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Abstract An exergy analysis, which only considers the unavoidable exergy destruction, is conducted for single, double, triple and half effect Water–Lithium bromide absorption cycles. Thus, the obtained performances represent the maximum achievable performance under the given operation conditions. The coefficient of performance (COP), the exergetic efficiencies and the exergy destruction rates are determined and the effect of the heat source temperature is evaluated. As expected, the COP increases significantly from double lift to triple effect cycles. The exergetic efficiency varies less among the different configurations. In all cycles the effect of the heat source temperature on the exergy destruction rates is similar for the same type of components, while the quantitative contributions depend on cycle type and flow configuration. Largest exergy destruction occurs in the absorbers and generators, especially at higher heat source temperatures.

The present work evaluates the environmental impact of including phase change materials (PCM) in a typical Mediterranean building. A Life Cycle Assessment (LCA) is developed for three monitored cubicles built in Puigverd de Lleida (Spain). It is possible to control the inner temperature of the cubicles using a domestic heat pump for cooling and an electrical radiator for heating: The energy consumption is registered to determine the energy savings achieved. The aim is to analyze if these energy savings are large enough to balance the environmental impact originated during the manufacturing of PCM. Some hypothetical scenarios, such as different systems to control the temperature different PCM types or different weather conditions are proposed and studied using LCA process to point out the critical issues. Furthermore, a parametric analysis of the lifetime of buildings is developed. Results show that the addition of PCM in the building envelope, although decreasing the energy consumption during operation, does not reduce significantly the global impact throughout the lifetime of the building. For the hypothetical scenario considering summer conditions all year around and a lifetime of the building of 100 years, the use of PCM reduces the overall impact by more than 10%.

Thermal energy storage (TES) is nowadays presented as one of the most feasible solutions in achieving energy savings and environmentally correct behaviors. Its potential applications have led to R&D activities and to the development of various technology types. However, so far there is no available data on a national scale in Spain and on a continental level in Europe, to corroborate the associated energetic and environmental benefits derived from TES. This is why, based on a previous potential calculation initiative model performed in Germany, this work intends to provide a first overview of the Spanish TES potential as well as an European overview. Load reductions, energy savings, and CO2 emissions reductions are tackled for the buildings and industrial sector. Results depend on the amount of implementation and show that, in the case of Europe for instance, yearly CO2 emissions may get to be cut down up to around 6% in reference to 1990 emission levels.

Public universities face the challenge of retrofitting the actual campus buildings into nearly zero-energy buildings (NZEB). In this study, a novel methodology for evaluating historical energy use and renewable energy production for all the buildings of a university, including hourly, daily and monthly data assessments is presented. This analysis is useful as a baseline for comparisons with future energy retrofits and enables determining the current gap between actual energy indicators at building and campus levels and the established limits for NZEB non-residential buildings in the European Union. The methodology is applied to a case study at the University of Lleida, a typical average-size university in Spain. Results show a wide variation in energy use among campus buildings, ranging between 50 and 470 kWh/m2 year. Constant or slightly increasing energy use and decreasing trends in renewable energy generation are observed. The daily electricity profiles have shown similar patterns among buildings and substantial potential energy savings during unoccupied periods. In the NZEB analysis, the average non-renewable primary energy use is about 4 times higher than the maximum estimated Spanish threshold range of 45-55 kWh/m2 year. Deep energy renovation strategies are, thus, needed for universities to meet EU NZEB targets. The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE).

Alveolar bricks are being introduced in building sector due to the simplicity of their construction system and to the elimination of the insulation material. Nevertheless, it is not clear if this new system is energetically efficient and which is its thermal behaviour. This paper presents an experimental and theoretical study to evaluate the thermal behaviour of the alveolar brick construction system, compared with a traditional Mediterranean brick system with insulation. The experimental study consists of measuring the thermal performance of four real house-like cubicles. The thermal transmittance in steady-state, also known as U-value, is calculated theoretically and experimentally for each cubicle, presenting the insulated cubicles as the best construction system, with differences around 45% in comparison to the alveolar one. On the other hand, experimental results show significantly smaller differences on the energy consumption between the alveolar and insulated construction systems during summer period (around 13% higher for the alveolar cubicle). These values demonstrate the high thermal efficiency of the alveolar system. In addition, the lack of agreement between the measured energy consumption and the calculated U-values, guides the authors to analyze the thermal inertia of the different building components. Therefore, several transient parameters, extracted from the heat transfer matrix and from experimental data, are also evaluated. It can be concluded that the alveolar brick construction system presents higher thermal inertia than the insulated one, justifying the low measured energy consumption.

Earthen architecture historically has been widely used for wall construction around the world, particularly in developing countries. Most of the earthen dwellings in Burkina Faso are built traditionally with adobe walls. This construction technique is low-cost but it is easily eroded by water and often lacks satisfactory thermal comfort. In this work an alternative low-cost earthen construction system, the earthbag technique is presented and combined with passive design measures to assess the improvements in thermal comfort. Inspired in a real domeshape earthbag dwelling constructed in a Medical Training Center in Ouagadougou (Burkina Faso), free-floating building energy simulations were performed for both the traditional adobe Burkinabe dwelling and the earthbag dwelling using EnergyPlus. Besides free-floating direct temperature results, two indicators of annual comfort were used, namely the hours of discomfort and the discomfort degree days. ASHRAE Standard 55 Adaptive Comfort model was used to assess comfort conditions. Results show that the combination of night ventilation and roof solar protection in the high-inertia earthbag building leads to an almost total elimination of thermal discomfort during the year (only 209 h not meeting adaptive comfort and 3.1 ºC-days of discomfort). The same combination of passive measures in the traditional Burkinabe dwelling improves significantly thermal comfort when compared to the base case, but it is not as effective in providing comfort, with more than 3000 h and 200 degree-days of annual discomfort. The authors would like to thank the “Oficina de Desenvolupament i Cooperació (ODEC)” of the University of Lleida (UdL), Spain, for the grant projects of 2014, 2015, 2016 and 2017, the “Escola Politècnica Superior” of UdL, the “Consell Social” of UdL for their donatives, and Domoterra association. The authors would also thank all the students that participated in the construction of the earthbag building. Ariadna Carrobé would like to thank the Catalan Government (AGAURGeneralitat de Catalunya) for her collaboration grant 2017-2018 in the Computer Sciences and Industrial Engineering Department at University of Lleida. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 659).

The main objective of this paper is to demonstrate experimentally that it is possible to improve the thermal comfort and reduce the energy consumption of a building without substantial increase in the weight of the construction materials with the inclusion of phase change materials (PCM). PCM are a suitable and promising technology for this application. This paper presents an experimental setup to test PCM with various typical insulation and construction materials in real conditions in Puigverd de Lleida (Lleida, Spain). Nine small house-sized cubicles were constructed: two with concrete, five with conventional brick, and two with alveolar brick. PCM was added in one cubicle of each typology. For each type of construction specific experiments were done. In all cubicles, free-floating temperature experiments were performed to determine the benefits of using PCM. A Trombe wall was added in both concrete cubicles and its influence was investigated. All brick cubicles were equipped with domestic heat pumps as Heating, Ventilation, and Air Conditioning (HVAC) system; therefore, the energy consumption was registered, providing real information about the energy savings. Results were very good for the concrete cubicles, since temperature oscillation were reduced by up to 4°C through the use of PCM and also peak temperatures in the PCM cubicle were shifted in later hours. In the brick cubicles, the energy consumption of the HVAC system in summer was reduced by using PCM for set points higher than 20°C. During winter an insulation effect of the PCM is observed, keeping the temperatures of the cubicles warmer, especially during the cold hours of the day.

Abstract Sandwich panels are a good option as building materials, as they offer excellent characteristics in a modular system. The goal of this study was to demonstrate the feasibility of using the microencapsulated PCM (Micronal BASF) in sandwich panels to increase their thermal inertia and to reduce the energy demand of the final buildings. In this paper, to manufacture the sandwich panel with microencapsulated PCM three different methods were tested. In case 1, the PCM was added mixing the microencapsulated PCM with one of the components of the polyurethane. In the other two cases, the PCM was added either a step before (case 2) or a step after (case 3) to the addition of the polyurethane to the metal sheets. The results show that in case 1 the effect of PCM was overlapped by a possible increase in thermal conductivity, but an increase of thermal inertia was found in case 3. In case 2, different results were obtained due to the poor distribution of the PCM. Some samples showed the effect of the PCM (higher thermal inertia), and other samples results were similar to the conventional sandwich panel. In both cases (2 and 3), it is required to industrialize the process to improve the results.