Geothermal Flashcards
Geothermal energy notes
Stored in the form of heat beneath the surface
every 1 km deeper you go it gets 30c hotter 3c/km
Crust is the outer surfaces of the earth and the core is deepest
the crust insulates us from the earths interior heat
Earh surfaces
Crust (the crust insulates us from the earths interior heat)
Mantle - semi molten
Outer core - is liquid
Inner core - is solid
Crust
earth crust is broken into huge plates that moves apart or push together
thinned or fractured crust allows magma to rise (lava)
Geothermal reserviors
Rising hot water or steam is trapped in porous rocks to form a geothermal reservoir
Direct use of geothermal
Geothermal reservours
hot springes
Gysters
Ground source heat pumps open and closed loops
Indirect use of geothermal
Electricity generation :
Dry steam power plant -
Flash steam power plant
binary cycle power plant-
Flash steam power plant
goethermal reservoir containing hot water and steam is required.
high-pressure fluid is brought to the surface and directed into a flash tank, the pressure drops suddenly. This drop in pressure causes part of the hot fluid to “flash” (or rapidly boil) into steam.
steam is then sperated from the other liquid (brine) the high speed flow of the steam is what drives the turbine and then condensed and reinjected together with the brine in the the geothermal reservior
Dry steam power plant
goethermal reservoir containg pure steasm is required - pure dry steam drives the turbines and generate power
after the steam exists the rubine now the low pressured steam gets condensed into liquid and reinjected to the geo reservoir
binary cycle power plant-
the geo thermal fluid is not directly used ,The geothermal fluid is passed through a heat exchanger where it transfers heat to a secondary working fluid (often a hydrocarbon like isobutane or isopentane) that has a lower boiling point than water.
After leaving the turbine, the secondary fluid enters a condenser, where it cools back into a liquid.
It is then recycled back into the heat exchanger to be used again in a closed loop.
and the cooled geothermal fluid is injected back to the reservoir
conventional geothermal systems
-Warm water systems
* Hot water systems
* Low enthalpy‐two phase systems
* Medium enthalpy‐two phase systems
* High enthalpy‐two phase systems
* Dry steam (vapor dominated) systems
Non conventional geothermal systems
-Supercritical (deep volcanic) systems
* Geo‐pressured systems
* Enhanced Geothermal systems
* Alternative Geothermal (man‐made)
systems
medium enthalpy 2 phase system
-Before use, the reservoir is mostly hot water. Any steam pockets are very small or absent.
-When pumping starts, pressure drops and more boiling occurs. This creates a water–steam mixture (two-phase) with moderate heat content.
-The fluid has more heat/steam than you’d predict from temperature alone, so it’s called “excess enthalpy.”
-These reservoirs don’t have extensive cracks or paths for fluid flow. Fluid movement is more contained compared to low-enthalpy systems.
“Reservoir and surrounding rock permeability is relatively low.”
-Smaller upflow zone, less overall heat flow, but more steam-heated areas compared to low enthalpy 2 phase system
super critical systems (deep volcanic systems)
involves drilling much deeper wells to two-phase geothermal systems to acces geothermal fluid at depth of 4 to 5 km.
enhanced geo systems
Using rocks as a heat sources as hot dry rocks store tempratures exceeding 200c . water underpressure is injected to break the rock thus releasing steam to drive the turbines.
