Field Demonstration of Active Desiccant Modules Designed to Integrate with Standard Unitary Rooftop Package Equipment - Final Report: Phase 3
This report summarizes the investigation of two active desiccant module (ADM) pilot site installations initiated in 2001. Both pilot installations were retrofits at existing facilities served by conventional heating, ventilating, and air-conditioning (HVAC) systems that had encountered frequent humidity control, indoor air quality (IAQ), and other operational problems. Each installation involved combining a SEMCO, Inc., ADM (as described in Fischer and Sand 2002) with a standard packaged rooftop unit built by the Trane Company. A direct digital control (DDC) system integral to the ADM performed the dual function of controlling the ADM/rooftop combination and facilitating data collection, trending, and remote performance monitoring. The first installation involved providing preconditioned outdoor air to replace air exhausted from the large kitchen hood and bathrooms of a Hooters restaurant located in Rome, Georgia. This facility had previously added an additional rooftop unit in an attempt to achieve occupant comfort without success. The second involved conditioning the outdoor air delivered to each room of a wing of the Mountain Creek Inn at the Callaway Gardens resort. This hotel, designed in the ''motor lodge'' format with each room opening to the outdoors, is located in southwest Georgia. Controlling the space humidity always presented a serious challenge. Uncomfortable conditions and musty odors had caused many guests to request to move to other areas within the resort. This is the first field demonstration performed by Oak Ridge National Laboratory where significant energy savings, operating cost savings, and dramatically improved indoor environmental conditions can all be claimed as the results of a retrofit desiccant equipment field installation. The ADM/rooftop combination installed at the restaurant resulted in a reduction of about 34% in the electricity used by the building's air-conditioning system. This represents a reduction of approximately 15% in overall electrical energy consumption and a 12.5-kW reduction in peak demand. The cost of gas used for regeneration of the desiccant wheel over this period of time is estimated to be only $740, using a gas cost of $0.50 per therm--the summer rate in 2001. The estimated net savings is $5400 annually, resulting in a 1-2 year payback. It is likely that similar energy/cost savings were realized at the Callaway Gardens hotel. In this installation, however, a central plant supplied the chilled water serving fan coil units in the hotel wing retrofitted with the ADM, so it was not metered separately. Consequently, the owner could not provide actual energy consumption data specific to the facility. The energy and operating cost savings at both sites are directly attributable to higher cooling-season thermostat settings and decreased conventional system run times. These field installations were selected as an immediate and appropriate response to correct indoor humidity and fresh air ventilation problems being experienced by building occupants and owners, so no rigorous baseline-building vs. test-building energy use/operating cost savings results can be presented. The report presents several simulated comparisons between the ADM/roof HVAC approach and other equipment combinations, where both desiccant and conventional systems are modeled to provide comparable fresh air ventilation rates and indoor humidity levels. The results obtained from these simulations demonstrate convincingly the energy and operating cost savings obtainable with this hybrid desiccant/vapor-compression technology, verifying those actually seen at the pilot installations. The ADM approach is less expensive than conventional alternatives providing similar performance and indoor air quality and provides a very favorable payback (1 year or so) compared with oversized rooftop units that cannot be operated effectively with the necessary high outdoor air percentages.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 885611
- Report Number(s):
- ORNL/SUB-01-40000081030; TRN: US200617%%85
- Country of Publication:
- United States
- Language:
- English
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