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Brandstetter, A. and S. Kaneff (1990). Materials and systems for phase change thermal storage. Proceedings 1st world renewable energy congress: 1460-1464.

Several potentially low cost hydrated salt phase change materials (PCMs) have been under study as candidate media for thermal storage, including calcium chloride hexahydrate, sodium sulphate decahydrate and sodium acetate trihydrate, and modified varieties covering a range of transition temperatures about 8° C to 58° C. Containment options were investigated and systems tested in actual operation, including off peak space heating and solar greenhouse climate control. The paper describes some of theses phase change materials and systems, and their current status, as well as heat transfer studies and validation procedures using specially designed equipment for multi-sample thermal analysis.

Eissenberg, D. and C. Wyman (1980). "What's in store for phase change thermal storage materials for active and passive solar applications." Solar Age (May 1980): 12-16.

Farid, M. M. and A. K. Mohamed (1987). "Effect Of Natural convection On The Process of melting And Solidification Of Paraffin Wax." Chem. Eng. Comm. 57: 297-316.

Temperature distribution and solid-liquid interface positions were measured during melting and solidification of paraffin wax (mixture of pentacosane and hexacosane) contained in a cylindrical cell, with an insulated wall to achieve one dimensional heat flow. The lower face of the cell was subjected to a sudden temperature change, while the condition of no heat flux was maintained at the upper face. Measurements of temperature distribution and interface positions during solidification from below were in excellent agreement with theoretical predictions based on pure conduction in both phases. Both the analytical solution of Neuman and the numerical solution of Murray and Landis were applied and found to have similar results. Although the experimental results of melting from below showed distinct temperature distribution in both phases, the agreement with the theoretical estimates base on pure conduction was very poor. In order to include the effect of convection, liquid thermal conductivity was replaced by an effective thermal conductivity according to a correlation of the form Ke/Kl = cRna. Values of c and n have been determined to achieve a good agreement between the experimental and theoretical values of the interface positions, and found to be different from those usually obtained with no phase change.

Feldman, D., M. M. Shapiro, et al. (1986). "Organic phase change materials for thermal energy storage." Solar Energy Materials 13: 1-10.

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 organic materials suitable for low cost packaging i.e. those that are insoluble in water and un-reactive with air and some of the common packaging films. we have done a preliminary survey of 12 such organic materials with melting points in the range 10-43oC. Measurements of melting point, freezing point, and the latent heats of melting and fusion are presented.

Feldman, D., M. M. Shapiro, et al. (1989). "Fatty acids and their mixtures as phase-change materials for thermal energy storage." Solar Energy Materials 18: 201-216.

An analysis of thermal properties of fatty acids and their binary mixtures has shown that they are attractive candidates for latent heat thermal storage in space heating applications. In this study, the method of differential scanning calorimetry was used to determine the transition temperatures and latent heat of transition of the fatty acids and their binary mixtures. These properties are of prime importance in the design of a latent heat thermal storage system. The melting range of the fatty acids (capric, lauric,palmitic and stearic) was observed to be approximately from 30ºC to 65ºC. Their heat of transition was observed to have a range from approximately 153 to 182j/g. The eutectic points were determined for the binary mixtures of the fatty acids. The melting points of the eutectics for the binary mixtures of the fatty acids. the fatty acids and their eutectics mixtures were examined with an infrared spectrophotometer to ascertain the polymorphic forms and material purities

Heine, D. and A. Abhat (1978). Investigation Of Physical and Chemical Properties Of Phase Change Materials for Space Heating/Cooling Applications. Proceedings Of the International Solar Energy Society Congress, New Delhi, India.

The physical and chemical properties of four paraffins (different oil contents), a wax-ester, a fatty acid and two inorganic salts are experimentally investigated. Heating and cooling curves for the materials are obtained and their compatibility with four conventional metals of construction, stainless steel 1.4301, Cu 99.9, Al 99.5 and A1mg3 determined. While all organic substances are found non-corrosive, only one paraffin with 5% oil content and lauric acid exhibit good freezing characteristics. The two inorganic salts suffer from acute supercooling. Moreover Na2S203

Lane, G. A. (1982). Congruent melting phase-change heat storage materials. ASHRAE Trans: 1043-1049.

For residential heating and cooling applications, the most promising heat storage phase change materials (PCMs) are the inorganic hydrates. Most of the common salt hydrates segregate during cyclic freezing and melting, losing storage capacity. A class of hydrates, congruent melting materials, does not suffer this disadvantage. Four of these are now available commercially as bulk chemicals, formulated with nucleating additives to supress supercooling. The properties of theses PCM's are discussed.

Lane, G. A. (1983). Solar heat storage: latent heat materials volume I: background and scientific principles. Florida, CRC Press, Inc.

Lane, G. A. (1983). Solar heat storage: latent heat materials Volume II: technology. Florida, CRC Press Inc.

Lane, G. A. (1991). "Phase change materials for energy storage nucleation to prevent supercooling." Solar energy materials and solar cells 27: 135-160.

Phase change materials (PCMs) are useful for storing heat as the latent heat of fusion. Such storage has potential in heating and cooling buildings, waste heat recovery, off peak power utilisation, heat pump systems, and many other applications.

Among the PCMs that have proven useful in heat storage applications are calcium chloride hexahydrateCaCL2 6H2O, magnesium chloride hexahydrate, MgCL₂ 6H₂O, and magnesium nitrate hexahydrate, Mg(NO₃)2 6h₂0.

Many salt hydrate PCMs including those listed above heave the disadvantage that during extraction of stored heat the material supercools before freezing. This reduces the utility of the materials, and if too severe can completely prevent heat recovery.

Many factors determine whether a particular additive will promote nucleation, for example, crystal structure, solubility, and hydrate stability. Candidate isomorphous and isotypic nucleating additives, with crystal structures that fit well with the PCM structure, were selected from tables of crystallographic data.

Epitaxial nucleators, with less obvious lattice structure features that promote nucleation, were selected mostly by intuition. Effective nucleators were discovered by both methods.

Based on laboratory test results, promising materials were developed into formulations based on CaCL₂ H₂O, MgCL₂ 6H₂O, Mg(NO₃)₂ 6H₂O-MgCL₂ 6H2O eutetic, and Mg Mg(NO₃)₂ 6H₂O –NH₄NO₃) eutectic salt hydrate PCMs. Subsequently, attempts were made to correlate crystal structure and hydrate stability with nucleating efficacy, and to speculate about active nucleating structures.

Mancini, N. A. (1980). Use Of Paraffins For Thermal Storage. Thermal Storage Of Solar Energy. C. Den Ouden. Holland, Martinus Nijhoff Publishers: 99-109.

Salyer, I. O., A. K. Sircar, et al. (1985). Advanced phase change materials for passive solar storage applications. Proceedings of the 20th Intersociety energy conversion: 3.699-3.709.

This research was sponsored by the Solar Passive Division of the Department of Energy and has continued to date. The objectives of the research were to find, test, and develop low-cost, effective phase change materials that freeze and melt near 25oC and can be economically incorporated into common building materials (cement, concrete, plaster, plasterboard, floor tiles, etc), by processes that are readily adaptable to the manufacture of these building materials. The goals of the research have been successfully attained using low-cost crystalline, alkyl hydrocarbons and economic processes for containing in building materials. However, scale up demonstrating and implementing the results, remains to be done. Three patent applications have been filed. Several large companies have expressed interest in acquiring rights to the technology.

Salyer, I. O. and A. K. Sircar. (1990). Phase change materials for heating and cooling of residential buildings and other applications. Proceedings of the 25th intersociety society energy conversion engineering: 236-243.

The program objectives were to define a cost/effective, environmentally acceptable phase change material (PCM), and methods of incorporating the PCM into building materials (egg, plasterboard) for applications in residential heating and cooling.

These program goals have been achieved through defining and developing a series of linear crystalline alkyl hydrocarbon phase change materials, that are commercially available from polymerisation of ethylene and from by-products of petroleum refining. These PCMS are preferred over their nearest alternatives for home heating and cooling and other applications as well.

Besides plasterboard for residential heating and cooling, applications of strong interest include hot and cold tableware of strong interest include hot and cold tableware service, hot and cold medical therapy, off peak electric cool storage for daytime air conditioning, preventing the overnight freezing of tree trunks, preventing overnight freezing of bridge decks, hot and cool textile fabrics, and waterproofing of concrete bridge decks and water pipes.

A detailed review of the prior years research is contained in references 1 to 10.

Tomlinson, J. (1985). Clathrates and conjugating binaries: new materials for thermal storage. ASHRAE trans: 1931-1937.

Clathrates and liquid conjugating binary systems form the basis foe new latent heat materials under investigation as storage media for off-peak building heating or cooling. Clathrate compounds formed with water as a constituent are particularly attractive for this application, because they freeze at temperatures higher than ice but still low enough for effective building cooling. Partially miscible binary systems that possess a usable heat of mixing in the building heating/cooling temperature range have also been identified. These offer an advantage of thermal storage media in that they remain in liquid form. This paper describes clathrate and conjugating binary storage concepts currently being explored and discusses the technical and practical issues involved with each.