Term
| What is geothermal power? |
|
Definition
heat energy that is
naturally released from the earth |
|
|
Term
| What is the temperature of the earth's core? |
|
Definition
|
|
Term
| What is the temperature of the molten rock beneath the earth's surface? |
|
Definition
|
|
Term
| What is the earth's temperature gradient? |
|
Definition
| 3°C for every 100m of depth |
|
|
Term
| What areas are targeted for economical geothermal extraction? |
|
Definition
have a 10-30 times greater
temperature gradient [2].
• This allows for temperature’s exceeding 300°C
at depths of only 1 km [2]. |
|
|
Term
| What happens with geothermal underground reserviors? |
|
Definition
are tapped at these
depths and brought to the surface |
|
|
Term
What is allowed to expand powering a
turbine which generates electricity? |
|
Definition
|
|
Term
| What happens with geothermal waste? |
|
Definition
either released
to the atmosphere or reinjected into the
reservoir |
|
|
Term
| What is the geothermal resource base? |
|
Definition
It is estimated the 44.2 TWyr/yr are leaked to the
earth’s surface [3].
• It is estimated that 40% of the resource base is
recoverable |
|
|
Term
| Where are the most active geothermal regions in the US? |
|
Definition
|
|
Term
| What are the consequences of improper placement of geothermal wells? |
|
Definition
Early
loss of heat/pressure, depletion of the
geofluid, or extermination of nearby thermal
manifestations |
|
|
Term
| What are the phases of a geothermal exploration program? |
|
Definition
– A Literature Survey
– An Airborne Survey
– A Geologic Survey
– A Hydrologic Survey
– A Geochemical Survey
– A Geophysical Survey |
|
|
Term
| What are the top 3 places for geothermal? |
|
Definition
1. Iceland
2. U.S.
3. Phillapines |
|
|
Term
| What is more costly than the exploration phase of geothermal? |
|
Definition
|
|
Term
| How many wells are generally dug after a successful exploratory phase? |
|
Definition
|
|
Term
| What is used to drill geothermal? |
|
Definition
|
|
Term
| What is "mud" in geothermal? |
|
Definition
a lubricating and cooling
fluid known as the
“mud”.
• The mud also removes
the rock chips and fills
the well hole as it rises,
reinforcing the well hole. |
|
|
Term
| What happens with geothermal when there is extreme pressure? |
|
Definition
These high pressure permeable zones are
hard to predict via exploration phase data and
are usually found during the drilling of the
well.
• This can cause a dangerous situation known as
blowout. |
|
|
Term
| What are blowout preventers? |
|
Definition
• These ram type valves
quickly shut during a
blowout.
• Valves attached to the
wellhead allow for the
controlled release of the
well pressure. |
|
|
Term
| What is a single flash steam power plant? |
|
Definition
The Single Flash plant is the main source of geothermal
energy extraction comprising of 32% of all geothermal
power plants and 42% of the world geothermal power
capacity [10].
• Unit power capacities range from 3 to 90MW with an
average power rating of 25.3MW per unit [10].
• The term flash refers to taking a pressurized fluid and
reducing the pressure such that part if not all of the
fluid vaporizes. |
|
|
Term
| What are typical pump and turbine efficiencies? |
|
Definition
70 to 80%
however efficiencies of the high 80% have been
obtained [11]. |
|
|
Term
| How much power does geothermal need? |
|
Definition
On average, a flash power plant needs about
1,200 m2/MW. This includes well pads, pipe
routes, power plant and substation [12].
• By comparison, a nuclear power plant needs
about 10,000 m2/MW (power station only), a
coal-fired plant needs 40,000 m2/MW (power
station plus area to be strip mined for 30
years), and a solar photovoltaic plant needs
66,000 m2/MW (power station only) |
|
|
Term
| What are the two main types of hazardous waste produced by geothermal? |
|
Definition
noncondensable gases and
the brine stream. |
|
|
Term
| What are the noncondensable gases produced by geothermal? |
|
Definition
| Hydrogen Sulfide, Carbon Dioxide and Methane. |
|
|
Term
| Does geothermal produce greenhouse gases? |
|
Definition
|
|
Term
| What is the main way to prevent contamination of drinking water with geothermal? |
|
Definition
reinject the brine into the formation.
• This also has the added effect of restoring the geofluid
in the reservoir. |
|
|
Term
| Double flash steam power plant |
|
Definition
Flashing the geofluid a second time can produce
15-25% more power output.
• This type of steam power plant makes up 14% of
all geothermal plants in operation as of mid-
2007.
• Power capacities for double flash steam power
plants range from 4.7 to 110MW with an average
of 32 MW per unit . |
|
|
Term
|
Definition
These types of power plants tend to be less
expensive in both construction and operation
due to there being no brine stream to deal with.
This may prove to be a problem in the future
when it comes to maintaining reservoir
performance.
There are only two major dry steam geothermal
fields in the world, Larderello and The Geysers.
This is because it is rare that a geofluid become
heated enough to produce superheated steam |
|
|
Term
|
Definition
• As of May 2007, dry steam plants maintain
12% of all geothermal plants with 61 units.
• Dry steam plants account for 2,471 MW or
about 26% of the total geothermal worldwide
capacity.
• Dry steam units have an average power
capacity of little over 40 MW. |
|
|
Term
| Binary Cycle Steam Power Plant |
|
Definition
This steam plant uses two fluids: The geofluid
and the working fluid.
• The two fluids never come in contact with
each other.
• The geofluid is left in its compressed liquid
state and passed through a heat exchanger
where it transfers its heat to the working fluid.
• The working fluid is then vaporized, allowed
to expand and pumped to a turbine. |
|
|
Term
| Advance cycle design geothermal plants: |
|
Definition
This steam plant uses two fluids: The geofluid
and the working fluid.
• The two fluids never come in contact with
each other.
• The geofluid is left in its compressed liquid
state and passed through a heat exchanger
where it transfers its heat to the working fluid.
• The working fluid is then vaporized, allowed
to expand and pumped to a turbine. |
|
|
Term
| Binary Cycle Steam Power Plants Info |
|
Definition
As of May 2007, there are 162 units in
operation providing 373 MW of power [15].
• This places 32% of all geothermal units in
operation as binary cycle but gives an average
power rating of 2.3 MW/unit [15].
• Units with 7-10 MW ratings are coming into
use with an advanced cycle design |
|
|
Term
| Binary cycle systems make use of hostile geofluids. What are hostile geofluids? |
|
Definition
Hostile geofluids can contain large amounts of
noncondensable gases or a large amount of
dissolved minerals which would cause scaling
if allowed to precipitate |
|
|
Term
| What are enhanced geothermal systems? |
|
Definition
• Brought about to attempt to stop our reliance
on an underground water reservoir.
• Many states contain underground Hot Dry
Rock “HDR” beds.
• EGS plans to artificially create an underground
reservoir by characterizing these HDR beds,
drilling at appropriate well sites and injecting
a geofluid. |
|
|
Term
| What does an enhanced geothermal system make use of? |
|
Definition
An EGS makes use of
nearby impermeable rock
to contain the injected
fluid.
A nearby production well
pumps the fluid back up,
creating a flow path for the
fluid from the injection well
to the production well.
The HDR bed has to be
characterized properly so
that the wells be placed a
distance that will allow for
enough heat transfer. |
|
|
Term
|
Definition
• Biofuels are energy sources derived from
biological materials that are considered
renewable.
• This excludes fossil energy sources which are
derived from biological materials but are not
non-renewable.
• Biofuels can solid, liquid, or gasous depending
on the their source material and how they are
formed. |
|
|
Term
| What are the main types of biomass? |
|
Definition
ethanol, biogas, biodiesel, straight
biomass, and synfuels from pyrolysis and
gasification of biomass |
|
|
Term
| The type of biofuel that can be produced depends on what? |
|
Definition
|
|
Term
| What is the ultimate energy input from which biofuels are created? |
|
Definition
|
|
Term
|
Definition
The solar energy comes from nuclear fusion reactions in the sun
and is transferred to earth through the radiation of photons.
• These photons are captured my organisms on earth and is stored
as chemical energy through a process called photosynthesis.
• Almost all stored energy sources on earth were originally captured
by photosynthetic organisms. This includes fossil energy sources |
|
|
Term
|
Definition
Photosynthesis captures photons through the use of pigments
produced by the photosynthetic organism.
• The main pigment used is chlorophyll. This pigment gives plants and
other photosynthetic organisms their characteristic green color.
• The photons interact with the pigments to excite electrons to higher
energies which then travel down an electron transport chain. As the
electrons move down the chain they move hydrogen ions to produce a
concentration and electric potential gradient.
• It is from this gradient that the organism produces chemical energy in
the form of adenosine triphosphate (ATP) and NADPH. These energy
molecules can then be used to synthesize other types of molecules in
the organism (sugars, lipids, etc.) with the use of carbon dioxide from
the atmosphere |
|
|
Term
| What is the most abundant protein on earth? |
|
Definition
|
|
Term
|
Definition
The enzyme that captures the carbon dioxide is called ribulose
bisphosphate carboxlyase/oxygenase (rubisco). The carbon is attached to
other molecules in the plant and then rearranged to form the desired
molecules using the ATP and NADPH created earlier in photosynthesis. |
|
|
Term
| What do photosynthic oranisms capture? |
|
Definition
carbon dioxide through the Calvin-
Benson cycle. |
|
|
Term
| What are the 3 main types of carbon capture processes in plants? |
|
Definition
|
|
Term
| What do the plant pathways determine? |
|
Definition
The pathway a plant uses really determines it photosynthetic efficiency,
and hence how much chemical energy it can store from sunlight captured |
|
|
Term
|
Definition
The C3 pathway is the most ancient and also less efficient than the C4
pathway. The reason for this is that the rubsico can attach to not only
carbon dioxide but also oxygen which produces unwanted molecules.
Photosynthetic organisms can counteract this through a process called
photorespiration, however this lowers the net return on the energy
from sunlight |
|
|
Term
|
Definition
The C4 pathway helps reduce photorespiration through the use of a
different enzyme, PEP carboxylase. This allows the plant to have
greater photosynthetic efficiencies compared to C3 organisms |
|
|
Term
|
Definition
The CAM pathway is used mostly by desert plants as a means of saving
on water loss. However this pathway slows down the growth of the
organism. |
|
|
Term
| Biomass photosynthesis efficiencies both theorectical and actual |
|
Definition
The theoretical photosynthetic efficiency of converting sunlight into
biomass energy is approximately 11%.
• This is because only about 45% of the light from the sun can be
absorbed by plants and the energy of those photons is downgraded to
two energies. Also there is a need of at least 10 photons per molecule
of carbon dioxide produced.
• In practice the 11% is not achievable due to non-optimum sunlight,
reflection of light, photorespiration, plant energy requirements for
upkeep of photosynthetic machinery.
• The net result is a photosynthetic efficiency between 3% to 6% of total
solar radiation, however this can be more or less depending on
condition and the type of pathway the plant uses. |
|
|
Term
| Photosynthetic effiency of plants, crop plants, and sugarcane |
|
Definition
Plants, typical
0.1%
0.2–2%
Typical crop plants 1–2%
Sugarcane 7-8% |
|
|
Term
| Average tonnes/ha of Corn, soybeans, spring barley, and winter wheat |
|
Definition
Corn 6.66
C3 Soybeans 2.42
C3 Spring barley 3.12
C3 Winter wheat 3.9 |
|
|
Term
| Molecules of life are generally classified into the following catagories |
|
Definition
| carbohydrates, lipids, proteins, and nucleic acid |
|
|
Term
| Describe the molecules of life: |
|
Definition
Carbohydrates are broken up into simple carbohydrates and complex
carbohydrates. Simple carbohydrates are molecules such as sugars,
while more complex ones can be from starches to cellulose. They
typically contain carbon, hydrogen, and oxygen in a ratio of 1:2:1
• Lipids are fats and oils, made mostly of carbon and hydrogen.
• Proteins make up many of the enzymes that perform reactions and
contain a lot of nitrogen.
• Nucleic acids are generally used for genitic material, but also are used
as enzymes and energy movement in cells. |
|
|
Term
The two most important molecules produced by plants
in terms of use in biofuels are |
|
Definition
|
|
Term
These two classes are what is used to produce the main
types of biofuels |
|
Definition
straight biomass, ethanol, biodiseal,
biogas, and synfuels |
|
|
Term
Nitrogen and protein content play a role in the
formation of biogas - what is the role? |
|
Definition
more as a nutrient than an
energy source. |
|
|
Term
|
Definition
The total amount of power that reaches the earth from
the sun at any given time is approximately 170,000 TW,
with about 86,700 TW reaching the surface.
• The estimated net primary productivity of all the earth’s
ecosystem is 130 TW.
• Assuming a 1% efficiency and that the photosynthetic
organisms absorb 45% of the sunlight that falls on
them, this amounts to 5850 TW being captured by
ecosystems. |
|
|
Term
| Currently the worlds power usage is approximately what? |
|
Definition
|
|
Term
| What needs to be considered when looking at how much biomass energy can be taken out of an ecosystem? |
|
Definition
First there is a certain amount of energy that has to remain in the
ecosystem for all of the other species that exist to survive. If too much
it taken then there will be a loss in biodiversity.
• Second most ecosystems on earth are a zero sum game in terms of the
chemical nutrients. This means that certain nutrients cannot be taken
out at too high of a rate or the ecosystem will become depleted of
them. |
|
|
Term
| What is a problem we already face in terms of industrial food production? |
|
Definition
The depletion of nitrogen from soils is a problem that we already face in
terms of industrial food production. By removing large amounts of protein
rich crops from the land the soils become depleted of fixed nitrogen. |
|
|
Term
| In order to have sustainable biomass what do we need to consider? |
|
Definition
In order to have a sustainable energy supply from biofuels we have to take
into account both the amount of energy that can be removed, and have
agriculture that replaces the chemicals taken out without large energy
input |
|
|
Term
| How do we make up for nitrogen depletion in soil? |
|
Definition
In order to make up for this loss we fix nitrogen ourselves in the Haber-
Bosch process, that we then use to fertilize fields to replace the nitrogen
that is removed.
• This process alone account for 2% of our total energy consumption or 13
TW x 0.02 = 0.26 TW or 260 GW. Also because of this about 40% of the
nitrogen in humans has gone through this process |
|
|
Term
|
Definition
Ethanol is a two carbon alcohol that is produced primarily through the
fermentation of sugars by micro-organisms (fungi, bacteria).
• Production of alcohol has been around since at least the start of
agriculture.
• Typically ethanol is fermented from sugar or starch rich plants such as
sugar cane, sugar beats, corn, or potatoes. However, ethanol can also
be produced from cellulose once it has been reduced down to its
component sugars.
• After ethanol has been produced it has to be distilled in order to get to
a high enough percentage to be used as a fuel. This also requires
energy input |
|
|
Term
|
Definition
Alcoholic fermentation proceeds in anaerobic conditions typically by
yeast, a single celled fungi.
• The mixture a the end of fermentation can varying in composition but
typically contains 10%-12% alcohol (depending on starting
components) with the rest being mostly water. |
|
|
Term
|
Definition
After fermentation the mixture is distilled by heating it and allowing it
to evaporate through a distillation column. Typically to get fuel grade
ethanol factional distillation is used. The mixture that comes out of the
end of the distillation column is 96% alcohol and 4% water. This is the
highest that it can be distilled to as this is its azeotropic point. To
remove the remaining water other techniques are used, or the fuel
mixture is used as is. |
|
|
Term
|
Definition
|
|
Term
| Ethanol’s anti-knocking index (octane rating) |
|
Definition
|
|
Term
| Gasoline’s anti-knocking index (octane rating) |
|
Definition
|
|
Term
|
Definition
The Otto cycle is the cycle that spark-ignited internal
combustion engines follow. |
|
|
Term
|
Definition
Even though ethanol has a lower energy content than
gasoline it can have a higher efficiency |
|
|
Term
|
Definition
A better option for all biofuels and fossil fuels, but
especially ethanol and methane is to use a fuel cell to
produce electricity from fuel rather than burning it to
run a heat engine.
• For ethanol: DG = DH -TDS |
|
|
Term
|
Definition
Biogas is produced through the anaerobic digestion of biomass by acid
producing microbes and methagens.
• Acid producing microbes breakdown much of the biomass in organic
acids, which are then converted into methane and carbon dioxide gas
by other methagenic microbes in the anaerobic environment.
• The gas produced is mostly methane but also contains other gases,
mainly carbon dioxide. It can be used in almost any function that
natural gas is as long as any hydrogen sulfide is removed.
• The gases released are from energy containing molecules and are
carbon based. Most other nutrients and minerals do not leave the biodigester
so that they are available in the waste stream output |
|
|
Term
|
Definition
Biogas is produced through the anaerobic digestion of biomass by acid
producing microbes and methagens.
• Acid producing microbes breakdown much of the biomass in organic
acids, which are then converted into methane and carbon dioxide gas
by other methagenic microbes in the anaerobic environment.
• The gas produced is mostly methane but also contains other gases,
mainly carbon dioxide. It can be used in almost any function that
natural gas is as long as any hydrogen sulfide is removed.
• The gases released are from energy containing molecules and are
carbon based. Most other nutrients and minerals do not leave the biodigester
so that they are available in the waste stream output |
|
|
Term
|
Definition
Biodiesel is formed through the transesterfication of triglycerides and an
alcohol. The alcohols typically used are methanol and ethanol.
• The transesterfication is performed by mixing the alcohol and triglycerides
with a catalyst, heating it and mixing. Glycerol separates from the three
fatty acids and an alcohol attaches to the acid site on each of the fatty
acids, giving three biodiesel molecules. The catalyst can be either basic or
acidic. Some catalyst include sodium hydroxide, potassium hydroxide, and
sulfuric acid.
• Biodiesel can be made from basically any triglyercide or animal and plant
fat.
• It has very similar properties to diesel fuel and can be run in an
unmodified diesel engine. |
|
|
Term
|
Definition
Algae 1500-3000
Chinese tallow 97
Palm oil 508
Coconut 230
Rapeseed 102
Soy (Indiana) 59.2-98.6
Peanut 90
Sunflower 82
Hemp 26 |
|
|
Term
|
Definition
Synthetic fuels can be made from biomass in much the same way
that they are from fossil fuels.
• The processes generally used are pyrolysis and gasification.
• In pyrolysis the biomass is heated up under anaerobic conditions.
Carbonaceous char is produced as well as liquids and gases.
• In gasification steam, oxygen, or hydrogen is introduced into the
system as well which produces a higher quality gas than pyrolysis.
• Because of the lower energy content of these products they have
to be used on site in order to get any benefit from them. (negative
EROEI) |
|
|
Term
| Direct burning of biomass |
|
Definition
Direct burning of biomass is one of the oldest
forms of heat energy that humans use.
• Direct burning can be used in any case where
heating is needed, such as heating building or
running a heat engine.
• The usage of biomass depends on how much
energy is contained with in it. |
|
|
Term
|
Definition
Biomass energy
Cord: a stack of wood comprising 128 cubic feet (3.62 m3); standard dimensions are 4 x 4 x 8
feet, including air space and bark. One cord contains approx. 1.2 U.S. tons (oven-dry) = 2400
pounds = 1089 kg
1.0 metric tonne wood = 1.4 cubic meters (solid wood, not stacked)
Energy content of wood fuel (HHV, bone dry) = 18-22 GJ/t (7,600-9,600 Btu/lb)
Energy content of wood fuel (air dry, 20% moisture) = about 15 GJ/t (6,400 Btu/lb)
Energy content of agricultural residues (range due to moisture content) = 10-17 GJ/t (4,300-
7,300 Btu/lb)
Metric tonne charcoal = 30 GJ (= 12,800 Btu/lb) (but usually derived from 6-12 t air-dry wood,
i.e. 90-180 GJ original energy content)
Metric tonne ethanol = 7.94 petroleum barrels = 1262 liters
ethanol energy content (LHV) = 11,500 Btu/lb = 75,700 Btu/gallon = 26.7 GJ/t = 21.1
MJ/liter. HHV for ethanol = 84,000 Btu/gallon = 89 MJ/gallon = 23.4 MJ/liter
ethanol density (average) = 0.79 g/ml ( = metric tonnes/m3)
Metric tonne biodiesel = 37.8 GJ (33.3 - 35.7 MJ/liter)
biodiesel density (average) = 0.88 g/ml ( = metric tonnes/m3) |
|
|
Term
| Replacing Transportation Fuel with Biomass |
|
Definition
Replacing Transportation Fuel
• Currently in the United States Transportation
consumes approximately 600 Mtoe.
• Volume of ethanol needed for heat engine
replacement.
• Volume of ethanol needed for fuel cell
replacement.
( ) MJ
J
MJ
toe
J
Mtoe
toe
Mtoe 13
6
6 10
2.52347 10
10
1
1
4.20579 10
1
10
600 ´ =
´
( ) L
MJ
L
13MJ 8.20753 1011
23.5
1
0.314
0.24
10 52347 . 2 ´ =
´
( ) L
MJ
L
13MJ 3.10502 1011
23.5
1
0.83
0.24
10 52347 . 2 |
|
|
Term
|
Definition
The future of biofuels will be in co-generation energy
plants that make use of all of the plant and return
nutrients back into the soils after energy has been
extracted from the biomass. ( return waste sludge from
digesters, etc.)
• This will be the only way to make biofuels sustainable
and practical.
• The will mostly be used in the transportation sector
where a high energy density of liquid fuels is needed. |
|
|
