Geothermal Heating and Cooling Applications

1
Geothermal Heating and Cooling Applications

• Rachel Kerekgyarto

2
Geothermal Energy

• Thermal energy stored in the Earth
• Sources
• Solar energy absorbed in Earths crust
• Radioactive decay at the core of the Earth
• Clean, sustainable energy source

3
Geothermal Resources

• Three Classifications
• Low Temperature 40oF - 100oF
• Widespread
• Heat Pump Applications
• Moderate Temperature 100oF - 300oF
• Direct-Use Heating Applications
• High Temperature gt 300oF
• Electricity Generation
• Focus Low Temperature

4
Geothermal Heating Principles

• Conventional heating systems (furnaces or
  boilers) create heat
• Heat pumps transfer existing heat from one area
  to another
• Ground temperatures are more stable than air
  temperaturesSmaller Lift
• Ground serves as a
• Heat source in the winter
• Heat sink in the summer

5
U.S. Ground Temperatures

• Range 37oF - 77oF

6
Changes in Ground Temperature

• Seasonal ground
• temperature change
• decreases with depth
• Depths greater then 20 ft constant ground
  temperature

7
Geothermal Heat Pump System

• Three Major Components
• Ground Loop Piping System
• Circulates a fluid serves as an underground
  heat exchanger
• Heat Pump
• Uses refrigerant loop to convert heat into
  useable heat
• Ductwork
• Distributes heat throughout building

8
Types of Ground Loops

• Open Loops
• Open to environment
• Circulate groundwater (or surface water) to the
  heat pump, then discharge the water
• Closed Loops
• Sealed loop of pipe in the ground or a body of
  water
• Continuously circulates a fluid to the heat pump

9
Open Loops

• Well Requirements
• 1.5 3.0 gpm per ton of
• heating capacity
• Water Quality Concerns
• Hardness, Acidity, Iron
• Water Discharge
• Surface water
• Drainage ditch
• Recharge groundwater

10
Closed Loops - Horizontal

• Shallow Trenches
• 4 6 ft deep
• Pipe Length
• 500 ft of pipe per ton of
• heat pump capacity
• Land Area
• 750 to 1500 ft2 per ton

11
Closed Loops - Vertical

• Drilled Boreholes
• Depths up to 250 ft
• Pipe Length
• 300 ft of pipe per ton
• Land Area
• 100 200 ft2 per ton

12
Closed Loops - Slinky

• Greater heat transfer in a given volume of soil
• Compact or Extended Coils
• Horizontal Configuration
• Uses 1/3 trench length
• of a 2-pipe loop
• Vertical configuration
• Depths of 20 30 ft

13
Closed Loops Lake

• Water Surface
• ¼ - ½ acre
• Water Depth
• Minimum 8 ft

14
Closed Loops

• Piping
• HDPE Plastic Pipe
• Joined by thermal fusion
• Minimum 50 yr warranty

15
Closed Loops

• Ground Loop Fluids
• Water warm climates only
• Antifreeze Solution
• Salts
• Non-toxic, good heat transfer, BUT corrosive
• Glycols
• Non-corrosive, fair heat transfer, BUT toxic
  viscous
• Alcohols
• Non-corrosive, fair heat transfer, BUT toxic
  flammable
• Potassium Acetate
• Non-toxic, non-corrosive, more efficient

16
Closed Loops - Geobag

• LDPE Plastic Bag
• 60 ml thick
• Horizontal Configuration
• Uses 1/5 trench length
• of a 2-pipe loop
• Undergoing Field Development

17
Closed Loop Direct Expansion

• Direct Refrigerant Ground Loop
• Higher Efficiency
• Copper Piping
• Undergoing Field Development

18
The Heat Pump

• Refrigeration device that works backwards
• Heating Schematic

19
The Heat Pump

• Cooling Schematic
• Domestic Hot Water Heating

20
Refrigerant

• R-22, an HCFC
• ODP 0.05 (Ozone Depletion Potential)
• 5 of CFC-1112 ODP
• Production Phase Out 2030
• Alternatives
• Blends of HFCs zero ODP

21
System Cost Comparison
22
Heat Pump Efficiency

• Coefficient of Performance 3.0 - 4.0
• Produce 3 to 4 times the energy used
• 40 to 60 Energy Savings
• 2 8 year Payback on Initial Cost
• Utility Rebates
• GHPs reduce peak load

23
Operating Cost Comparison
24
Eliminating Emissions

• Galt House East Hotel
• Louisville, Kentucky
• Open Groundwater Loop (58oF)
• Annual Energy Savings 5.6 mil kWh
• Annual Emission Reductions
• 1.8 mil lb of CO2
• 44,000 lb SOX
• 33,000 lb NOX

25
Conclusion

• Estimated 400,000 GHP Systems in U.S.
• Increasing Popularity
• Residential Commercial Installations
• Advantages
• High Efficiency
• Reduce Emissions
• Renewable Resource
• Economical
• Constant Availability