Institut Politècnic d’Innovació i Recerca en Sostenibilitat (INSPIRES)

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INSPIRES és un centre de recerca de la Universitat de Lleida. Conforma un grup multidisciplinari que posa especial atenció a la recerca al voltant de la millor gestió energètica, l’eficiència, la usabilitat, la seguretat, la computació d’altes prestacions i la resolució i optimització de problemes, entre altres temes. Tot amb nexes comuns, girant al voltant de l’àmbit de la sostenibilitat i la tecnologia. Suposa una unió d’esforços dels diferents centres de recerca que de manera separada tractaven diferents línies i àrees, ara aquests esforços es comparteixen generant sinèrgies.[Més informació].

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128 x 128 CMOS Image Sensor With Analog Memory for Synchronous Image Capture
(Institute of Electrical and Electronic Engineers, 2002) Chapinal, Genis; Bota, Sebastian A.; Moreno, Mauricio; Palacín Roca, Jordi; Herms, Atilà
A 128 x 128 CMOS imager that permits synchronous capture is presented. The sensor combines the best of CMOS imagers (low-power, random readout, nondestructive readout, single supply voltage…) and synchronous capture [available in high-end charge coupled device (CCD) imagers]. The key point in obtaining such characteristics is the separation of the photosensor and the storage element. Although some sensors with these characteristics have been reported, in this sensor, the storage capability has been brought a step further, having storage times in the order of tens of seconds, and being able to use the array itself as a random access memory (RAM). This could avoid the use of external RAM, making the system simpler, more compact, and of low-power consumption.
Open Access
A Comparative Analysis of Scopus and Web of Science (WoS) Literature on the Autism Crisis
(Springer, 2021) Díaz Llobet, Manel; Teixidó Cairol, Mercè; Gil Iranzo, Rosa María; Cabeza, Luisa F.; Aras, Luis Miguel
Autism is a neurobiological developmental disorder that is detected at around 3 years old. This disorder affects their communication, socialization, and behavioral skills. Its ratio is 1 per 150 and the possibility is greater for boys (2 girls for every 6 boys). A bibliometric analysis, comparing documents in the Scopus and Web of Science databases, has been carried out. It includes some new features such as the evaluation of growth, maturity, conceptual and intellectual maps and trends of a scientific community on top of the bibliometrics traditional approach. This study shows that, although the interest in different aspects related to autism is very high (from the year 2000), there is a significant lack on the prevention or prediction crisis topic.
Open Access
A comparative life cycle assessment (LCA) of different insulation materials for buildings in the continental Mediterranean climate
(Elsevier, 2020) Llantoy, Noelia; Chàfer, Marta; Cabeza, Luisa F.
The construction industry is one of the less sustainable activities on the planet, constituting 40% of the total energy demand and approximately 44% of the total material use and the generation of 40-50% of the global output of greenhouse gases. The biggest environmental impact caused by buildings is generated during their operational phase due to the energy consumption for thermal conditioning. Hence, in order to reduce this energy consumption, insulation materials must be used and from a life-cycle perspective, the use of insulation materials reduces the building impact over time. This paper develops a comparative life cycle assessment (LCA) of different insulation materials (polyurethane, extruded polystyrene, and mineral wool) to analyse the environmental profile of each insulation material type in the Mediterranean continental climate. Significantly, all three insulation materials demonstrated a net positive benefit over a fifty-year life span due to the reduced heating requirements of the building. Results showed that the highest environmental impact was associated with the polystyrene insulation material and the best environmental performance was for the mineral wool. Moreover, regarding the consumption, polyurethane and mineral wool had similar thermal performance during the whole year. Furthermore, the environmental payback period shows that the cubicles with insulation material are environmentally efficient, if they are used for at least 7 years (for mineral wool), 10 years (polyurethane), and 12 years (extruded polystyrene). The results of this research give new insights into the effect on building insulation materials.
Open Access
A comparative life cycle assessment between green walls and green facades in the Mediterranean continental climate
(Elsevier, 2021) Chàfer, Marta; Pérez Luque, Gabriel; Coma Arpón, Julià; Cabeza, Luisa F.
The building and construction sector is a large contributor to anthropogenic greenhouse gas emissions and consumes vast natural resources. Improvements in this sector are of fundamental importance for national and global targets to combat climate change. In this context, vertical greenery systems (VGS) in buildings have become popular in urban areas to restore green space in cities and be an adaptation strategy for challenges such as climate change. However, only a small amount of knowledge is available on the different VGS environmental impacts. This paper discusses a comparative life cycle assessment (LCA) between a building with green walls, a building with green facades and a reference building without any greenery system in the continental Mediterranean climate. This life cycle assessment is carried according to ISO 14040/44 using ReCiPe and GWP indicators. Moreover, this study fills this gap by thoroughly tracking and quantifying all impacts in all phases of the building life cycle related to the manufacturing and construction stage, maintenance, use stage (operational energy use experimentally tested), and final disposal. The adopted functional unit is the square meter of the facade. Results showed that the operational stage had the highest impact contributing by up to 90% of the total environmental impacts during its 50 years life cycle. Moreover, when considering VGS, there is an annual reduction of about 1% in the environmental burdens. However, in summer, the reduction is almost 50%. Finally, if the use stage is excluded, the manufacturing and the maintenance stage are the most significant contributors, especially in the green wall system.
Open Access
A comprehensive review on sub-zero temperature cold thermal energy storage materials, technologies, and applications: State of the art and recent developments
(Elsevier, 2021) Yang, Lizhong; Villalobos, Uver; Akhmetov, Bakytzhan; Gil, Antoni; Khor, Jun Onn; Palacios, Anabel; Li, Yongliang; Ding, Yulong; Cabeza, Luisa F.; Tan, Wooi Leong; Romagnoli, Alessandro
The energy industry needs to take action against climate change by improving efficiency and increasing the share of renewable sources in the energy mix. On top of that, refrigeration, air-conditioning, and heat pump equipment account for 25-30% of the global electricity consumption and will increase dramatically in the next decades. However, some waste cold energy sources have not been fully used. These challenges triggered an interest in developing the concept of cold thermal energy storage, which can be used to recover the waste cold energy, enhance the performance of refrigeration systems, and improve renewable energy integration. This paper comprehensively reviews the research activities about cold thermal energy storage technologies at sub-zero temperatures (from around 􀀀 270 ◦C to below 0 ◦C). A wide range of existing and potential storage materials are tabulated with their properties. Numerical and experimental work conducted for different storage types is systematically summarized. Current and potential applications of cold thermal energy storage are analyzed with their suitable materials and compatible storage types. Selection criteria of materials and storage types are also presented. This review aims to provide a quick reference for researchers and industry experts in designing cold thermal energy systems. Moreover, by identifying the research gaps where further efforts are needed, the review also outlines the progress and potential development directions of cold thermal energy storage technologies.
Open Access
A correlation of the convective heat transfer coefficient between an air flow and a phase change material plate
(Elsevier, 2013) Gracia Cuesta, Alvaro de; David, Damien; Castell, Albert; Cabeza, Luisa F.; Virgone, Joseph
This paper provides a new correlation to determine the heat transfer coefficient between an air flow and a plate made of phase change material (PCM). This correlation was built for the simulation of heat storage units containing PCM plates subjected to an inlet temperature step. The presented correlation has the following form: NuPCM x;t ¼ NuPSM$f PCM. The first term NuPSM is for a plate made of traditional material. The term fPCM is a perturbation due to the phase change in the plate. Each term depends on 5 non-dimensional parameters. One of them represents the advance in the total heating or cooling process, in order to take into account the transient evolution of the convective coefficient. The correlations are built using the Least Squares Method, from series of CDF simulation data. The shape of the perturbation fPCM reveals a complex evolution of the temperature repartition in the PCM plate. Finally, a nodal model of the plate has been developed in order to test the provided new correlation and other correlations available in the literature. The results obtained with the present correlation show better agreements with the CFD results, which make this correlation suitable for the simulation of PCM heat storage systems.
Open Access
A detailed energy analysis of a novel evaporator with latent thermal energy storage ability
(Elsevier, 2021) Mselle, Boniface Dominick; Zsembinszki, Gabriel; Vérez, David; Borri, Emiliano; Cabeza, Luisa F.
The direct integration of phase change materials (PCM) into refrigeration and air conditioning systems through compact modules is an identified literature gap. In response to the literature gap, this paper provides a detailed energy analysis of a novel compact thermal energy storage module, that allows its direct integration into a refrigeration system as the evaporator. The study addresses key aspects of thermal energy storage (TES) and heat transfer mechanism that complement the previous analyses of the novel concept. Here the total energy stored in the module (including in all auxiliary parts), the charging/discharging power, and the behaviour of the module when used as a TES module and as a heat exchanger (HEX) are assessed. The results demonstrate the feasibility of the module to work as a TES and as a HEX. When working as a TES, complete charging and discharging was achieved, and 54% of the total energy was stored in the PCM although the PCM only accounts for around 14% of the total mass. Moreover, the highest charging/discharging power was obtained within the temperature range where most of the phase change occurred. When the module works as a HEX, it initially charges/discharges partially until a thermal equilibrium is achieved and the level of charge responds to the variation in the energy supply and demand.
Open Access
A distributed argumentation algorithm for mining consistent opinions in weighted Twitter discussions
(Springer, 2019) Alsinet, Teresa; Argelich Romà, Josep; Béjar Torres, Ramón; Cemeli Sánchez, Joel
Twitter is one of the most powerful social media platforms, reflecting both support and contrary opinions among people who use it. In a recent work, we developed an argumentative approach for analyzing the major opinions accepted and rejected in Twitter discussions. A Twitter discussion is modeled as a weighted argumentation graph where each node denotes a tweet, each edge denotes a relationship between a pair of tweets of the discussion and each node is attached to a weight that denotes the social relevance of the corresponding tweet in the discussion. In the social network Twitter, a tweet always refers to previous tweets in the discussion, and therefore the underlying argument graph obtained is acyclic. However, when in a discussion we group the tweets by author, the graph that we obtain can contain cycles. Based on the structure of graphs, in this work we introduce a distributed algorithm to compute the set of globally accepted opinions of a Twitter discussion based on valued argumentation. To understand the usefulness of our distributed algorithm, we study cases of argumentation graphs that can be solved efficiently with it. Finally, we present an experimental investigation that shows that when solving acyclic argumentation graphs associated with Twitter discussions our algorithm scales at most with linear time with respect to the size of the discussion. For argumentation graphs with cycles, we study tractable cases and we analyze how frequent are these cases in Twitter. Moreover, for the non-tractable cases we analyze how close is the solution of the distributed algorithm with respect to the one computed with the general sequential algorithm, that we have previously developed, that solves any argumentation graph.
Open Access
A framework for sustainable evaluation of thermal energy storage in circular economy
(Elsevier, 2021) Abokersh, Mohamed Hany; Norouzi, Masoud; Boer, Dieter; Cabeza, Luisa F.; Gasa, Gemma; Prieto, Cristina; Jiménez, Laureano; Vallès Rasquera, J. Manel
The circular economy can be promoted as a solution to support the sustainability market position of renewable energy systems. To design a circular and sustainable system, a structured approach is needed. The present study develops a methodology framework for sustainable circular system design (SCSD), aiming to assess thermal energy storage (TES) technologies from a sustainable perspective. To this end, a composite indicator, namely, environmental sustainability and circularity indicator (ESC) is provided. This indicator combines the environmental impacts of the TES system via the conduction of a life cycle assessment and its circulatory performance using the product-level material circularity indicator (MCI). The developed methodology is applied to a case study of high-temperature TES using molten salts as a part of a concentrated solar power plant. The SCSD embraces the analysis for the most relevant processes through proposing different ecological scenarios including, increasing the recycling rates (Modest Scenario), increasing the reuse rates (Medium Scenario), and a combination of both (Optimistic scenario). The circularity analysis showed that for the Modest, Medium and optimistic scenarios, the MCI moves from 20.6% for the current situation to 30.3%, 38.6%, and 46.4%, respectively. Accordingly, the optimistic scenario showed the most environmentally sustainable and circular scenario with ESC of 7.89%, whereas the Modest and Medium scenarios exhibited ESCs of 1.20% and 2.16%, respectively. A major obstacle for substantial improvement of the circulatory and ESC is the high share of unrecyclable molten salts in the system and therefore, any effort to improve the circulatory and the environmental benefits of this system can be reached by using more environmentally friendly alternative materials. The study concludes that the integration of reusing and recycling at the initial design should be sought in order to achieve a more environmentally sustainable and circular outcome.
Open Access
A framework for the optimal integration of solar assisted district heating in different urban sized communities: A robust machine learning approach incorporating global sensitivity analysis
(Elsevier, 2020) Abokersh, Mohamed Hany; Vallès Rasquera, J. Manel; Cabeza, Luisa F.; Boer, Dieter
A promising pathway towards sustainable transaction to clean energy production lies in the adoption of solar assisted district heating systems (SDHS). However, SDHS technical barriers during their design and operation phases, combined with their economic limitation, promote a high variation in quantifying SDHS benefits over their lifetime. This study proposes a complete multi-objective optimization framework using a robust machine learning approach to inherent sustainability principles in the design of SDHS. Moreover, the framework investigates the uncertainty in the context of SDHS design, in which the Global Sensitivity Analysis (GSA) is combined with the heuristics optimization approach. The framework application is illustrated through a case study for the optimal integration of SHDS at different urban community sizes (10, 25, 50, and 100 buildings) located in Madrid. The results reveal a substantial improvement in economic and environmental benefits for deploying SDHS, especially with including the seasonal storage tank (SST) construction properties in the optimization problem, and it can achieve a payback period up to 13.7 years. In addition, the solar fraction of the optimized SDHS never falls below 82.1% for the investigated community sizes with an efficiency above 69.5% for the SST. Finally, the GSA indicates the SST investment cost and its relevant construction materials, are primarily responsible for the variability in the optimal system feasibility. The proposed framework can provide a good starting point to solve the enormous computational expenses drawbacks associated with the heuristics optimization approach. Furthermore, it can function as a decision support tool to fulfill the European Union energy targets regarding clean energy production.
Open Access
A Fully Scalable and Distributed Architecture for Video-on-Demand
(Springer Verlag, 2001) Cores Prado, Fernando; Ripoll, A.; Luque, Emilio
In spite of the attractiveness of Video-on-demand (VoD) services, their implantation to the present has not been as widespread as could have been desired due to centralized VoD systems have a limited streaming capacity and its grown is costly. One level proxy-based systems have been proposed to increase the system capacity but their scalability are still limited by the main network bandwidth. Our investigation are focussed on designing a flexible LVoD (large-scale Video-on-Demand) system capable of easy scaling with limited costs, which can adapt its size to the needs of the system. To achieve a scalable LVoD system, it is essential that the communications system bandwidth is able to grow in keeping with system growth (with a reasonable cost and limited loss of efficiency). To get these requirements we have proposed a hierarchical tree topology based on the use of independent local networks with proxies. To allow the system’s grow, the functionality of the proxy has been modified in such a way that it works at the same time as cache for the most watched movies, and as a mirror for the remaining movies. The evaluation of these systems has been done using an analytical model. The results shows that this architecture guarantees unlimited and low-cost growth for LVoD systems, the VoD system capacity can easily be adapted to any number of users and the system is fault-tolerant.
Open Access
A Green Strategy for Federated and Heterogeneous Clouds with Communicating Workloads
(Hindawi Publishing Corporation, 2014-07) Mateo Fornés, Jordi; Vilaplana Mayoral, Jordi; Solsona Tehàs, Francesc; Pla Aragonés, Lluís Miquel; Lérida Monsó, Josep Lluís
Providers of cloud environments must tackle the challenge of configuring their system to provide maximal performance while minimizing the cost of resources used. However, at the same time, they must guarantee an SLA (service-level agreement) to the users. The SLA is usually associated with a certain level of QoS (quality of service). As response time is perhaps the most widely used QoS metric, it was also the one chosen in this work. This paper presents a green strategy (GS) model for heterogeneous cloud systems. We provide a solution for heterogeneous job-communicating tasks and heterogeneous VMs that make up the nodes of the cloud. In addition to guaranteeing the SLA, the main goal is to optimize energy savings. The solution results in an equation that must be solved by a solver with nonlinear capabilities. The results obtained from modelling the policies to be executed by a solver demonstrate the applicability of our proposal for saving energy and guaranteeing the SLA.
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A Hybrid Approach for Modelling Early Prototype Evaluation Under User-Centred Design Through Association Rules
(Springer Verlag, 2007) González Azconegui, María Paula; Granollers i Saltiveri, Toni; Lorés Vidal, Jesús
One of the main activities in User Centred Design (UCD) is prototype evaluation, which is traditionally performed by means of an Evaluation Stage that looks for the redefinition of the prototype requirements, involving quantitative and qualitative usability testing techniques. This paper describes a new approach in which the traditional methodology for performing the Evaluation Stage under UCD is embedded in a framework with capabilities for mining association rules. This allows to minimise the impact of the interpretation bias of the evaluation team when analysing ambiguous user statements in natural language.
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A Max-SAT Solver with Lazy Data Structures
(Springer Verlag, 2004) Alsinet, Teresa; Manyà Serres, Felip; Planes Cid, Jordi
We present a new branch and bound algorithm for Max-SAT which incorporates original lazy data structures, a new variable selection heuristics and a lower bound of better quality. We provide experimental evidence that our solver outperforms some of the best performing Max- SAT solvers on a wide range of instances.
Open Access
A methodology for developing Distributed Generation scenarios in urban areas using geographical information systems
(Inderscience, 2008) Medrano Martorell, Marc; Brouwer, Jack; Carreras-Sospedra, Marc; Rodriguez, Marco A.; Dabdub, Donald; Samuelsen, G. Scott
The implementation of Distributed Generation (DG) may lead to increased pollutant emissions that adversely affect air quality. This work presents a systematic methodology to characterise DG installation in urban basins. First, a set of parameters that characterise a DG implementation scenario is described. Second, a general approach using Geographic Information Systems (GIS) data is presented. Third, the methodology is demonstrated by application to the South Coast Air Basin (SoCAB) of California. Results show that realistic scenarios in the SoCAB concentrate DG technologies nearby industrial zones and introduce pollutant mass increments no larger than 0.43% with respect to baseline emissions.
Open Access
A mobile robot agent for gas leak source detection
(Springer International Publishing Switzerland, 2014) Martínez Lacasa, Daniel; Pallejà Cabrè, Tomàs; Moreno Blanc, Javier; Tresánchez Ribes, Marcel; Teixidó Cairol, Mercè; Font Calafell, Davinia; Pardo, Antonio; Marco, Santiago; Palacín Roca, Jordi
This paper presents an autonomous agent for gas leak source detec-tion. The main objective of the robot is to estimate the localization of the gas leak source in an indoor environment without any human intervention. The agent implements an SLAM procedure to scan and map the indoor area. The mobile robot samples gas concentrations with a gas and a wind sensor in order to estimate the source of the gas leak. The mobile robot agent will use the in-formation obtained from the onboard sensors in order to define an efficient scanning path. This paper describes the measurement results obtained in a long corridor with a gas leak source placed close to a wall.
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A MOF-Compliant Approach to Software Quality Modeling
(Springer Verlag, 2005) Burgués i Illa, Xavier; Franch, Xavier; Ribó i Balust, Josep M. (Josep Maria)
Software quality is a many-faceted concept that depends on the kind of artifact to be measured, the context where measurement takes place, the quality framework used, and others. Furthermore, there is a great deal of standards, white papers, and in general proposals of any kind related to software quality. Consequently, a unified software quality framework seems to be needed to compare, combine or select these proposals and to define new ones. In this paper we propose a MOF-compliant approach for structuring quality models in order to formalise software quality issues and deal with quality information modelling. We propose two types of models: a generic model, situated in the M2 MOF layer; and a hierarchy of reference models, defined in the M1 and M0 MOF layers. The generic model elements are derived from the UML metamodel by specialization. Then, we can instantiate them to get reference models that formalise (combinations of) existing proposals which may be further refined for defining quality frameworks to be used in different experiences. Each of these models is divided into three parts, namely fundamental concepts, metrics and context. We illustrate our proposal providing a multi-level reference model in the context of collection libraries quality evaluation.
Open Access
A new methodological approach for the evaluation of scaling up a latent storage module for integration in heat pumps
(MDPI, 2021) Zsembinszki, Gabriel; Mselle, Boniface Dominick; Vérez, David; Borri, Emiliano; Strehlow, Andreas; Nitsch, Birgo; Frazzica, Andrea; Palomba, Valeria; Cabeza, Luisa F.
A clear gap was identified in the literature regarding the in-depth evaluation of scaling up thermal energy storage components. To cover such a gap, a new methodological approach was developed and applied to a novel latent thermal energy storage module. The purpose of this paper is to identify some key aspects to be considered when scaling up the module from lab-scale to full-scale using different performance indicators calculated in both charge and discharge. Different normalization methods were applied to allow an appropriate comparison of the results at both scales. As a result of the scaling up, the theoretical energy storage capacity increases by 52% and 145%, the average charging power increases by 21% and 94%, while the average discharging power decreases by 16% but increases by 36% when mass and volume normalization methods are used, respectively. When normalization by the surface area of heat transfer is used, all of the above performance indicators decrease, especially the average discharging power, which decreases by 49%. Moreover, energy performance in charge and discharge decreases by 17% and 15%, respectively. However, efficiencies related to charging, discharging, and round-trip processes are practically not affected by the scaling up.
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A New Task Graph Model for Mapping Message Passing Applications
(Institute of Electrical and Electronics Engineers, 2007) Roig Mateu, Concepció; Ripoll, A.; Guirado Fernández, Fernando
The exploitation of parallelism in a message passing platform implies a previous modeling phase of the parallel application as a task graph, which properly reflects its temporal behavior. In this paper, we analyze the classical task graph models of the literature and their drawbacks when modeling message passing programs with an arbitrary task structure. We define a new task graph model called Temporal Task Interaction Graph (TTIG) that integrates the classical models used in the literature. The TTIG allows us to explicitly capture the ability of concurrency of adjacent tasks for applications where adjacent tasks can communicate at any point inside them. A mapping strategy is developed from this model, which minimizes the expected execution time by properly exploiting task parallelism. The effectiveness of this approach has been proved in different experimentation scopes for a wide range of message passing applications.
Open Access
A novel numerical methodology for modelling simple vapour compression refrigeration system
(Elsevier, 2017) Zsembinszki, Gabriel; Gracia Cuesta, Alvaro de; Moreno Argilés, Pere; Rovira, Ricard; González, Miguel Ángel; Cabeza, Luisa F.
The extended use of cooling and refrigeration systems in industrial, building and transport sectors may have a negative impact on the climate change and ozone depletion. Thus, important aspects related to these systems, such as refrigerant charge level, malfunction, or refrigerant leakage, must be taken into account. In this sense, the study of refrigeration system performance under different conditions can be very useful. In this paper, a novel methodology for modelling a simple compression refrigeration system is described. Starting from three input parameters, i.e. the ambient air temperature, the cold room air temperature, and the degree of superheating, a calculation algorithm based on iterative loops is used in the model to determine the operating point of the system. An experimental set-up consisting of a walk-in freezer unit was used for the development and validation of the model. The model is system dependent, i.e. empirical correlations must be derived for determining some of the features of system components. The numerical results are in good agreement with the experiment, therefore the model can be a reliable tool for the detection of a system malfunction.

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