Yellowknife considers abandoned mine as geothermal heat source

CBC ^

[Uncledave]

Yellowknife considers abandoned mine as geothermal heat source Last Updated: Monday, November 5, 2007 | 5:03 PM CT CBC News

The abandoned Con Mine in Yellowknife could one day keep the city's residents warm, depending on the results of a feasibility study the city will launch in the new year.

City officials will assemble a team to study whether geothermal energy can be harnessed from the former underground mine site, which produced five million ounces of gold from 1938 to 2003.

Earlier this year, a preliminary report by Mory Ghomshei, a mining professor at the University of British Columbia, concluded that the former mine's high temperatures — reaching upward of 34 C — and its underground location directly below the city could make it a prime source of geothermal energy.

"The feasibility study will look into the nuts and bolts of how much heat is in the mine, how much is available to be used within the community. And then we'll start looking at where in the community can we utilize this heat and how to move that heat to the surface," Yellowknife energy co-ordinator Mark Henry told CBC News.

"We'll obviously have to look at the economics to determine whether we want to move ahead with it."

Ghomshei's report said the city is one of the best Canadian markets for geothermal heat, since it uses 70 per cent of its energy to heat homes and buildings. Going with geothermal heat, the report said, would cut down on Yellowknife's heavy reliance on fossil fuels for heat, thus cutting down on greenhouse gas emissions.

The city has set aside almost $300,000 from the federal Indian and Northern Affairs department and Federation of Canadian Municipalities to conduct the feasibility study.

[Uncledave]

smart use of a hole already dug.

[Uncledave]

Renewable Energy Ping

Please Freep Mail me if you'd like on/off

[null and void]

Not a very high ∆T.

[sinanju]

34C?! That does not even qualify as sweltering!

“The Western Desert, lives and breathes, at forty-five degrees..”

Aussie rock band, Midnight Oil: “Burning Beds,” 1984.

[Abathar]

I have geothermal heat in my new home, a water furnace with the coils running out to the bottom of my lake 30' down. Smartest thing I ever invested in.

Now if Duke Energy would stop raising cost of our KWH every other day things would be just rosie.

[Uncledave]

Great song.

But 34 degrees is certainly a heat resource when it’s below zero outside.

If that’s the ambient air temp in the mine then sinking pipes in the mine floor will exchange at even higher differentials.

[USFRIENDINVICTORIA]

It often gets to -50C there, so that's a bid ∆T over the outside temperatures. I would guess that the idea is to also use a heat pump to increase the ∆ substantially before the heat is distributed to buildings.

[sinanju]

I thought the disadvantage with heat pumps was the fairly narrow temperature range over which they are effective. If it’s really hot or really cold outside they just can’t hack it.

[sinanju]

If its for a building sitting right over an air duct that might be do-able.

Snaking huge warm-air ducts all over town in spit-freezing weather is obviously ridiculous.

[USFRIENDINVICTORIA]

That’s right — but, in this case “outside” is the mine where it’s nice and warm & “inside” would be the heat exchanger where distribution begins.

Air-to-air heat exchangers don’t work efficiently in the far north; but, ground-to-air exchangers can. If there’s a permafrost layer, you obviously have to go below that. There’s solid granite bedrock near or at the surface around Yellowknife — that would make installing a ground-to-air heat pump enormously expensive. That’s why it’s handy that the miners already dug down to where it’s warm.

[sinanju]

But keep in mind that once you have pumped that nice toasty-warm air into the frigid world above, you can’t blow it more than ten yards through standard ductwork before it becomes an icy blast.

[USFRIENDINVICTORIA]

"Snaking huge warm-air ducts all over town in spit-freezing weather is obviously ridiculous."

It's more likely that hot water would be piped around. In Yellowknife, they could probably put the pipes underground. In the high arctic, communities use above-ground utilidors for water and sewer pipes. The supply water is heated, and the insulation in the utilidors keeps everything from freezing. They can't put these things below ground because of the permafrost. If the permafrost melts, an awful mess results. Houses are usually built off the ground, with good insulation in the floor, to preserve the permafrost. Here's a picture of a utilidor in Inuvik.

[USFRIENDINVICTORIA]

Air-to-air heat exchangers = Air-to-air heat pumps.

ground-to-air exchangers = ground-to-air heat pumps.

[Uncledave]

You’d want a heat exchanger and pipe around the heated glycol or water.

[RightWhale]

They should do something with this heat source since the hard part—digging the mine—has been done. It’s sitting there waiting.

[eraser2005]

It isn’t the temperature of the mine that matters, but rather the difference in temperature between the high and low temp parts of your heat pump that matters.

That’s why geothermal heat pumps work great in many environments even when the ground temp is only 55 F.... a heat source at 93 F will actually allow you to reach working fluid temperatures MUCH higher than that by just a little energy input into a compressor....

[NotJustAnotherPrettyFace]

34 degrees Celsius equals 93 degrees Fahrenheit.

Get back to Science class! :-)

[NotJustAnotherPrettyFace]

The article says 34 degrees “C”. See my post above.