Geothermal Flashcards
Why is geothermal energy a renewable resource?
because heat is continuously transferred from within the earth
The origin of geothermal energy is from the earths _____, because of the ______________
core
decay of radioactive material
how does the heat reach us from the center of the earth
internal heat flows naturally to the surface by conduction and creates a gradient where temperature of the solid earth rises with increasing depth
geothermal gradient slope increases from the _________ to the __________ to the __________ to the _________ to the _________
lithosphere to the asthenosphere to the mantle to the outer core to the inner core
which layer of the earth does rock melt
the asthenosphere
Which is the only current resources of geothermal that is currently exploited
hydrothermal
describe hydrothermal
These are known geothermal fields containing high temperature water in steam, mixture, or liquid phases
Describe geopressurized
Hot liquid water at 150 C to 180 C at a very high pressure, up to 600 bar. They contain high volumes of methane and dissolved solids.
What is the difficulty of geopressurized
The fluid is highly corrosive and thus very difficult to harvest and handle
describe magma
molten rock contained under active volcanoes at temp above 650 C
Describe enhanced and how it works
hot, dry rock geothermal systems. Water is injected into the hot rock formation at high pressure and then the steam is brought back to the surface
Which of the following are not natural geothermal resources: Hydrothermal, geopressurized, and enhanced
enhanced is not natural
how do we make an enhanced geothermal resource. Include depth and temp
drill injection and production wells to a depth of 3 to 5km. The temp of the hot rock in this depth can be around 250C
where does the petrothermal (EGS) system get the energy to create power
from granite intrusions
where does hydrothermal system get their direct heat use
from deep aquifers
Hypothetical example of a geothermal reservoir of the magmatic type showing hot magma,
the associated reservoir containing water, and recharge of the reservoir through _________
Fractures
what is considered as a high temp resources for geothermal
T > 150 C
what is considered as a medium temp resources for geothermal
90 C < T < 150 C
what is considered as a low temp resources for geothermal
< 90 C
what are the components of the enhanced geothermal system
- Reservoir
- Pump house
- Heat exchangers
- Turbine hall
- Production well
- injection well
- Hot water to district heating
- Porous sediments
- observation well
- crystalline bedrock
what are the 3 state of geothermal water in the reservoir
- superheated or saturated stream (dry steam)
- saturated steam-liquid mixture
- Liquid (usually compressed liquid)
rank the 3 states of geothermal water in the reservoir based on quality, lowest to highest
liquid, steam-liquid mixture, dry steam
The quality of a geothermal resource depends on its ______ (and temperature). The higher the quality, the higher the _____ _____
phase
work potential
how high does the temperature need to be to produce electricity
150 C or higher for economic power production
Geothermal heat pumps – _____ initial cost for installation, but ____
maintenance cost
high
low
what are the direct uses of geothermal
space heating, drying, greenhouses, agriculture, resorts and pools, melting snow
describe cogeneration and how it applies to geothermal applications
generates heat and electricity from the same energy source. heat that would normally be wasted when producing electricity is saved
describe the characteristics of the shallow geothermal heating and cooling
Types: open loop GTHP, closed loop GTHP array, mine water energy
In shallow aquifer
temp -5 to 80C
describe the characteristics of the deep geothermal heating
in basement or deep aquifers
Types: Hydrothermal system and deep closed loop GTHP array
temp 50 to 150 C
describe the deep geothermal power
Types: engineered geothermal system and advanced geothermal system
temp 130 to 180
in granite
What are the advantages of geothermal energy
reliability, flexibility, availability, green technology, small footprint, sustainability
describe a geothermal heat pump
The pump uses electricity to derive the working fluid from the closed loop system using a liquid heat exchange medium and the delivery system, which can be an air delivery system or radiant heating
describe deep closed loop geothermal
circulates working fluids like water and CO2 through closed wellbores several km deep. The system extracts heat from hot rock through conduction, as opposed to traditional geothermal and EGS through convection. As hot rock is universal deep beneath the surface, this technology can be applied anywhere. The working fluid in the closed loop brings thermal energy to the surface for direct heat application or converted to electricity.
deep closed loop geothermal and EGS uses what kind of heat transfer
deep closed loop geothermal uses conduction
EGS and traditional geothermal use convection
What is the main purpose of IDDP (Iceland deep drilling project)
is to find out if it is economically feasible to extract energy and chemicals out of hydrothermal systems at supercritical conditions(400-600C, superheated steam, <220 bar subcritical pressures). If it works, it could produce about ten times more power.
Huff ‘n’ puff geothermal: Sage injects high-_________ dense drilling mud into abandoned oil
wells, to push slim __________ apart, then pumps ________ in to keep the
fractures open. This is done using excess renewable energy collected
during daylight hours, and then a valve is closed to __________ the
water.
pressure
fractures
water
soak/heat
Huff ‘n’ puff geothermal: When it comes to recover the geothermal energy, the reservoir
_________ squeezes water back to the surface, where it can be run
through a turbine to harvest electricity.
Indeed, the same electric motor and pump that forced it down there
in the first place become the _______ and _________ that get the
energy back out when the system runs in reverse
pressure
turbine and generator
describe huff ‘n’ puff geothermal
inject high pressure drilling mud into abandoned oil wells to get fractures, put water (pump and electric motor) in to keep the fractures open. close the valves and let the water heat. When opening the valve the pressure causes the water to return to the surface and create electricity by the (turbine and generator)
Geothermal heat pumps: The working fluid is circulated through the loop pipes buried beneath the
surface. Heat is taken from the ground in the __________ for heating, while
the heat inside buildings can also be exchanged to cool in the __________.
wintertime
summertime
define what a resource is considered as in geothermal
portion of the accessible resource base that can be recovered as useful heat under current and potential economic technological conditions. How much recoverable resources we think there are totally, estimate
define what a reserve is considered as in geothermal
the identified portion of the resource that can be recovered economically using existing technology. Resources we know about and that can be 100% recovered
what is heat in place used as
a standard method to estimate geothermal resources. It represents the quantity of energy stored in each volume element of the geothermal reservoir.
what is the equation for HIP
HIP = V * pcp *(Tx - To) *10^-15
volume times volumetric specific heat times the difference between the reservoir temp and the re-injection temp
What is the theoretical technical potential
It is the power that can be produced by each volume element of the reservoir having T > minimum temp required for the specific technology(120C for electricity production)
The USGS volumetric estimation methodology consists of
combining estimates with uncertainties for the ________ ______, and ________of a geothermal reservoir into an estimate of the stored
energy (“heat in place”) with uncertainty
temperature, area, and thickness
The probability distribution function for the stored energy can be
obtained using a ______________ approximation
monte carlo
Which of the following parameters vary a lot among different reservoirs: Resevoir area, volumetric heat capacity, rejection temperature, reservoir depth, reservoir thickness, reservoir temperature, conversion efficiency, thermal recovery factor, plant or project life, and plant load factor
reservoir area, reservoir depth, reservoir thickness, reservoir temperature, and thermal recovery factor
Which of the following parameters are relatively unchanged among different reservoirs: Reservoir area, volumetric heat capacity, rejection temperature, reservoir depth, reservoir thickness, reservoir temperature, conversion efficiency, thermal recovery factor, plant or project life, and plant load factor
volumetric heat capacity, rejection temperature, conversion efficiency, plant or project life, plant load factor
what does P10 mean
in this distribution, 10% of the observations will exceed the value x
What is MWe
a measure of the electricity output of a plant
give the characteristics for the dry steam power plant
dry steam spins the turbine
the most efficient type
Dry steam reservoir is not common
How does the flash steam power plant differ from the dry steam power plant
Coming from the well it has a section that catches the brine an lets the steam pass before it enters the turbine
How does the binary cycle power plant differ from the dry steam power plant?
From the well, there is a heat exchanger, it sends hot brine back to the well and the iso butane vapor transfers its heat to the water that travels to the turbine
give the characteristics of a flash steam power plant
single flash and double flash
use separator to separate into distinct steam and liquid
mainstream of geothermal power industry
give the characteristics of the binary cycle power plant
uses a secondary working fluid with a lower boiling point than water: pentane, butane
also known as organic rankine cycle (ORC) plant
with geofluid temperature < 150 C
