Yellowknife To Re-Purpose Gold Mine For Heat Extraction
by John Laumer, Philadelphia on 12.30.07
The City of Yellowknife, Canada is considering using heat extracted from a recently-closed gold mine to warm its buildings. Early in 2008, Yellowknife will formally study what could eventually become Canada's first large-scale geothermal heat plant.
The miners are already laid off; and the mine pumps are shut down, allowing the 2.5 Km deep shafts to fill with water that is consistently close to 50 degrees F. It's estimated that by pumping the naturally warm water out of the mine for distribution through a district heating network, the former Con mine could provide up to 20 megawatts of heat - enough for half the City's population
By preliminary engineering estimates, the pay-back period for a 20 megawatt system may be under three years. The planned feasibility study in 2008 would firm up the cost effectiveness figures.
Wondering how much time after payback would be needed to equal cumulative profits taken by all previous mine owners?
For more information on district heating schemes in North America, see this earlier TH post.
See background and history at this link. (pdf file)
Via::The Canada Press, "Yellowknife looks to old gold mine for new source of energy" Image credit::Northwest Territories GeoScience Offices, Con Mine Head Frame
Is 50 degrees F seriously warm enough to do anything useful? Maybe it should be C?
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Starting from 50 degrees is much more efficient than starting from 1 degree water in a heat extraction system.
10 degrees Celsius is a good start for heating homes in the arctic. Even in the colder parts of southern Canada I imagine that's a good start during winter, although I don't know much about geothermal systems and how well that water temperature would translate to air temperature in a building.
It's still a stretch to say that this system can provide enough heat for the city. In reality, you'll have to use electricity to run the heat pumps to extract the heat from the water. Still an interesting post...
50 degrees F is a big jump start for the frozen white north. Couldn't they use it for a heat sink in the summer as well?
I have always wondered how easy it would be to use waste heat from bakeries and pizzerias to heat neighbouring homes. Here in Toronto you see all sorts of pizzerias with their front doors open in the dead of winter just to get rid of all the waste heat from the ovens.
Isn't Spring Hill in Nova Scotia the first large scale Geothermal in Canada.. Seems to be working out quite well for the business in that park.
I always wondered if the coal mines under Edmonton are full of warm water and if the city could use the heat that radiates through the water in the shafts.
It is 50 degrees Celsius. (see CBC version of the story)
50 degrees Celsius = 122 degrees Fahrenheit
http://www.cbc.ca/technology/story/2007/12/26/geothermal-heat.html
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Thank you very much for the follow up and fact checking. Indeed I was surprised that other sources referred to degrees F, because had I thought that Canadians were mostly on the metric system. The article I linked to mentioned workers in the mine having to go shirtless to cope with the heat so something did not add up.
JL
Keep in mind that approx. 50F (not C) is the temp of the ground below the frost line in most areas, and this is the temperature used by ground-sourced heat pumps for heating and cooling. (most homes and businesses use air-sourced heat pumps and A/C units today). Its a lot more efficient to heat a house to 72F from a 50F source than from a 20F source, or to cool a house to 72F from a 50F source than from a 95F source.
122F sounds about right for a deep mine. Mine temps are usually well over 100F. That temp will be extremely efficient for heating, but will be useless for summer cooling, so hopefully the efficiencies from heating outweigh the downtime of the system in the summer.
Re: Summer cooling
there is no "summer" in Yellowknife. In June and July the hottest that could be expected is 25 degrees Celsius (77F). It is also a dry climate. Air Conditioners are not sold there. (: The economics are based on heating 8-9 months of the year. It is presently -25C up there (-13F).
They can use that 50 F water with heat pumps. Finland has an experimental system based on low temperature distributed heating:
Seawater is pumted from muddy and relatively warm layers to residential area via pipes. All households extract required heat with water source heatpumps, the cooled down water is returned to the sea. Such system can easily achieve a COP of 5 or greater, because the brine they use is above the temperature normaly used in water source heat pumps. And if the people in yellowknife have a steady source of 50F water and already have the pipes and pumps, they can implement a similar system with minimal amount of investment and even greater COP.
Thanks a lot, now I wish I had an abandoned mine on my property:(