Graphene oxide (GO) sheets are introduced to stabilize the shape of the most widely studied phase change material for thermal storage, polyethylene glycol (PEG) during the solid-liquid phase change process. In this composite, a maximum weight percentage of PEG as high as 96% without any leakage up to a temperature as high as 150 degrees C, far above the melting temperature of PEG, has been achieved. Such a weight percentage of PEG is the highest value among PEG based shape-stabilized PCMs to the best of author's knowledge. The shape-stable PCM presents a high heat storage capacity of 142.8 J g(-1) and excellent thermal reliability within at least 200 melting/freezing cycles. The thermal properties of the PEG/GO composite PCMs with various GO contents are also investigated. The present study provides a highly potential shape-stabilized composite PCM with a high content of PEG for thermal energy storage as well as a way to enhance the heat storage density of PEG based shape-stabilized PCM. (C) 2014 Elsevier B.V. All rights reserved.