• Energy Research

Today, our society has the duty of reducing the energy consumed in the building sector. A promising technology to achieve this goal is the implementation of thermal energy storage (TES) solutions in buildings envelope. Lately, much literature dealing with the effect of the inclusion of latent heat storage materials in construction materials to provide higher thermal inertia has appeared, mostly focusing on the evaluation of the thermal properties, density, or porosity of these new materials. However, few of them evaluated the long stability properties of the materials with embedded PCM when included in a building, very much needed since the lifetime of a building is about 50 years. Therefore, in this study, an evaluation of a house‐like cubicle of concrete with micro‐encapsulated PCM after a decade of its construction is carried out. The results are compared to the tests done in 2005 concluding that the thermal performance of this cubicle presented no degradation in the PCM effect. The work partially funded by the Spanish Government (ENE2015‐64117‐C5‐1‐R (MINECO/FEDER), ULLE10‐4E‐1305, and ENE2005‐08256‐C02‐01). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2014 SGR 123) and the city hall of Puigverd de Lleida. GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. Financiado por el proyecto RTC‐2015‐3583‐5 (INPHASE) del Ministerio de Economía y Competitividad, dentro del Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, en el marco del Plan Estatal de Investigación Científica y Técnica y de Innovación 2013‐2016, y ha sido cofinanciado con FONDOS FEDER, con el objetivo de promover el desarrollo tecnológico, la innovación y una investigación de calidad.

Abstract The study of the thermal comfort of the occupants of a building represents an important challenge, due to its close relation with energy efficiency. Facing the application of set-point temperatures, the adaptive comfort model proposes the linking of the comfort temperature to the outdoor temperature which would potentially reduce the use of the HVAC system. Although there are studies that propose experimental adaptive models, few verify their effectiveness. In the current study an adaptive comfort algorithm for hybrid buildings is experimentally validated based on a 17-month field study in office buildings in Spain. The implementation of the algorithm in the HVAC control system, both during the cooling and the heating period, allowed for the evaluation of the energy consumption, obtaining savings of 27.5% and 11.4% respectively. The percentage of thermal sensation votes in comfort evolved from 94% (prior to implementing the comfort algorithm) to 87.5% (once implemented) for the summer season and from 79.5% to 81.6% for the winter season. The results demonstrate that the adaptive model is effective for the optimization of HVAC systems, and that it is possible to achieve energy savings without impairing the comfort of its occupants for the type of climate and buildings considered.

The use of 3D city models combined with simulation functionalities allows to quantify energy demand and renewable generation for a very large set of buildings. The scope of this paper is to determine the solar photovoltaic potential at an urban and regional scale using CityGML geometry descriptions of every building. An innovative urban simulation platform is used to calculate the PV potential of the Ludwigsburg County in south-west Germany, in which every building was simulated by using 3D city models. Both technical and economic potential (considering roof area and insolation thresholds) are investigated, as well as two different PV efficiency scenarios. In this way, it was possible to determine the fraction of the electricity demand that can be covered in each municipality and the whole region, deciding the best strategy, the profitability of the investments and determining optimal locations. Additionally, another important contribution is a literature review regarding the different methods of PV potential estimation and the available roof area reduction coefficients. An economic analysis and emission assessment has also been developed. The results of the study show that it is possible to achieve high annual rates of covered electricity demand in several municipalities for some of the considered scenarios, reaching even more than 100% in some cases. The use of all available roof space (technical potential) could cover 77% of the region’s electricity consumption and 56% as an economic potential with only high irradiance roofs considered. The proposed methodological approach should contribute valuably in helping policy-making processes and communicating the advantages of distributed generation and PV systems in buildings to regulators, researchers and the general public.

Solar cooling plants can work in multiple operation modes. A numerical model of the whole plant can be used to choose the adequate operation mode and optimizing the energy production by using hierarchical control strategies. Simplified models are required for solving the control problem in a suitable time-window using systems such as Programmable Logic Controllers (PLCs) or microcontrollers. The storage system is an important component of a solar cooling plant. They are useful in solar systems for helping to satisfy the energy demand when solar energy is not available. Those based on phase change materials (PCMs) have the advantage of high storage density at a small temperature range. Unión Europea DPI2008-05818

Extending set-point temperatures in residential buildings has a significant impact on energy demand and thermal comfort. European governments have adopted this strategy to mitigate the energy crisis. Previous studies attempting to quantify energy savings by extending set-point temperatures were limited due to a lack of building stock characterisation, poor climate representation, and the absence of uniformity in the reference set-point temperature. In this study, a large-scale simulation was conducted, which included six building models covering 90% of southern Europe Köppen–Geiger climates, where 20 °C and 25 °C were the reference heating and cooling set-point temperatures, respectively. This also accounted for the thermal characteristics of the older building stock, built more than 15 years ago, and the new buildings built under the latest version of Directive 2010/31/EU. The results show that reducing the heating set-point temperature by 1 °C can lead to an average demand reduction of 20%, while raising the cooling set-point temperature by 1 °C can lead to a 25% cooling demand reduction. The oldest building stock shows a higher absolute savings potential. Adjusting thermostats by 1 °C in Spanish homes during the winter season could represent a saved natural gas volume of 1.8 million normal cubic meters, nearly 40% of the gas demand of households in 2022. These findings suggest that extending the set-point temperatures in residential buildings can be a promising strategy towards a more energy-efficient society without compromising the occupant’s thermal comfort.

The aim of this paper is to assess the performance of several designs of hybrid systems composed of solar thermal collectors, photovoltaic panels and natural gas internal combustion engines. The software TRNSYS 17 has been used to perform all the calculations and data processing, as well as an optimisation of the tank volumes through an add-in coupled with the GENOPT® software. The study is carried out by analysing the behaviour of the designed systems and the conventional case in five different locations of Spain with diverse climatic characteristics, evaluating the same building in all cases. Regulators, manufacturers and energy service engineers are the most interested in these results. Two major contributions in this paper are the calculations of primary energy consumption and emissions and the inclusion of a Life Cycle Cost analysis. A table which shows the order of preference regarding those criteria for each considered case study is also included. This was fulfilled in the interest of comparing between the different configurations and climatic zones so as to obtain conclusions on each of them. The study also illustrates a sensibility analysis regarding energy prices. Finally, the exhaustive literature review, the novel electricity consumption profile of the building and the illustration of the influence of the cogeneration engine working hours are also valuable outputs of this paper, developed in order to address the knowledge gap and the ongoing challenges in the field of distributed generation.

Overheating, a general problem both in urban spaces and inside buildings, calls for the deployment of passive cooling techniques to reduce energy consumption, protect the environment and institute satisfactory comfort levels. A key factor in such techniques is the capitalisation on the cooling potential of natural heat sinks. The sky, one such sink, has essentially limitless cooling power. In addition, its temperature on fair nights is lower than that of other environmental sinks (ground and air). The sky’s promise in that respect prompted this exploration of the potential of nocturnal radiation cooling. A review of the state of the art revealed that in all the radiative dissipators developed and tested to date the dissipation fluid (water) transferred heat indirectly to the heat sink (the sky) by circulating water inside solar collector pipes. The highest values reported for maximum dissipation power were on the order of 100 W/m2. The present study aimed to asses night time dissipation power in a dual system in which water circulated either inside pipes or flowed down the outer surface of the collector. The two modes, one involving in-pipe circulation and the other outer surface downflow, were compared experimentally, for whereas the former has been analysed and assessed by earlier researchers, the latter has not. The empirical findings verified that downflow setups enhanced cooling, delivering up to five-fold the dissipation power obtained with the conventional arrangement. This study was funded by the Spanish Ministry of the Economy and Competitiveness under DACAR project ‘Zero-Energy Balance Districts through Algorithms of Adaptive Comfort and Optimal Management of Energy Networks’ (BIA2016-77431-C2-2-R); the ERDF under Urban Innovative Actions programme CartujaQanat project (UIA03-301) ‘Recovering Street life in a Climate-Changing World’; and the University of Seville under Research Plan VI (VPPI-US). Peer reviewed