Innovative exergy indicators for analyzing an nZEB building to promote new areas of improvement

This study evaluates the energy and exergy performance of buildings towards achieving nearly Zero Energy Building (nZEB) standards by introducing three exergy-based indicators alongside conventional energy metrics. Focused on the LEED Platinum-certified LUCIA building at Valladolid University (Spain), the analysis examines energy and exergy transformations throughout the building’s lifecycle, emphasizing resource consumption, generation systems, and environmental equilibrium across seasons. The study reveals a Non-Renewable Primary Energy Ratio of 67 kWh/m2, closely mirrored by an exergy ratio of 67.2 kWh/m2 due to the high-quality factor of fuel resources. Conversely, the Renewable Primary Energy Ratio stands at 121 kWh/m2, with a corresponding exergy ratio of 88.36 kWh/m2, reflecting the significant contribution of geothermal energy while highlighting areas for demand side optimization. For the same reason, the Renewable Energy Ratio is 0.66 and the Exergy Ratio is 0.56. Despite meeting nZEB criteria, exergy indicators underscore untapped energy-saving potential by aligning resource qualities with demand characteristics. Identifying system weaknesses informs future improvement strategies, potentially enhancing LEED scores. The study advocates for incorporating exergy-based indicators alongside traditional energy metrics in European regulations to accurately assess building performance and define low-ex buildings. Overall, the exergy analysis reveals equipment-specific losses and underscores the qualitative match between energy demand and supply.Funding for open access charge: Universidad de Málaga/CBU

Molten salt-based nanofluids as efficient heat transfer and storage materials at high temperatures. An overview of the literature

Publisher Copyright: © 2017 Elsevier LtdThe research in the field of nanofluids has experienced considerable advances from their discovery two decades ago. These liquid mixtures with tiny quantities (< 10% in volume) of nanometric size solid particles (< 100 nm) in suspension have a great potential for thermal management applications due to their excellent thermophysical properties. The so-called traditional nanofluids (based on water or industrial oils) have been extensively studied so far with a special focus on the enhancement observed in their thermal conductivity. Experimental results, mechanisms and models regarding these materials have been published and reviewed on a large number of articles. A new kind of nanofluids based on inorganic salts has been developed in the last few years with the aim of storing and transferring thermal energy at high temperatures. These Molten Salt-Based Nanofluids (MSBNFs) are characterized by a considerable increase of their specific heat due to the presence of particles at the nanometric scale. On the contrary, the specific heat of the traditional nanofluids is lower compared to that of the base fluid. This surprising behaviour has caused an opened debate in the scientific community, which is currently dealing with these controversial results and the lack of theories and models for these materials. This article reviews the published scientific contributions on MSBNFs. The influence of several facts on the specific heat is deeply analysed, as well as the synthesis methods. Other important aspects related to the behaviour and development of the MSBNFs such as the stability of the NanoParticles (NPs) in the molten salt, their latent heat, viscosity and thermal conductivity, have also been reviewed in this article. Finally, the difficulties and challenges concerning the further development of these materials have been summarized and the main conclusions have been listed.This work was supported by the University of the Basque Country UPV/EHU (Zabalduz 2012 research program, Ph.D. thesis of Belén Muñoz Sánchez); the Basque Governement (Etortek 2014 project on thermal storage) and the MInisterio de Economía y Competitividad, MINECO ( ENE2015-71083-R ).Peer reviewe