In this paper, the primary aim is to look at the fundamental melting/solidification processes of polyethylene glycol 1500 (PEG 1500) for energy storage – insulation to prolong the cooling time of pipelines in unexpected shut-down conditions, prevent/minimize the wax deposition, and hydrate formation. Polyethylene glycol 1500 was selected because its melting temperature is >317 K making it a suitable candidate as lagging material to prevent wax deposition and hydrate formation in subsea oil pipelines. Experimental apparatus was designed with the Perspex to give an insight into the melting process. Vertical and horizontal annular geometries were used to consider the real-life cases. The vertical annular enclosure length is 950 mm and 34 mm width (Height/Width=27.94). The horizontal annular enclosure length is 300mm and 15.9 mm width (Height/Width=18.87). The thermocouples and camera are used to collect the data for three cases of inner wall temperature of 333 K,343 K and 353 K where is the heat added to the phase change material (PCM) for both cases. The main conclusions are: i) the horizontal annular case melt faster than the vertical case, in particular, at higher heating surface temperature of 353 K, ii)The temperature of the inner region was remained hot for long time which provide a good evidence that support the concept of using the PCM as heat storage–insulation material; iii) the melting percentage for horizontal case is 100% higher from the melting percentage of vertical case at 333 K which reduced to about 20% for 343 K, iv) increasing the heating surface temperature substantially reduces the total melting time for both orientations.