Advances in sorption systems for energy efficient heating and cooling

At present there is important R&D in the field of sorption heating, cooling and thermal energy storage systems going on worldwide. Sorption systems can enable a more efficient use of renewable energies (solar, geothermal, etc.) both for domestic and industrial applications. This special issue presents the recent advances in the following key-sorption technologies: • Ad-sorption and ab-sorption closed- cycle heat pumps and chillers. • Ad-sorption and ab-sorption open-cycle systems for air conditioning, dehumidification, solar cooling, etc. • Sorption and thermochemical systems for thermal energy storage

Comparative Analysis of Web of Science and Scopus on the Energy Efficiency and Climate Impact of Buildings

Although the body of scientific publications on energy efficiency and climate mitigation from buildings has been growing quickly in recent years, very few previous bibliometric analysis studies exist that analyze the literature in terms of specific content (trends or options for zero‐energy buildings) or coverage of different scientific databases. We evaluate the scientific literature published since January 2013 concerning alternative methods for improving the energy efficiency and mitigating climate impacts from buildings. We quantify and describe the literature through a bibliometric approach, comparing the databases Web of Science (WoS) and Scopus. A total of 19,416 (Scopus) and 17,468 (WoS) publications are analyzed, with only 11% common documents. The literature has grown steadily during this time period, with a peak in the year 2017. Most of the publications are in English, in the area of Engineering and Energy Fuels, and from institutions from China and the USA. Strong links are observed between the most published authors and institutions worldwide. An analysis of keywords reveals that most of research focuses on technologies for heating, ventilation, and air‐conditioning, phase change materials, as well as information and communication technologies. A significantly smaller segment of the literature takes a broader perspective (greenhouse gas emissions, life cycle, and sustainable development), investigating implementation issues (policies and costs) or renewable energy (solar). Knowledge gaps are detected in the areas of behavioral changes, the circular economy, and some renewable energy sources (geothermal, biomass, small wind). We conclude that i) the contents of WoS and Scopus are radically different in the studied fields; ii) research seems to focus on technological aspects; and iii) there are weak links between research on energy and on climate mitigation and sustainability, the latter themes being misrepresented in the literature. These conclusions should be validated with further analyses of the documents identified in this study. We recommend that future research focuses on filling the above identified gaps, assessing the contents of several scientific databases, and extending energy analyses to their effects in terms of mitigation potentials.This work was funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018‐ 093849‐B‐C31), by ICREA under the ICREA Academia programme, and by the foundation SIVL

Novel inorganic binary mixture for low‐temperature heat storage applications

In this study, an inorganic mixture based on bischofite (industrial by‐product) was developed and characterized for its application as a phase change material for low‐temperature thermal energy storage. The most appropriate composition was established as 40 wt% bischofite and 60 wt% Mg(NO3)2 · 6H2O. Thermophysical properties were defined and compared with those of the mixture with synthetic MgCl2 · 6H2O. The heat of fusion and melting temperature were measured as 62.0°C and 132.5 kJ kg−1 for the mixture with MgCl2 · 6H2O and 58.2°C and 116.9 kJ kg−1 for the mixture with bischofite. The specific heat capacity values, cycling, and thermal stability for both mixtures were also determined. For the mixture with MgCl2 · 6H2O, the densities of the solid and liquid states were 1517 kg m−3 (ambient temperature) and 1515 kg m−3 (at 60‐70°C), respectively. For the mixture with bischofite, the densities of the solid and liquid states were 1525 kg m−3 (ambient temperature) and 1535 kg m−3 (at 60‐70°C), respectively. Both mixtures show supercooling of about 23.4 and 34.1°C for the mixture with bischofite and MgCl2 · 6H2O, respectively. In addition, it was shown that supercooling may be reduced by increasing the quantity of material tested. Thereby, it was established that an inorganic mixture based on bischofite is a promising PCM for low‐temperature thermal energy storage applications.Funding informationComisión Nacional de InvestigaciónCientífica y Tecnológica, Grant/AwardNumber: CONICYT/FONDAP 15110019,CONICYT‐PCHA/Doctorado Nacional paraEstudiantes Extranjeros 2014/Folio63140052, ERANet‐LAC 2nd Joint Call,ERANET‐LAC 2015‐2016, projectELAC2015/T06‐0988; FONDECYT, Grant/Award Number: 1170675; Spanish Govern-ment, Grant/Award Number: ENE2015‐64117‐C5‐1‐R (MINECO/FEDER); CatalanGovernment, Grant/Award Number: GREA(2014 SGR 123); European CommissionSeventh Framework Programme, Grant/Award Number: PIRSES‐GA‐2013‐610692(INNOSTORAGE); European Union0s Hori-zon, Grant/Award Number: 657466(INPATH‐TES

Review on system and materials requirements for high temperature thermal energy storage. Part 1: General requirements

High temperature thermal energy storage offers a huge energy saving potential in industrial applications such as solar energy, automotive, heating and cooling, and industrial waste heat recovery. However, certain requirements need to be faced in order to ensure an optimal performance, and to further achieve widespread deployment. In the present review, these requirements are identified for high temperature (>150 °C) thermal energy storage systems and materials (both sensible and latent), and the scientific studies carried out meeting them are reviewed. Currently, there is a lack of data in the literature analysing thermal energy storage from both the systems and materials point of view. In the part 1 of this review more than 25 requirements have been found and classified into chemical, kinetic, physical and thermal (from the material point of view), and environmental, economic and technologic (form both the material and system point of view). The enhancements focused on the thermal conductivity are addressed in the Part 2 of this review due to their research significance and extension.The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R, ENE2011-22722 and ULLE10-4E-1305). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). This project has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under Grant agreement No. PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 657466 (INPATH-TES). Laia Miró would like to thank the Spanish Government for her research fellowship (BES-2012-051861). Jaume Gasia would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2016FI_B 00047)

Development and experimental validation of a transient 2D numeric model for radiant walls

An experimental set-up consisting of a house like cubicle exposed to outdoor weather was used to validate a numerical model of a radiant wall. The 2D transient finite volume model used as inputs the indoor temperature, outdoor temperature, global solar radiation incident on a vertical surface, and temperature and flow of the supply water. The simulation results closely agreed with the temperature profiles and heat fluxes for the three studied orientations (East, South, and West). Furthermore, a parametric study was carried out with the radiant wall model, concluding that pipes spacing between 125 mm and 150 mm and depth between 45 mm and 65 mm minimized the temperature difference on the surface while maximizing the heat flux. Furthermore, a control strategy with shorter activation periods improved the heat transfer efficiency.The work was partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER), ENE2015-64117-C5-3-R (MINECO/FEDER), and ULLE10-4E-1305). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. 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. This projects has received funding from the European Commission Seventh Framework Programme (FP/2007–2013) under Grant agreement Nº PIRSES-GA-2013-610692 (INNOSTORAGE) and from European Union's Horizon 2020 research and innovation programme under grant agreement Nº 657466 (INPATH-TES). Alvaro de Gracia would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940

Passive cooling of buildings with phase change materials using whole-building energy simulation tools: A review

Buildings contribute to climate change by consuming a considerable amount of energy to provide thermal comfort for occupants. Cooling energy demands are expected to increase substantially in the world. On this basis, technologies and techniques providing high energy efficiency in buildings such as passive cooling are highly appreciated. Passive cooling by means of phase change materials (PCM) offers high potential to decrease the cooling energy demand and to improve the indoor comfort condition. However, in order to be appropriately characterized and implemented into the building envelope, the PCM use should be numerically analyzed. Whole-building energy simulation tools can enhance the capability of the engineers and designers to analyze the thermal behavior of PCM-enhanced buildings. In this paper, an extensive review has been made, with regard to whole-building energy simulation for passive cooling, addressing the possibilities of applying different PCM-enhanced components into the building envelope and also the feasibility of PCM passive cooling system under different climate conditions. The application of PCM has not always been as energy beneficial as expected, and actually its effectiveness is highly dependent on the climatic condition, on the PCM melting temperature and on the occupants behavior. Therefore, energy simulation of passive PCM systems is found to be a single-objective or multi-objective optimization problem which requires appropriate mathematical models for energy and comfort assessment which should be further investigated. Moreover, further research is required to analyze the influence of natural night ventilation on the cooling performance of PCM.The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER) and ENE2015-64117-C5-3-R (MINEDO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation g iven to their research group GREA (2014 SGR 123). This project has received funding from the European Commission Seventh Framework Program (FP/2007-2013) under Grant agreement Nº PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 research and innovation program under grant ag reement No 657466 (INPATH-TES). Alvaro de Gracia would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940

The connection between the heat storage capability of PCM as a material property and their performance in real scale applications

Using phase change materials (PCM) for Thermal Energy Storage, the most important material property is their heat storage capability, usually given as h(T). Ideally, h(T) changes suddenly at a single temperature. However, many PCM change phase in a temperature range and show hysteresis. In addition, experience shows that even measurements with the same device on the same material can give different results when the heating rate, the amount of sample mass or the equipment device are varied. The question thus arises how to deal with different h(T) results when trying to predict the performance of a real scale application. This paper identifies the main origins of these effects and gives strategies for dealing with them.The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP/2007-2013) under grant agreement n° PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 research and innovation program under grant agreement No 657466 (INPATH-TES). The authors would like to thank the Catalan Government for the quality accreditation given to their research groups GREA (2014 SGR 123) and DIOPMA (2014 SGR 1543). GREA and DIOPMA are certified agents TECNIO in the category of technology developers from the Government of Catalonia. This work has been partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER)). Dr. Camila Barreneche and Dr. Aran Solé would like to thank Ministerio de Economía y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-22886 and FJCI-2015-25741, respectively