geothermal

Question 2

Three categories of renewable energy resources

Answer 2

demand-side, no bearing on availability, careful management

Question 3

Which category is geothermal?

Answer 3

renewable if carefully managed, not depleted

Question 4

Three ways to use geothermal energy

Answer 4

electric power, direct use of heat, ground source heat pumps

Question 5

Which of the three geothermal uses require a hot resevoir?

Answer 5

electric power, direct heat use (not GS heat pumps)

Question 6

How geothermal works (in the earth!)

Answer 6

Really hot core stays hot even as heat escapes earth b/c of energy release from radioactive decay

Question 7

subduction zone

Answer 7

lithosphere folds downward, under adjacent lithosphere–might get molten and rise to surface

Question 8

where are most geothermal areas?

Answer 8

on plate margins

Question 9

what countries rely on geothermal?

Answer 9

Phillippines (22% of elec), Iceland (27% elec, 90% heat), El salvador (24% elec)

Question 10

Four structures of a geothermal reservoir

Answer 10

heat source, reservoir, water convection/recharging system, seal

Question 11

heat source

Answer 11

a place where earths crust is thin or broken by faulting = heat upward from conduction or magma

Question 12

reservoir

Answer 12

fractured rock area that stores heated water and permits flow so heat can reach surface–> must be porous and permeable

Question 13

water convection/recharge system

Answer 13

water management to keep reservoir sustainable

Question 14

seal

Answer 14

contains the heat and water flow; optional; rock structure performs as heat insulator (“cap”), maintains high water temps

Question 15

geothermal vs oil/NG drilling similarities (5)

Answer 15

exploration and drilling basics, site prep, site identification, speed = cost, reliance on down-hole telemetry/diagnostics

Question 16

geothermal vs oil/NG drilling differences (many)

Answer 16

different kind of reservoir: harder rocks (abrasive, slow, many bits), higher temps (tough on equip, need air instead of drilling mud), fracture porosity vs interstitial, generation is nearby (no pipelines), mostly vertical drilling, more fracing?

Question 17

geothermal & property rights

Answer 17

90% of resources on fed lands, BLM deals; the rest on state/private is up to the state laws

Question 18

world geothermal growth rate

Answer 18

grown 5%/year

Question 19

Big geothermal users

Answer 19

US, Phillippines

Question 20

big geothermal producer

Answer 20

Chevron (>1/2 all private geothermal)

Question 21

Geothermal in US

Answer 21

peaked in mid 90s; Geysers is 1/3 of US capacity

Question 22

Geothermal in CA

Answer 22

4.6% of CA electricity! More installed geothermal than any one country

Question 23

3 types of geothermal plant

Answer 23

dry steam, flash steam, binary

Question 24

dry steam geothermal

Answer 24

“direct steam, very hot steam, little water. Goes directly to generatory. 27% of world. Rare, but easy to extract–also easy to deplete

Question 25

flash steam geothermal

Answer 25

61% of world. Combination of really hot water and steam–water is at high pressure and when released, vaporizes–>generator

Question 26

binary geothermal

Answer 26

12% of world, but fastest growing. Moderately hot water goes to heat exchanger, makes working fluid boil–>generator

Question 27

Flash to flush

Answer 27

Geysers depleted too quickly, lost pressure; Calpine decided to inject recycled water to combat Geysers decline (then seismicity became a concern)

Question 28

“hot dry rock”

Answer 28

heated geo formation, but without water–associated with EGS

Question 29

EGS

Answer 29

enhanced geothermal systems

Question 30

Requirements for EGS to be viable (3)

Answer 30

1. commercial level of fluid production w/acceptable flow impedance 2.Establish modularity, repeatability at multiple sites 3. lower development costs

Question 31

Geothermal drivers (6)

Answer 31

abundant supply, baseload power, technological advances, RPS compliance, clean operations, economically competitive

Question 32

geothermal barriers (6)

Answer 32

site specific, markets and transmission, operational constraints, seismicity, environment/NIMBY, depletion

Question 33

Geothermal LCOE depends on_

Answer 33

technology, capacity factor, and capital cost/financing

Question 34

direct use geothermal

Answer 34

open/closed loop w/geothermal water, working fluid that delivers heat–usually for space heating, cooling

Question 35

ground source heat pump

Answer 35

make use of earth’s heat capacity–don_t need a hot spot! Uses pump to move heat to and from ground; most effective in places with temp swings; cost effectiveness is site-specific, but improving