Balakrishnan Sruthy, Sofianos M Veronica, Humphries Terry D, Paskevicius Mark, Buckley Craig E
Physics and Astronomy, Fuels and Energy Technology Institute, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
Phys Chem Chem Phys. 2020 Nov 18;22(44):25780-25788. doi: 10.1039/d0cp04431h.
CaH2 has 20 times the energy density of molten salts and was patented in 2010 as a potential solar thermal energy storage material. Unfortunately, its high operating temperature (>1000 °C) and corrosivity at that temperature make it challenging to use as a thermal energy storage (TES) material in concentrating solar power (CSP) plants. To overcome these practical limitations, here we propose the thermodynamic destabilization of CaH2 with Zn metal. It is a unique approach that reduces the decomposition temperature of pure CaH2 (1100 °C at 1 bar of H2 pressure) to 597 °C at 1 bar of H2 pressure. Its new decomposition temperature is closer to the required target temperature range for TES materials used in proposed third-generation high-temperature CSP plants. A three-step dehydrogenation reaction between CaH2 and Zn (1 : 3 molar ratio) was identified from mass spectrometry, temperature-programmed desorption and in situ X-ray diffraction studies. Three reaction products, CaZn13, CaZn11 and CaZn5, were confirmed from in situ X-ray diffraction studies at 190 °C, 390 °C and 590 °C, respectively. The experimental enthalpy and entropy of the second hydrogen release reaction were determined by pressure composition isotherm measurements, conducted between 565 and 614 °C, as ΔHdes = 131 ± 4 kJ mol-1 H2 and ΔSdes = 151 ± 4 J K-1 mol-1 H2. Hydrogen cycling studies of CaZn11 at 580 °C showed sufficient cycling capacity with no significant sintering occurring during heating, as confirmed by scanning electron microscopy, demonstrating its great potential as a TES material for CSP applications. Finally, a cost comparison study of known destabilized CaH2 systems was carried out to assess the commercial potential.
氢化钙的能量密度是熔盐的20倍，于2010年获得专利，是一种潜在的太阳能储热材料。不幸的是，其较高的工作温度（>1000°C）以及该温度下的腐蚀性使得它在聚光太阳能发电（CSP）厂中用作储热（TES）材料具有挑战性。为了克服这些实际限制，我们在此提出用锌金属使氢化钙发生热力学失稳。这是一种独特的方法，在1巴氢气压力下，可将纯氢化钙的分解温度（1100°C）降至597°C。其新的分解温度更接近拟议的第三代高温CSP厂中使用的TES材料所需的目标温度范围。通过质谱、程序升温脱附和原位X射线衍射研究确定了氢化钙与锌（摩尔比1∶3）之间的三步脱氢反应。原位X射线衍射研究分别在190°C、390°C和590°C下证实了三种反应产物，即CaZn13、CaZn11和CaZn5。通过在565至614°C之间进行的压力组成等温线测量，确定了第二次氢释放反应的实验焓和熵，分别为ΔHdes = 131±4 kJ mol-1 H2和ΔSdes = 151±4 J K-1 mol-1 H2。扫描电子显微镜证实，CaZn11在580°C下的氢循环研究显示出足够的循环容量，加热过程中未发生明显烧结，证明其作为CSP应用的TES材料具有巨大潜力。最后，对已知的失稳氢化钙系统进行了成本比较研究，以评估其商业潜力。
