Research Article Synthesis and Thermal Energy Storage Properties of Erythritol Tetrastearate and Erythritol Tetrapalmitate Erythritol tetrapalmitate (ETP) and erythritol tetrastearate (ETS) were synthe- sized as novel solid-liquid phase change materials (PCM) by means of the direct esterification reaction of the erythritol with palmitic and stearic acids. The ETP and ETS esters were characterized chemically using FT-IR and 1 H NMR techni- ques. The energy storage properties of the esters were determined by DSC analy- sis. The results indicated that the ETP and ETS esters synthesized as novel solid- liquid PCMs are promising materials for thermal energy storage applications at large scale such as solar energy storage, building heating or cooling, indoor tem- perature controlling, and production of smart textile and insulation clothing. Keywords: Erythritol, Palmitic acid, Phase change materials, Stearic acid, Thermal energy storage Received: July 17, 2010; revised: August 25, 2010; accepted: September 28, 2010 DOI: 10.1002/ceat.201000306 1 Introduction Thermal energy can be stored as a change in internal energy of a material as sensible heat, latent heat, and thermochemical heat, or combinations of these [1]. Among these methods latent heat energy storage is one of the most attractive since it is able to store and release very large quantities of energy per weight of phase change material (PCM). In addition, the tem- perature remains nearly constant during the phase change of PCM [2]. A large number of PCMs such as inorganic com- pounds, organic compounds, and their eutectic mixtures have been investigated in terms of their thermophysical properties and utility potential for latent heat thermal energy storage for several decades [3–5]. PCMs are applied in solar energy stor- age, central air-conditioning systems, energy-efficient build- ings, industrial waste heat recovery, temperature-adaptable greenhouses, and thermo-regulating fibers [6–10]. A suitable phase change temperature and a high melting enthalpy are two essential requirements for a PCM. Therefore, in recent times, research work has been directed towards the synthesis of different kinds of solid-liquid PCMs with these criteria. Latent heat characteristics of fatty acid derivatives concerning phase change material applications were studied by Suppes et al. [11]. Nicolic et al. investigated new materials for solar thermal storage solid-liquid transitions in fatty acids esters [12]. Li and Ding prepared a series of distearates and butanediol distearate as novel solid-liquid PCMs and charac- terized these substances by spectroscopic and calorimetric techniques [13, 14]. Alkan et al. synthesized ethylene glycol distearate as novel PCM using the Fisher esterification method and characterized it by FT-IR, DSC, and TG analysis [15]. Alkan [16] sulfonated slightly paraffin samples to increase the energy storage efficiency without changing thermophysical properties. Canik and Alkan synthesized hexamethylene di- lauroyl, dimyristoyl, and dipalmytoyl amides as PCMs for thermal energy storage and determined their thermal energy storage properties [17]. Sari et al. synthesized some fatty acid esters with glycerol, n-butyl alcohol, and isopropyl alcohol and measured their latent heat energy storage properties [18, 19]. Stearic acid and palmitic acid as members of the fatty acid class have superior properties such as easy availability, congru- ent melting/freezing, good thermal and chemical stability, nontoxicity, and suitable phase change temperature [20, 21]. In spite of these desirable properties of the mentioned fatty acids, their high phase change temperature, low corrosivity, bad odor (especially sublimating during heating), poor ther- mal stability, and thermal conductivity limit their applications in latent heat storage systems. On the other hand, erythritol has a high latent heat storage capacity (339–354 J g –1 ) and a too high melting point (117–119 °C) [22, 23] to use it in most of thermal energy storage applications such as solar energy storage, building heating or cooling, indoor temperature controlling, or production of smart textile and insulation clothing. The other disadvantage of erythritol is its subcooling property [24]. Chem. Eng. Technol. 2011, 34, No. 1, 87–92 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.cet-journal.com Ahmet Sari 1 Ramazan Eroglu 1 Alper Biçer 1 Ali Karaipekli 1 1 Gaziosmanpasa University, Department of Chemistry, Tokat, Turkey. – Correspondence: Dr. A. Sari (asari@gop.edu.tr), Gaziosmanpasa University, Department of Chemistry, TR-60150 Tokat, Turkey. Thermal energy storage 87