• Energy Research

Abstract Geothermal energy production consists of two main types: low temperature or low enthalpy for temperatures below 150oC, and high temperature or high enthalpy systems for temperatures over than 150oC. In mainland Portugal the most common ground temperature varies from 20 to 40oC, depending on the place where the geothermal boreholes are placed, which means that low enthalpy systems can be considered. Currently the increased development of ground source heat pumps (GSHP) lead to a continuous development and innovation of ground heat exchangers (GHE). The geothermal systems can contribute with savings between 25-75% of the energy demands of buildings’ HVAC systems, making it a very appealing solution mainly in northern and central Europe. The goal of this paper is to analyse the performance of a geothermal system installed in a department of the University of Aveiro, in the center of Portugal. Firstly, an introduction about different GHE systems is done and after a real case study is described and the methodology applied. To achieve the goal established, the building was analysed, audit and modeled, and an energy simulation was carried out with EnergyPlus® 8.6 (EP) software. After the results obtained it can be concluded that even in regions with mild climate as Aveiro, the geothermal system contributes with 34% of savings of the annual global primary energy needs.

Abstract The buildings natural ageing along with the absence of planned maintenance actions and the effects of climate changes accelerate the building materials degradation. So, to extend the materials’ service life, the application of appropriate maintenance actions is imperative. This work aims to assess the building performance and to prioritize the maintenance actions employing Key Performance Indicators using Building Information Modelling-(BIM) as a supporting tool for Building Condition Assessment-(BCA) and maintenance management. To achieve these goals a methodology was proposed and applied to a case study involving 1) Building data collection; 2) Building Life Cycle Cost estimation, and 3) Automated calculation of Building Performance Indicator. This research application highlights the importance of BIM role in buildings' Facility Management, allowing the model's permanent update of information, in this case for BCA purposes. It also has high potential to prioritize the building maintenance actions, extending its materials service life, which contribute to attain a sustainable built environment.

Abstract The large energy consumption of the building sector is mainly resourcing to active systems for cooling and heating of indoor spaces. According this, the external envelopes of offices and commercial buildings are systematically composed by large glazed areas that lead to high energy losses in the winter and large solar gains in summer. The incorporation of phase change materials into building elements is a growing trend for improving the thermal energy storage capacity in the latent form and the thermal inertia. Thermal Energy Storage systems (TES), using phase change materials (PCM) in buildings, are widely investigated technologies and a fast developing research area. Therefore, there is a lack of publish research reviews on PCM solutions applied into glazed areas. This review focuses on PCM technologies developed for the translucent and transparent building envelope, such as windows, shutters and other shading devices. This review gives special attention to describe and to discuss the thermal properties, the energy storage and the saving potentials of innovative PCM solutions and presents the main results of research carried out on this domain. The most used strategy to apply the PCM into these building elements is the direct incorporation using macro capsules containers (composed by different materials). The main conclusions taken from the research studies on prototype solutions show the PCM potential to enhance the thermal performance of buildings through the glazing and shading devices. This studies show that the PCM technology applied to the glazed areas of the building envelope can significantly improve the energy efficiency, and with the reduction of the product costs this technology will appear soon into the typical building construction systems.

Nowadays, the importance of implementing energy efficiency (EE) measures is growing significantly worldwide, based on its potential to reduce energy demands and mitigate climate change effects. Paraguay is a developing country with the highest per capita hydroelectric energy generation in the world, but only 18% of local consumption is hydroelectric and 41% of its energy matrix corresponds to oil products. This paper aims to analyse the importance the Country places on EE as a strategy towards sustainable development and to highlight as EE is an effective pathway to mitigate the climate changes and contrast their effects. The authors initially provide an insight into the climate scenarios for Paraguay and underline the effects of the climate changes on the buildings’ comfort. Subsequently, the authors provide, by resourcing a bibliographic review, a description of the Paraguayan sectors of greater energy consumption, its policies and targets set for increasing EE. Besides, the main EE projects developed by other neighbouring South American countries are analysed to show the level of development of each one in the scope of EE and to offer a reference basis of potential virtuous solutions to be adopted in Paraguay. A focus on the building sector is also made to provide a foundation for policy analyses to enhance EE in this sector. As a result of this review, evidence that EE is beginning to take part in Paraguay’s public policies was found, with the leaders becoming aware of its importance. Nevertheless, many concrete results could not be achieved as of yet and overcoming these barriers still involve a great challenge. Regarding the building sector, few advances have been noticed regarding the regulations of buildings’ thermal performance, a reason for which the National objectives set need to be more specific to achieve greater collective awareness to enforce them. Finally, key actions are recommended for Paraguay aiming to improve EE levels to face the climate change phenomenon.

This research seeks to evaluate the impact of climate change (CC) on the thermal performance of buildings. In particular, it is focused on historical residential buildings located in Asuncion, Paraguay, a city characterised by a humid subtropical climate. Energy dynamic simulations of a representative building in its original state and an energy efficient version were assessed to evaluate the effectiveness of common energy retrofit measures under future climate conditions. Low and high Representative Concentration Pathways climate scenarios for 2030, 2050 and 2070 are employed with a CORDEX climate model and compared with observed weather data of 2009. Two thermal comfort assessment methods are considered, the statistic and the adaptive thermal comfort approach, where operative temperatures and overheating and underheating rates are analysed. As expected, the results show that the projected temperature rise will lead to an increment of discomfort rates, but it could be mitigated by energy refurbishment measures. Thus, CC effects on thermal performance of buildings are relevant and must be considered for the development of adaptation strategies able to manage this phenomenon. At present, Paraguay does not have any energy building codes and, instead, the results of this paper underline their needs with a substantial impact on society and building industry of Paraguay since it demonstrates that the creation of energy buildings codes is highly necessary to face CC impact on buildings.

Currently, the upgrade of existing reinforced concrete (RC) buildings focuses only on energy retrofitting measures due to the current policies promoted in the scope of the European Green Deal. However, the structural deficiencies are not eliminated, leaving the building seriously unsafe despite the investment, particularly in seismic-prone regions. Moreover, the envelopes of existing RC buildings are responsible for their energy efficiency and seismic performance, but these two performance indicators are not usually correlated. They are frequently analyzed independently from each other. Based on this motivation, this research aimed to perform a holistic performance assessment of five different types of masonry infill walls (i.e., two non-strengthened walls, two walls with seismic strengthening, and one wall with energy strengthening). This performance assessment was performed in a three-step procedure: (i) energy performance assessment by analyzing the heat transfer coefficient of each wall type; (ii) seismic performance assessment by analyzing the out-of-plane seismic vulnerability; (iii) cost–benefit performance assessment. Therefore, a global analysis was performed, in which the different performance indicators (structural and energy) were evaluated. In addition, a state-of-the-art review regarding strengthening techniques (independent structural strengthening, independent energy strengthening, and combined structural plus energy strengthening) is provided. From this study, it was observed that the use of the external thermal insulation composite system reduced the heat transfer coefficient by about 77%. However, it reduced the wall strength capacity by about 9%. On the other hand, the use of textile-reinforced mortar improved the strength and deformation capacity by about 50% and 236%, but it did not sufficiently reduce the heat transfer coefficient. There is a need to combine both techniques to simultaneously improve the energy and structural energy performance parameters.

Nowadays, awareness concerning the need to use energy efficiently is increasing significantly worldwide, thus, improving the energy efficiency levels in the building sector has acquired high importance because of their energy saving potential. However, several intervention options are available to achieve high energy efficiency levels in buildings, and the choice must be made considering the efficiency of the solution and the costs involved. Considering this, the present research aimed to develop a parametric study of several energy retrofit solutions for buildings located in the hot-humid climate of Paraguay, in order to analyse their efficiency in terms of comfort rates and cooling energy needs. Furthermore, the Analytic Hierarchy Process (AHP) is employed as a decision-making method to choose the most suitable intervention considering the investment costs required. Thus, threshold values of thermal transmittance for the building thermal envelope components are established through a parametric study and sensitivity analysis of the simulations results. Considering that Paraguay does not have national building energy codes, the outcomes of this research will constitute a support and contribute for the thermal parameters regulation of buildings aiding to improve the energy efficiency of Paraguayan buildings.