Synthesis of hierarchical porous and hollow MgO microspheres for solar energy storage

Solar energy is a future prospect of depleted energy resources in which Saudi Arabia gain location benefits to become one of the largest solar energy receiver. However, due to intermittent nature of solar energy source their storage become vital necessity for better utilization and constant output. Phase change materials (PCMs) have attracted great attention due to its ability to store solar thermal energy in the era of energy crisis. Designing a perfect PCM is very tedious matter due to its critical requirement for adequate storage. Only fifty PCMs are commercially available after testing a huge number of organic and inorganic PCMs in a real application. Compared to organic PCMs, inorganic PCMs possesses unique properties viz. higher thermal conductivity, low volume change, recyclable, non-flammable and low cost. In addition, the PCM does not crystallize and exist in a liquid form for a portion of time under phase change temperature or below its freezing point due to supercooling problem of inorganic PCM. As a result, serious problems such as controlling temperature shift and an increase of the energy consumption can occur during real application. On the other hand, due to few shortcoming of organic PCM i.e. low latent heat value, low conductivity and leakage effects there real scale application is limited. Several research groups aim to solve these problems using shape-stabilized PCMs (ss-PCMs). These systems maintain the phase change process within a carrier matrix so that the liquid PCMs remain encapsulated within a porous matrix. Recently, we have fabricated a hollow pockets of MgO petaloid microspheres using pamoic acid (PA) and the microspheres assembled in two-dimensional nanosheet-like structures. Considerably a high amount of polyethylene glycol (PEG) PCMs can be loaded and able to retain into new type MgO structure system. The microspheres, comprising puff-like nanosheet MgO, provided a high thermal stability, higher latent heat value and considerably low supercooling. The supportive microsphere system enhanced the thermal conductivity of the ss-PCMs by a factor of 130% compared to PEG PCMs. Compared with the reported PEG-containing PCMs, which usually have latent heat ranges of 78140 J g1, our PCM composites displayed a very high latent heat of 173 J g1 over the temperature range 3658C. The relatively high value was attributed to the inherent large latent heat of PEG and its ability to retain a high amount PEG. In this study, we will fabricate MgO with different concentration of PA to optimize their unique morphology. The thermal and chemical stability of MgO-PEG sample will be examine using 200 meltingfreezing cycles. The main goal of this project is to obtain a PCM system with large latent heat value, suitable phase change temperature, and little supercooling effect for real application. A high thermal stability with above mention characteristics of new ss-PCM material will be a promising candidate for solar energy storage and other applications, particularly in the hot climatic conditions of gulf region.