Sinergy Flow (€2M to develop cheap, environmentally friendly, and high-energy flow battery for renewable energy storage)

Sinergy Flow, an Italian energy storage startup founded in 2022, develops zinc-polysulfide rechargeable flow batteries that are environmentally friendly, cheap, and high-energy for stationary energy storage. The Sinergy Flow battery uses electrolytes made from zinc and sulfur, which are earth abundant and low-cost. This means that it can reuse sulfur waste from the oil and gas industry, which is in line with the Circular Economy principles. Sinergy Flow's battery system is modular and scalable, so it can be used for both on-grid and off-grid energy storage on a large scale.

Challenges: Flow battery for renewable energy storage

To reduce global carbon emissions, more and more renewable energy sources of solar cells and wind turbines are being installed. In the meantime, the need for energy storage systems that are easy to use, scalable, and compact is growing. The ability to store this clean electricity would significantly increase the efficiency and reliability of these intermittent renewable energy sources.

Flow batteries use the movement of electrolytes to store and release electrical energy. A typical flow battery has two half-cells that are separated by a membrane. Each half-cell has an electrode and an electrolyte. The electrolytes, called anolyte and catholyte, contain the redox-active species dissolved in an aqueous or non-aqueous solvent. They are stored outside the battery. When the battery is charged or discharged, they flow through the half-cells in contact with the electrodes, thanks to external pumps. This is very different from lithium-ion batteries.

Most flow battery systems are based on vanadium, Fe—Cr, and Zn—Br. They are simple systems and easy to scale up. They can have a long lifespan of over 20 years. This makes them good candidates for storing renewable energy.

However, the high cost of vanadium salts, as well as the capacity decay and toxicity of the last two systems, has limited their application worldwide. The capital cost of flow batteries is around $800 per kilowatt-hour, which is more than twice that of lithium-ion batteries. Therefore, we need flow battery systems that are cheap, high-energy, and environmentally-friendly.

Sinergy Flow Technology

Sinergy Flow (Sinergy) has developed a safe, cost-effective, and high-energy rechargeable flow battery system for long-term (> 10 h) storage of renewable energy. The flow battery uses acid-free aqueous electrolytes that are made from zinc (Zn) and sulfur (S), which are earth-abundant and environmentally-friendly. Sulfur can be obtained from the oil and gas industry. This low-cost Zn-polysulfide flow battery can provide a power source with high energy efficiency of 70-85%.

Sinergy battery

The diagram below depicts the Sinergy battery system.

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