Micro/nano encapsulated n-tetracosane and n-octadecane eutectic mixture with polystyrene shell for low-temperature latent heat thermal energy storage applications Ahmet Sarı ⇑ , Cemil Alkan ⇑ , Derya Kahraman Do ¨g ˘u ¨s ßcu ¨, C ¸ ınar Kızıl Department of Chemistry, Gaziosmanpas ßa University, 60240 Tokat, Turkey Received 10 September 2014; received in revised form 29 December 2014; accepted 23 February 2015 Available online 12 March 2015 Communicated by: Associate Editor Halime Paksoy Abstract A series of micro/nano capsules of polystyrene(PS)/tetracosane(C24)–octadecane(C18) eutectic mixture were synthesized as encapsu- lated phase change material (PCM) using emulsion polymerization method. The encapsulated PCMs were characterized chemically using FT-IR spectroscopy. The surface morphology and particle size of the synthesized capsules were investigated POM, SEM and PSD tech- niques. The results proved that the surfaces of the capsules had not completely spherical appearances and bimodal particle size dis- tributions changed within 0.01–115 lm. The thermal characteristics measured using DSC and TGA techniques indicated that the capsules containing highest amount of the eutectic mixture had a melting temperature of 25.96 °C, latent heat of 156.39 J g 1 and high thermal durability. The thermal cycling test confirmed that the PS/(C24–C18) micro/nano capsules with 1:2 shell/core ratio had good thermal reliability after 5000 thermal cycling number. Furthermore, the synthesized PS/(C24–C18)(1:2) micro/nano capsules had a con- siderable high thermal conductivity. By taking account of all results, it can be drawn a conclusion that especially PS/(C24–C18)(1:2) micro/nano capsules can be considered as promising encapsulated PCM for low-temperature latent heat thermal energy storage applications. Ó 2015 Elsevier Ltd. All rights reserved. Keywords: Micro/nano; Encapsulation; PCM; Eutectic mixture; PS; Latent heat storage 1. Introduction Energy storage is the most important part in saving energy, as available energy sources are limited and energy consumption increases rapidly. Nowadays the world energy consumption is roughly 4.1  10 20 J yr 1 and until end of the this century energy demand is estimated to increase three times more due to economic growth and population increase (Lewis and Crabtree, 2005). Thermal energy is stored one way of coping with the problem which the rapid depletion of energy. The storage thermal energy may be in the form of sensible heat or latent heat. Unlike sensible heat storage materials, phase change materials (PCMs) can absorb, store and release large amounts of latent heat a very small variation sur- roundings during phase change from liquid to solid and from solid to liquid. Thermal energy storage and utilization has been grow- ing interest last decades by using PCM, which has been widely applied in passive solar latent heat thermal energy http://dx.doi.org/10.1016/j.solener.2015.02.035 0038-092X/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: ahmet.sari@gop.edu.tr (A. Sarı), cemil.alkan@gop. edu.tr (C. Alkan). www.elsevier.com/locate/solener Available online at www.sciencedirect.com ScienceDirect Solar Energy 115 (2015) 195–203