A Review on Solar Water Distillation Using Sensible and Latent Heat

Advanced 3D-printed phase change materials

A review on phase change energy storage: materials and applications

06/01505 Heat transfer enhancement in energy storage in spherical capsules filled with paraffin wax and metal beads: Ettouney, H. et al. Energy Conversion and Management, 2006, 47, (2), 211–228

Thermal energy storage (TES) system integrated with concentrated solar power provides the benefits of extending power production, eliminating intermittency issues, and reducing system LOCE. Infinia Corporation is under the contract with DOE in developing TES systems. The goal for one of the DOE sponsored TES projects is to design and build a TES system and integrate it with a 3 KWe free-piston Stirling power generator. The Phase Change Material (PCM) employed for the designed TES system is a eutectic blend of NaF and NaCl which has a melt temperature of 680° C and energy storage capacity of 12 KWh. This PCM was selected due to its low cost and desired melting temperature. This melt temperature ensures the Stirling being operated at designed operating hot end temperature. The latent heat of this eutectic PCM offers 5 to 10 times the energy density of a typical molten salt. The technical challenges associated with low cost molten salt TES systems are the low thermal conductivity of the salt and large thermal expansion. To address these challenges, an array of sodium filled Heat Pipes (HP) is embedded in the PCM to enhance the heat transfer from solar receiver to PCM and from PCM to Stirling engine. The oversized dish provides sufficient thermal energy to operate a 3KWe Stirling engine at full power and to charge up the TES. The HP arrays are optimally distributed so that the solar energy is transferred directly from receiver to Stirling engine heat receiver. During the charge phase, the Stirling engine absorbs and converts the transferred solar energy to electricity and the excess thermal energy is re-directed and stored to PCM. The stored energy is transferred via distributed HP from PCM to Stirling engine heat receiver during discharge phase. The HP based PCM thermal energy storage system was designed, built, and performance tested in laboratory. The TES/engine assembly was tested in two different orientations representing the extremes of system operation when mounted on sun-tracking dish, horizontal and vertical. Horizontal represents the zero elevation at sun rise and the vertical represents the extreme of solar noon. The testing allows the examination of orientation effect on the heat pipe performance and the maximum charge and discharge rates. The total energy stored and extracted was also examined. The areas for further system refinements were identified and discussed.

Flexible engineering of advanced phase change materials

Compared to Solar Photovoltaics (PV), Concentrated Solar Power (CSP) can store the excess solar thermal energy, extend the power generation at night and cloudy days, and levelize the mismatch between energy demand and supply. To make CSP competitive, Thermal Energy Storage (TES) system filled with phase change material (PCM) is a promising indirect energy storage technique, compared to the TES system using concrete or river rocks. It is of great interests to solar thermal community to apply the latent heat thermal energy storage (LHTES) system for large scale CSP application, because PCMs can store more thermal energy due to the latent heat during the melting/freezing process. Therefore, a comprehensive parametric analysis of LHTES system is necessary in order to improve its systematic performance, since LHTES system has a relatively low energy storage efficiency compared to TES systems using sensible materials. In this study, an 11-dimensionless-parameter space of LHTES system was developed, by considering only the technical constraints (materials properties and operation parameters), instead of economic constraints. Then the parametric analysis was performed based on a 1D enthalpy-based transient model, and the energy storage efficiency was used as the objective function to minimize the number of variables in the parameter space. It was found that Stanton number (St), PCM radius (r), and void fraction (ε) are the three most important ones. The sensitivity study was conducted then based on the three dimensionless-parameter space which will significantly influence the system performance. The results of this study make LHTES system competitive with TES system using sensible materials in terms of energy storage efficiency.

Thermal energy storage (TES) is a promising technique that conserves accumulated thermal energy from heat and cold mediums, making it available for future use. This method allows energy to be stored under various conditions, presenting an attractive solution for harnessing solar radiation efficiently and in large quantities. TES is becoming increasingly important as renewable electricity integration grows and the demand for low-carbon energy rises. Concentrating solar power plants benefit from TES, enabling them to store excess solar energy during peak times and utilize it during periods of lower solar radiation, ensuring a continuous power supply. Additionally, standalone TES systems for grid applications are gaining popularity, especially with the declining costs of renewable energy. These systems facilitate energy integration and help meet the increasing energy demands sustainably. Phase change materials (PCMs) play a vital role in thermal energy storage systems, contributing to effective energy conservation. Their high thermal storage density and moderate temperature volatility make them ideal for storing and releasing significant amounts of thermal energy. As a result, PCMs have gained popularity in this field. This study examines various aspects of thermal energy storage systems, with a particular focus on research articles related to storage materials and methods. It explores sensible heat storage, which involves altering material temperatures to store energy, latent heat storage that capitalizes on phase change properties like those of PCMs, chemical storage utilizing chemical reactions for energy storage, and cascaded thermal storage systems that combine different methods for optimized energy storage. By exploring these areas, this research aims to advance the understanding of thermal energy storage and contribute to the ongoing efforts in achieving sustainable and low-carbon energy solutions for the future.

Latent thermal energy storage for solar process heat applications at medium-high temperatures – A review

Salt hydrate phase change materials used for thermal storage in space heating and cooling applications have low material costs, but high packaging costs. A more economic installed storage may be possible with medium priced, high latent heat. Latent heat storage is one of the most efficient ways of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method provides much higher storage density, with a smaller temperature difference between storing and releasing heat. This paper work on latent heat storage and provides an insight to recent efforts to develop new classes of phase change materials (PCMs) for
 use in energy storage. There are large numbers of phase change materials that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. Hydrated salts have larger energy storage density and higher thermal conductivity but experience super cooling and phase segregation, and hence, their application requires the use of some nucleating and thickening agents. Sodium carb-onate, sodium phosphate and sodium sulfate tested as phase change material by crystallization in this work.

Challenges of the application of PCMs to achieve zero energy buildings under hot weather conditions: A review

Solar-powered compact thermal energy storage system with rapid response time and rib-enhanced plate via techniques of CFD, ANN, and GA

A review on the applications of PCM in thermal storage of solar energy

Due to the efficient performance in energy storage density, solar thermal energy storage (TES, especially latent type) applications are drawing more attention in the research field of solar energy. Among all of the types of solar thermal storage technologies, the latent heat storage system using phase change materials is the most efficient way of storing thermal energy. It has some dominant factors such as high density energy storage and isothermal operations, i.e., very small temperature range for heat storage and removal. Thus, latent heat storage systems have greater applicability over the other types of TES systems. This chapter initially presents an analysis of a latent-type solar thermal energy storage (TES) system involving some of the important cases carried out comprising the application of ambient conditions with various geometries and working conditions. The analysis is carried out in MATLAB® and COMSOL®, which contains transient simulations of latent heat storage functioning with 1D and 2D modeling. It comprises the validation of numerical 1D analysis with corresponding analytical solution, observation of the change in thermophysical properties at the melting point, etc. Further in this study, the phase change material (PCM) is assumed to be incorporated in a brick wall structure, which can improve its thermal performance. A 1D numerical model on COMSOL Multiphysics is developed to analyze the thermal performance of the PCM-filled brick wall unit. The numerical model and the adopted hypotheses are illustrated in detail. The comparison between temperature distributions of a simple brick wall and a brick wall with a PCM layer is presented. The results show that using the numerical tool, it can be observed that the thermal performance of the PCM-filled brick wall is efficient over the simple brick wall without PCM. This concept of the PCM-impregnated building structure is found to be successful in shifting the energy requirement of the equipped building sector from a high peak electricity demand period to an off-peak period.

This article reviews recent research on phase-change materials (PCMs) used in thermal energy storage systems with the aim of enhancing their performance. The study explores various methods to improve heat transfer in PCMs, such as microencapsulation, infill materials, fins and nanofluids. Additionally, it evaluates techniques to boost heat transfer in latent heat thermal energy storage (LHTES) systems and investigates ways to increase thermal conductivity using porous and low-density materials. PCMs store thermal energy, making them suitable for use in solar energy systems when solar energy is not available. The need for eco-friendly alternatives to conventional heating and cooling in global construction and the significant energy consumption of buildings has driven research on this topic. As such, this study additionally examines current advancements in free cooling systems with latent heat storage to identify the key factors affecting their effectiveness. The findings show that using PCMs for overnight cooling maintains the room temperature within the comfort zone and reduces the cooling loads in various climates. Using machine learning methods, this study also compares recent advancements in the use of PCMs in various solar energy systems, including solar thermal power plants, solar air purifiers, solar water heaters and solar appliances. Results derived feature key factors crucial for the optimal selection of PCMs and the challenges associated with sustainable green transitions in built environments. HIGHLIGHTS This review provides an in-depth examination of PCM thermal energy storage systems. This study investigates the use of fillers, nanofluids, and nanoparticles for enhanced heat transfer. Analytical methods for boosting the PCM thermal conductivity are briefly outlined. Geometric design and thermal conductivity enhancement affect the Latent Heat Thermal Energy Storage (LHTES). The assessment also evaluates advanced free-cooling systems using the LHTES. PCMs help to store heat energy in solar systems and bridge supply gaps. GRAPHICAL ABSTRACT

Influence of functionalized and non-functionalized 2D graphene nanomaterial with organic phase change materials: Thermal performance comparison