Linking GSHP with Linking GSHP with solar and district heating systemssolar and district heating systems

GGööran Hellstrran HellströömmLund University, SwedenLund University, SwedenNeoEnergy Sweden LtdNeoEnergy Sweden Ltd

GroundGround--Source Heat PumpsSource Heat Pumps

Uran areas / city centresUran areas / city centresSingleSingle--family housefamily house

LargeLarge--scale groundscale ground--source heat pump applications:source heat pump applications:

Resource limitations?Resource limitations?Underground energy storageUnderground energy storage

Energy StorageEnergy Storage

Underground energy storage unit (0,6 kWh/(mUnderground energy storage unit (0,6 kWh/(m33,K)),K))

GroundGround--Source Heat PumpsSource Heat Pumps

GorundGorund--source heat pumps in the suburbssource heat pumps in the suburbsIncreased areal extractionIncreased areal extraction–– (ca 35 kWh/m(ca 35 kWh/m22,year) ,year) –– thermal influence of neighboursthermal influence of neighbours

7 kW heat pump, 125 m, heat capacity of property ca 80 MWh/K, ex7 kW heat pump, 125 m, heat capacity of property ca 80 MWh/K, extract ca 20 MWh/yeartract ca 20 MWh/year

GroundGround--Source Heat PumpsSource Heat Pumps

MultiMulti--family housefamily houseFurther increase of areal extractionFurther increase of areal extraction–– (ca 100 kWh/m(ca 100 kWh/m22, year) , year)

--

Borehole depth 200 m

Property area

ca 10000 m2

Thermal capacity 1200 MWh/K

Net extracted heat 1000 MWh/year

Temperature change ≈ -1000/1200 ≈ -0,8 K/year

Ground Loop Sizing Ground Loop Sizing –– Thermal capacityThermal capacity

Reality check!

Example

Unbalanced energy loadUnbalanced energy load

Due to net heat extraction rate!

5 10 15

Time (years)

Heat carrier fluid temperature variation during 15 years for a large installationOnly extraction of heat

Balanced energy loadBalanced energy load

Heat carrier fluid temperature variation for system with heat

pump and extraction and recharge by outdoor air

ENDAST VÄRMEUTTAG

Heat extraction by heat pump and recharge by outdoor air

5 10 15

Time (years)

Net heat extraction reduced by recharge!

Extraction in

balance with

recharge!

GSHP/Outdoor air hybridGSHP/Outdoor air hybrid

Dry cooler

Heat pump efficiencyHeat pump efficiency

Nominal heat pump capacity 10 kW

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

Entering heat carrier fluid temperature (C)

Power (kW)

Compressor electric power

Heat pump output

Heat pump capacity vs. source temperature

1 degree lower temperature causes a 3-4 % reduction of heating output

Heat pump efficiencyHeat pump efficiency

Nominal heat pump capacity 10 kW

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

Entering heat carrier fluid temperature (C)

Power (kW)

Compressor electric power

Heat pump output

Heat pump capacity vs. source temperature

1 degree lower source temperature causes a 3-4 % reduction of heat pump output

Energy balance?Energy balance?

HEAT COLD

Energy balance for the ground determines choice of system design of ground source

Imbalance may cause undesirable long-term temperature changes

Energy balanceEnergy balance

Cooling the groundCooling the ground�� Comfort heatingComfort heating�� Hot waterHot water�� Process heatingProcess heating

�� Surface waterSurface water�� Outdoor airOutdoor air�� Snow and iceSnow and ice

Heating the groundHeating the ground�� Comfort coolingComfort cooling

�� Process coolingProcess cooling

�� Exhaust airExhaust air

�� Surface waterSurface water

�� Outdoor airOutdoor air

�� SolarSolar

�� Waste heatWaste heat

GSHP in central StockholmGSHP in central Stockholm

�� Total heated areaTotal heated area 16500 m16500 m22

�� Flats 13800 mFlats 13800 m22

�� Commercial (ground floor) 2700 mCommercial (ground floor) 2700 m22

�� Heat demandHeat demand 2500 MWh/year2500 MWh/year

�� Exhaust air Exhaust air 10 m10 m33/s/s

Urban GSHPUrban GSHP

Areal heat extraction rate 250 kWh/mAreal heat extraction rate 250 kWh/m22,year,yearGround heat capacity 800 MWh/K, extracted heat 1600 MWhGround heat capacity 800 MWh/K, extracted heat 1600 MWh

�� Temperature change Temperature change ≈≈ ----1600/800 1600/800 ≈≈ --2 K/year2 K/year

RechargeRecharge

AprilApril--OctoberOctober NovemberNovember--MarchMarch

Exhaust airExhaust air Heat source Heat source RechargeRecharge

Heat sourceHeat source(Recharge)(Recharge)

Outdoor airOutdoor air Heat source Heat source RechargeRecharge

Solar coll. Solar coll. (glazed)(glazed)

Hot water Hot water RechargeRecharge

Solar coll. Solar coll. (unglazed)(unglazed)

RechargeRecharge

Ground air source hybrid Ground air source hybrid –– heat also in winterheat also in winter

GSHP/Exhaust air hybridGSHP/Exhaust air hybridSimulation results:Simulation results:

�� ca 600 MWh/year ca 600 MWh/year recoveredrecovered from exhaust air from exhaust air as heat source for heatas heat source for heat

�� ca 600 MWh/year ca 600 MWh/year rechargedrecharged from exhaust air from exhaust air to ground storeto ground store

�� Ca 600 MWh/year extracted from the ground Ca 600 MWh/year extracted from the ground as heat source for heat pumpas heat source for heat pump

�� Total heat pump production 1700 MWh/yearTotal heat pump production 1700 MWh/year

�� Energy supply ratio ca 70 %Energy supply ratio ca 70 %

�� Demand capacity ratio ca 50 % Demand capacity ratio ca 50 %

Energy balance for groundEnergy balance for ground--sourcesource

GSHP/Outdoor air hybridGSHP/Outdoor air hybrid

GSHP with cooling tower

(Hackel et al, 2008)

Hybrid GSHPHybrid GSHP

System simulation with TRNSYS and DST GSHP model

(Hackel et al, 2008)

Glazed solar collectorsGlazed solar collectors

Glazed solar collectors absorb about 850 kWh/m2/year of which 500 kWh/m2/year for hot water and 350 kWh/m2/year deliveredconnected to evaporator side of GSHP (heat source and recharge)

COOLING

HP

HEATING

• Hot water

• Space heating

• Increasing HP

evaporator

temperature

• Recharging of

ground loop

Glazed

solar

collectors

GSHP/Solar hybridGSHP/Solar hybrid

GSHP/Solar hybridGSHP/Solar hybrid

Kallvatten

Radiatorkrets

Varmvatten

VX1

VXS

E

V

K

D

Ps

Pv

Pb

VX2

Hot water

Cold water

Radiators

Heat pump

Solar collector

Borehole

Tank

Caveat: Parasitic loads of pumps and fans (undersized pipework)

Unglazed solar collectors absorb about 850 kWh/m2/year connected to evaporator side of GSHP as heat source and for recharge

Unglazed Unglazed solarsolar collectorscollectors

Seasonal storage of solar heatSeasonal storage of solar heat

Examples: Neckarsulm, Germany, and Anneberg, SwedenExamples: Neckarsulm, Germany, and Anneberg, Sweden

HighHigh--temperature seasonal energy storagetemperature seasonal energy storage

Project Anneberg, Danderyd

• 70 single-family houses

• Summer: Storage of excess solar heat in ground store

• Winter: Heating without heat pump using under-floor heating

• 100 borehole to 65 meters depth

• In operation: March 2002

• Solar fraction estimated to 70 % of total energy demand

Storage pe r form ance

0

50

100

150

200

250

J F M A M J J A S O N D

He

at

[MW

h/m

on

th]

0

15

30

45

60

75

Te

mp

. [°

C]

Coll. Gain Storage losses

To coll. Temp. Storage temp.

COOLING

HP

HEATING

• Solar recharge of

ground loop

• Increasing HP

evaporator

temperature

Unglazed

solar

collectors

GSHP/Solar hybridGSHP/Solar hybrid

Alternative

Unglazed solar collectors absorb about 1700 kWh/m2/year connected to evaporator side of GSHP

Unglazed solar collectorsUnglazed solar collectors

Sea WaterSea Water

Hybrid system Hybrid system -- Boreholes with summer recharge from lakeBoreholes with summer recharge from lake

Boreholes

Water intake

Water outlet

GSHP with recharge from sea waterGSHP with recharge from sea waterNNääsby park slott, Swedensby park slott, Sweden

HP48

boreholes

Lake

Cost of borehole

storage

230,000 EUR

Borehole storage without

lake recharge:

80 boreholes

400,000 EURCost of recharge

system

40,000 EURInitial cost reduction with recharge about 30 %

Project Lulevärme

� Summer: Storage of waste heat from steel plant

� Stored heat: ca 2000 MWh (maximum temp 82 °C)

� Winter: University building heated with/without heat pump

� Extracted heat: 1000-1200 MWh

Seasonal storage of waste heat

Common ground sourceCommon ground source

RESIDENTIAL OFFICE

Combining groundCombining ground--source for source for buildings with different load buildings with different load

Community clustersCommunity clusters

Area : 180,000 m2

Energy store : 90 boreholes, depth 200 m

+ 70 borehole, depth 260 m

Hotel

University

OfficesFlats

Combining groundCombining ground--source for source for buildings with different loadbuildings with different load

AvantorAvantor--Nydalen, Oslo, NorwayNydalen, Oslo, Norway

Combining different loadsCombining different loads

Chemistry

IKDC

Architecture

Lund University, SwedenLund University, Sweden

Energy store 153 boreholes

Borehole depth 230 m

Heating loadHeating load

ChemistryIKDC

Cooling loadCooling load

ChemistryIKDC

Architecture

Common ground sourceCommon ground source

ICE RINK

Cooled sep-may

OFFICE

Heated sep-may

Katrineholm Sport CentreKatrineholm Sport CentreCommunity clustersCommunity clusters

Outdoor ICE RINK

Cooled when air

below 0 C

GYMNASIUM

Heated sep-may

Outdoor SOCCER

Heated when air

above 0 C

SWIMMING POOL

Heated all year

Hybrid GSHPHybrid GSHP

�� Ground sourceGround source

�� Exhaust air sourceExhaust air source

�� Outdoor air source Outdoor air source

�� Water source (lake, river)Water source (lake, river)

�� Solar sourceSolar source

�� Waste heatWaste heat

�� Important to aspire to thermally balanced Important to aspire to thermally balanced

ground systemground system

�� Toolbox of techniques using freely available Toolbox of techniques using freely available

energy sources for recharge/hybrid schemesenergy sources for recharge/hybrid schemes

SummarySummary