Geothermal Energy District Heating

1. Geothermal EnergyDistrict Heating San Jose State University FX Rongère March 2008

2. District Heating • Direct use of geothermal hot water

3. Geothermal District Heating in the World • Applications are homes and offices, commercial greenhouses, fish farms, food processing facilities, etc. • In 2005, Residential gas consumption in the USA was 4.4 Millions of MMcf, i.e. 45 Billions of Therms Source: International Geothermal Association,http://iga.igg.cnr.it/geoworld/geoworld.php?sub=duses

4. Example: California Correction Center in Susanville • 5,800 minimum custody inmates, and 1,100 custodial and support staff • Two wells, 460 m deep built in 1982, temperature 72oC and 76oC • Water is not re-injected • 75hp-300 gpm • About 525,000 Therms/y • Cost:$200,000 per well • Total estimated: $500,000 • Pump consumption: 1 GWh/y • Electricty: $.12/kWh • Gas heating: $ 1.2/Therm • Pay back period < 1 year Source: Geoheat Center – Case Study – 2002 www.geoheat.oit.edu

5. Example: California Correction Center in Susanville • Sketch of the equipment Source: Geoheat Center – Case Study – 2002 www.geoheat.oit.edu

6. Geology • Crust depth reduction zone, Volcanic activity • Fault, igneous granite covered by low conductivity sedimentary rocks

7. Normal thermal gradient Susanville

8. Example: Geothermal District Heating (France) • Warm aquifer (60oC – 80oC) between 500m and 1,500m

9. Normal thermal gradient Susanville La Courneuve

10. General lay-out • Double well by directional drilling

11. La Courneuve Nord • Characteristics: • 2,800 dwellings • A double well 1,500m deep built in 1983, 59oC • Pump: 320 kW for 180 m3/h • About 720,000 Therms/y • Estimated cost: $ 500,000 per well • Total estimated: $ 1.5M • Pump Consumption: 3,200 MWh/y • Electricity: $.12/kWh • Gas heating: $ 1.2/Therm • Pay back period < 4 years Source: Arene Ile de France