1,473 research outputs found
Building thermal storage technology: Compensating renewable energy fluctuations
Emerging technologies and new intelligent management systems will be needed to rise to the energy challenges posed by buildings today. Thermally activated building systems (TABS) are attracting growing interest on the back of their energy savings potential. The TABS studied in this article, a new prefabricated panel designed for installation in residential building façades, was characterised by the high thermal inertia afforded by the phase change materials in its composition. The design and assessment of the potential savings derived from TABS require specific characterisation methodologies to estimate the amount of useful energy available to control the indoor environment. A two-stage approach was adopted for the TABS studied here with ``ideal'' operating control (the building is assumed to be at a constant desired temperature). The first stage involved a simplified method for characterising system behaviour based on performance maps developed from CFD simulations. Such maps can be used to quickly assess changes in system energy performance following on variations in design and operating parameters. In the second, the TABS was integrated into a building with a simplified model to assess monthly energy demand to evaluate the system potential for energy savings in representative types of Spanish single-family housing in different climate zones. The first-stage findings showed that given the system significant inertia, it discharged for several days, even when charging occurred only on the first, ensuring a wide operating range adaptable to renewable resource limitations. The analysis of potential, in turn, revealed that savings of over 40% in heating demand are possible even under the least favourable circumstances.This study was funded by Spanish Ministry of Economy and Competitiveness under the INPHASE (RTC-2015-3583-5) and DACAR (BIA2016-77431-C2-2-R), the European Regional Development Fund (ERDF) and the University of Seville under its Research Plan VI (VPPI-US). Prof. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group GREiA (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme
Evaporative Mist Cooling as Heat Dissipation Technique: Experimental Assessment and Modelling
The severity of extreme weather conditions brought on by climate change are conditioning
quality of life, economic development, and well-being in today’s cities. Conventional measures have
been shown to be insu cient for tackling climate change and must be supplemented with ecofriendly
approaches. Hence, the scientific community’s endeavor to develop natural cooling techniques that
lower energy consumption while delivering satisfactory comfort levels. For its simplicity and low
cost, evaporative cooling has gained in popularity in recent years. The substantial cooling power to
be drawn from evaporative mist cooling, makes it an attractive alternative to conventional systems.
Research conducted to date on the technique has focused on producing cold air, whilst cooling
the water involved has been neither assessed nor experimentally validated. No readily applicable
simplified model for the system able to use operating parameters as input variables has been defined
either. The present study consequently aimed to experimentally assess the cooling power of the
evaporation of sprayed water and experimentally validate a simplified model to assess and design
such systems. The findings confirmed the cooling power of the technique, with declines in water
temperature of up to 6 C, and with it the promise a orded by this natural air conditioning method.
Finally, simplified model developed allows to evaluate this technique like a conventional system for
producing fresh water.Urban Innovation Actions by the CartujaQanat UIA03-30
Design of the Refurbishment of Historic Buildings with a Cost-Optimal Methodology: A Case Study
The transformation of existing buildings into Near Zero Energy Buildings or even positive
energy buildings remains a major challenge. In particular, historic buildings are an important cultural
heritage that, in most cases, may be rehabilitated and reused for new purposes. However, achieving
higher e ciencies in those buildings presents many di culties, since there is a need to preserve
aesthetic values and minimize impact on the buildings’ initial construction. In this work, a roadmap
that allows rehabilitating a building from the eighteenth century is developed, turning it into a
landmark building, to be used as a museum in the near future. The procedure is based on 3D models
using REVIT software and detailed energy simulations supported by a cost-optimal methodology.
The results reveal how conventional methodologies shown in the literature may improve the energy
performance of the buildings during the heating regime, but performance may deteriorate during
the cooling season. For that reason, the present study includes the design of a night ventilation
system which allows not only solving this problem but also to reducing the cooling demands by more
than 43% with little additional costs. In conclusion, historic buildings (which traditionally have a
high thermal mass) have increased thermal storage potential by using the structures of the buildings
themselves as well as passive cooling techniques
Systematic Simplified Simulation Methodology for Deep Energy Retrofitting Towards Nze Targets Using Life Cycle Energy Assessment
The reduction of energy consumption in the residential sector presents substantial potential
through the implementation of energy e ciency improvement measures. Current trends involve the
use of simulation tools which obtain the buildings’ energy performance to support the development
of possible solutions to help reduce energy consumption. However, simulation tools demand
considerable amounts of data regarding the buildings’ geometry, construction, and frequency of
use. Additionally, the measured values tend to be di erent from the estimated values obtained with
the use of energy simulation programs, an issue known as the ‘performance gap’. The proposed
methodology provides a solution for both of the aforementioned problems, since the amount of data
needed is considerably reduced and the results are calibrated using measured values. This new
approach allows to find an optimal retrofitting project by life cycle energy assessment, in terms of
cost and energy savings, for individual buildings as well as several blocks of buildings. Furthermore,
the potential for implementation of the methodology is proven by obtaining a comprehensive energy
rehabilitation plan for a residential building. The developed methodology provides highly accurate
estimates of energy savings, directly linked to the buildings’ real energy needs, reducing the di erence
between the consumption measured and the predictions
Experimental analysis of atmospheric heat sinks as heat dissipators
Artículo premiado ETSI 1er trimestre 2020Overheating, a general problem both in urban spaces and inside buildings, calls for the deployment of passive cooling techniques to reduce energy consumption, protect the environment and institute satisfactory comfort levels. A key factor in such techniques is the capitalisation on the cooling potential of natural heat sinks. The sky, one such sink, has essentially limitless cooling power. In addition, its temperature on fair nights is lower than that of other environmental sinks (ground and air). The sky's promise in that respect prompted this exploration of the potential of nocturnal radiation cooling. A review of the state of the art revealed that in all the radiative dissipators developed and tested to date the dissipation fluid (water) transferred heat indirectly to the heat sink (the sky) by circulating water inside solar collector pipes. The highest values reported for maximum dissipation power were on the order of 100 W/m2. The present study aimed to asses night time dissipation power in a dual system in which water circulated either inside pipes or flowed down the outer surface of the collector. The two modes, one involving in-pipe circulation and the other outer surface downflow, were compared experimentally, for whereas the former has been analysed and assessed by earlier researchers, the latter has not. The empirical findings verified that downflow setups enhanced cooling, delivering up to five-fold the dissipation power obtained with the conventional arrangement.Ministerio de Economía y Competitividad BIA2016-77431-C2-2-RFondos FEDER UIA03-30
Adaptative Cover to Achieve Thermal Comfort in Open Spaces of Buildings: Experimental Assessment and Modelling
The global need for healthy and safe open spaces faces continuous temperature rise due to the heat island phenomenon and climate change. This problem requires new strategies for improving the habitability of open spaces (indoor and outdoor conditions in buildings). These techniques include reducing solar radiation, reducing the temperature of surrounding surfaces, and reducing the air temperature. The radiant solutions are essential for outdoor comfort, both in summer and in winter. They are easy to integrate into open spaces. This study explores a new concept of radiant solutions adapted for outdoor spaces. The solution was evaluated in a test cell to obtain its thermal behaviour in different operation conditions. Solutions were optimised for operating in a cooling regimen since it has been identified that the demands for comfort in open spaces in hot climates during the most severe summer months are more pronounced. Experimental results have allowed getting an inverse model to analyse the thermal behaviour of the solution. The inverse model achieved high precision in its estimations. Also, it facilitated knowing the radiant and convective effects. Only the radiant heat flux is relevant in open spaces with a low level of air confinement. Finally, the discussion describes the application of the proposed model. The model allows the replicability of the solution—creating new designs (integration) or evaluating into different operating conditions of the system. This discussion demonstrates the high level of knowledge acquired in the characterisation of the solution studied.e European Commission / European Regional Development Funds (ERDF) UIA03-301-CartujaQanat of Urban Innovative Action (UIA
CartujaQanat: Recovering the street life in a climate changing world. Bioclimatic lattices and confinement of air in exterior conditions
Article number 03205
On the crystal structure thermal evolution of formamidinium lead tribromide, CH(NH2)2PbBr3
Although methylammonium lead triiodide (CH3NH3PbI3) is recognized as the best candidate for photovoltaic applications, unfortunately it undergoes fast degradation when exposed to moisture and mild temperatures. Among hybrid organic-inorganic perovskites, formamidinium lead tribromide (FA: formamidinium, CH(NH2)2+) is an excellent alternative given its long-term stability. Here we present a structural study from synchrotron X-ray and neutron diffraction of an undeuterated FAPbBr3 specimen, carried out to follow its crystallographic behaviour in the 1-298 K temperature range. Two phase transitions are identified; at 256-261 K from the cubic structure observed at RT (Pm3m), to a tetragonal symmetry (P4/mbm), and at 159-160 K to an orthorhombic phase (space group Pnma). Our neutron diffraction data allowed us to unveil the configuration of the organic FA units and their full localization within the mentioned temperature range, thus improving the crystallographic description of this compound. The evolution with temperature of the H-bonds between the organic molecule and the inorganic cage is followed. The UV-Vis diffuse reflectance spectrum shows a band gap of 2.23 eV, making it a suitable material for optoelectronic devices.Fil: Abia, Carmen. Instituto de Ciencia de Materiales de Madrid; España. Institut Laue Langevin; FranciaFil: Lopez, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Investigaciones en Tecnología Química. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Investigaciones en Tecnología Química; Argentina. Instituto de Ciencia de Materiales de Madrid; EspañaFil: Álvarez Galván, María Consuelo. Consejo Superior de Investigaciones Científicas; EspañaFil: Canadillas Delgado, Laura. Institut Laue Langevin; FranciaFil: Fernández Díaz, María Teresa. Institut Laue Langevin; FranciaFil: Alonso, José Antonio. Instituto de Ciencia de Materiales de Madrid; Españ
Low prevalence of vancomycin-resistant enterococci in clinical samples from hospitalized patients of the Canary Islands, Spain
Over the last decade vancomycin-resistant enterococci (VRE) have emerged as nosocomial pathogens. The aim of this study was to determine the prevalence of VRE in clinical samples from hospitalized patients in the Canary Islands. From April to November 2000, 437 enterococci were isolated from patients hospitalized at the four main health care centers in those islands. Identification to the species level was performed with the GPS-TA (Vitek 1) or the Wider I system. A PCR assay was used to determine the genotype of glycopeptide resistance (vanA, vanB, vanC1, and vanC2/C3 genes). Only three (0.7%) VRE were detected: one vanA Enterococcus faecalis, and two vanC1 Enterococcus gallinarum. To our knowledge, this is the first VRE study carried out in the Canary Islands hospitals, and the results showed a low prevalence of VRE
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