The use of a latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy and has the advantages of high-energy storage density and the isothermal nature of the storage process. PCMs have been widely used in latent heat thermal-storage systems for heat pumps, solar engineering, and spacecraft thermal control applications. The uses of PCMs for heating and cooling applications for buildings have been investigated within the past decade. There are large numbers of PCMs that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. This paper also summarizes the investigation and analysis of the available thermal energy storage systems incorporating PCMs for use in different applications.

Review on thermal energy storage with phase change materials and applications

This paper reviews the development of latent heat thermal energy storage systems studied detailing various phase change materials (PCMs) investigated over the last three decades, the heat transfer and enhancement techniques employed in PCMs to effectively charge and discharge latent heat energy and the formulation of the phase change problem. It also examines the geometry and configurations of PCM containers and a series of numerical and experimental tests undertaken to assess the effects of parameters such as the inlet temperature and the mass flow rate of the heat transfer fluid (HTF). It is concluded that most of the phase change problems have been carried out at temperature ranges between 0 °C and 60 °C suitable for domestic heating applications. In terms of problem formulation, the common approach has been the use of enthalpy formulation. Heat transfer in the phase change problem was previously formulated using pure conduction approach but the problem has moved to a different level of complexity with added convection in the melt being accounted for. There is no standard method (such as British Standards or EU standards) developed to test for PCMs, making it difficult for comparison to be made to assess the suitability of PCMs to particular applications. A unified platform such as British Standards, EU standards needs to be developed to ensure same or similar procedure and analysis (performance curves) to allow comparison and knowledge gained from one test to be applied to another.

A review of materials, heat transfer and phase change problem formulation for latent heat thermal energy storage systems (LHTESS)

The continuous increase in the level of greenhouse gas emissions and the climb in fuel prices are the main driving forces behind efforts to more effectively utilise various sources of renewable energy. In many parts of the world, direct solar radiation is considered to be one of the most prospective sources of energy. However, the large-scale utilisation of this form of energy is possible only if the effective technology for its storage can be developed with acceptable capital and running costs. One of prospective techniques of storing solar energy is the application of phase change materials (PCMs). Unfortunately, prior to the large-scale practical application of this technology, it is necessary to resolve numerous problems at the research and development stage. This paper looks at the current state of research in this particular field, with the main focus being on the assessment of the thermal properties of various PCMs, methods of heat transfer enhancement and design configurations of heat storage facilities to be used as a part of solar passive and active space heating systems, greenhouses and solar cooking.

Solar energy storage using phase change materials

Seawater desalination using renewable energy sources

Desalination technologies improve water quality, greatly reduce water shortage problems, and improve quality of life and economic status. Two main technologies are currently used in water desalination: thermal (phase-change) processes and membrane processes. The primary thermal distillation processes include multistage flash distillation (MSF), multi-effect distillation (MED), and vapor compression (VC). The VC process encompasses two types: mechanical (MVC) and thermal (TVC). The common membrane desalination processes include reverse osmosis (RO) and electrodialysis (ED and EDR). Energy cost, operational and maintenance cost, and capital investment are the main contributors to the water production cost of any of these processes. The energy cost is responsible for about 50% of the produced water cost. For thermal distillation processes (MSF, MED, and TVC), two energy forms are required for the operation: (1) low-temperature heat, which represents the main portion of the energy input and is usually supplied to the system by a number of external sources (e.g., fossil fuel, waste energy, nuclear, solar) and (2) electricity, which is used to drive the system's pumps and other electrical components. For the MVC thermal distillation process, only electricity is needed. For membrane processes (RO and ED), only electricity is required as an energy input. Renewable energy systems such as solar thermal, solar photovoltaic, wind, and geothermal technologies are currently used as energy suppliers for desalination systems. These renewable resources are now a proven technology and remain economically promising for remote regions, where connection to the public electric grid is either not cost effective or feasible, and where water scarcity is severe. As the technologies continue to improve, and as fresh water becomes scarce and fossil fuel energy prices rise, renewable energy desalination becomes more viable economically. The technical features, energy consumption, environmental considerations, and potential of renewable energy use in driving the main desalination processes are reviewed and analyzed in this paper. The current and projected costs of water produced from conventional and renewable-energy-driven processes are discussed and compared.

Energy Consumption and Water Production Cost of Conventional and Renewable-Energy-Powered Desalination Processes

Thermal performance of a single basin solar still with PCM as a storage medium

Global, direct and diffuse solar radiation on horizontal and tilted surfaces in Jeddah, Saudi Arabia

The use of solar energy in recent years had reached a remarkable edge. The continuous research for an alternative power source due to the perceived scarcity of fuel fossils is its driving force. It had become even more popular as the cost of fossil fuel continues to rise. Of all the renewable sources of energy available, solar energy is the most abundant one and is available in both direct as well as indirect forms. Solar energy applications were divided mainly into two categories: the first is the direct conversion to electricity using solar cells (electrical applications). The second is the thermal applications. The latter include solar heating, solar cooling, solar drying, solar cooking, solar ponds, solar distillation, solar furnaces, solar-thermal power generation, solar water heating, solar air heating, etc. Detailed description, fundamentals and previous work performed on solar dryers and solar air heaters, as the vital element for the indirect and mixed modes of solar dryers, were presented in the present review paper.

A.A. El-Sebaii

Papers

Thermal performance of a single basin solar still with PCM as a storage medium

Global, direct and diffuse solar radiation on horizontal and tilted surfaces in Jeddah, Saudi Arabia

Solar drying of agricultural products: A review

Experimental investigation of an indirect type natural convection solar dryer

Thermal performance investigation of double pass-finned plate solar air heater