(156b) Thermochemical Storage of Solar Energy Via Metal Oxide/Metal Sulfate Water Splitting Cycle

Solar
thermochemical water splitting cycles are considered as one of the most
promising options for hydrogen production. In a long list of solar
thermochemical water splitting cycles, the sulfur-iodine cycle and its
variation the hybrid sulfur cycle are more appealing as the required operating
temperatures are lower as compared to other thermochemical cycles. For both
cycles, the most energy intensive step is the dissociation of SO₃
into SO₂ and O₂, which is possible only under catalytic
conditions. As sulfation poisoning is a major concern related to such
reactions, simply the noble metal catalysts were observed to be active towards
the endothermic dissociation of SO₃. Although, the noble metal
catalysts are attractive for such reactions, they are less preferable due to
the limited availability and high cost.  To
overcome this issue, we propose a solar driven metal oxide – metal sulfate
(MO-MS) based water-splitting cycle for the production of hydrogen. In this
study, the thermodynamic and experimental analysis of the MO-MS based water
splitting cycle was studied. At first, the computational thermodynamic analysis
was performed to identify the required temperatures, pressures, and inert gas
flowrates to operated MO-MS water splitting cycle. This analysis also helps to
find the efficiency of this cycle in terms of the conversion of solar energy
into hydrogen. After performing the computational thermodynamic analysis, the MO-MS
based water splitting cycle was experimentally investigated using a high
temperature TGA and a packed-bed reactor set-up. Obtained thermodynamic and
experimental results will be presented and compared with other thermochemical
cycles in detail.

Figure 1: Process
flow configuration of iron oxide – iron sulfate water splitting cycle.