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Breakthrough Engineering Revolutionizes Heat Pump Systems
Ketchum, Idaho — When accepting the request to design the heating, ventilating, and air conditioning systems for the new, multi-use Christiania building in Ketchum, Idaho, Beaudin Ganze Consulting Engineers, Inc., (BGCE) was well aware of the many challenges involved in designing in an often politically-charged and environmentally-sensitive mountain resort community, but unaware of the unique opportunities this particular project would come to offer. At first blush, this 60,000 square foot building appeared to warrant very basic and time-proven heating and cooling systems to serve the building, and to snowmelt over 20,000 square feet of exterior walkways, parking stalls, and roadways. However, as the Owner's goals were incorporated into the design along with considerations for the local political and physical environments, BGCE went back to the drawing board and invented a first-of-its-kind, shallow geothermal heat pump rejection system utilizing the extensive snowmelt system. This system provides the ability to reject heat to the ground in the summer and melt snow and ice in the winter. This breakthrough design will revolutionize the way engineers design and specify heat pump systems in mountain environments worldwide, especially in similar snowmelt/cooling scenarios where excavation is prohibitive physically and/or financially.
BGCE's unique system design utilizes time-proven geothermal heat pump technologies that absorb heat from the building and reject it into a condenser water piping system. Typically, the heat in the condenser water loop is rejected to the earth through piping buried deep (50'-300') in the ground, or to the atmosphere using a cooling tower fan system. Unable to make deep, cost-prohibitive excavations to bury conventional heat rejection loops, BGCE took advantage of the 40°F temperature swings in this high-altitude, mountain environment to integrate the snowmelt system and the condenser loop system to reject heat through the snowmelt tubing. The snowmelt system tubing was buried only 4"-6" below the surface, but is still able to reject heat since, in this mountain environment, ground temperature at this depth remains relatively cool year round. The system provides the added benefit of augmenting the snowmelt system in the winter months by utilizing the waste heat from the building to melt snow and prevent ice formation. A reduced-size cooling tower was integrated into the loop to assist with heat rejection during peak cooling hours in the summer. Even when the ground loop is unable to keep up, the tower is only expected to run less than 10% of the cooling design days. Boilers were also integrated into the system to supplement the snowmelt system, as needed, during the winter months.
(Breakthrough Engineering cont'd)
Detailed computer modeling of the building heat gain and heat loss, and prolonged study of the local environmental variables (both personal observations and national weather data) were completed to determine the amount of heat rejection that could be expected from the building under different conditions. Using this information, BGCE was able to maximize the use of waste heat available for snowmelt in the winter and minimize boiler size; and, alternately, maximize the heat rejected to the snowmelt in the summer and minimize the size of the cooling tower.
Accessibility requirements on all sides of the building, and height and noise restrictions on the roof prevented locating any conventional equipment in these areas. With special coordination, BGCE was able to integrate all the major equipment and piping into the underground parking structure, minimizing aesthetic impact and increasing the square footage that can be marketed to tenants and residents. Since the cooling tower is located in the underground parking garage, BGCE was able to use the cooling tower fan with the garage carbon monoxide sensors to ventilate the garage as necessary. The fan is activated by the computer control system when carbon monoxide sensors in the garage indicate a build-up.
This unique system provides considerable energy savings by minimizing run time of a conventional cooling tower system in the summer and minimizing boiler run time in the winter for snowmelt, as well as reducing first costs. Rejecting heat to the ground using circulation pumps is up to 6 times more efficient than rejecting heat to the atmosphere using a cooling tower fan system. This results in significantly lower electrical consumption in the summer months. Reductions in equipment and space requirements maximized marketable square footage, and, ultimately, resulted in significant construction savings for the Owner.
The snowmelt system affords further economic benefits to the Owner and public in both savings and increases in potential revenue. Snowmelting precludes the need and cost associated with snow removal for the site, minimizes various liability concerns, and reduces the wear and tear on the paving system, extending its usable life. Snowmelting provides safe, year-round access for automobiles and pedestrians to shops and offices, increasing potential sales and tax revenues for the merchants and the town, and, thus, sustaining the local economy.
Beaudin Ganze Consulting Engineers, Inc. has been providing mechanical, electrical, technology, lighting, and sustainable design services since its inception, over ten years ago. The firm serves clients from its three offices in Vail and Denver, Colorado, and Lake Tahoe, California.
For additional information about BGCE's services, please call 970-949-6108.
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