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Abstract The present work compares the environmental impact of three different thermal energy storage (TES) systems for solar power plants. A Life Cycle Assessment (LCA) for these systems is developed: sensible heat storage both in solid (high temperature concrete) and liquid (molten salts) thermal storage media, and latent heat storage which uses phase change material (PCM). The aim of this paper is to analyze if the energy savings related to the stored energy of the different systems are enough to balance the environmental impact produced during the manufacturing and operation phase of each storage system. Some hypothetical scenarios are studied using LCA methodology to point out the differences between each TES system. The system based on solid media, due to his simplicity, shows the lowest environmental impact per kWh stored of all three systems compared. In addition, the liquid media (molten salts) shows the highest impact per kWh stored because it needs more material and complex equipment.

Abstract Sandwich panels are a good option as building materials, as they offer excellent characteristics in a modular system. The goal of this study was to demonstrate the feasibility of using the microencapsulated PCM (Micronal BASF) in sandwich panels to increase their thermal inertia and to reduce the energy demand of the final buildings. In this paper, to manufacture the sandwich panel with microencapsulated PCM three different methods were tested. In case 1, the PCM was added mixing the microencapsulated PCM with one of the components of the polyurethane. In the other two cases, the PCM was added either a step before (case 2) or a step after (case 3) to the addition of the polyurethane to the metal sheets. The results show that in case 1 the effect of PCM was overlapped by a possible increase in thermal conductivity, but an increase of thermal inertia was found in case 3. In case 2, different results were obtained due to the poor distribution of the PCM. Some samples showed the effect of the PCM (higher thermal inertia), and other samples results were similar to the conventional sandwich panel. In both cases (2 and 3), it is required to industrialize the process to improve the results.

Hot water heat stores with stratification are a common technology used in solar energy systems and reuse of waste heat. Adding a PCM module at the top of the water tank would give the system higher storage density, and compensate heat loss in the top layer. The work presented here includes experimental results and numerical simulation of the system using an explicit finite-difference method. Experiments and simulations were carried out using different cylindrical PCM modules. With only 1/16 of the volume of the store being PCM, 3/16 of water at the top of the store was held warm for 50% to 200% longer and the average energy density was increased by 20% to 45%. Furthermore, these 3/16 of water were reheated by the heat from the module after being cooled down in only 20 min.

Abstract An exergy analysis, which only considers the unavoidable exergy destruction, is conducted for single, double, triple and half effect Water–Lithium bromide absorption cycles. Thus, the obtained performances represent the maximum achievable performance under the given operation conditions. The coefficient of performance (COP), the exergetic efficiencies and the exergy destruction rates are determined and the effect of the heat source temperature is evaluated. As expected, the COP increases significantly from double lift to triple effect cycles. The exergetic efficiency varies less among the different configurations. In all cycles the effect of the heat source temperature on the exergy destruction rates is similar for the same type of components, while the quantitative contributions depend on cycle type and flow configuration. Largest exergy destruction occurs in the absorbers and generators, especially at higher heat source temperatures.

In 2008, following its R&D strategy roadmap for Concentrated Solar Power, Abengoa designed, built and tested a unique Molten Salts pilot plant at the representative scale of 8 MWhth, coupled with a trough oil loop. The objectives of this project were based on evaluating the technology at a scale at which the results are sufficiently representative of the real circumstances facing a commercial plant that utilizes this storage technology. To this end, the MS-TES plant was brought into operation on January 19th, 2009, been the first demo plant of indirect double tank storage in operation in the world. Key points such a material corrosion, analysis of possible leakage points, calculation of performance or true efficiency of the storage (including a thorough assessment of thermal losses) and analysis of plant operation are the lines that have been analysed at this plant. Operational aspects such as the mechanical assembling, the pre-heating, the filling up and plant performance were deeply addressed. Key components as the storage tanks, the heat exchanger, the molten salts pumps, the heat-tracing systems or valves and instrumentation were tested. In this first paper, the description and commissioning of the plant is presented together a set of lessons learnt to be applied at the commercial plant scale.

Abstract Storage and transport of temperature sensitive products have become an important issue worldwide. The enhancement of thermal performance of cold application is under investigation and implementing thermal energy storage (TES) systems by using phase change materials (PCM) is one of the solutions to better storage. Hence, the selection of the suitable PCM for each specific application is an important matter. In this paper, a TES system using PCM for low temperature applications such as commercial freezers is studied. A set of PCM formulations based on ammonium chloride – water binary system were tested and analyzed to provide information useful for the selection of PCM with regards to their melting range, latent heat, stability under cycling, and cost. Thermal cycling was conducted to determine the thermal reliability of the PCM and the thermal properties were determined using differential scanning calorimetry (DSC) analysis.

Abstract This paper focuses on a novel energy management approach, namely Building to Vehicle to Building, in which electric vehicles act as vector devices for renewable energy exchanges among buildings. The main goal behind this concept is to benefit from the potentiality of electric vehicles toward the achievement of the zero-energy target extended to a buildings cluster level, by exploiting renewable generation on- and off-site. To this aim, a dynamic simulation tool is developed to assess the energy and economic performance of the proposed V2B2 scheme applied to a cluster of multiple users made of non-residential buildings and electric vehicles with bidirectional charging, used as a back-up power supply for increasing self-consumption of energy produced on-site by PV panels integrated in one of the buildings, to be also exploited off-site by other users. A case study analysis is conducted for a sample cluster of 3 building sand 3 electric vehicles, located in a Mediterranean city (Naples, Italy) with the aim at conducting the proof of concept. Simulation results show that the proposed V2B2 scheme enhances the match between the on-site renewable generation and the whole system demand, i.e. buildings and electric vehicles’ needs, by reducing the grid operation and boosting the system economic convenience. The proposed energy management scheme represents an example of novel aggregator energy and business model which will play a crucial role in the next generation of smart cities and communities.

The goal of this study is to implement and to test a thermal energy storage (TES) system using different phase change materials (PCM) for solar cooling applications. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly by three parts: heating system, cooling system, and different storage tanks. The pilot plant uses synthetic thermal oil as heat transfer fluid (HTF) and has a working temperature range from 100 to 400 C. Two different PCM were selected after a deep study of the requirements of a real solar cooling plant and the available materials in the market through literature review and DSC analysis. Finally D-mannitol with phase change temperature of 167 C and hydroquinone which has a melting temperature of 172.2 C were used at pilot plant scale. For both PCM, no hysteresis was detected, and at pilot plant only D-mannitol showed subcooling even though both showed it during the DSC analysis. An effective heat transfer coefficient between the storage material and the heat transfer fluid (HTF) was calculated. For the same boundary conditions, the energy stored by D-mannitol was higher than that for hydroquinone. Moreover, D-mannitol has polymorphism that needs to be taken into account when the material is used as PCM, but experiments in this paper showed that polymorphism did not interfere its performance as PCM.