Their ability to decouple power and energy makes them a suitable option for grid-scale stationary applications in terms of scalability, moderate maintenance cost and recyclability. In addition, these batteries based on highly stable redox active materials have a long cycle life (>10,000 cycles) and calendar life (10-20 years), as components can be replaced independently.

The European Union´s commitment to sustainability

The battery industry in Europe is undergoing an important process of evolution aimed at achieving compliance with the European Commission´s proposed amendment to the regulation on batteries and battery waste, repealing the Directive 2006/66/EC and amending the Regulation (EU) No. 2019/1020. The ultimate goal is to ensure that batteries placed on the EU market are sustainable, high-performing and safe throughout their entire life cycle.

Since the launch of the European Battery Alliance, EBA250, in 2017, stakeholders along the value chain have called for this regulation as an important tool to build a truly sustainable European battery industry that supports Europe´s transition to electrification. Thus arises the battery passport whereby from January 1, 2026 every industrial and electric vehicle battery placed on the market or into service whose capacity exceeds 2 kWh must have an electronic registration, which "shall be unique for each battery and identified by a single identifier," according to the regulatory language itself.

The redox flow battery sector driven by the recently created FLOW BATTERIES EUROPE, which was created to set up a long-term strategy for this sector, has included in its roadmap to comply with the sustainability criteria required for their use, not forgetting the equally necessary technical and cost requirements.

The environmental impact of redox flow batteries, as with other batteries, depends on the components used as raw materials, the associated manufacturing process, their lifetime and end of life, in other words, their life cycle.

Life cycle analysis, such as the one led by CIC energiGUNE in the HIGREEW project that it coordinates, is a recognized tool for assessing the environmental impact during the entire life cycle of stationary storage systems, i.e., their sustainability.

As far as the source raw materials are concerned, the current state of the art is based on non-flammable aqueous electrolytes. However, vanadium can be recycled at will, which guarantees unlimited use of this material. Thus, vanadium redox flow batteries rely on the flow of large quantities of corrosive materials, but it cannot be claimed that these batteries have a very large environmental footprint compared to other technologies, such as lithium batteries, which rely on a scarce active material and potentially toxic and flammable components.

On the other hand, the use of redox flow batteries has been extended to components based on ubiquitous elements (organic or non-toxic abundant metals), such as the water-based organic electrolytes on which CIC energiGUNE is working within its polymer-based electrolytes research line, resulting in safe non-corrosive aqueous solutions that will have a minimal environmental impact and allow for large deployment. These abundant materials are expected to be economically manufactured on a large scale.

In terms of flow battery production, as with other technologies, the aim is for both manufacturing and the supply chain to be local within the EU, which not only accelerates the scale-up of innovations, but also allows cost reduction to be controlled by reducing dependence on external sources of critical materials.

Compared to other battery technologies, the manufacture of flow battery stacks responds to a simple component assembly process, which can be robotized and does not require special rooms such as dry rooms or clean rooms. The economic and environmental cost of manufacturing flow batteries therefore has lower environmental effects than other technologies.

Source: Rongke Power

Advances in materials, as well as new designs aimed at reducing start-up costs, offer realistic expectations of unbeatable LCOS levels.

The development and prospects for redox flow batteries are in line with the SET Plan for cyclability and cost (10,000 cycles, <0.05 €/kWh/cycle) and stand as a low environmental impact option for energy storage. Also, the carbon footprint in battery production is fairly equal for vanadium redox flow batteries (183 kgCO2/kWh) and lithium batteries (168 kgCO2/kWh), although recent advances may further reduce the current gap.

In conclusion, redox flow technology could be one of the technologies that could contribute to the decarbonization of the economy, strengthen the flexibility of the electricity system, facilitate the deployment of renewables and to technological and industrial sovereignty based on the use of sustainable and low LCOS materials.