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Austin Energy Upgrades Chilled Water Storage System

Linda Hardesty

Ameresco has started work on an energy savings performance contract for Austin Energy’s Domain District Cooling Plant.

The $5.2 million budget-neutral project includes the installation of a new chilled water storage system that will help reduce the plant’s peak electricity usage by shifting the chilled water load and associated electric consumption from on-peak to off-peak hours.

Trip Bhoopendra, vice president, Ameresco, explained that in Austin Energy’s territory, the highest electricity rates are between 4 pm and 8 pm. By cooling chilled water during off-peak hours and storing the chilled water in a tank, Austin Energy saves money.

As the nation’s eighth largest community-owned electric utility, Austin Energy serves 425,000 residents in Austin, Travis and Williamson Counties. Austin Energy’s district cooling plant installs and maintains the piping and heat exchangers that distribute chilled water from its plant to individual buildings via a network of underground pipes.

Prior to starting the energy savings performance contract, Ameresco performed a comprehensive audit and identified energy savings measures at the Domain District Cooling Plant, which will include the installation of a 24,000-ton-hour chilled water storage system large enough to shift a major portion of the chilled water load from on-peak to off-peak over a four-hour period. The upgraded system will be comprised of a 2.4 million gallon concrete thermal energy storage tank, 92 feet in diameter by 48 feet in height. The system circulation will be maintained by three 200 horsepower horizontal splitcase pumps controlled by variable frequency drives.

A new energy management system from Ameresco will be upgraded to control and monitor the new thermal energy storage tank system along with upgrades to the existing plant controls. New mechanical piping and associated mechanical devices will connect the new pumps to the tank. In addition, all the existing domestic water closets, showerheads and faucet aerators will be replaced with more efficient fixtures.

Under the performance contract model, Ameresco coordinates the upfront project costs and the City repays that investment with their savings over time. This model enables the City to benefit from budget-neutral upgrades by guaranteeing a minimum level of savings over the 15-year term of the contract.

The Domain District Cooling Plant is located in northwest Austin and provides continuous cooling services to a mix of industrial, retail, office, and residential customers. The project is expected to be completed by December 2013.



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