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Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

The united nations educational, scientific and cultural organization (UNESCO) considers the historic urban landscapes as the world heritages. Managing historic city centers and maintaining historic cores are the emerging challenges for sustainable urban planning. Today, the historic cores form an important part of the economic, social, environmental, and physical assets and capacities of contemporary cities, and play a strategic role in their development. One of the most important approaches to the development of central textures, especially in historical and cultural cities, is the sustainable urban regeneration approach, which encompasses all aspects of sustainability, such as the economic, social, cultural and environmental aspects. To maintain sustainability and regeneration of historic cores of cities, it is necessary to provide insight into the underlying characteristics of the local urbanization. Furthermore, the fundamental assets are to be investigated as indicators of sustainable regeneration and drivers of urban development. In the meantime, a variety of research and experience has taken place around the world, all of which has provided different criteria and indicators for the development of strategies for the historic cores of cities. The present study, through a meta-analytic and survey method, analyzing the experience and research reported in 139 theoretical and empirical papers in the last twenty years, seeks to provide a comprehensive conceptual model taking into account the criteria and indices of sustainable regeneration in historic cores of cities. The quality of the survey has been ensured using the preferred reporting items for systematic reviews and meta-analysis (PRISMA).

Solar photovoltaic (PV) energy systems are one of the most widely deployed renewable technologies in the world. The efficiency of solar panels has been studied during the last few decades, and, to date, it has not been possible to displace the production of energy using crystalline silicon wafer-based technology whose efficiency has reached values around 26.1%. Moreover, using solar tracking PV systems has become a feasible alternative to increase the electric output of PV silicon technologies instead of using the conventional fixed PV installation on a flat or sloping surface. The following study has compared fixed and dual-axis sun-tracking PV panels in order to quantify the enhancement associated with the amount of energy harvested when using dual-axis tracking PV systems in the city of Manta, located in a coastal region of Ecuador. In order to carry out this study, an IoT monitoring system based on Raspberry Pi3 and Arduino platforms was used. Measurements of solar radiation (W/m2), light intensity (Lux), temperature (°C), short-circuit current (A), and open-circuit voltage (V) were taken every minute for both systems. The results prove that the dual-axis tracking PV system produces, on average, 19.62% more energy than the static PV system. These results present an 8.62% energy increase with respect to a previous study carried out in an equatorial region with similar characteristics to those of the city of Manta, where a one-axis tracking PV system was used.

Abstract Thermal properties of the different building envelopes, such as thermal transmittance in steady state, heat storage capacity and dynamic thermal responses, must be taken into account during the design phase of buildings. The evaluation and measurement of these parameters in multilayered samples are difficult because of the irregular morphology of the used materials and the difficulty in providing the well-controlled environment needed for the measurements. A new equipment has been designed to measure the thermal response and heat capacity of composite walls of different materials simulating real building envelopes. The equipment presented in this paper was used to test the improvement in the thermal response of a building envelope due to the incorporation of PCM. This study is focused on wood structural panels attached to a gypsum board, which is either impregnated or not with PCM. The four edges of the composite sample are properly insulated to ensure one-dimensional heat flow. The two faces of the sample are exposed to controlled environments heated and cooled by copper coils with thermo stated water supplied by water baths. The measured surface heat fluxes at both surfaces of the sample and temperature distribution in the sample provide accurate assessment to thermal mass and dynamic response of the composite wall, while the steady state measurements provide an accurate estimate of its effective thermal transmittance.

La primera biorrefinación con lignina del álamo nórdico para producir fibras de celulosa podría desplazar la producción de algodón en tierras agrícolas Al cruzar Populus trichocarpa 3 P. trichocarpa de una población distante, se obtuvieron álamos híbridos que pueden crecer rápidamente en tierras marginales en climas del norte. Estos híbridos pueden transformarse mediante fraccionamiento catalítico reductor para producir una fibra textil deslignificada que puede ser un sustituto del algodón, así como un biocombustible alimentado con lignina en el rango de gasolina-aviación-diesel. La sostenibilidad de esta cadena de valor fue evaluada por LCA y mostró beneficios sustanciales en términos de uso de agua en comparación con la producción de algodón. Le bioraffinage en lignine du peuplier nordique pour produire des fibres de cellulose pourrait déplacer la production de coton sur les terres agricoles En croisant Populus trichocarpa 3 P. trichocarpa d'une population éloignée, des peupliers hybrides ont été obtenus qui peuvent croître rapidement sur des terres marginales dans les climats nordiques. Ces hybrides peuvent être transformés par fractionnement catalytique réducteur pour donner une fibre textile délignifiée qui peut remplacer le coton ainsi qu'un biocarburant ligninérisé dans la gamme essence-aviation-diesel. La durabilité de cette chaîne de valeur a été évaluée par LCA et a montré des avantages substantiels en termes d'utilisation de l'eau par rapport à la production de coton. Lignin-first biorefining of Nordic poplar to produce cellulose fibers could displace cotton production on agricultural lands By crossing Populus trichocarpa 3 P. trichocarpa from a distant population, hybrid poplar trees were obtained that can grow rapidly on marginal lands in northern climates.These hybrids can be transformed by reductive catalytic fractionation to yield a delignified textile fiber that can be a substitute for cotton as well as a ligninderived biofuel in the gasoline-aviation-diesel range.The sustainability of this value chain was evaluated by LCA and showed substantial benefits in terms of water use compared with cotton production. يمكن للتكرير الحيوي الأول لليجنين للحور الشمالي لإنتاج ألياف السليلوز أن يحل محل إنتاج القطن في الأراضي الزراعية من خلال عبور Populus trichocarpa 3 P. trichocarpa من مجموعة سكانية بعيدة، تم الحصول على أشجار الحور الهجينة التي يمكن أن تنمو بسرعة على الأراضي الهامشية في المناخات الشمالية. يمكن تحويل هذه الهجينة عن طريق التجزئة التحفيزية المختزلة لإنتاج ألياف نسيج منزوعة الكرامة يمكن أن تكون بديلاً عن القطن بالإضافة إلى وقود حيوي خفيف في نطاق البنزين والطيران والديزل. تم تقييم استدامة سلسلة القيمة هذه من قبل LCA وأظهرت فوائد كبيرة من حيث استخدام المياه مقارنة بإنتاج القطن.

To fulfill the ever-increasing power demands of deep space exploration, the output performance of radioisotope thermoelectric generators, the only accessible power source, must be enhanced in several aspects, including thermoelectric properties of materials, geometry, welding, etc. In this study, we present our results on the development of a novel thermoelectric slurry suitable for the 3D printing of thermoelectric generators with optimized leg geometry. The rheological properties of the slurry are optimized by combining proper amounts of organic solvent, binder, and bismuth telluride-based thermoelectric powder. The addition of Cu to the slurry as a conductive additive are also investigated. The homogeneous dispersion of Cu within the material not only increases the electrical conductivity of the final thermoelectric leg significantly but also promotes the crystallization of the thermoelectric particles during the sintering process. These effects result in 3D-printed thermoelectric composites exhibiting ZT values up to 0.91 and extended optimum operating temperature range. Thermoelectric modules composed of 3D-printed thermoelectric legs show excellent output performance and structural strength. This work could also produce other special shaped thermoelectric devices to match irregularly shaped heat sources to reduce contact heat loss and improve output performance.