Keeping Austin's Ground Temperature Cool

Photo of Kathryn Alexander, Eduardo Mellado, Nicholas Walsh Students: Kathryn Alexander, Eduardo Mellado, Nicholas Walsh

Sponsor: The University of Texas at Austin

Date: Spring 2010

The primary requirement is to cool the return fluid by 5° to 10° F. Equally important is finding a solution, in accordance with the hot climate of Texas, that has low upfront and operational costs. Ideally the SHR method should apply to both residential and commercial buildings. Constraints on the ground loop system include maintaining a closed-loop system with a constant flow rate of 3 gallons per minute per cooling ton. Within these few boundaries, the project is open-ended and the team has a great deal of freedom in developing a creative and cost effective solution.

The purpose of this project is to increase the applicability of ground-source heat pumps for hot, arid to semi-arid climates like Texas by improving their efficiency. Our primary task is to minimize ground heating that occurs over time from the large heating/cooling imbalance in hot climates. Specifically, we focused on supplementary heat rejection/recovery (SHR) methods to cool the ground loop fluid before reentering the ground.

We considered three approaches to providing supplementary heat rejection/recovery: thermoelectric cooling, evaporative cooling, and use of municipal or rain water as a heat sink. Our engineering analysis proved three concepts to be technically feasible, as they were designed to achieve a 5° to 10°F temperature drop in the ground loop. Because of its low upfront and operating costs, we recommend the evaporative cooler design for heat rejection from the ground loop.

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Photo related to Keeping Austin's Ground Temperature Cool project
Photo related to Keeping Austin's Ground Temperature Cool project
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