Underneath street level, Cordia, a commercial energy services company, is freezing water, melting ice and transporting it to provide air conditioning for the Phoenix Convention Center, hotels, municipal and office buildings throughout downtown. The Phoenix Business Journal reports even the towns pro baseball stadium, Chase Field, receives the cold air.

The process runs 24 hours a day, 365 days a year. Cordia recools the water with an ice storage tank overnight, which is located below the Phoenix Convention Center. The trick is to make ice at night when electricity is cheap and then melt it during the day.

The firm is now working on developing a fourth plant to expand its chilled water output by 10,000 tons and serve the University of Arizona’s medical campus buildings downtown and potentially other buildings nearby.

The firm is currently designing the plant to try and get it online by the spring of 2025. Cordia estimates it could cost between $40 million and $50 million.