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The performance of different thermal energy storing systems to provide over-night air-conditioning for a limited space in an institutional building in south Spain are compared with conventional air-conditioning (both for refrigeration and heating). In summer, the storage tanks are charged with a solar-assisted absorption chiller during day-time, and used to cover the over-night demand, whereas in winter a heat exchanger is used during the day to charge the tanks. Thermal energy has been stored in two chilled water tanks (with total capacity of 5000 L) or in two tanks (total volume 4000 L) containing two phase change materials (PCM): a PCM with melting point of 10 ° C for refrigeration, and a PCM with melting temperature of 46 ° C for heating. Our results show that the storing in PCM is more convenient, providing air-conditioning service for approximately 4 h 30 min in refrigeration, with a significant reduction of the electricity consumption with respect to the conventional system. The chilled water tanks can cover the demand for 4 h (scaled down to 3 h 12 min if the capacity is 4000 L), with even lower electric consumption. In winter, on the other hand, the tanks can cover fully the demand of overnight heating. Our results prove the viability of thermal storing, in particular using PCM, to extend the application solar cooling and heating to night-time, which is economically feasible, in a fully operational building.

Storage of thermal energy in packed beds of encapsulated phase change materials (PCM) is becoming nowadays a common strategy, but its modeling requires deep knowledge of the physical processes of h...

To meet the demands of a more resource-efficient future, innovative solutions are needed to generate sustainable energy conversion technologies and processes. Renewable energies offer a potent and viable solution to counter the effects of this problem since they are inexhaustible, pollution-free and affordable energy resources. This work compares different food chamber's cooling and power systems (FCP). The main purpose is to find a more favorable, design for South Spain from energy management and environmental perspective. The further comparison versus the conventional FCP system is made between the two possible technologies. Hence we investigate here the solar-assisted FCP system working with thermal energy in latent “phase change materials” (PCM) or sensible heat storage. We will provide new, advanced eco-design solutions using PCMs to store cold in industrial food chambers - those characterized by intense cooling demand. The energy performance of both compared systems has been assessed considering as a benchmark the energy infrastructure operating today in the Solar Energy Research Center (CIESOL). The results of the comparison demonstrated that only the solar-assisted PCM-based FCP system presents flexibility potential to handle its generation and demand according to local climate conditions, grid requirements and final refrigeration load.

The integration of an off-grid solar-assisted heat pump (SHP) and a sequencing batch biofilter granular reactor (SBBGR) for thermal energy recovery from wastewater was assessed by means of a prospective life cycle assessment (LCA) and life cycle costing (LCC), by theoretically scaling up a pilot installation in Bari, Italy, to a full-scale unit designed for 5000 person-equivalents. The LCA and LCC included all activities in the life cycle of the SHP and wastewater treatment plant (WWTP), namely construction, operation and end-of-life. The thermal energy produced by the SHP was assessed as supplying heating and cooling for an air-conditioning system, displacing a conventional air-source heat pump powered by electricity from the grid. This integrated system was compared to a reference situation where wastewater is treated in a conventional WWTP applying activated sludge with no thermal energy recovery system, showing clear environmental benefits in all impact indicators, such as a 42% reduction in greenhouse-gas emissions and a cost reduction of 53%. Several sensitivity analyses confirmed these findings, with the exception of the price rebound effect, which showed that the lower cost of the integrated system could lead to overturning the environmental benefits. As a limitation of the study, the distribution of the supplied air-conditioning to meet a demand off-site the WWTP premises, such as in residential buildings or hotels, was not included. Therefore, our results constitute only a preliminary positive outcome that should be validated in a real-life application. (C) 2018 Elsevier Ltd. All rights reserved.

In this work, which is related to the current European Parliament Regulation on restrictions affecting refrigeration, four new three-component refrigerants have been proposed, all were created using low Global Warming Potential(GWP) synthetic and natural refrigerants. The considered mixtures consisted of R32, R41, R161, R152a, R1234ze (E), R1234yf, R1243zf, and RE170. These mixtures were theoretically tested with a 10% step in mass fraction using a triangular design. The analysis covered two theoretical cooling cycles at evaporating temperatures of 0 and −30 °C, and a 30 °C constant condensing temperature. The final stage of the work was the determination of the best mixture compositions by thermodynamic and operational parameters. R1234yf–R152a–RE170 with a weight share of 0.1/0.5/0.4 was determined to be the optimal mixture for potentially replacing the existing refrigerants.

An important element of a solar installation is the storage tank. When properly selected and operated, it can bring numerous benefits. The presented research relates to a project that is implemented at the Solar Energy Research Center of the University of Almeria in Spain. In order to improve the operation of the solar cooling and heating system of the Center, it was upgraded with two newly designed storage tanks filled with phase change materials (PCM). As a result of design works, commercial material S10 was selected for the accumulation of cold, and S46 for the accumulation of heat, in an amount of 85% and 15%, respectively. The article presents in detail the process of selecting the PCM material, designing the installation, experimental research, and exergy analysis. Individual tasks were carried out by research groups cooperating under the PCMSOL EUROPEAN PROJECT. Results of tests conducted on the constructed installation indicate that daily energy saving when using a solar chiller with PCM tanks amounts to 40% during the cooling season.

Photovoltaic (PV) systems are the reference technology in the solar-based electricity generation market. Rapid changes in solar radiation can alter PV power output; for this reason, knowledge of future atmospheric scenarios helps system operators to control the PV production in advance, reducing the instabilities that the electrical grid may suffer in electricity integration, and managing the auto consumption power output. With this is mind, we present a model to forecast (up to 3 h ahead) the building integrated photovoltaic (BIPV) system’s power output, which is installed on the roof of the Solar Energy Research Center (CIESOL), Almeria, Spain. The satellite images have been combined with Artificial Neural Networks (ANN) primarily to predict power output using the lowest number of input variables. The results, which can be considered highly satisfactory, demonstrate the ANN’s prediction accuracy with an normalized root mean square error for all sky conditions of less than 26%, and with practically no deviation. We demonstrate how beneficial matching of two already proven techniques can bring about spectacular results in energy generation prediction for the BIPV system.

We present in this work simulations using the finite difference approximation in 2D for the melting of an encapsulated phase-change material suitable for heat storage applications; in particular, we study CaCl2·6H2O in a cylindrical encapsulation of internal radius 8 mm. We choose this particular salt hydrate due to its availability and economic feasibility in high thermal mass building walls or storage. Considering only heat conduction, a thermostat is placed far from the capsule, providing heat for the melting of the phase-change material (PCM), which is initially frozen in a water bath. The difference in density between the solid and liquid phases is taken into account by considering a void in the solid PCM. A simple theoretical model is also presented, based on solving the heat equation in the steady state. The kinetics of melting is monitored by the total solid fraction and temperatures in the inner and outer surfaces of the capsule. The effect of different parameters is presented (thermostat temperature, capsule thickness, capsule conductivity and natural convection in the bath), showing the potential application of the method to select materials or geometries of the capsule.