Honeywell has invested $27.5 million in iron flow battery energy storage system company ESS Tech.

The two companies will also partner on long-duration energy storage solutions.

“The demand for long-duration energy storage represents a compelling market opportunity within the energy transition and the combination of Honeywell and ESS technology can accelerate decarbonization for the commercial, industrial, and utility sectors,” Bryan Glover, chief growth officer at Honeywell performance materials and technology (PMT) group, said.

“Our strategic collaboration with ESS will accelerate Honeywell’s ability to bring comprehensive solutions to our customers while working to advance long-duration energy storage across all industries requiring expansive energy storage.”

ESS Eric Dresselhuys added: “Today, we are creating superior technology in the critical long-duration energy storage industry. Combining ESS’ innovative technology and deployment experience with Honeywell’s storage and control system expertise will enable us to drive the clean energy transition and deliver value to our customers, shareholders, and communities.”

Formed in 2011, the company's batteries rely on "iron flow" technology, made with iron, salt, and water. ESS claims its systems have a design life of over 25 years, up to 12 hours of energy storage, and more than 20,000 cycles.

After being awarded an ARPA-e grant in 2012, ESS began commercial deployments in 2015, and launched on the stock exchange in 2015. Last year, the company's CTO penned a piece for DCD explaining why data centers need long-duration energy storage.

Shares in ESS jumped more than 40 percent following the Honeywell partnership, but remain 80 percent down from its initial IPO.