Abstract
A new concept for seasonal energy storage (both heat and power) for low and zero energy buildings based on an aluminium redox cycle (Al→Al3+→Al) is proposed. The main advantage of this seasonal energy storage concept is the high volumetric energy density of aluminium (21 MWh/m3), which exceeds common storage materials like coal. To charge the storage, oxidized aluminium (Al3+) is reduced to elementary aluminium (Al) in a central processing plant using renewable electricity in summer. In winter, during discharging process, the energy stored in aluminium is released in form of hydrogen and heat via the aluminium – water reaction. Hydrogen is directly converted to electricity and heat in a fuel cell. The discharging phase has been investigated using a laboratory-scale experimental setup. In optimized conditions, heat and hydrogen is reliably produced for all types of aluminium forms (grit, pellets, foil). A high efficiency of the conversion to hydrogen was obtained (>95%). The remaining challenge is to optimize the entire cycle, e.g. the aluminium recovery process via the use of climate-neutral inert electrodes.
Highlights
The EU goal to cut greenhouse gas emissions by 80–95% by 2050 requires a new energy system
Being abundantly available in summer and scarce in winter when more energy is needed to supply heat for space heating, the potential of solar energy utilization is hindered by a lack of suitable, energy and cost efficient, seasonal storage technologies
A new concept of seasonal energy storage based on a redox cycle of aluminium Al→Al3+→Al is proposed
Summary
The EU goal to cut greenhouse gas emissions by 80–95% by 2050 requires a new energy system. A substantial increase of using renewable energy sources for heat and electricity production in buildings is required. Seasonal thermal energy storage is needed for future buildings. Photovoltaic (PV) and heat pump systems in combination with short-term electric and thermal storage and intelligent control are able to provide 50% of the electricity and heat consumption of a new building on-time and on-site, i.e without exchange with the electricity grid and without net-balancing over the year [3]. For covering the heat demand all over the year, an economic seasonal energy storage would be needed to store the heat and/or electricity from summer to wintertime (Fig. 2). Large scale seasonal thermal energy storage in combination with solar thermal collectors are able to cover up to. The large volumes needed for thermal energy storage are limiting the multiplication potential for this concept in denser populated areas or zones with high cost of built volume and of real estate
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