Copper battery for heat to power conversion and energy storage

An important part of the electricity production relies on heat conversion. Indeed power plants burn fuels like natural gas, coal or use nuclear fission to produce heat that can be transformed into electricity through a thermodynamic cycle and the mechanical work of a turbine. However, with such methods, high efficiencies are only reached with high temperatures according to the Carnot theory. Large amounts of waste heat or low-temperature heat are not converted into electrical power during these processes and are usually simply not exploited. Therefore, there is an opportunity to improve the way in which the heat is used and especially for electricity production, if waste heat can be recovered. Low-grade heat (below 200 ℃) is available in vast quantities from industry, but also from renewable sources such as solar thermal or geothermal energy. As renewable energies are often available intermittently during specific time of the day or according to the season, the storage of the low-temperature heat coming from these sources is particularly interesting for a more efficient distribution and consumption. However, production of electric power from these heat sources is challenging with existing technologies. Thermally regenerative batteries allow both the conversion and the storage of thermal energy into electric power, but they suffer from low operation voltages and low output powers. Here, we propose a thermally regenerative flow battery based on copper complexation with acetonitrile in non-aqueous solutions operating at voltages above 1V. Cu(I) complex can be destabilized by removal of acetonitrile by distillation, leading to production of solid copper and Cu(II) in a solution of propylene carbonate, thereby charging the battery. With this reaction, we demonstrate the electricity production at power densities up to 200 W·m−2, and estimate the theoretical efficiency of the full system between 5-14%. The results demonstrate a proof-of-concept for producing and storing electricity from low-quality heat.