• Energy Research
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The first step in order to comply with the European Union goals of Near to Zero Energy Buildings is to reduce the energy consumption in buildings. Most of the building consumption is related to the use of active systems to maintain the interior comfort. Passive design strategies contribute to improve the interior comfort conditions, increasing the energy efficiency in buildings and reducing their energy consumption. In this work, an analysis of the passive strategies used in Net Energy Plus Houses has been made. The participating houses of the Solar Decathlon Europe 2012 competition were used as case studies. The passive design strategies of these houses were compared with the annual simulations, and the competition monitored data, especially during the Passive Monitored Period. The analysis included the thermal properties of the building envelope, geometric parameters, ratios and others passive solutions such as Thermal Energy Storage systems, evaporative cooling, night ventilation, solar gains and night sky radiation cooling. The results reflect the impact of passive design strategies on the houses' comfort and efficiency, as well as their influence in helping to achieve the Zero Energy Buildings category.

Given the global energy and environmental situation, the European Union has been issuing directives with increasingly demanding requirements in term of the energy efficiency in buildings. The international competition of sustainable houses, Solar Decathlon Europe (SDE), is aligned with these European objectives. SDE houses are low energy solar buildings that must reach the near to zero energy houses’ goal. In the 2012 edition, in order to emphasize its significance, the Energy Efficiency Contest was added. SDE houses’ interior comfort, functioning and energy performance is monitored. The monitoring data can give an idea about the efficiency of the houses. However, a jury comprised by international experts is responsible for carrying out the houses energy efficiency evaluation. Passive strategies and houses services are analyzed. Additionally, the jury's assessment has been compared with the behavior of the houses during the monitoring period. Comparative studies make emphasis on the energy aspects, houses functioning and their interior comfort. Conclusions include thoughts related with the evaluation process, the results of the comparative studies and suggestions for the next competitions.

Abstract Thermal mass combined with other passive strategies can play an important role in buildings energy efficiency, minimizing the need of space-conditioning mechanical systems. However, the use of lightweight materials with low thermal mass is becoming increasingly common. Phase Change Materials (PCMs) can add thermal energy storage benefits to lightweight constructions. There are many studies about the use of PCM in buildings, but there are still some difficulties for effective use and practical application of these materials. The study of applications used in real buildings could help us find solutions to these difficulties. This paper analyzed different PCM applications presented in highly efficient lightweight construction houses that have participated in the American Solar Decathlon, an international competition organized by U.S. Department of Energy. These houses have been tested and monitored in Washington DC, place with suitable climate conditions for short term thermal storage systems. The study started with a classification of the PCM applications and included an analysis of the systems, materials, switching temperatures, containments and design strategies used to improve the houses energy performance. Also, it included results of numerical simulations and experimentation that the participant team had done, complemented with information available in the literature about similar materials or applications.

Abstract Building retrofitting is one of actions promoted by the European Union in order to reduce the energy dependence, the consumption of fossil fuels and the CO 2 emissions. In climates with high thermal variability, thermal mass can increase the hours of thermal comfort and reduce the need for mechanical conditioning systems, helping to reduce the energy consumption in both new and existing buildings. However, it is not always feasible to use traditional materials to increase thermal energy storage in building retrofitting. The use of Phase Change Materials (PCM) can be an alternative to provide high thermal storage capacity to rehabilitated buildings as their applications have relatively low weight and need little or no additional space. Different ways in which PCM can be used in building rehabilitation have been analyzed, and the influence of PCM drywall panels and fenestration was evaluated in different Spanish cities. The results reflect the importance of the Window to Wall ratio and the Shading Factor in the thermal behavior of buildings. Also, they show that, with proper selection of these parameters, the use of PCM drywall can contribute to increase the thermal comfort, reducing the peaks and temperature fluctuations in existing buildings, particularly under overheating conditions.

The building sector consumes as much as 80% of generated electricity in the UAE; during the COVID-19 pandemic, the energy consumption of two sub-sectors, i.e., commercial (50%) and residential (30%), was significantly impacted. The residential sector was impacted the most due to an increase in the average occupancy during the lockdown period. This increment continued even after the lockdown due to the fear of infection. The COVID-19 pandemic and its lockdown measures can be considered experimental setups, allowing for a better understanding of how users shift their consumption under new conditions. The emergency health measures and new social dynamics shaped the residential sector’s energy behavior and its increase in electricity consumption. This article presents and analyzes the identified issues concerning residential electricity consumers and how their behaviors change based on the electricity consumption data during the COVID-19 period. The Dubai Electricity and Water Authority conducted a voluntary survey to define the profiles of its residential customers. A sample of 439 consumers participated in this survey and four years of smart meter records. The analysis focused on understanding behavioral changes in consumers during the COVID-19 period. At this time, the dwellings were occupied for longer than usual, increasing their domestic energy consumption and altering the daily peak hours for the comparable period before, during, and after the lockdown. This work addressed COVID-19 and the lockdown as an atypical case. The authors used a machine learning model and the consumption data for 2018 to predict the consumption for each year afterward, observing the COVID-19 years (2020 and 2021), and compared them with the so-called typical 2019 predictions. Four years of fifteen-minute resolution data and the detailed profiles of the customers led to a better understanding of the impacts of COVID-19 on residential energy use, irrespective of changes caused by seasonal variations. The findings include the reasons for the changes in consumption and the effects of the pandemic. There was a 12% increase in the annual consumption for the sample residents considered in 2020 (the COVID-19-affected year) as compared to 2019, and the total consumption remained similar with only a 0.2% decrease in 2021. The article also reports that machine learning models created in only one year, 2018, performed better by 10% in prediction compared with the deep learning models due to the limited training data available. The article implies the need for exploring approaches/features that could model the previously unseen COVID-19-like scenarios to improve the performance in case of such an event in the future.

The authors would like to acknowledge Dubai Electricity and Water Authority (DEWA) for funding this research, Dr. Sgouris Sgourdis, Director of Research from DEWA R&D, for his valuable inputs, and Dr. Jim John, Ahmad Safieh, Ammar Elnosh, and Omar Albadwawi, members of the DEWA R&D Solar Area, for their support.

Solar Decathlon Europe is an international competition among universities which promotes interdisciplinary learning in engineering and architecture. Students from different disciplines participate in teams guided by several professors during a 29 month preparation period plus five weeks of on-site contest. The educational project involves designing, building and testing a solar energy house connected to the electrical grid with the strategy of maximizing self-consumption, supported by bioclimatic technologies and maintaining a low environmental footprint. It culminates in a on-site contest in which teams must assembly the house themselves, test it with ordinary real life tasks and finally disassembly it. The event has also a divulgative aim, trying to make students and visitors get interested in discovering the problems presented by real engineering and architecture applications. In addition, SDE covers R&D aspects in different fields such as energy efficiency, solar energy and bioclimatic architecture. This article presents the methodology followed during the SDE 2012 edition, in which more than 850 students participated. The obtained results show that the educational competition was a success according to the technical and professional ambitions of the students, most of them considering that their knowledge had increased in areas related to technical and multidisciplinary aspects.