Search

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.

This study describes an innovative occupancy and chilled-water storage-based operation sequence implemented in a solar-assisted air-conditioning system. The core purpose of this solar-assisted air-conditioning system is to handle the cooling and heating load of the Solar Energy Research Centre (CIESOL), thus minimising its environmental impact. In this study, the cooling mode was investigated with special attention focused on the chilled-water storage circuit. The critical concern is that the solar-assisted air-conditioning system should always operate considering the actual load conditions, not using an abstract maximum load that is predetermined during the system’s design process, which can lead to energy waste during periods of low occupancy. Thus, the fundamental problem is to identify the optimum operation sequence for the solar-assisted air-conditioning system that provides the best energy performance. The significance of this work lies in the demonstration of a new operation strategy that utilises real-time occupancy monitoring and chilled-water storage tanks to improve the efficiency of solar-assisted air-conditioning systems, thereby reducing their electricity consumption. Adopting this strategy resulted in a large energy-saving potential. The results demonstrate that during one cooling period, it is possible to conserve approximately 42% of the total electrical energy consumed by the system prior to the adoption of this operation strategy.

In the last few years the solar-assisted air-conditioning systems have been in intensive development and are considered as the viable application for the thermal solar systems more often, especially in regions of southern Europe. This is driven by the increasing higher electrical consumption in many countries (especially in Spain) during the summer months due to expanding usage of cooling systems. Another important aspect to consider is that the traditional cooling systems require additional power consumption and studies have shown that the refrigerants used in those systems cause ozone layer depletion and greenhouse effect. This paper presents and compares different building cooling, heating and power systems (BCHP) based on renewable energy sources with the conventional BCHP system. The main goal here is to find a more favourable, design for Solar Energy Research Center (CIESOL) from environmental and energy management perspective. The further comparison versus the reference system (conventional BCHP) is made between the three possible technologies. Hence we investigate here the solar absorption BCHP system and two other solutions: solar geothermal electric compression BCHP and solar electric compression BCHP system. We used the primary energy and CO2 savings, initial cost, operating cost, maintenance cost, avoided costs and payback period as key performance indicators (KPIs). The energy performance of solar-assisted BCHP systems has been assessed considering as a benchmark the entire energy infrastructure operating today in the CIESOL building situated on the Campus of the University of Almeria. The results of the comparison demonstrated that only the solar absorption BCHP system presents energy saving potential. During 1 year it uses 61% less primary energy than the conventional BCHP system and is technically and economically feasible. At the same time, we used solar resource, abundant in the Almeria region, in an efficient way, making CIESOL building consumption less energy intensive and ensuring environmental protection.

This study presents the performance of solar-assisted air-conditioning system with two chilled water storage tanks installed in the Solar Energy Research Center building. The system consists mainly of solar collectors’ array, a hot-water driven absorption chiller, a cooling tower, two hot storage tanks, an auxiliary heater as well as two chilled storage tanks. The chilled water storage tank circuit was further investigated in order to find the optimum solar system’s operation sequence while providing the best energy performance. Firstly, we carried out a study about the dynamics of building’s cooling load and the necessity of the integration of chilled water storage tanks to solar system. Subsequently, the new system’s operation mode was proposed to reduce the energy consumption. The results demonstrate that we can save about 20% of the total energy consumption and about 30% of water consumption applying the new operation sequence, which takes into account the chilled water tanks action. Moreover, it was demonstrated that the integration of chilled water storage tanks allows to reduce the sudden absorption chiller on/off cycles, thereby improving the efficiency of the solar-assisted system.

This paper proposes Artificial Neural Networks (ANN) to model a solar-assisted air-conditioning system installed in the Solar Energy Research Center (CIESOL). This system consists mainly of the single-effect LiBr-H20 absorption chiller fed by water provided from either solar collectors or hot water storage tanks. The present work describes the total solar cooling systems based on absorption chiller and provided only with solar collectors. The experimental data were collected during the cooling period of 2008. ANN was used with the main goal of predicting the efficiency of the chiller and global system using the lowest number of input variables. The configuration 7-8-4 (7 inputs, 8 hidden and 4 output neurons) was found to be the optimal topology. The results demonstrate the accuracy ANN’s predictions with a Root Mean Square Error (RMSE) of less than 1.9% and practically null deviation, which can be considered very satisfactory.

The knowledge of the solar irradiation in a certain place is fundamental for the suitable location of solar systems, both thermal and photovoltaic. On the local scale, the topography is the most important modulating factor of the solar irradiation on the surface. In this work the global daily irradiation is estimated concerning various sky conditions, in zones of complex topography. In order to estimate the global daily irradiation we use a methodology based on a Digital Terrain Model (DTM), on one hand making use of pyranometer measurements and on the other hand utilizing satellite images. We underline that DTM application employing pyranometer measurements produces better results than estimation using satellite images, though accuracy of the same order is obtained in both cases for Root Mean Square Error (RMSE) and Mean Bias Error (MBE).

This paper presents a study of feasibility of different existing methodologies linked to field’s data acquisition from remote meteorological stations. The data transmission serves to collect field’s meteorological information, such as temperature, humidity and radiation. In our study the experimental data is registered in a weather station located about 100 km from the University of Almeria. Various existing techniques are studied, especially Radio, GSM (global system of mobile communication) and GPRS (general packet radio service). In the result of these studies has been designed a system of field’s data acquisition (herein referred as Meteologger) which we are going to present in this paper. The system is based on an ATmega 16 microcontroller, which scans 8 sensors together at any programmable intervals. This paper presents the study of the mentioned project, application and some main characteristics of the prototype system and its program. We attempt to implement the system, and subsequently present the performance of tests regarding the mentioned system. To verify its functioning some comparison of this measurement system with two others commercial data-acquisition system (Campbell and Hobo H8) has been carried out.

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.

Life cycle assessment is applied to assess the environmental benefits and trade-offs of a solar-assisted heating, ventilating, and air-conditioning (HVAC) system installed in the CIESOL building in Almeria (southeastern Spain). The environmental performance of this system is compared to that of a conventional HVAC system using a heat pump. The study evaluates these systems from cradle to grave, and the impact assessment includes, in addition to the CML2001 method, an impact category dealing with impacts on freshwater resources. The results show that the solar-assisted HVAC involves lower impacts in many impact categories, achieving, as an example, a reduction of 80% in greenhouse-gas emissions. On the other hand, key weak points of this system are the production of capital goods, but specially water use for cooling, due to its high impact on freshwater resources. Minimization of water requirements should be a priority for further development of this promising technology.