The Music City Center and Hyatt Place Nashville Downtown have helped change the Nashville landscape. Perhaps not as evident—at least from the outside—is the fact that both properties are customers of the Metro Nashville District Energy System (DES).
For facilities such as these, district energy offers a more space-efficient alternative to stand-alone heating and cooling systems, since steam and chilled water are delivered to the buildings from a central plant. This eliminates the need for chillers and boilers at each building.
Buildings are connected to the system via four pipes: a chilled water supply and chilled water return line, as well as a high-pressure steam supply and condensate return line.
Buildings on the DES system use chilled water for space cooling/air conditioning and steam for space heating and domestic water heating.
Most buildings pump the DES chilled water supply directly through their building cooling system and then return it to the DES. However, some customers have “decoupled” systems; the chilled water from the DES does not circulate directly through their building air handling units. Instead, it passes through one side of a plate and frame heat exchanger while the building circulates its own cooling system water through the other side of the heat exchanger.
Chilled water is delivered to customer facilities at approximately 40-42 degrees Fahrenheit, used for cooling purposes and then returned back into the DES system at approximately 55 degrees Fahrenheit.
The majority of DES steam customers utilize hot water for space heating. A few customers use steam directly at the heating coils. Many also use steam to provide domestic water heating, and some use steam as a heating source for kitchen and laundry purposes. High-pressure steam is delivered to each customer location through the DES system, used for heating purposes and returned into the system as condensate.