Phase change materials for thermal energy storage

Energy is a vital input for social and economic development. As a result of the generalization of agricultural, industrial and domestic activities the demand for energy has increased remarkably, especially in emergent countries. This has meant rapid grower in the level of greenhouse gas emissions and the increase in fuel prices, which are the main driving forces behind efforts to utilize renewable energy sources more effectively, i.e. energy which comes from natural resources and is also naturally replenished. Despite the obvious advantages of renewable energy, it presents important drawbacks, such as the discontinuity of generation, as most renewable energy resources depend on the climate, which is why their use requires complex design, planning and control optimization methods. Fortunately, the continuous advances in computer hardware and software are allowing researchers to deal with these optimization problems using computational resources, as can be seen in the large number of optimization methods that have been applied to the renewable and sustainable energy field. This paper presents a review of the current state of the art in computational optimization methods applied to renewable and sustainable energy, offering a clear vision of the latest research advances in this field.

Optimization methods applied to renewable and sustainable energy: A review

PROMETHEE: A comprehensive literature review on methodologies and applications

Thermal energy storage technologies and systems for concentrating solar power plants

A review of experimental/computational studies to enhance the thermal conductivity of phase change materials (PCM) that were conducted over many decades is presented. Thermal management of electronics for aeronautics and space exploration appears to be the original intended application, with later extension to storage of thermal energy for solar thermal applications. The present review will focus on studies that concern with positioning of fixed, stationary high conductivity inserts/structures. Copper, aluminum, nickel, stainless steel and carbon fiber in various forms (fins, honeycomb, wool, brush, etc.) were generally utilized as the materials of the thermal conductivity promoters. The reviewed research studies covered a variety of PCM, operating conditions, heat exchange and thermal energy storage arrangements. The energy storage vessels included isolated thermal storage units (rectangular boxes, cylindrical and annular tubes and spheres) and containers that transferred heat to a moving fluid medium passing through it. A few studies have focused on the marked role of flow regimes that are formed due to the presence of thermally unstable fluid layers that in turn give rise to greater convective mixing and thus expedited melting of PCM. In general, it can be stated that due to utilization of fixed high conductivity inserts/structures, the conducting pathways linking the hot and cold ends must be minimized.

Thermal conductivity enhancement of phase change materials for thermal energy storage: A review ☆

Multi-Criteria Decision Making (MCDM) techniques are gaining popularity in sustainable energy management. The techniques provide solutions to the problems involving conflicting and multiple objectives. Several methods based on weighted averages, priority setting, outranking, fuzzy principles and their combinations are employed for energy planning decisions. A review of more than 90 published papers is presented here to analyze the applicability of various methods discussed. A classification on application areas and the year of application is presented to highlight the trends. It is observed that Analytical Hierarchy Process is the most popular technique followed by outranking techniques PROMETHEE and ELECTRE. Validation of results with multiple methods, development of interactive decision support systems and application of fuzzy methods to tackle uncertainties in the data is observed in the published literature.

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Application of multi-criteria decision making to sustainable energy planning—A review

Phase change material (PCM) based latent heat thermal storage (LHTS) systems offer a challenging option to be employed as an effective energy storage and retrieval device. The performance of LHTS systems is limited by the poor thermal conductivity of PCMs employed. Successful large-scale utilization of LHTS systems thus depends on the extent to which the performance can be improved. A great deal of work both experimental and theoretical on different performance enhancement techniques has been reported in the literature. This paper reviews the implementation of those techniques in different configurations of LHTS systems. The influence of enhancement techniques on the thermal response of the PCM in terms of phase change rate and amount of latent heat stored/retrieved has been addressed as a main aspect. Issues related to mathematical modeling of LHTS systems employing enhancement techniques are also discussed.

Performance enhancement in latent heat thermal storage system: A review

Phase change material (PCM) based latent heat thermal storage (LHTS) systems provide an attractive solution to bridge the gap between energy source and demand, if source is intermittent and time dependent. The optimization of LHTS systems is not necessarily on the basis of performance study through energy analysis, but on the basis of exergy based performance study. The exergy based performance evaluation and subsequent optimization of LHTS units have been a growing interest among the researchers in recent years. This can be seen through the various works reported in the literature. This paper reviews the various procedures adopted for the exergy based performance evaluation of LHTS units. The influence of operating and design parameters on the exergy stored/retrieved and thus, on the optimization is addressed as a main aspect. The need of exergy analysis for the comparative evaluation of LHTS systems with performance enhancement techniques is emphasized. Thermoeconomics methods applicable to LHTS systems are also presented in this paper.

Exergy based performance evaluation of latent heat thermal storage system: A review

Energy requirements for cooking account for 36% of total primary energy consumption in India. The rural and urban populaces, depend mainly, on non-commercial fuels to meet their energy needs. Diverse urban growth patterns have led to structural changes in economy, and have important ramifications on energy consumption in household sector. It is observed that India follows income-based ladder starting with fuelwood and ending with sophisticated fuels like liquefied petroleum gas (LPG) and electricity. This paper discusses cooking energy dissemination in the country with an objective of understanding the underlying socioeconomic factors governing the utilization of various fuels/energy carriers in cooking. The diffusion of renewable energy devices is observed to be far below their estimated potential. Policy interventions required for better dissemination of renewable energy based devices are also discussed.

S.D. Pohekar

Papers

Application of multi-criteria decision making to sustainable energy planning—A review

Performance enhancement in latent heat thermal storage system: A review

Exergy based performance evaluation of latent heat thermal storage system: A review

Dissemination of cooking energy alternatives in India—a review

Multi-criteria evaluation of cooking energy alternatives for promoting parabolic solar cooker in India