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Minewater as an environmental heat source or sink: “Geothermal” heating and cooling
ThermalEnergyfromMineWorkingsDaveBanks
UniversityofGlasgowHolymoorConsultancy,Chesterfield
“No;thismyhandwillratherThemultitudinousseasincarnadine,Makingthegreenonered.”
Macbeth,Crucible,Sheffield.
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“....makingtheredonegreen”
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Minewater
Water
Pyrite+water+O2 =acid+sulphate+iron
Water
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Pumpandtreat
Caphouseminewatertreatmentscheme,nearWakefield
Katowicemine,Poland
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Closedloop– thelowriskway
HeatpumpHeattoabuilding
Heatabsorbedfromrockinshaft/boreholewall
Ifadvectionofwaterinshaft:greaterheatyieldsachievable
Advantages:
No abstraction of mine water
No risk of geochemical fouling of heat exchanger
Disdvantages:
May interfere with desludging of basins
Modest heat yield
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Heatpump/exchanger
Totreatmentsystem/surfacewaterrecipient
Ortore‐injection
Typicalopenloopsystem
TheBigRisksGeochemistry
Thermalfeedback
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Inwinter
Warmwaterabstractedfromdeepinshaft(ultimatelythroughdeeproadways)
Thermally“spent”coolerwaterflowsawayviahigherroadways
Ifminewaterthroughflowisbigenough…..Heatpump/exchanger
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Whyminewater?
MostGSHPschemesdeliversavingsonCO2 emissionsandonOPEX.BUTtheyrequireconsiderableCAPEXonboreholedrillingandsubsurfaceheatexchangers.
Theuseofminesandminewatercanreducecapitalexpenditurebecause:
1. Flooded,interconnectedmineworkingsallowaccesstoahugereservoirofwarmmine‐waterviaonlyoneortwoboreholes,orviaexistingshafts.
2. Theinterconnectednetworkoftunnelswithinthemineitselfrepresentsanenormousheatexchangesurface.
3. Someabandonedminesarealreadycommittedtoexpenditureonpumpingand/ortreatmentmerelyforthepurposesofenvironmentalprotection,whileregardingthepumpedwatermerelyasatroublesome“waste”product.
4. TheUKCoalAuthoritypumpsand/ortreatsaround3000L/swaterfromabandonedmines,withtemperaturesof9‐18°C,3000L/sx4200J/K/Lx5°C=63MW
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GlenalmondStreet,Shettleston,GlasgowWorkingsinEllCoalSeam
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GlenalmondStreet,Shettleston,Glasgow
Photos by D Banks
Completed1999Serves16newly‐builtdwellings(1600m2)Source=100mboreholeinfloodedcoalmine
workingsoftheEllSeamWaterpumpedat12°Ccirculatedviawater‐to‐water
heatpump(65kWpeakoutput),andreturnedviashallowerreinjectionborehole
Heatpumpoutput=55°Ctothermalstore.Designedwithsupplementarysolarthermalheating.
FeedsDHW(withsupplementaryimmersionheater)andcentralheating
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20kWheatpump
2‐3L/sat15.4°Cfrom235m
Returnto255mat12°C
Heatat60°CtoAlkane’soffices
Alkane,MarkhamColliery,nearBolsover
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Alkane,MarkhamColliery,nearBolsover
Feat4mg/L
Nocloggingorfeedbackproblemsobserved
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Ochil View, Lumphinnans, nr. Cowdenbeath, Fife
Photos by D Banks
pH 6.16Eh +29 mV (reducing, H2S smell)Temperature 12.1oCAlkalinity 6.5 meq/LSulphate 1339 mg/LChloride 20.3 mg/LCalcium 315 mg/LMagnesium 224 mg/LSodium 15.6 mg/LPotassium 21.6 mg/LIron 57.9 mg/LManganese 3 mg/L
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Hitherto...
TheShettlestonschemehashadnoproblemsofcloggingatall...
ButtherechargewelloftheLumphinnansschemewasvandalised(2005)...
DegassingofCO2
ExposuretoO2
Precipitationofochre,other
metalhydroxides,calcite
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CoalAuthorityTrialatDawdon,Co.Durham
75to150L/sminewatertreatmentcapacityDanfoss12kWheatpumpheatsofficeandDHW1.5L/softreatedminewateratc.20°CsupportsheatpumpMinewatersaline,withc.0.8mg/Liron(peaksof2‐4mg/L)
fromCoalAuthoritywebsite
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CoalAuthoritytrialatDawdon
Whentreated(aerated)waterused,heatexchangerandfilterrapidlybecameclogged
but,afterraw(unoxygenated)waterused,fewproblems
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Thesecretsofsuccess
A good understanding of subsurface geometry and hydraulics of mine workings
A good understanding of hydrochemistry
Gas management!