Power generation systems are attracting a lot of interest from researchers and companies. Storage is becoming a component with high importance to ensure system reliability and economic profitability. ...A few experiences of storage components have taken place until the moment in solar power plants, most of them as research initiatives. In this paper, real experiences with active storage systems and passive storage systems are compiled, giving detailed information of advantages and disadvantages of each one. Also, a summary of different technologies and materials used in solar power plants with thermal storage systems existing in the world is presented.
Concentrated solar thermal power generation is becoming a very attractive renewable energy production system among all the different renewable options, as it has have a better potential for ...dispatchability. This dispatchability is inevitably linked with an efficient and cost-effective thermal storage system. Thus, of all components, thermal storage is a key one. However, it is also one of the less developed. Only a few plants in the world have tested high temperature thermal energy storage systems. In this paper, the different storage concepts are reviewed and classified. All materials considered in literature or plants are listed. And finally, modellization of such systems is reviewed.
Sugar alcohols as phase change materials (PCM) are very promising due to their high storage capacity, safety and economic reasons. Their phase change temperatures make them suitable for medium ...temperature storage, which is needed for solar process heat or waste heat recovery applications. To guarantee a long PCM working lifetime they should be tested under a repeated number of freezing/ melting cycles to check whether the thermophysical properties remain constant or not. The cycling stability of D-mannitol, myo-inositol and galactitol has been studied with DSC and the chemical stability with FT-IR. Myo-inositol shows a good cycling stability under the chosen measuring parameters. The cycling and chemical stability of D-mannitol up to 20 cycles can be achieved by controlling some parameters. The variable affecting it the most is the amount of oxygen in contact with it. Hence, in the storage unit this could be prevented with an inert or vacuum atmosphere.
Growing environmental awareness has prompted a resurgence in traditional building techniques that rely on natural or recycled materials since many believe that structures made from these resources ...are ecologically friendly. Using Life Cycle Assessment (LCA) for construction materials offers valuable insights into the impacts produced during their production and construction processes. This study aims to assess the environmental impacts of two different constructions-an Earthbag Building (EB) and a conventional Sahrawi Cement Blocks Building (CBB). It also determines whether it is more environmentally beneficial to construct traditionally, utilizing local materials and aligning with the principles of the circular economy, which is one of the Sustainable Development Goals (SDGs) in Europe. This study specifically examines a cradle-to-gate LCA, using the software Simapro v. 9.4.0.1. Results show that in 21 out of the 22 impact categories analyzed, the CBB performs worse, in some cases presenting an impact of 70% higher than the EB. The highest impact is obtained for fine particulate matter formation and Global Warming related to Human Health categories, whilst impact categories related to water consumption and eutrophication obtained an impact of less than 0.001 for both constructions.
Since ancient times, raw earth has been used worldwide as a construction material. Today, it is well known for its good environmental properties of recyclability and low embodied energy along the ...production process. Earthen walls regulate the interior temperature of the buildings, providing comfortable temperatures with a very low carbon footprint. As a result of those advantages, earthen building techniques have been revived and used for contemporary architecture. The aim of this paper is to review the state of the art about the thermal behaviour of earthen building, including all the monitoring and simulation analysis of real earthen constructions up to now. The paper presents the different earthen techniques known nowadays, analysing the most important thermal parameters and the thermal comfort achieved with each technique. Regardless the wide differences among the analyzed cases, the authors conclude that earth building is a suitable solution in hot and arid climates, since it preserves the indoor temperature within the thermal comfort limits most part of the time without any active system.
Solar energy can be efficiently used if thermal energy storage systems are accordingly designed to match availability and demand. Thermal energy storage by thermochemical materials (TCM) is very ...attractive since these materials present a high storage density. Therefore, compact systems can be designed to provide both heating and cooling in dwellings. One of the main drawbacks of the TCM is corrosion with metals in contact. Hence, the objective of this study is to present the obtained results of an immersion corrosion test following ASTM G1 simulating an open TCM reactor, under humidity and temperature defined conditions. Four common metals: copper, aluminum, stainless steel 316, and carbon steel, and five TCM: CaCl2, Na2S, CaO, MgSO4, and MgCl2, were studied. Aluminum and copper show severe corrosion when combined with Na2S, aluminum corrosion is more significant since the specimen was totally destroyed after 3 weeks. Stainless steel 316 is recommended to be used as a metal container material when storing all tested TCM.
•Thermochemical materials under study are solid salt hydrates that store thermal energy.•Corrosion tests of thermochemical materials under real conditions are performed.•Stainless steel 316 is resistant to all tested salt hydrates.•Na2S is not recommended with aluminum nor copper.•Copper is recommended with CaCl2 and MgCl2.
Polyethylene has widely been used in radiative cooling applications because of high transmittance values in the atmospheric window. However, it presents optical and mechanical degradation when ...exposed to environmental conditions and must be replaced every few months. This paper aims to find an alternative to polyethylene to be used in a unique device, the Radiative Collector and Emitter (RCE), that combines solar collection and night-time radiative cooling. The aging evolution analysis of five cheap and market available plastic films (two low density polyethylene, one high density polyethylene, one polypropylene, and one fluorinated ethylene propylene) exposed to environmental conditions was performed. FT-IR spectra and mechanical traction tests were performed before and after 90 days of exposure to the environment. Results confirm that polyethylene undergoes a degradation process both when it is covered by a glass and when it is uncovered. However, it maintains high average transmittance values in the atmospheric window. Polypropylene has average transmittance values slightly lower than polyethylene, but its aging behaviour is better since no oxidative processes are detected when the material is covered with glass. For all this, PP-35 is an interesting candidate for night-time radiative cooling wind-shields.
Nearly 30% of humanity lives in earthen dwellings. Earthbag is a sustainable, cheap, feasible and comfortable option for emergency housing. A comparative monitoring-simulation analysis of the ...hygrothermal behavior of an Earthbag dwelling in Mediterranean continental climate, designed under bioclimatic criteria, is presented. The dome shape Earthbag dwelling has a net floor area of 7.07 m2, a glass door facing south and two confronted windows in the east and west facades. A numerical model (EnergyPlus v8.8) was designed for comparison. Twenty-four hour cross ventilation, night cross ventilation, and no ventilation in free floating mode and a controlled indoor temperature were the tested scenarios. Comparisons between experimental data and simulation show a good match in temperature behavior for the scenarios studied. Reductions of 90% in summer and 88% in winter, in the interior thermal amplitude with respect to exterior temperatures are found. Position of the glazed openings was fundamental in the direct solar gains, contributing to the increase of temperature in 1.31 °C in winter and 1.37 °C in the equinox. Night ventilation in the summer period had a good performance as a passive system. Passive solar gains made a reduction of heating energy consumption of 2.3% in winter and 8.9% in equinox.
This review paper organizes and summarizes the literature on Vertical Greenery Systems (VGS) when used as passive tool for energy savings in buildings. First, with the information obtained in the ...reviewed literature some key aspects to consider when working with VGS are clarified, such as the classification systems, the climate influence, the plant species used and the different operating mechanisms. Then, the main conclusions of this literature, sorted by construction system (Green Walls or Green Façades) and climatic situation, are summarized. In general, it can be concluded that VGS provide great potential in reducing energy consumption in buildings, especially in the cooling periods. However, a lack of data on operation during the heating period as well as during the whole year has been found. On the other hand, results show that the investigations of VGS are not equally distributed around the world, being basically concentrated in Europe and Asia. Moreover, the review concludes that some aspects must be studied in depth, such as which species are the most suitable for each climate, influence on energy savings of the façade orientation, foliage thickness, presence of air layers, and finally, substrate layer composition and thickness in the case of green walls.
Radiative cooling is a promising technology for space cooling. This technology can be combined with solar heating applications, enabling the production of both energy demands –heat during daytime and ...cold during nighttime– in a single device; thus, reducing the non-renewable primary energy consumption for space conditioning and domestic hot water. Radiative cooling and solar heating appear in different wavelength ranges, 8–14 μm and 0.25–2.5 μm respectively, thus the device must be able to switch between ranges in each mode. An adaptive cover placed on top of the radiator/absorber can provide this switch by combining materials with suitable optical properties for each mode. Another effect derived from the usage of covers is the reduction of convective heat losses, enhancing the performance of the device. This paper aims to review the existing materials used in solar collectors, and radiative coolers as well as available smart materials used in other fields for its potential use as adaptive covers for combined radiative cooling and solar heating applications.
•First review on adaptive covers for combined radiative cooling and solar heating.•Overview on radiative cooling and mixed solar collector/radiative cooling system.•Empirical correlations for convection coefficients in radiators and collectors.•Discussion on main materials used in solar collectors and radiative coolers.
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