YUKON OPEN LOOP GEOEXCHANGE CASE STUDY Na-Cho Nyak Dun First Nation Government House Presented by:...
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Transcript of YUKON OPEN LOOP GEOEXCHANGE CASE STUDY Na-Cho Nyak Dun First Nation Government House Presented by:...
YUKON OPEN LOOP GEOEXCHANGECASE STUDY
Na-Cho Nyak Dun First Nation Government House
Presented by: Katherine Johnston, EIT
EBA Engineering Consultants Ltd.
What is Geoexchange?
Geoexchange is the coupling of low-grade heat from earth sources (soil, rock, groundwater, surface water, ocean, waste heat) which is transformed using heat pump technology to higher-grade heat for building conditioning, domestic hot water or process purposes.
How Does it Work?
Heating/Cooling
Load
Heat Pump and/or Heat Exchanger
Earth Energy Source
Return line
Loop within
building
Supply line
Ground coupling side
Building side
How Does it Work?
Heating/Cooling
Load
Heat Pump and/or Heat Exchanger
Earth Energy Source
Return line
Loop within
building
Supply line
Ground coupling side
Building side
Our domain
Two Types of Ground Heat Exchanger
Well Water System (Open
Loop)
Vertical Borehole
System (Closed Loop)
Village of Mayo “Heart of the Yukon”
• 407 km north of Whitehorse
• Population 450• Centre for mineral
exploration in the central/ north Yukon
• Annual “Midnight Marathon” held on the summer solstice
Village of Mayo Wells- History
PW -1/ PW-2
Drilled in the 1970’s
Approx. 255 m deep (Drilled Mud Rotary)
15 L/s (“Safe Yields”)
14 ° C (GW Temp)
Village of Mayo – Geoexchange History
• 1987-1988 GSHP commissioned to heat central building group using the existing water distribution system installed in the Village
• System failure after approximately 1 yr because….
Village of Mayo – Geoexchange History
• Heat pump incompatibility with existing space heating systems
• Power availability issues related to the Keno Hill Mine (operation until 1989)
• Failure to account for groundwater quality resulted in severe encrustation/ bio-fouling of the system
Village of Mayo – Key Lessons Learned
1) Water quality consideration in system design
2) Need for ongoing monitoring and maintenance
Pre-Feasibility Study Results
• Potential for existence of shallow “perched” aquifer (water supply potential)
• Potential for existence of deeper “warm” aquifer• Need for potable water system regardless• Decision to proceed with combined drinking water/
geoexchange supply drilling program
NNDFN Building – Expected Drilling Conditions
0 – 100 ft Sand, gravel
100 ft – 800 ft Silt/ clay
> 800 ft Target aquifer
Actual Drilling Conditions
0 – 30 ft Sand, gravel
30 ft – 298 ft Silt/ clay
298 ft – 560 ft Medium to coarse sand aquifer
Key Design Recommendations:
• Continuous operation of the system• Implementation of a regular monitoring and
maintenance schedule• Use of a single, central heat exchanger• Batch chemical injection system upstream of the
injection well (CO2 and Sodium Hypochlorite) to inhibit biological activity and maintain a neutral pH
Where are we now?
• Yukon water license requirements for groundwater extractions above 100 m3/day (20 USgpm)
• First time the Yukon water board is addressing both extraction and re-injection
• Injection well construction and commissioning will follow water board approval
Acknowledgements:
• Diana M. Allen• Broadway Architects• DEC Design• Quest Engineering Group• Na-Cho Nyak Dun First Nation