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Abstract: Oleochemical carbonates are biobased materials that were readily prepared through a carbonate interchange reaction between renewable C10–C18 fatty alcohols and dimethyl or diethyl carbonate in the presence of a catalyst. These carbonates have various commercial uses in cosmetic, fuel additive, and lubricant applications. Oleochemical carbonates have not been examined for their applicability as phase change materials (PCM). The latent heats of melting and freezing for a series of symmetrical oleochemical carbonates ranging from 21-37 carbon atoms were evaluated to develop a fundamental understanding of the solid–liquid transitions for utilization in thermal energy storage (TES) applications. The phase transitions and associated thermal properties were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl carbonates had peak melting and freezing points of −2.2, 19.3, 33.7, 44.9, and 51.6 and −6.3, 14.3, 28.7, 40.3, and 46.9°C, respectively. In general, these carbonates exhibited sharp phase transitions and good latent heat properties. The latent heats of melting and freezing for decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl carbonates were 144, 200, 227, 219, and 223 and 146, 199, 229, 215, and 215J/g, respectively. These carbonates represent novel renewable-based PCM chemicals that compliment fatty acids, fatty alcohols, and their fatty acid esters while providing a potentially valuable biobased alternative to paraffin wax and salt hydrate PCM currently dominating the PCM market. [Copyright &y& Elsevier]

Abstract: Mesophase pitch based graphite foams (GFs) with different thermal properties and pore-size were used to increase the thermal diffusivity of phase change material (PCM), paraffin wax, for latent heat thermal energy storage application. To predict the performance of the Paraffin-GFs as a thermal energy storage system, their structure, thermal diffusivity and latent heat were characterized. Results indicated that thermal diffusivity of the Paraffin-GF can be enhanced 190, 270, 500, and 570 times as compared with that of pure paraffin wax. Latent heat of Paraffin-GF systems increased with the increasing of the mass ratio of the paraffin wax in the composite. Moreover, pore-size and thickness of ligaments of the foam played a key role in improving the thermal diffusivity and the storage capacity of the Paraffin-GF system: small pore-size (less paraffin wax were filled) and thicker ligament in GF resulted in a higher thermal diffusivity; large pore-size (less paraffin wax were filled) and thinner ligament in GF resulted in a larger latent heat. [Copyright &y& Elsevier]

The current challenge for the application of organic phase change materials is to compromise the conflicting influence of high thermal conductivity matrix content on the heat storage performance and thermal conductivity of phase change composites. Herein, we prepared graphene aerogel (GA) and GA-based paraffin phase change composite (GAP) by the widely reported hydrothermal method and studied the application potential of GA in GAP. The underlying mechanism of paraffin latent heat enhancement caused by GA was discussed from the perspective of the crystallization and phase change process of paraffin. X-ray diffraction and differential scanning calorimetry results showed that as the GA content increased, the paraffin in GAP had an increased crystallinity and exhibited increased latent heat. Activation energy of paraffin's phase change process calculated according to Kissinger model was effectively reduced when GA content was greater than 7.3 wt%, implying a considerable increase in the thermal response rate of GAP. In addition, in order to improve the thermal conductivity enhancement efficiency of GA, thermal conductivity of GAP was predicted by finite element numerical simulation. A good agreement was observed between the experimental and numerical results and some practical suggestions were made for the experimental preparation process. Image 1 • Improvement of PCMs' latent heat caused by graphene aerogel (GA) is explained. • A numerical model is built to predict the thermal conductivity of GA based PCC. • Practical suggestions were made for the preparation process of GA based PCC. [ABSTRACT FROM AUTHOR]

Pentaerythritol (PE), pentaglycerine (PG), and neopentylglycol (NPG) are non-ionic plastic crystal with high potential for latent heat thermal energy storage (TES) in solar heating applications. These molecules undergo reversible solid phase transitions with unusually large enthalpy of transition (110 J/g - 300 J/g) in the temperature range from 44 °C to 185 °C. To further enhance their heat storage capacity while lowering their price and preserving the advantage of solid phase transitions, a new class of shape-stabilized phase change materials (SSPCMs) in which a polyalcohol with adjustable solid phase transition properties (NPG/PG or PE/PG mixture) supports a cheaper and with higher latent heat solid-liquid PCM (paraffin wax) is proposed in this work. Combined with properly chosen paraffin waxes, NPG/PG mixtures allow tailoring the working temperature of corresponding SSPCMs between 24 °C and 81 °C, whereas PE/PG mixtures allow SSPCMs with phase change adjusted within 81 °C–190 °C temperature range. Produced SSPCMs were thoroughly characterized and their efficiency in terms of heat storage capacity and delivered power upon heat discharge were evaluated. The results achieved show proper anti-leakage effect due to good wettability between paraffins and polyalcohols and inner microstructure of SSPCMs promoting capillarity. In addition, volumetric latent heat storage capacity has been proven to be enhanced up to 45% compared to pure polyalcohols without detrimental effect in discharging power. • TES capacity of plastic crystal based composites was enhanced by adding paraffins. • Transition temperature was tailored by means of binary plastic crystal systems. • SSPCMs microstructure was related to their high paraffin retention capacity. • SSPCMs have potential to enhance TES systems compactness up to 2–3 times. • Capex reduction up to 40% for TES systems could be achieved with the proposed SSPCMs. [ABSTRACT FROM AUTHOR]