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?

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)

Open Loop

Well Water System (Open

Loop)

Location Map – Village of Mayo

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

Geologic Setting

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

Village of Mayo – Well Drilling

Village of Mayo – Well Drilling

Village of Mayo – Well Drilling

Actual Drilling Conditions

0 – 30 ft Sand, gravel

30 ft – 298 ft Silt/ clay

298 ft – 560 ft Medium to coarse sand aquifer

Open Loop - Well Screen Design

Open Loop – Well Screen Installation

Village of Mayo – Well Development

Well Chemical Treatment and Testing

Well Chemical Treatment and Testing

Hydraulic Testing Results – Constant Rate Test

Open Loop – Water Quality Analysis

Water Quality Analysis Con’t

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

Other Yukon Geoexchange Applications

Acknowledgements:

• Diana M. Allen• Broadway Architects• DEC Design• Quest Engineering Group• Na-Cho Nyak Dun First Nation

Thank You!

Questions?

ksjohnston@eba.caEBA Kelowna1-250-862-4832