Part 1

1. Part 1 Geothermal Power

2. Why? Growing demand for energy Concern about CO2 from fossil-fuel burning Recent Report, The Future of Geothermal Energy, gives favorable assessment

4. Indian Point Power Plants 1 and 2, big energy producers in the NY City area

5. Electric Power Primer Typical Big Power Plant generates 1GW One billion watts … 109 J/s of energy In a year it generates 109 J/s x 3.1x107 s/year = 3.1x1016 J/year A nice round number is 1018 J That’s the amount of power a 1GW plant Generates in its nominal 30-year lifetime

6. US Electrical Power Production Capacity906 GW in 2006rate of increase 1% per yearabout 1000 big power plantsneed 10 new ones each year

7. An aside …controversial Cape Wind project offshore Cape Cod would generated 0.4 GW by 120 turbines Offsets growth of New England power demand for about a year or two …

8. Geothermal lumped into “Other Renewable” … not much!

9. Where is the Heat? Typical Geothermal Gradient: typical region: 20 K/km volcanic region: 100 K/km Power production needs temperatures well above 100 deg-C So drilling needed to access heat

10. 3.5 km – easy to drill, but not very hot What’s that hot spot?

11. Yellowstone CalderaBiggest Volcano in UShere I amstanding by Old Faithfulabove 10,000 cubic kmof magma

12. 6.5 km – expensive but routine, areas of western US are hot

13. 10 km – very hot, but pushing limits of technology

14. Heat in Rock: Q = r Cp V DT Heat = density * heat capacity * Volume * change in Temperature Density = 2500 kg/m3 Heat Capacity = 1000 J/kgK Volume = 1 cubic km = 109 m3 DT = 100 K So Q = 2.5 x 1017 J A 1 GW power plant generates 3.1x1016 J/year, so this is about tens years of a 1GW power plant

15. Remember 1018 J is roughly the amount of energy produced by a power plant in its nominal 30 year lifetime, so these estimates indicate a huge supply of heat energy

16. How to access heat? Drill 2 holes, one to inject cold water, another to extract hot water Circulate fluid Use hot water to generate steam that turns turbine of more-or-less standard design

18. Issues Drill 2 holes … expense of drilling Circulate fluid … low permeability of rock Generate steam … dissolved minerals in water

19. Money Counts! Any sort of mining or extraction is an Economic Activity that competes by price against alternatives If the economics are not right It will not be done even if it is in theoretically possible to do

21. Solution to low permeabiliy Artificially increase permeability by creating fractures “Hydrofracture” … pressurize well until you crack the surrounding rock, routinely used in oil extraction, at least for small volumes of rock

22. 60 MW Krafla power plant, Iceland: heat from 33 wells drilled into volcano Tiny by US standards Lots of wells

23. Power plant Magma chamber

24. Part 2 Fresh Water Possibly the most Limiting Resource

25. How much water do you use in a day?

26. Public Supply Domestic Supply Irrigation Livestock & Aquaculture Industrial Mining Thermoelectric Power US Water Usage, % 11 1 34 2 5 1 48

27. US Water Usage, billion gallons / day Public Supply 27.3 Domestic Supply 0.6 Irrigation 80 Livestock & Aquaculture 3.4 Industrial 14.9 Mining 1.2 Thermoelectric Power 135 Total 262

30. Ogallala Aquifer

31. US Water Usage, billion gallons / day Public Supply 27.3 Domestic Supply 0.6 Irrigation 80 Livestock & Aquaculture 3.4 Industrial 14.9 Mining 1.2 Thermoelectric Power 135 Total 262

32. Total 262 billion gallons/day 362 cubic kilometers per year H20 7 km

33. 27.9 billion gallons/day Public & Domestic Supply 266 gallons per person per day drinking cooking & washing dishes washing clothes flushing toilet

34. Cooling water for power plants 135 billion gallons/day 450 gallons per person per day 40 kWh average daily electrical consumption per person in US So 0.08 kWh per gallon a gallon lights the bulb for an hour

35. 80 billion gallons/day Irrigation 266 gallons per person per day 2750 calories average daily food consumption per person in US So 10.3 calories per gallon 2.7 calories per liter a gallon gets you a chip

36. Wheat: 3500 calories/kg Wheat: 4.6 calories/liter About 750 liters of water to grow a kilogram

37. Rice: 3700 calories/kg Rice: 2.4 calories/liter About 1550 liters of water to grow a kilogram

38. How much irrigation water does the world need? 2000 calories/day minimum At 3 cal/liter 670 liters/day  6 billion people  365 days/year = 1.46 1015 liters/year = 14700 cubic kilometers per year So how much is available ?

39. The Hydrologic Cycle 108,000 km3/year precipitated on land 46,000 km3/year transported on shore 62,000 km3/year evaporated from continental reservoirs 46,000 km3/year runoff to oceans

40. Need 14,700 km3 Available 46,000 km3 So superficially about three times as much water is available than is needed. But consider …

41. Some runoff is in uninhabited regions Runoff is uneven during the year and may be lost to sea before it can be used The rest of the biosphere uses water, too Human populations are growing

42. Runoff is uneven during the year and may be lost to sea before it can be used Solution – Reservoirs (“Impoundments”) created by damming rivers

43. Global impoundments of water 8400 km3 Not much growth in last decade, except in Asia-Australia

44. Regional distribution of large dams

45. Dams in the US. Note that the red symbols indicate high hazard potential. Dam maintenance has not been a high priority for many municipalities and other dam owners.