Preparation of n-OD@PMMA/PDA photothermal conversion microencapsulated phase change material and application of the suspensions in DASC

A novel photothermal conversion microencapsulated phase change material (PDA-MPCM) was successfully prepared, contained n-octadecane (n-OD) as the core material, polymethyl methacrylate (PMMA) as the middle layer, and polydopamine (PDA) as the shell material. The incorporation of PDA enabled PDA-MPCM can obtain excellent photothermal conversion efficiency (73.92 %) and maintain good thermal energy storage capacity (1570 J kg −1  K −1 ). The PDA-MPCM suspension (PDA-MPCMS) prepared by the two-step method has a long time dispersion stability (more than 72 h) and an ultra-low transmittance (close to 0) in the wavelength range of 200–650 nm. To investigate the photothermal conversion ability of suspension, the stuffy bask experiments were carried out under the real sunlight in the direct absorption solar collector (DASC) with PDA-MPCMS. The experimental results showed that the peak temperature rise of 0.10 wt% PDA-MPCMS was 27.80 % higher than that of the base fluid, and the zero-loss collector efficiency reached 93.6 %. The PDA-MPCMS are expected to play an important role in promoting solar applications.