indicador exergético adecuado para cerramientos, se han propuesto una serie de nuevos indicadores específicos para su uso en cerramientos. Mediante la aplicación en un edificio de referencia del método desarrollado en esta tesis, se han analizado dichos indicadores y se ha seleccionado el de mayor interés, tanto teórico como práctico.Como aplicación práctica de la metodología y del parámetro propuesto en la tesis, se han analizado un conjunto de soluciones constructivas reales y se ha determinado cual es la óptima desde el punto de vista exergético para cada zona climática definida en el Código Técnico de la Edificación.En definitiva, con el fin de promover la mejora de la eficiencia energética de los edificios, se ha desarrollado una metodología de estudio basada en el análisis exergético, que permitirá comparar diferentes soluciones constructivas de fachada. Asimismo, permitirá aprovechar todas las ventajas que el análisis exergético ofrece en cuanto a identificación de las irreversibilidades, asignación de costes económicos a los flujos, etc. Palabras clave:Exergía, análisis exergético, inercia, régimen dinámico, cerramientos, edificios

Simplified model for the short-term forecasting of heat loads in buildings

A data-driven model is used to predict one-hour ahead heat loads based on present and recent history of weather and heat loads. A computationally inexpensive method is built to deliver load forecasting based on existing data quality and resolution from smart meters. Optimal model formulation is discussed and optimized at 4-hour historical values. The model is trained and tested against synthetic data from a building energy simulation, resulting in absolute error <4% and R2 values in the range of 0.92 to 0.94

Analysis of New Strategies to Reach Nearly Zero Energy Buildings (nZEBs)

The need to reduce CO2 emissions makes it necessary to review most areas of human activity because we are the main source of these emissions. In particular, the building sector is one of its main responsible. Through a State of the Art, several papers published in various scientific journals about nearly Zero Energy Building (nZEB) studies are reviewed. After carrying out an analysis of said documentation, it is considered that a new way of study can be developed with a multidisciplinary approach. For this, another series of articles are analyzed, where different advances in the field of building construction have been developed and are summarized. It is concluded that the Model Predictive Control (MPC) can also be a useful tool to optimize energy consumption in buildings, especially for public use, in order to achieve the goal of achieving nZEB, through the use of Renewable Energy Sources (RES)

Cities4ZERO: Overcoming Carbon Lock-in in Municipalities through Smart Urban Transformation Processes

How can local authorities effectively address the decarbonization of urban environments in the long run? How would their interests and expertise be aligned into an integrated approach towards decarbonization? This paper delves into how strategic processes can help to integrate diverse disciplines and stakeholders when facing urban decarbonization and presents Cities4ZERO, a step-by-step methodology for local authorities, able to guide them through the process of developing the most appropriate plans and projects for an effective urban transition; all from an integrated, participatory and cross-cutting planning approach. For the development of the Cities4ZERO methodology, plans, projects, and strategic processes from five European cities that are part of the Smart Cities and Communities European Commission program have been monitored for 4 years, in close collaboration with local authorities, analyzing ad-hoc local strategic approaches to determine key success factors and barriers to be considered from their transitioning experiences. The study indicates that an iterative strategic approach and a project-oriented vision, combined with a stable institutional commitment, are opening a window of opportunity for cities to achieve effective decarbonization.This research was funded by the European Commission, grant number 691,883

Energy and thermal modelling of an office building to develop an artificial neural networks model

[EN] Nowadays everyone should be aware of the importance of reducing CO2 emissions which produce the greenhouse effect. In the field of construction, several options are proposed to reach nearly-Zero Energy Building (nZEB) standards. Obviously, before undertaking a modification in any part of a building focused on improving the energy performance, it is generally better to carry out simulations to evaluate its effectiveness. Using Artificial Neural Networks (ANNs) allows a digital twin of the building to be obtained for specific characteristics without using very expensive software. This can simulate the effect of a single or combined intervention on a particular floor or an event on the remaining floors. In this paper, an example has been developed based on ANN. The results show a reasonable correlation between the real data of the Operative Temperature with the Energy Consumption and their estimates obtained through an ANN model, trained using an hourly basis, on each of the floors of an office building. This model confirms it is possible to obtain simulations in existing public buildings with an acceptable degree of precision and without laborious modelling, which would make it easier to achieve the nZEB target, especially in existing public office buildings

Defining the cooling and heating solar efficiency of a building component skin: application to a modular living wall

[EN] The thermal evaluation of building components composed of a base wall with a solar passive skin solution, such as a vertical/roof greenery system, ventilated facade, reflective painting, etc., is usually performed as a whole. In this research, it has been proven that, independently of the base wall thermal inertia and insulation level, the temperature of the outermost surface layer of any building component during sunny hours is mainly dependent on the ambient air temperature and relative humidity, the incident global solar radiation and the building skin behaviour. The latter assumption has been proven on the south wall of a reference building simulated with TRNSYS. The south wall properties have been varied and the building has been subjected to different climates. The assumption's validity has been checked for twelve south wall cases: a combination of 2 thermal transmittance, 2 thermal inertia and 3 climates. Each case has been simulated for a whole year. Based on this finding and the local ambient conditions for sunny hours, the hypothetical achievable maximum and minimum temperatures for the outermost surface layer have been defined. Then, based on the outermost surface temperature experimental measurements, the cooling and heating solar efficiencies valid for any skin solution have been defined. Furthermore, the developed methodology has been applied to a vertical living wall tested for a whole year under the accuracy and quality procedure of the PASLINK method. In this way, the cooling and heating solar efficiencies were experimentally determined for this skin solution for both, the hot cold seasons. The study has shown that the cooling efficiency during the hot season is 90.8%. As expected, even during sunny summer hours, the presence of water positively affects the performance of the facade, as it brings the base wall external surface temperature close to the ambient wet bulb temperature, therefore reducing the cooling load of the building. For the cold season, the cooling efficiency was similar, at 90.3%, which means a heating efficiency of 9.7%. Again, even for sunny winter hours, the values of the external surface temperature tend towards the ambient air wet bulb temperature, resulting in an increase in the heating demand. These experimental efficiency values allow the heating or cooling behaviour of different skin solutions to be comparable with a single number that is independent of the base wall composition. In addition, independently of the base wall composition, once the experimental efficiency value of a given skin solution is known, it allows (during sunny hours) the base wall outermost surface temperature to be calculated with precision. The latter makes it possible to increase the accuracy of the estimation of the heating and cooling demands of such methods as the degree-day method.This work was supported by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (grant number RTI2018-096296-B-C22) through the MONITHERM project 'Investigation of monitoring techniques of occupied buildings for their thermal characterization and methodology to identify their key performance indicators', project reference: RTI2018-096296-B-C22 (MCIU/AEI/FEDER, UE). Open Access funding provided by University of Basque Country

Towards an Integrated Approach to Urban Decarbonisation in Practice: The Case of Vitoria-Gasteiz

How can local authorities effectively approach the decarbonisation of urban environments? Recent efforts to redirect cities into a less energy-intensive model have been mostly approached from a sectoral perspective, with specific energy policies and plans being issued without deeply considering their ties with other urban aspects. In this sense, well-established urban planning procedures have not been part of those, with the consequence of barriers in the implementation phase of those energy plans. The Cities4ZERO methodology was developed to guide effective integration between urban planning and energy policies, plans, and practices. It provides a holistic approach to strategic municipal processes for urban decarbonisation in the mid-long term, which includes key local stakeholders’ engagement into integrated energy planning processes, as well as tools for effective energy decarbonisation modelling. This paper analyses the application of the Cities4ZERO decarbonisation methodology on its strategic stage in the development of Vitoria-Gasteiz’s Action Plan for an Integrated Energy Transition 2030 (APIET 2030). It suggests that in order to accelerate urban decarbonisation, it is critical to: (a) foster interdepartmental collaboration; (b) allow for flexibility on the land-use planning regulations; (c) back decisions with detailed urban-energy models; and (d) truly engage key local stakeholders in the planning and implementation processes.European Commission for funding SmartEnCity project, the frame of this research, and Basque Government for its significant support to the Basque research and innovation paradigm

Design of a Microscale Refrigeration System for Optimizing the Usable Space in Compact Refrigerators

This research aims to enter the miniature refrigeration machine sector with the objective of designing a small scale unit while maintaining a competitive coefficient of performance (COP), comparing with a Peltier plates system. To this end, a research of the current technology was carried out in order to obtain indicative values on the scales that were being worked on and their application. After the previous research, a refrigeration cycle was designed in EES (engineering equation solver). From this design, different conclusions were obtained: (1) The correct sizing of the compressor revolutions together with its displacement is crucial for the equipment to be able to provide the desired cooling capacity. (2) In order to obtain the desired cooling capacity in the microscale refrigeration system, the heat exchangers must have fins. (3) Of the analysed refrigerants, R600a is the best choice, as it shows favourable characteristics (high COP and low compression ratio) when working in this type of cycle.This work was supported by the Basque Government in the Elkartek call through the SOLRUC project “Knowledge acquisition for the design of new ultra-compact cooling solutions”, project reference: KK-2020/00115

Accounting for homeowners? decisions to insulate: A discrete choice model approach in Spain

This paper assesses Spanish households' willingness to thermally insulate their homes and the drivers that influence such a decision-making process. Stated preference data were collected through a discrete choice experiment (DCE). The final sample of 191 respondents and 1,145 observations was analysed by the use of a mixed logit model, weighing the factors that encourage homeowners to carry out facade energy renovations or not. The model enables the quantitative estimation of renovation adoption rates depending on the households' characteristics and public support instruments in place. The results show that homeowners are extremely interested in increasing the thermal insulation of their homes. The actual investment cost required in the existing building stock is lower than the obtained willingness-to-pay. Furthermore, it was found a relevant effect of a variety of household features on renovation choice (income, age, heating system, etc.), which should be contemplated in the energy efficiency policy design. Additionally, a case analysis is performed which comprises 3 household categories. The results reveal that the required subsidy level is different in each case, sometimes even unnecessary, although all of them lower than the grants set by existing aid programs. Thus, to reduce the free-riding effect, a closer perspective would enable targeted support mechanisms towards each household category. Moreover, the policy performance can be improved by combining subsidies with other measures such as low-interest loans or increased tax rebates, which could contribute to improving the cost effectiveness of the public expense associated with direct grants. Overall, an increased tax rebate is preferred to soft financing, although the influence of the latter increases in low-income households

Combination of Diagnostic Tools for the Proper Identification of Moisture Pathologies in Modern Residential Buildings

A study of moisture pathologies in a modern residential multifamily building is presented. The housing block was designed under the regulation NBE-CT of 1979 in northern Spain. After the appearance of some moisture problems in the façades, three complementary studies were conducted to analyze the situation of the envelope and diagnose the best improvement possibilities. First, indoor conditions of temperature and humidity of the apartments with moisture pathologies were monitored. During 40 winter days, the occupancy, heating operation, and natural ventilation were analyzed. Second, the inner and outer surface temperatures of the studied façades were measured. Thermal insulation degree, thermal capacity, and thermal bridge effects were measured to assess the risk of interstitial condensation under the real conditions of use. Third, an infrared thermographic survey was carried out, which allowed the detection of irregularities and the assessment of moisture problems. The wrong interpretations, which would have been made if the complementary studies had not been done, are exposed. The key towards the accurate diagnosis was the combination of tools. Finally, some technical solutions based on ventilation or thermal insulation enhancement are proposed as different ways to reduce the high levels of relative humidity indoors and minimize the risk of condensation in the futur