Thermochemical heat-storage materials such as magnesium, zinc and iron sulfates offer high energy-storage densities and a reliable means of long-term storage of solar energy. In this research study, the dynamic properties of these three salts were investigated based on their hydration and dehydration characteristics. To investigate the effect of regeneration temperatures on the physio-chemical properties of the materials, four sets of temperatures were used. At 100°C, zinc sulfate showed a significant loss of water as compared to magnesium and iron salts, while in the hydration process at lower temperatures, zinc sulfate showed the highest sorption enthalpy and energy density. Furthermore, the crystallinity of salt hydrates was characterised using powder X-ray diffraction measurements, which revealed that dehydration of water molecules occurred only in magnesium sulfate, whereas partial distortion occurred in iron sulfate with a rise in temperature. Collating the results together indicated that zinc sulfate is more energy efficient than both magnesium and iron sulfate. With a calculated hydration energy density at 100°C of 1·26 GJ/m³, zinc sulfate is the best option among the three salts for its use as a thermochemical material.

中文翻译：

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用于热化学存储的硫酸镁，锌和铁的表征

硫酸镁，硫酸锌和硫酸铁等热化学储热材料具有很高的储能密度，是长期储存太阳能的可靠手段。在本研究中，根据这三种盐的水合和脱水特性对其动力学特性进行了研究。为了研究再生温度对材料的物理化学性质的影响，使用了四组温度。与镁盐和铁盐相比，在100°C时硫酸锌显示出明显的水损失，而在较低温度下的水合过程中，硫酸锌显示出最高的吸附焓和能量密度。此外，使用粉末X射线衍射测量来表征盐水合物的结晶度，结果表明，水分子的脱水仅发生在硫酸镁中，而硫酸铁随温度升高而发生部分变形。将结果汇总在一起表明，硫酸锌比硫酸镁和硫酸铁更具能源效率。计算出的100°C时的水合能量密度为1·26 GJ / m^{如图3所示}，硫酸锌是用作热化学材料的三种盐中的最佳选择。