AlEnCycles - Aluminium-Redox-Cycles for the Production of Heat and Electricity for Buildings based on Renewable Energies

Within the AlEnCycles project, the use aluminium scrap from recycling streams for the production of heat and hydrogen was investigated. Advantages of this concept are the high energy storage density (23.6 MWh/m3) of aluminium as an energy carrier, the possibility to produce heat and electricity anywhere, anytime, and a potential low-cost source of the aluminium. Heat and hydrogen was produced from seven different aluminium scrap sources. Conversion efficiency was close to 100 % for six of the samples. Analysis of the obtained solid reaction products showed that, due to the presence of certain metal impurities, the resulting reaction products cannot be used directly for calcination and production of elementary aluminium in a conventional smelter process. In order to reach an ecologically and economically viable solution, reaction products would have to be treated and purified or used in – currently not existing - smelters dedicated only for the production of aluminium for energetic purposes. However, if a solution for this problem can be found, the concept has the potential for seasonal energetic energy storage with cost in the range of 9 €-cts/kWh, excluding cost of energy input and cost for converting the stored energy into heat and hydrogen or electricity. According to the LCA analysis that was performed in this project, providing heat and electricity for buildings from Al-to-Energy units reduces GWP, depending on the available (renewable) electricity mix by 33-80% compared to a mini-CHP unit that is based on natural gas. The large range of these GWP value is a result of different environmental burdens associated with different technologies and datasets for renewable electricity production.

M. Y. Haller, D. Amstad, M. Dudita, Y. Bäuerle, 2022
SFOE - Swiss Federal Office of Energy, Rapperswil