Case Studies

Fort Polk Training Center:

Fort Polk, Louisiana

With the implementation of a large-scale energy savings performance contract (ESPC) at Ft. Polk Joint Readiness Training Center outside of Leesville, Louisiana, the heating and cooling systems (primarily air-source heat pumps) in each of the military base's 4003 family housing units was retrofitted with a geothermal (ground source) heat pump (GHP). Detailed models of all 200 apartments served by one of the electric feeders on this base were created in TRNSYS for the pre-retrofit condition. These simulations were then "tuned" until the total energy consumption of the 200 apartments closely matched that of the measured pre-retrofit consumption for the feeder. The simulations were then "retrofit" with geothermal heat pumps, desuperheaters for hot water, low-flow shower heads, compact fluorescent lighting, and increased attic insulation. As the purpose of this exercise was to demonstrate that calibrated pre-retrofit models can and should be used to predict the impacts of energy efficiency retrofits, Oak Ridge National Laboratory withheld the post-retrofit energy consumption from us – only providing us with details on the retrofits (kind, size, etc.) The energy conservation measures were then implemented in our calibrated models: the air source heat pumps were replaced by geothermal heat pumps equipped with desuperheaters; hot water loads were reduced to account for the low-flow shower heads; lighting loads were reduced to account for fixture de-lamping and replacement with compact fluorescent lights (CFLs); and attic insulation upgrades were modeled where appropriate.

The ORNL analysis of pre- and post-retrofit measured data indicated that the retrofits saved 30.3% of pre-retrofit electrical energy consumption on the feeder modeled for this project. Using only pre-construction energy consumption data, as-built drawings and equipment specifications and data from one pilot test site, we were subsequently able to predict the energy savings well within 1% of its measured value.

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