Desarrollo de un composite ácido cáprico/ácido mirístico/soporte poroso para el almacenamiento de energía térmica

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMEN: Un composite constituido del eutéctico binario ácido cáprico/ácido mirístico (CA:MA) y un soporte mineral poroso colombiano fue desarrollado para aplicaciones de almacenamiento de energía térmica alrededor de los 26 °C. Diferentes porcentajes de impregnación de CA:MA (25%, 35% y 40%) en el soporte fueron estudiados para determinar los valores óptimos en términos de filtración. El mejor composite obtenido, con el 35% de CA:MA y menos del 1,5% de filtración, fue caracterizado térmicamente mediante calorimetría diferencial de barrido (DSC), así mismo, se evaluaron su conductividad térmica, capacidad calorífica y estabilidad térmica a través de las técnicas del hilo caliente, calorimetría diferencial de barrido modulada (MDSC) y ciclado térmico, respectivamente.ABSTRACT: A composite consisting of the binary eutectic capric acid/myristic acid (CA:MA) and a Colombian porous mineral support was developed for thermal energy storage applications around 26 °C. Different percentages of CA:MA impregnation (25%, 35% and 40%) in the support were studied to determine the optimal values in terms of leakage. The best composite obtained, with 35% CA:MA and less than 1.5% of leakage, was thermally characterized by differential scanning calorimetry (DSC). Besides, its thermal conductivity, heat capacity and thermal stability were evaluated through the techniques of hot wire, modulated differential scanning calorimetry (MDSC) and thermal cycling, respectively.info:eu-repo/semantics/publishedVersio

Chapter 9 - Buildings

This chapter aims to update the knowledge on the building sector since the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) from a mitigation perspective. Buildings and activities in buildings are responsible for a significant share of GHG emissions, but they are also the key to mitigation strategies. In 2010, the building sector accounted for approximately 117 Exajoules (EJ) or 32% of global final energy consumption and 19% of energy-related CO2 emissions; and 51% of global electricity consumption. Buildings contribute to a significant amount of F-gas emissions, with large differences in reported figures due to differing accounting conventions, ranging from around an eighth to a third of all such emissions. The chapter argues that beyond a large emission role, mitigation opportunities in this sector are also significant, often very cost-effective, and are in many times associated with significant co-benefits that can exceed the direct benefits by orders of magnitude. The sector has significant mitigation potentials at low or even negative costs. Nevertheless, without strong actions emissions are likely to grow considerably - and they may even double by mid-century - due to several drivers. The chapter points out that certain policies have proven to be very effective and several new ones are emerging. As a result, building energy use trends have been reversed to stagnation or even reduction in some jurisdictions in recent years, despite the increases in affluence and population. The chapter uses a novel conceptual framework, in line with the general analytical framework of the contribution of Working Group III (WGIII) to the IPCC Fifth Assessment Report (AR5), which focuses on identities as an organizing principle

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

Heat transfer enhancement of fatty acids when used as PCMs in thermal energy storage

Phase change materials (PCM) used in latent heat storage systems usually have very low thermal conductivities. This is a major drawback in maintaining the required heat exchange rate between PCM and heat transfer fluid. This paper investigates the enhancement of the heat transfer between PCM and heat transfer fluid, using high thermal conductivity as additives like stainless steel pieces, copper pieces and graphite-PCM composite material. In the experiments, palmitic-lauric acid (80:20) (PL) and stearic-myristic acid (80:20) (SM) were used as PCMs. Test results show that heat transfer enhancement of copper pieces was better at 0.05 L s-1 flow rate compared to 0.025 L s-1. Using copper as an additive increased the heat transfer rate 1.7 times for melting and 3.8 times for freezing when flow rate was 0.050 L s-1. Decreasing the flow rate from 0.050 to 0.025 L s-1, increased the melting times 1.3 times and freezing times 1.8 times, decreasing heat transfer rates accordingly. The best result of heat transfer enhancement was observed for the PCM-graphite composite. However, changing the flow rate did not affect the heat transfer rate when graphite was used as additive. Copyright © 2007 John Wiley &amp; Sons, Ltd

Optimization of three new compositions of stabilized rammed earth incorporating PCM: Thermal properties characterization and LCA

10.1016/j.conbuildmat.2013.05.01

Life cycle assessment of a ventilated facade with PCM in its air chamber

10.1016/j.solener.2013.07.023In the buildings sector, the use of ventilated double skin facades in order to reduce the energy demand and the environmental impact of the building during its operational phase has grown significantly. However, the use of this constructive system could lead to high environmental costs during the manufacturing and dismantling phase of the building. This paper presents a life cycle assessment (LCA) study based on the EcoIndicator 99 of a ventilated facade with PCM in its air chamber. Two cubicles were built in an experimental set-up located in Puigverd de Lleida (Spain), one with this ventilated facade system and the other without. The differences in the electrical energy consumption of the HVAC systems were registered and used to determine the environmental savings produced during the operational phase of each building. The results of the LCA show that considering a lifetime of 50 years, the use of this particular ventilated facade reduces by 7.7% the overall environmental impact of the whole building. It also highlights that the environmental payback of this active system is significantly lower than other systems which use PCM in the building envelopes. The environmental payback of the system is 30 years, which can be reduced to only 6 years if instead steel wood would have been used in the structure

Experimental evaluation of commercial heat exchangers for use as PCM thermal storage systems

Phase change materials (PCM) possess a great capacity of accumulation of energy in their temperature of fusion thanks to the latent heat. These materials are used in applications where it is necessary to store energy due to the temporary phase shift between the offer and demand of thermal energy. Thus, possible applications are the solar systems as well as the recovery of residual heat for its posterior use in other processes. In spite of this great potential, the practical feasibility of latent heat storage with PCM is still limited, mainly due to a rather low thermal conductivity. This low conductivity implies small heat transfer coefficients and, consequently, thermal cycles are slow and not suitable for most of the potential applications. This work investigates experimentally the heat transfer process during melting (charge) and solidification (discharge) of five small heat exchangers working as latent heat thermal storage systems. Commercial paraffin RT35 is used as PCM filling one side of the heat exchanger and water circulates through the other side as heat transfer fluid. Average thermal power values are evaluated for various operating conditions and compared among the heat exchangers studied. When the comparison is done for average power per unit area and per average temperature gradient, results show that the double pipe heat exchanger with the PCM embedded in a graphite matrix (DPHX-PCM matrix) is the one with higher values, in the range of 700-800 W/m2-K, which are one order of magnitude higher than the ones presented by the second best. On the other hand, the compact heat exchanger (CompHX-PCM) is by large the one with the highest average thermal power (above 1 kW), as it has the highest ratio of heat transfer area to external volume. © 2009 Elsevier Ltd. All rights reserved.ENE2005-08256-C02-01/ALT, 2005-SGR-00324Marc Medrano would like to thank the Spanish Ministry of Education and Science for his Ramon y Cajal research appointment. Metin Yilmaz would like to thank his Erasmus fellowship. The work was partially funded with the Project ENE2005-08256-C02-01/ALT and the Project 2005-SGR-00324

Utilization of phase change materials in solar domestic hot water systems

Thermal energy storage systems which keep warm and cold water separated by means of gravitational stratification have been found to be attractive in low and medium temperature thermal storage applications due to their simplicity and low cost. This effect is known as thermal stratification, and has been studied experimentally thoughtfully. This system stores sensible heat in water for short term applications. Adding PCM (phase change material) modules at the top of the water tank would give the system a higher storage density and compensate heat loss in the top layer because of the latent heat of PCM. Tests were performed under real operating conditions in a complete solar heating system that was constructed at the University of Lleida, Spain. In this work, new PCM-graphite compounds with optimized thermal properties were used, such as 80:20 weight percent ratio mixtures of paraffin and stearic acid (PS), paraffin and palmitic acid (PP), and stearic acid and myristic acid (SM). The solar domestic hot water (SDHW) tank used in the experiments had a 150 L water capacity. Three modules with a cylindrical geometry with an outer diameter of 0.176 m and a height of 0.315 m were used. In the cooling experiments, the average tank water temperature dropped below the PCM melting temperature range in about 6-12 h. During reheating experiments, the PCM could increase the temperature of 14-36 L of water at the upper part of the SDHW tank by 3-4 °C. This effect took place in 10-15 min. It can be concluded that PS gave the best results for thermal performance enhancement of the SDHW tank (74% efficiency). © 2008 Elsevier Ltd. All rights reserved.Ministry of Education and Science: ENE2005-08256-C02-01/ALTThis study was supported by The Scientific and Technical Research Council of Turkey (TUBITAK) and The Ministry of Education and Science of Spain through the project ENE2005-08256-C02-01/ALT

Materials used as PCM in thermal energy storage in buildings: A review

In recent years the use of thermal energy storage with phase change materials has become a topic with a lot of interest within the research community, but also within architects and engineers. Many publications have appeared, and several books, but the information is disseminated and not very much organised. This paper shows a review of the latest publications on the use of phase change materials (PCM) in buildings. The paper compiles information about the requirements of the use of this technology, classification of materials, materials available and problems and possible solutions on the application of such materials in buildings.Review Phase change materials (PCM) Thermal energy storage (TES) Building Energy efficiency

Multi-objective optimization coupled with life cycle assessment for retrofitting buildings

10.1016/j.enbuild.2014.07.001In this work we present a systematic tool for the optimal retrofit of buildings that considers several economic and environmental criteria simultaneously at the design stage. Our approach is based on a rigorous mixed-integer linear program (MILP) that identifies in a systematic manner the best alternatives for reducing the environmental impact of buildings. These include the use of different insulation materials and windows as well as the installation of solar panels. Environmental concerns are explicitly accounted for in this MILP by means of Life Cycle Assessment (LCA) principles, which allow evaluating the impact of each alternative being assessed considering all the stages in its life cycle. We illustrate the capabilities of our approach using a case study that considers weather data for Central Portuga