DOBBIE ENGINEERS LTD

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1 DOBBIE ENGINEERS LTD Direct Use Of Geothermal Energy Greg Moore

2 DOBBIE ENGINEERS DIRECT USE PROJECTS Clean steam production plant Timber drying kilns Pool heating Glass house heating Hotel and hospital heating DOBBIE ENGINEERS DIRECT USE PROJECTS 3

3 1. Evaluation of Energy Source for Direct Use Determine the extent and Quality of Resource Determine limitations on Extraction Identify potential uses for the energy 2. Options for energy extraction Down Hole Heat Exchangers Low Temperature Doublet Production System High temperature and pressure systems 3. Examples of Direct Heat Use 1. Hotel/ Motel Direct Use 2. Mineral Pools and Aquatic Parks 3. Glass Houses 4. Industrial Applications 4. Health and Safety Requirements CONTENTS 4

4 Determine the extent and Quality of Resource 1. The Depth of the resource will influence well costs Shallow well, 100 to 200m deep, 100 to 150mm diameter,$30k to $50K Deep well, 1500 to 2000m deep, 300 to 450mm diameter$7m to $10M 2. Fluid Temperature and Pressure will influence the suitable end use (bathing, space heating, industrial applications) 3. What are acceptable extraction rates? Affect size of development 4. Chemistry? Is it corrosive, will it cause fouling, is it water, steam or gas dominated? These generate the challenges and how we use the resource. 5

5 How Do We Resolve These Questions 1. Look at other users 2. Use scientific measurements to establish reservoir depth and size, resistivity measurements etc 3. Sample and analyze fluid from natural features 4. Drill slim or test holes to sample the aquifer 5. Perform discharge tests on wells 6

6 What Are The Production Limitations Discuss with Environment BOP/Environment Waikato Consider existing resource consents Evaluate impacts on natural features and other users Will the gas or liquid discharges generated be significant? Will subsidence be an issue? 7

7 Identify Potential Uses Lindal diagram ex GNS 8

8 Options For Heat Extraction 1. GSHP, Ground Source Heat Pumps 2. DHHE, Down Hole Heat Exchangers 3. Low Temperature Doublet Production Wells 4. Deep Source Production Wells 9

9 DHHE 10

10 Down Hole Heat Exchanger Performance 1. Output 20 to 70 kw but up to 150kW seen in Rotorua 2. Typically low temperature heat (40 to 80 o C) 3. Wells are 50 to 100m deep, minimum diameter 150mm, larger wells overseas 4. Piped secondary fluid pumped through the coil 5. Requires permeability and a horizontal flow in the aquifer, this limits performance and increases risk DHHE 11

11 Down Hole Heat Exchanger Typical Uses 1. Most Rotorua applications are one home plus a pool 2. 5 to 10 homes is likely best case scenario 3. Maybe a small Motel 5 to 40 units 4. Pool 20 to 100m 2 DHHE 12

12 Down Hole Heat Exchanger Features 1. Relatively low output 2. Does not extract fluid from the reservoir. Considered more sustainable and minimizes pressure impacts in the reservoir. 3. Only one well is required, Typical costs $35k to $60k, plus additional $20k - $25k per home connected 4. Output is very dependent on local permeability and horizontal flow in the aquifer. Relatively high risk of variable results DHHE 13

13 Low Temperature Doublet Production system 14

14 Low Temperature Doublet Well Types 15

15 Low Temperature Doublet System Performance 1. Output 200kW to 1 MW 2. Typically low temperature heat (80 to 160 o C) 3. Wells are typically 50 to 200m deep, diameter mm, larger wells are possible 4. Typically uses a plate heat exchanger to separate geothermal fluids and heating system fluids 5. Output more predictable than DHHE Low Temperature Doublet System 16

16 Low Temperature Doublet System Typical Uses to 100 homes 2. Large Hotel 200 to 300 rooms plus conference facility 3. Pool of 500 to 1000m 2 (50m Olympic pool or aquatic park) 4. Commercial development (1000 to 10,000 m 2 ) 5. Glass House 500 to 5,000 m 2 Low Temperature Doublet Systems 17

17 Low Temperature Doublet System Features 1. Moderate output, 120 to 160 o C, 100 to 200 tonnes/day 2. Requires two wells to provide supply and reinjection, can impact on reservoir pressures 3. Typical costs $100k to $250k for wells and heat exchanger plant, plus additional heating system. Annual energy savings range from $20k/year to $100k/year or more 4. Output is more predictable output than DHHE s 5. Often use antiscalant dosing to prevent calcium carbonate deposition Low Temperature Doublet Systems 18

18 High Temperature & Pressure Systems 19

19 High Temperature and Pressure Systems 1. Output 2MW T to 50 MW T 2. Typical temperature (180 to 240 o C) 3. Wells are typically 1,000 to 2,500m deep, diameter mm 4. Typically uses a separator to separate geothermal fluids and then uses steam in a shell and tube heat exchanger to heat a secondary fluid. High Temperature & Pressure Systems 20

20 High Temp. & Pressure System Typical Uses 1. Timber drying kilns (90 to 160 o C) 5 to 10 kilns 2. Large Glass Houses (90 to 160 o C) 5 to 15 Ha 3. Clean Steam Production for product drying or Dairy, 25 to 50 t/hr of steam 4. Aquaculture 2 to 20 Ha 5. Other Process Plants: ethanol distillation, rendering plants, pulp and paper, High Temperature & Pressure Systems 21

21 High Temperature & Pressure System Features 1. High Temperature and Pressure output requires more detailed design to appropriate codes with robust safety systems 2. Requires two wells to provide supply and reinjection 3. Typical costs: $5M to $10M per well, plus separation and heat transfer plant and piping which is variable and may range from $2M to $10M. Capital cost is extensive 4. Some advantages if linked with an existing steam field, production and standby wells can be shared. High Temperature & Pressure Systems 22

22 Case Studies 1. Low Temperature Hotel System 2. Low Temperature Mineral Spa System 3. Low Temperature Pool Theme Park Complex 4. High Temperature Glass House application 5. High Temperature Timber Kiln Drying 6. High Temperature Clean Steam Application. Case Study Hotel Application 23

23 Low Temperature Hotel System 1. Minimum two wells (production and reinjection) 2. Fluid 130 to 140 o C, 150 to 200 tonnes/day 3. Typically might heat 200 rooms plus restaurant and conference facilities, pools? 4. Plate Heat Exchangers transfer energy to space heating and hot water systems 5. Significant hot water storage is required to meet peak domestic hot water requirements 6. Geothermal fluid use can be cascade down to finally heat pools 7. Geothermal System costs $150k to $200k. Annual might save $300 to $500/year per room plus other savings for public spaces and pools Case Study Hotel Application 24

24 Case Study Hotel System 25

25 Case Study Hotel System Production Well 26

26 Case Study Hotel System Reinjection Well 27

27 Case Study, Hotel System Heat Exchanger Plant Room 28

28 Case Study Hotel System Heat Exchanger 29

29 Case Study Hotel System Heat Exchanger 30

30 Case Study Hotel System, 500kW Heat Exchanger 31

31 Case Study Hotel System, 7.5 m 3 Hot Water Storage Tank 32

32 Low Temperature Mineral Spa System 1. Require a low temperature geothermal water supply Cooled water from a well or heating system Natural spring or pool 2. Degassing system to remove CO 2 and H 2 S 3. Storage system is needed to meet instantaneous demands 4. Water treatment system is required to adjust temperatures and maintain constant temperatures 5. Systems require regular flushing and cleaning Case Study Mineral Pools 34

33 Case Study Mineral Pool Spa 33

34 Low Temperature Mineral Spa System, Rules 1. Water Quality. NZS 5826 has section on geothermal pools Once through water use. Water change rate of at least one per 4 hours Empty, scrub and disinfect pools daily 2. Degassing system is essential to remove CO 2 and H 2 S 3. Control temperatures at or below 40 o C, 4. Ensure spaces are well ventilated (see RDC Bylaws) 5. Pools shall overflow via the rim without any low points to capture gases 6. As no water treatment, heads shall not be immersed 7. Provide a physical barrier between pools and grass or soils Case Study Mineral Pools 35

35 Low Temp. Mineral Spa System, Possibilities 1. Cooled geothermal water from one production well, 200 tonnes/day 2. Cooling pond or heat exchange system to cool fluid down 3. Provide gas removal from water by flashing or aeration 4. Sufficient for 15 to 20m 2 of pool, or 10 spa pools 5. Can be recycled if filtered and sterilized. Chemical treatment has been unsuccessful in most cases. Pasteurization has been used. Case Study Mineral Pools 36

36 Case Study Aquatic Theme Park 37

37 Aquatic Theme Park 1. Could provided year round heated complex : Themed for Rotorua? Indoor Spa complex Indoor 25m training pool Outdoor Spa 70 m 2 Indoor/Outdoor Leisure and Wave Pool 1300m 2 Outdoor 25m pool Lazyriver/hydroslides Geothermal Spa Domestic hotwater and space heating Case Study Aquatic Theme Park 40

38 Case Study Hotel System 25

39 Aquatic Theme Park 1. Would Require Two low temperature supply wells (i.e. Typical Rotorua wells 650 to 700kJ/kg 130 to 140 o C) Reinjection Well Approximately 400 tonnes/day of geothermal fluid or 2.5 MW of energy. Cascaded use of geothermal to maximize use Fluid cooled to 26 o C to recover all energy Pools covered at night to minimize losses Cooled fluid could be used in a geothermal spa complex Case Study Aquatic Theme Park 41

40 Aquatic Theme Park Features Year round hot water pools and climate control Central Geothermal Heating Plant costs $300k to $500k. (Pool heating systems extra) Annual Energy could be 20,000 to 30,000 GJ Energy savings of $300k to $400k per annum Case Study Aquatic Theme Park 42

41 Case Study Large Glass House (5 to 15 Ha) 43

42 Large Glass House 5 to 15 Ha Features High Temperature/pressure well. Fluid at 18 barg, 200 o C Energy approx 2MW per Ha. (20MW for 10Ha) Peak Fluid use 8 tonnes/hr/ha (fluid at 1200kJ/kg) Requires standby capacity and large storage tank to store heat during day to meet peak loads at night Capital cost to serve 10 Ha requires deep supply and reinjection well ($1M-$10M each) plus $500k to $1M for central plant and piping Case Study Large Glass House (5 to 15 Ha) 45

43 Case Study Large Glass House (5 to 15 Ha) 44

44 Case Study Large Glass House (5 to 15 Ha) 47

45 Case Study Large Glass House (5 to 15 Ha) 48

46 NTGA CLEAN STEAM PLANT CASE STUDY Kawerau plant that generates clean steam suitable for use in paper machines. Could be any clean steam application Owned by Ngati Tuwharetoa Geothermal Assets Supplies up to 26 tonnes/hr of 16barg clean steam to SCA Hygiene Australasia's Kawerau tissue paper plant. Enabled SCA to shut down its gas boilers Commissioned in September 2010 GEOTHERMAL FLUID TO CLEAN STEAM 49

47 COMMISSIONED PLANT 50

48 FLOW DIAGRAM 2 PHASE GEOTHERMAL TO CLEAN STEAM 53

49 GEOTHERMAL CONDENSATE STRIPPING PLANT 54

50 CLEAN STEAM HEAT EXCHANGER 55

51 56

52 TIMBER DRYING CASE STUDY Energy needed to: Heat the air (90 C to 140 C) to be circulated in the kilns Boil water is required to produce a humid atmosphere to precondition or recondition timber Geothermal energy can be used as separated geothermal steam within the heating coils or to heat pressurised water that passes through the heating coils TIMBER DRYING 58

53 Geothermal Steam NCG Stack Other users and vent Separator NCG Condensate Flash Vessel Kiln Separated Geothermal Water Production well Reinjection well SEPARATED GEO STEAM IN KILN (KAWERAU) 59

54 TAUHARA GEOTHERMAL HEAT PLANT Conversion of Tenon s 9 timber drying kilns from natural gas to geothermal. Uses two phase fluid and heat exchangers Contact Energy supplied the geothermal source and the heat plant Tenon modified the kilns piping to connect to the plant Loads ranged from 5 to 30MW Dobbie Engineers designed and commissioned the plant HOT WATER SYSTEM CONVERTED FROM GAS BOILER TO GEO HX 60

55 Heat Dump 150C Water Kiln 1 180C Water 135C Water Kiln 2 Kiln 3 Kiln 4 165C Water Kiln 5 Kiln barg 197C HEX 1 HEX 2 170C HEX 3 Kiln 7 Kiln 8 Kiln 9 Heat Dump TH6 TH2 TH7 TH8 TENON FLOW DIAGRAM WITH GEO HEAT EXCHANGERS 61

56 NCG DISCHARGE TO STACK TIMBER DRYING KILNS HX 1 HX 2 Ø400 GEO SUPPLY INSULATED TENON HEAT EXCHANGERS 62

57 Health and Safety Issues For Geothermal Use High Pressure and Temperature Well Drilling and Operation. Covered by Gary Brown later today Pressure Piping and Vessels Piping and pressure vessels operating over 65 o C and at pressures above 50 kpa must comply with Pressure Equipment, Cranes and Passenger Ropeways Act Requires design, design verification and fabrication in accordance with recognized standards. Plant must be maintained and operated in accordance with recognized standards Health and Safety 64

58 Health and Safety Non Condensable Gases (CO 2 and H 2 S) All plant areas need good ventilation, eliminate low points, hollows etc where gas can accumulate. At plant start-up gas levels needs to be considered Mineral pools are of particular risk if fluids are not degassed Geothermal fluid shall not taken into inhabited areas Hot Pipes over 55 o C should be insulated for personnel protection Health and Safety 65

59 Health and Safety Bylaws: Rotorua District Council Geothermal Bylaws. These cover a number of issues including the use of mineral pools, plant locations, drilling geothermal wells, maximum exposures limits for H 2 S and the safe operation and maintenance of plant. Health and Safety 66

60 DOBBIE ENGINEERS LTD Direct Use Of Geothermal Energy Greg Moore PO Box 1055 Rotorua Ph