How it works: Making Water Street Tampa cool

Frederick Dela Cruz, Director of Engineered Solutions for Frederick Dela CruzTampa Bay TRANE and Founder of the new Tampa Bay Energy Efficiency Alliance, explains how the new Water Street Tampa District Cooling system uses three basic components that work together.

“The Water Street District Cooling plant is not your typical central plant; it has a thermal energy storage system,” explains Dela Cruz. “It is where we leverage our Calmac ice tanks to maximize off-peak utility rates and ambient relief conditions; air is colder at night, so the process is more efficient.” 

Dela Cruz explains below the three main components of the chilled water circuit for Water Street Tampa's new District Cooling loop:
 
The Chilled Water Loop -- This is where we send out very cold water to the different buildings of the Water Street District. These are pumped through the air handler units, similar to the ones in your home cooling system. As the air passes across these chilled water coils, the air is cooled and the heat is transferred to the water. The water leaving the cooling coils is now much warmer than what the central plant had provided. The water then returns back to the central plant and passes through the chiller which cools it back down again and repeats the process.

The Condenser Water Loop -- In order to make colder water, you need to transfer heat from that water to another source. This is the loop that performs that task. The water is sent through giant cooling towers that are on the roof of the central plant. Large fans rotate at the top and the water slowly trickles down the sides of the cooling towers, called the cooling tower fill, and the water evaporates. This evaporation has an incredible amount of energy, as it’s considered a phase change, and it goes from liquid to gas. This allows the heat captured from the buildings in the chilled water return to be rejected into the atmosphere. This is similar to your home system where your outside unit is blowing out very hot air, rejecting the heat from your house into the atmosphere.

The Glycol Loop/Thermal Energy Storage -- This is the component of the plant that is unique. We have one chiller that is capable of making a 23-degree glycol-water mixture. We use this chiller to make a very cold solution to freeze the 98 ice storage tanks. We freeze these tanks during off-peak times per TECO rate schedules and typically at night when there is ambient relief, allowing for the entire system to work more efficiently. These plants are massive consumers of energy and having the ability to turn them off during the peak times the rest of Tampa Bay is using energy is the first step to a distributed energy storage smart grid.  

“The control system and the programming behind it can be seen as the brains behind the machines,” Dela Cruz says. “This plant has some of the most advanced control systems and programming implemented, and this will only continue to evolve as we see innovations in technology.”