J.M. Sala

• Ph D
• Professor at University of the Basque Country

It is pointed out that Hantush's \emph{M} function, commonly used in groundwater pumping modeling, is identical to the function known in the problems of heat conduction in the ground. A modified Hantush function $E$ used in the steady-state solutions for heat conduction that take into account advection due to groundwater flow around borehole heat e...

Los sistemas de monitorización de edificios proporcionan grandes volúmenes de información y existen herramientas avanzadas de análisis de datos. Un problema de detección y diagnóstico de fallos (FDD) en los sistemas energéticos de los edificios también puede considerarse un problema de aprendizaje automático puro. El objetivo de este trabajo es pro...

This work, analyzes ventilated façades through the first and second law of thermodynamics. In addition to the energy-balances, it presents the exergy-balances on the interior and exterior surface of a façade, taking into account the different mechanisms of heat exchange. It proposes two new indexes (EQC and ExQC) to characterize the behavior of ven...

Klima-aldaketaren eraginez, tokian-tokiko energia-eskaria aldatzen ari da. Honek, energia-eskaria asetzeko sistemen dimentsionamendu eta operazio moduan eragiten du; batez ere, epe luzerako proiektatzen diren sistemetan. Hala, jatorri berriztagarria duten energia-iturriak ezagutzea, modu jasangarrian ustiatzea eta ustiaketa klima-aldaketaren eskaki...

In this work thermoeconomics is applied to a central thermal system covering three buildings that consists of a cogeneration engine, an aerothermal heat pump and a natural gas condensing boiler. Cogeneration systems integrated with renewable energy technologies are very attractive solutions in the building sector. Nevertheless, the use of cogenerat...

This work defines and analyzes the performance of a polygeneration system in five different locations in Spain to maintain the thermal comfort and air quality of an office building. The facility is based on a chiller and a CHP engine with PV panels that provide almost all the electricity demand of the chiller. According to the energy performance an...

This work describes the project submitted to the University-Society-Business 2021 call for proposals whose aim is to integrate the knowledge and university practices in the field of energy in buildings into secondary school students. The aim is to define the energy strategies to be implemented to strengthen the relationship between secondary educat...

Before applying energy improvement strategies to real energy supply facilities, it is necessary to have an accurate model of their dynamic energy behaviour in order to predict and optimize the results. However, contrary to experimental facilities, in real operating facilities, budget constraints and fast access to recorded data limit the number of...

This work develops a software to control and diagnose building thermal facilities based on thermoeconomics. It is tested with the data obtained from three building blocks in the Basque Country (northern Spain) with the aim of detecting the potential energy saving points and mitigating environmental impacts. Some obstacles, solved, are related to th...

The energy performance certificate (EPC) is the core source for the European Union (EU) to obtain information about the efficiency levels of building stock and plan energy target paths. For this reason, and due to its wide variety of applications, it is important to ensure its quality. This study evaluates the quality of a representative EPC sample...

Thermoeconomics combines the concepts of economics and thermodynamics to assess the cost formation process of thermal systems. It has great applicability in the allocation, optimization and diagnosis of product costs. However, some aspects need to be gathered and solved, to have common criteria for its implementation. That is precisely what happens...

This work tries to present some reflections that help to understand the bases and the interest of the application of the exergetic analysis method and of thermoeconomics in buildings, both in what refers to their envelope and to their facilities. A brief introduction is made to the concept of exergy and the interest in incorporating the exergetic m...

This work analyses deeply and critically the behavior of a heat recovery device of the ventilation system, in a dwelling of the Basque Country, under the energy and the exergy point of view. The aim is to show the different results that come from both perspectives. Heating period was monitored and data of the velocities and temperatures of the extr...

The purpose of this paper is to apply thermoeconomics in a HVAC&R facility in order to implement the dynamic behaviour as well as to solve the direct problem of diagnosis. New methodological aspects of thermoeconomic applications are developed, such as a new method for setting the productive dynamic structure, in particular to define the commonly u...

In order to achieve a sustainable society, the energy consumption in buildings must be reduced. The first step toward achieving this goal is to detect their weak points and analyze the energy-saving potential. to detect the units with higher consumption and cost. Exergy is very useful for analyzing pieces of equipment, systems or entire buildings....

This work applies the Dynamic Advanced Exergy Analysis (DAEA) to a heating and domestic hot water (DHW) facility supplied by a Stirling engine and a condensing boiler. For the first time, an advanced exergy analysis using dynamic conditions is applied to a building energy system. DAEA provides insights on the components’ exergy destruction (ED) by...

Purpose Understanding the dynamic hygrothermal behavior of building elements is very important to ensure the optimal performance of buildings. The Laboratory for Quality Control in Buildings of the Basque Government tested a flat roof designed by a construction company that developed a building to be constructed using prefabricated modules. This is...

Thermoeconomic analysis allows for a deep understanding of the cost formation process within an energy system, providing insights into the possible routes for improvement. Several thermoeconomic approaches are well-established for application in systems with steady operating conditions, such as power plants, while a limited number of applications t...

Heat transfer during melting and solidifying processes in phase change materials, is a highly non-linear phenomenon. Artificial Neural Networks seem a suitable approach to deal with highly non-linear processes. The present work uses dynamic neural networks to simulate the behavior of a phase change material layer of a building envelope, which typic...

Oral communication presented in the 9th edition of the European Congress on Energy Efficiency and Sustainability in Architecture and Urbanism (EESAP 9), hosted in Bilbao in September, 2018 (In Spanish)

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 impr...

Resumen Hoy en día, las ciudades están experimentando radicales cambios operacionales. Estos nuevos modelos conocidos como Smart Cities tienen como objetivo mejorar la calidad de vida de los ciudadanos mediante el uso de datos recopilados sobre el entorno a través del uso de Tecnologías de la Información y la Comunicación (TIC). Además, el Interne...

Individual metering and charging of heat and domestic hot water is one of the possibilities for reducing the energy consumption in existing multifamily buildings and, with this aim in mind, the EU-directive 2012/27/EU enforced the installation of individual heat consumption meters. Even though some experimental evaluation of energy savings that may...

Microcogeneration systems guarantee the reduction of primary energy consumption and greenhouse gas emissions in residential sector, by reducing fossil fuels demand and grid losses with respect to conventional energy conversion systems. Energy, environmental and economic benefits can be obtained sharing the cogenerated thermal and electric energy am...

Thermoeconomic analysis of building energy supply systems are usually performed following the input-output approach, where the supply chain is divided into several subsystems directly related to each other. However, in this paper Symbolic Thermoeconomics has been applied and a dynamic analysis and comparison has been performed between the old and t...

Minimum airflow rates are either recommended or required based on the number of occupants, the intended use of the space or the floor plan area. This paper focuses on a new proposal for Spanish Technical Building Code based on limitations of the ventilation using the CO2 concentration as an indicator. The aim of the proposal is to introduce indoor...

This paper deals with the design and development of a low cost building environmental monitoring system, and it is based on Open Source Platforms and on the Internet of Things. To achieve this aim, a wireless microcontroller with attached sensors has been used to collect the environmental data. The information obtained from the sensors is collected...

The research in the field of nanofluids has experienced considerable advances from their discovery two decades ago. These liquid mixtures with tiny quantities (< 10% in volume) of nanometric size solid particles (< 100. nm) in suspension have a great potential for thermal management applications due to their excellent thermophysical properties. The...

One of the key factors that currently limit the commercial deployment of latent heat thermal energy storage (LHTES) systems is their complex design procedure. The optimization of such kind of systems requires a compromise between the storage capacity and the charging/discharging power, and therefore, there is a need of modeling tools that allow the...

Se trata de una instalación de calefacción y producción de ACS a partir del aprovechamiento de la energía geotérmica de muy baja temperatura mediante una bomba de calor BC agua-agua de 68 kW, en un edificio de 26 viviendas en el País Vasco. La generación cuenta con un sistema de apoyo mediante caldera de condensación CC a gas natural para las punta...

The building energy performance not only depends on the thermal parameters related to the building’s envelope, but also with the installed services and its intended use. The building’s use is a difficult parameter to control; therefore, to reduce the discrepancies between the designed energy performance and the real one, is critical to correctly ch...

To achieve an efficient use of energy in building energy supply systems not only an adequate design of the equipment is required, but also the detection and immediate determination of the costs of the products through the appropriate sensors. The comparison of these costs with the reference ones will allow us to detect the failures and establish th...

In this paper, a general model for the optimization of the energy supply systems of buildings is proposed. The model is based on a general superstructure that allows to include all the existing and future technologies, covering heating, domestic hot water, cooling and electricity. The model is linked to a Mixed Integer Linear Programming (MILP) pro...

The paper is based on the exergoeconomic study of an installation which covers the heating and DHW demand of a 176 dwellings nZEB in Vitoria-Gasteiz. It is composed by 2 cogeneration engines, 5’5 kWe and 12’5 kWt each and two 5’5 kWt each auxiliary conventional boilers. The novelty of this paper is that Symbolic Thermoeconomics (ST) is applied in t...

Concerning the building environment HVAC facilities, even if a great effort has been made in developing components and systems with high nominal efficiencies, less attention has been paid to the problem of system maintenance. The main objective of the thermoeconomic diagnosis is to detect possible anomalies and their location inside a component of...

The two spaces office module is usually considered as a representative case-study to analyse the energetic improvement in office buildings. In this kind of buildings, the use of a model predictive control (MPC) scheme for the climate system control provides energy savings over 15% in comparison to classic control policies. This paper focuses on the...

The present article studies the binary mixture comprised by erythritol and urea for its application as a phase change material (PCM) in latent hat thermal energy storage systems for heating and domestic hot water applications. A sequential methodology was employed to evaluate the suitability of the mixture as a PCM. First, a preliminary evaluation...

Application of Thermoeconomics in the diagnosis of building energy supply systems allows the localization and quantification of an abnormal operation, which can cause significant increase in energy consumption to obtain the same product. To do that, a comparison between the real operation of the energy system and the reference operation must be don...

In order to improve energetic efficiency and reduce environmental impact (and therefore, improve the sustainability of buildings), new tools are being developing for the building sector, which are commonly used within the industrial field. Thermoeconomics in one of those new science, which is the one that connects the physics of buildings with econ...

The advantages in applying the exergy concept and exergy efficiencies to evaluate the performance of energy systems in the building environment, contributing to the reduction in the use of high quality energy sources is currently known. Although Thermoeconomics has been widely applied in energy systems at building level Symbolic Thermoeconomics has...

This research studies a binary mixture composed of sodium nitrate and urea for use as a phase change material in latent thermal energy storage systems between 75 and 90. °C. This temperature is suitable for heating and domestic hot water applications, such as solar thermal systems and cogeneration devices. This work is divided into two parts. In Pa...

This work presents the implementation of a Model Predictive Control (MPC) scheme used to study the improvement of the thermal quality in aged residential buildings without any rehabilitation. The controller manages the heating system of an experimentally characterized model of a residential dwelling in a social block built during the decade of the...

Cogeneration and trigeneration systems may operate more efficiently if the production of electricity and heat are uncoupled by using thermal energy storage, where heat that is not needed during the production period is stored. A review is made of the different methods that have been developed to size thermal energy storage to maximize benefits in c...

A solution to the finite cylinder-source model for the ground heat exchangers at a different buried depths that takes into account the heat capacity inside them and allows arbitrary heat rate changes is presented. Analytical expressions for the average ground temperature are derived by integrating the exact solutions over the cylinder-source depth...

The development of mathematical models that can reliably simulate the energy performance of a whole building or a building component with minimal discrepancy between the real and simulated data is a major aim of Building Physics science. In order to create models that accurately represent real physical phenomena it is necessity to perform tests on...

Experimental work to assess the thermal performance of complex building components often requires testing under real and therefore variable conditions. The PASLINK methodology developed during many years by a European network of outdoor test centres is a dynamic methodology that provides high quality data sets and makes it possible to study the the...

Analytical and simulation models of ground heat exchangers (GHE) are necessary for proper sizing piles with smaller depth to radius ratio than boreholes. Most existing methods of design ignore the transient thermal processes within the piles or boreholes: some software programs are based on the classical “hollow” cylindrical surface source or line-...

Grey box models are a solution for evaluating and quantifying the effect on building thermal performance of different energy saving measures. They are usually used to predict a building thermal performance, and applied to energy systems. This paper presents the application of a grey box model to evaluate the thermal performance of a reference socia...

In this paper an economic analysis of a 1 kWe Stirling engine-based micro-CHP (combined heat and power) residential plant is developed, approaching the case of a Spanish detached house sited in a cold climatic zone. The work focuses on analysing how the latest modifications in the Spanish micro-CHP and renewable energies regulation affect viability...

In order to reduce the required volume for thermal energy storage, a finned plate latent heat thermal energy storage system for domestic applications is presented in this paper. This innovative design allows the exchanging of energy between water and the RT60, used as the phase change material. The simulation of that system is covered by a validate...

Great research effort is currently carried out to develop Energy-efficient Buildings. In particular, the control community is in a privileged position to help new buildings to comply with the European Energy Performance of Buildings Directive obligations and thus meet 'nearly zero-energy'. This work presents energy efficient studies on a dwelling i...

The objective of this paper is to present a laboratory program designed for the Thermodynamics course offered in the Department of Thermal Engineering at the University of the Basque Country. With reference to one of the examples given in the textbook by Moran, Shapiro, Boettner and Bailey (2012), the balances of mass, energy, entropy and exergy ar...

This paper presents an innovative finned-plate latent heat thermal energy storage system for its integration in cogeneration systems. For optimization purposes it is very important to maximize the efficiency of the computational calculations. Therefore, three approaches are presented for the simulation of the same storage system: a numerical model,...

In order to evaluate the accuracy and performance of two different heat transfer models for PCM containing systems, a thermal testing has been performed in a conductivimeter. A mixture of PCM and gypsum was submitted to a cyclic surface temperature change inside the conductivimeter, measuring heat fluxes and temperatures. The results of this test w...

Although there are specific rules in the standard ISO 10211 for the characterization of thermal bridges, they are mainly focused on steady state calculations to obtain the linear thermal transmittance (Ψ) or the temperature factor at the internal surface (fRsi). These parameters are respectively indicators of the additional heat flow and the risk o...

The approval of the Technical Building Code has meant major changes in the construction of multi-storey buildings in Spain. One of the most important revisions, with respect to the buildings erected prior to the Technical Building Code, has been the obligation to ventilate each one of its rooms. Depending on the use and occupancy a minimum flow rat...

Nowadays, several regulations exist covering different general guidelines that must be considered in order to decrease the energy demand in residential buildings. One of the main ones consists in increasing the insulation of the building envelope with the aim of minimizing heat losses or gains. As a result, a proper treatment of thermal bridges and...

The present article evaluates the influence of the experimental conditions in the determination of the subcooling of sodium sulfate decahydrate (Glauber's salt) nucleated with anhydrous and hydrated sodium tetraborate (borax). Experiments have been carried out by means of Differential Scanning Calorimetry (DSC) and by two other custom experimental...

Thermal characterization of building envelope systems is a complex task requiring both, a level of certainty and realistic prediction models, i.e. dynamic exterior conditions instead of laboratory stationary conditions. Normally in the analysis of hygrothermal performance of envelope systems, especially in the thermal and solar characterization of...

The aim of this research is to quantify the influence of a louvered blind in a double-glazed unit during night-time conditions. First, an analytical study of free convection was conducted to obtain a set of correlations for the Nusselt numbers of the cavity. Second, a parametric study was performed to calculate the total heat transfer (convective a...

This paper considers the effect that different hot water storage tank modelling approaches have on the global simulation of residential CHP plants as well as their impact on their economic feasibility. While a simplified assessment of the heat storage is usually considered in the feasibility studies of CHP plants in buildings, this paper deals with...

One of the variables that have a greater influence on the determination of the moisture buffering capacity of a material to be used as inner surface layer of an enclosure is the value of the vapour resistance of the surface film layer. In this paper, the influence of such a surface resistance on the moisture buffering value (MBV) is studied by mean...

The importance of calculating the effect of thermal bridges in building energy demand is growing. This is because new energy saving regulations are being applied in different countries making builders to increase the level of insulation in homes, and therefore raising the percentage of thermal bridges in total heat loss.This paper makes an introduc...

La excelencia en los proyectos arquitectónicos pasa por una óptima complementación de la infinidad de aspectos técnicos implicados, siendo la componente térmica un factor de gran impacto en el uso posterior de los ocupantes y en la repercusión medioambiental del edificio. El control del comportamiento térmico se hace más sólido en la medida en que...

One of the most simple and intuitive methods employed to characterise a building solution in transient regime is based on the use of response factors. Its acquisition by calculation is an appropriate approach when the thermo-physical properties of the materials are known. However, in a great number of building products these data are not available...

A Window Energy Rating System (WERS) provides a simple, approximate method to compare the energy performance of the various windows and to determine the different potential savings for the various weather conditions. The main aim of this paper is to obtain a WERS for two climatic zones in Spain.For this purpose, the heating loads and energy savings...

This article presents the results of a study about the corrosion behaviour of four aluminium alloys (EN AW 2024, 3003, 6063, and 1050) in contact with a commercial thermal storage material based in the Glauber’s salt (Na2SO4·10 H2O). Results indicate that the Al 2024 alloy is not compatible with this material due to the extense formation of NaAlCO3...

This article explains the adjustment procedure of a calibrated hot-box unit and the execution of the corresponding tests to measure the dynamic thermal properties of walls needed to calculate the thermal load of buildings. The results of a test for a heterogeneous wall are also presented, in a dynamic temperature rating. These results are compared...

Friction phenomena are extremely important in the suspension mechanisms used in automotive vehicles. Currently, there is no theory capable of explaining all the friction phenomena from a global perspective. In the case of telescopic hydraulic shock absorbers, the additional contribution of force given by the friction in the range of low damping vel...

Enclosed are the results of a feasibility study for a cogeneration facility at a company manufacturing large ship and off-shore oil-platform chains. The sizing of the main cogeneration equipment has been based on the assumption that the main energy demand is that needed to keep the quench bath at a temperature of 12 °C, thus compensating for the...

If sustainability criteria are to be applied properly in the construction sector it is essential to characterize the moisture capacity properties of building materials. This is the first step in studying the influence of moisture in the transmittance of exterior walls and in the occurrence of condensation, and in understanding the associated mechan...

Economic development in recent decades has been characterised by the increased use of fossil fuels. Clearly, a significant amount of this energy does not fall in line with the principles of sustainable development, either because of its contaminating effect or because of its non-renewable nature.Today, Navarre generates around 60% of its electricit...

A previous paper (Gómez et al., 2007) details the results of the characterization of two types of lightened clay made by two manufacturers who use different additives. This article shows the results of the characterization of the moisture transfer properties of those same materials. Lightened clay is widely used in the construction sector because o...

The implementation of the emissions market should imbue renewable energies with a greater degree of competitiveness regarding conventional generation. In order to comply with the Kyoto protocol, utilities are going to begin to factor in the cost of CO2 (environmental costs) in their overall generating costs, whereby there will be an increase in the...