geothermal Flashcards
Three categories of renewable energy resources
demand-side, no bearing on availability, careful management
Which category is geothermal?
renewable if carefully managed, not depleted
Three ways to use geothermal energy
electric power, direct use of heat, ground source heat pumps
Which of the three geothermal uses require a hot resevoir?
electric power, direct heat use (not GS heat pumps)
How geothermal works (in the earth!)
Really hot core stays hot even as heat escapes earth b/c of energy release from radioactive decay
subduction zone
lithosphere folds downward, under adjacent lithosphere–might get molten and rise to surface
where are most geothermal areas?
on plate margins
what countries rely on geothermal?
Phillippines (22% of elec), Iceland (27% elec, 90% heat), El salvador (24% elec)
Four structures of a geothermal reservoir
heat source, reservoir, water convection/recharging system, seal
heat source
a place where earths crust is thin or broken by faulting = heat upward from conduction or magma
reservoir
fractured rock area that stores heated water and permits flow so heat can reach surface–> must be porous and permeable
water convection/recharge system
water management to keep reservoir sustainable
seal
contains the heat and water flow; optional; rock structure performs as heat insulator (“cap”), maintains high water temps
geothermal vs oil/NG drilling similarities (5)
exploration and drilling basics, site prep, site identification, speed = cost, reliance on down-hole telemetry/diagnostics
geothermal vs oil/NG drilling differences (many)
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?
geothermal & property rights
90% of resources on fed lands, BLM deals; the rest on state/private is up to the state laws
world geothermal growth rate
grown 5%/year
Big geothermal users
US, Phillippines
big geothermal producer
Chevron (>1/2 all private geothermal)
Geothermal in US
peaked in mid 90s; Geysers is 1/3 of US capacity
Geothermal in CA
4.6% of CA electricity! More installed geothermal than any one country
3 types of geothermal plant
dry steam, flash steam, binary
dry steam geothermal
“direct steam, very hot steam, little water. Goes directly to generatory. 27% of world. Rare, but easy to extract–also easy to deplete
flash steam geothermal
61% of world. Combination of really hot water and steam–water is at high pressure and when released, vaporizes–>generator
