Inorganic salt hydrate for thermal energy storage application: A review

Abstract

Salt hydrates are one of the most common inorganic compounds that are used as phase change material (PCM). These are available for a wide range of phase transition temperature for thermal energy storage (TES) application. They have some most desired properties for TES applications like high latent heat value, good thermal conductivity, nonexpensive, and were nonflammable. Besides these, due to the undesirable properties like phase segregation, supercooling, and corrosion to the containers, this PCM not recommended for TES application. To mitigate these issues and to make salt hydrates suitable in TES application, much research has been carried out in past years. This main highlight of this article is to provide a comprehensive overview of the use of salt hydrates, their applications and summarize the research outcomes reported by various researchers to every issue for its TES application. This summarized information will be useful to those who are interested to work on this research area. Along with this literature focuses on the advantages, disadvantages, and mechanism of salt hydrates for TES system during its thermal cycle process.

Thermal Properties of the H2O–CO2–Na2CO3/CH3OH/NH3 Systems at Low Temperatures and Pressures up to 50 MPa

“…Changes in CO 2 surroundings along the studied pressure–temperature paths must be considered while interpreting the results of the present study, where the molecule is first dissolved in the aqueous solutions, then “enclathrated” upon cooling, and finally released by heating. The addition of salts, methanol, or ammonia to water-rich phases decreased both specific heat capacity and enthalpy. − These values for these compounds in the solid state, forming salt hydrates, are usually within the ranges of 1–2 J g –1 K –1 and 100–300 J g –1 . , …”

Effect of Static Magnetic Field on Nucleation of Cobalt Nitrate Hexahydrate

“…When all the samples had melted and reached the same temperature of 60 °C, they were suddenly exposed to a magnetic field and cool temperature environment inside the adiabatic bath, in conjunction with the temperature data recording until all the samples solidified. The experiment was repeated 20 times with a new sample for each measurement, which was used to evaluate each set of parameters due to the complex thermal properties of CoNHH and the possibility of the phase separation effect, which commonly occurs during the freezing-thawing cycle for salt hydrate PCMs [4][5][6][7]10 .…”

“…Organic or inorganic PCMs, however, have their advantages and disadvantages 5 . In particular, a relatively high supercooling degree and phase separation effect are the main considerations for inorganic salt hydrate PCMs, besides the possibility of a change in the stoichiometric composition during heating and cooling 6,7 .…”

Alginate–Sodium Sulfate Decahydrate Phase Change Composite with Extended Stability

“…However, SSD suffers from supercooling and phase separation induced by incongruent melting, that reduce its enthalpy of fusion and limit its practical applications. , Different methodologies have been developed to solve these issues and form stable PCMs. For example, it has been demonstrated that the addition of nucleating agents can effectively decrease the supercooling degree. − The most suitable nucleating agent for SSD is borax, which can reduce its supercooling from 15 to 1–2 °C. − In addition, several approaches have been proposed to overcome phase separation, including adding thickening agents, , adding excess water, , and incorporating SSD within a porous medium. − However, in many cases the reduction in phase segregation is occurred at the cost of a reduced thermal energy storage capacity of SSD, with a wide range of values reported in the literature (∼100–200 kJ/kg). , …”

“…18−20 However, in many cases the reduction in phase segregation is occurred at the cost of a reduced thermal energy storage capacity of SSD, with a wide range of values reported in the literature (∼100−200 kJ/ kg). 21,22 There is a growing interest in developing polymeric phase change composites, whereby the PCM can either be entrapped in the matrix or encapsulated into the polymer shell. 23 The use of polymers offers several benefits that are missing in the case of molecular modifiers.…”