Batteria a celle di flusso zinco-polisolfuri

In order to promote the full transition to renewable energy sources, it is necessary to integrated different types of stationary energy storage systems within the electricity network. In this regard, it is estimated that storage devices with limited duration (<10 h) will guarantee a penetration of solar and wind energy limited between 20-50 %, while, with long-duration devices (> 10 h), it is possible to reach the 70 -90 %. Unfortunately, in both cases, the solutions currently on the market are characterized by a series of disadvantages, which considerably limit their diffusion and application. The dominant technology on the market, namely lithium-ion batteries, is extremely penalized by the short life cycle, the high flammability of the components, the poor sustainability, and the strong geolocation of raw materials. As far as redox flow batteries are concerned, the most common ones exploit vanadium or zinc-bromine chemistry which relies on expensive, rare or toxic elements, reducing their diffusion on the market, especially for applications with a high energy-to-power ratio. For the latter scenario, systems other than electrochemical storage are currently used, such as pumped-hydro and compressed air, both characterized by geographical constraints, high costs for infrastructures, and low response time, which limits their exploitation.

The zinc-polysulfides redox flow battery has a strong potential for stationary energy storage applications thanks to its high efficiency (> 70 %), the low cost of raw materials, and its remarkable environmental sustainability. The low installation cost (50-150 $/kWh) makes this technology compatible with the requirements necessary for the development of large plants (MWh-GWh) capable of sustaining long discharge times, over 10 h. The integration of storage of this type would allow the effective penetration of renewable sources in the energy production system up to 90 %. The low cost and high versatility of installation also allow the implementation of this battery in smart grids or microgrids, increasing the reliability and flexibility of electrical networks. Furthermore, the possibility of exploiting a waste material, such as sulfur deriving from oil and natural gas refining processes, provides a high added value. In this broad application scenario, the first step aimed at creating a business case is the implementation of the electrolyte obtained from the waste containing sulfur in the electrochemical device, in turn, integrated with an energy production plant from renewable sources. This would reduce the overall CO2 emissions generated by the waste management of this by-product, thus establishing a virtuous circular process.

The patented technology has been characterized and optimized in the laboratories of the Politecnico di Milano, currently at a TRL 4. Thanks to the funds raised by the “Switch2Product Innovation Challenge 2020”, the next research and development activities will be aimed at the realization of a prototype of medium-scale (1-2 kW, 5-10 kWh) and its integration with a small photovoltaic system. This will increase the TRL up to 6-7. Additional funds would ensure the development of a pre-commercial module (10 kW,> 100 kWh) that can be tested in a relevant environment.