YUKON OPEN LOOP GEOEXCHANGE CASE STUDY Na-Cho Nyak Dun First Nation Government House Presented by: Katherine Johnston, EIT EBA Engineering Consultants.
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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
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
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