Importance of reactor design on efficient utilisation of thermochemical heat storage materials for background space heating

Thermochemical storage materials allow harvesting and storage of thermal energy (e.g. from industrial waste heat) potentially reducing emissions to atmosphere and time-shifting the hitherto wasted energy for later use in heating buildings. Reported thermochemical storage densities vary widely, with many studies overestimating laboratory-scale data when linearly scaling to practical reactor sizes. Presently, an experimental and design model analysis has been carried out on a stacked bed reactor using varying material depths to evaluate thermal performance, energy storage capacity and environmental impact in a modelled industrial scenario. Using a bench top reactor, the depth of the thermochemical storage material (CaCl2/ vermiculite) was varied between 30 and 60 mm with variations in input flow rate of moist air between 5 and 40 LPM. Maximum temperature uplift (11–13 °C) and energy densities (80–110 kWh/m³) were obtained with 30–40 mm of material with high flow rates. The experimental results were utilised in a design simulation to identify the optimum thermodynamic and low carbon impact material depth and inter gap spacing in order maximise the effective reactor storage density. Multiple 30 mm layers with a small interlayer gap provided the best energy density (59.2 kWh/m³), opposed to fewer 60 mm layers with a large interlayer gap (15.1 kWh/m³). Thermal performance of a single space cabin heated via harvested industrial waste heat is modelled, with subsequent LCA analysis to determine carbon impact compared with heating via electricity and gas alternatives. The carbon impact varies with reactor design and operational use, but cabins utilised over multiple years show a significantly improved carbon footprint.