Classification Renewable/ non conventional Non renewable/
conventional
Slide 3
How much solar energy? The surface receives about 47% of the
total solar energy that reaches the Earth. Only this amount is
usable.
Slide 4
Direct Conversion into Electricity Photovoltaic cells are
capable of directly converting sunlight into electricity. A simple
wafer of silicon with wires attached to the layers. Current is
produced based on types of silicon (n- and p-types) used for the
layers. Each cell=0.5 volts. Battery needed as storage No moving
parts do no wear out, but because they are exposed to the weather,
their lifespan is about 20 years.
Slide 5
PH 0101 Unit-5 Lecture-25 A proper metal contacts are made on
the n-type and p-type side of the semiconductor for electrical
connection Working: When a solar panel exposed to sunlight, the
light energies are absorbed by a semiconduction materials. Due to
this absorded enrgy, the electrons are libereted and produce the
external DC current. The DC current is converted into 240-volt AC
current using an inverter for different applications.
Slide 6
PH 0101 Unit-5 Lecture-26 Mechanism: First, the sunlight is
absorbed by a solar cell in a solar panel. The absorbed light
causes electrons in the material to increase in energy. At the same
time making them free to move around in the material. However, the
electrons remain at this higher energy for only a short time before
returning to their original lower energy position. Therefore, to
collect the carriers before they lose the energy gained from the
light, a PN junction is typically used.
Slide 7
PH 0101 Unit-5 Lecture-27 A PN junction consists of two
different regions of a semiconductor material (usually silicon),
with one side called the p type region and the other the n-type
region. During the incident of light energy, in p-type material,
electrons can gain energy and move into the n-type region. Then
they can no longer go back to their original low energy position
and remain at a higher energy. The process of moving a light-
generated carrier from p- type region to n-type region is called
collection. These collections of carriers (electrons) can be either
extracted from the device to give a current, or it can remain in
the device and gives rise to a voltage.
Slide 8
PH 0101 Unit-5 Lecture-28 The electrons that leave the solar
cell as current give up their energy to whatever is connected to
the solar cell, and then re-enter the solar cell. Once back in the
solar cell, the process begins again:
Slide 9
PH 0101 Unit-5 Lecture-29 The mechanism of electricity
production- Different stages Conduction band High density Valence
band Low density E The above diagram shows the formation of p-n
junction in a solar cell. The valence band is a low-density band
and conduction band is high- density band.
Slide 10
PH 0101 Unit-5 Lecture-210 Stage-1 Therefore, the hole (vacancy
position left by the electron in the valence band) is generates.
Hence, there is a formation of electron- hole pair on the sides of
p-n junction. When light falls on the semiconductor surface, the
electron from valence band promoted to conduction band. Conduction
band High density Valence bandLow density E
Slide 11
PH 0101 Unit-5 Lecture-211 Stage-2 In the stage 2, the electron
and holes are diffuse across the p-n junction and there is a
formation of electron-hole pair. Conduction band High density
Valence bandLow density E junction
Slide 12
PH 0101 Unit-5 Lecture-212 Stage-3 In the stage 3, As electron
continuous to diffuse, the negative charge build on emitter side
and positive charge build on the base side. Conduction band High
density Valence bandLow density E junction
Slide 13
PH 0101 Unit-5 Lecture-213 Stage-4 When the PN junction is
connected with external circuit, the current flows. Conduction band
High density Valence bandLow density E junction Power
Slide 14
PH 0101 Unit-5 Lecture-214 A solar panel (or) Solar array
Single solar cell The single solar cell constitute the n-type layer
sandwiched with p-type layer. The most commonly known solar cell is
configured as a large-area p-n junction made from silicon wafer. A
single cell can produce only very tiny amounts of electricity It
can be used only to light up a small light bulb or power a
calculator. Single photovoltaic cells are used in many small
electronic appliances such as watches and calculators
Slide 15
PH 0101 Unit-5 Lecture-215 N-type P-type Single Solar cell
Slide 16
PH 0101 Unit-5 Lecture-216 Solar panel (or) solar array (or)
Solar module The solar panel (or) solar array is the
interconnection of number of solar module to get efficient power. A
solar module consists of number of interconnected solar cells.
These interconnected cells embedded between two glass plate to
protect from the bad whether. Since absorption area of module is
high, more energy can be produced.
Slide 17
PH 0101 Unit-5 Lecture-217
Slide 18
PH 0101 Unit-5 Lecture-218 Based on the types of crystal used,
soar cells can be classified as, 1.Monocrystalline silicon cells
2.Polycrystalline silicon cells 3.Amorphous silicon cells 1.The
Monocrystalline silicon cell is produced from pure silicon (single
crystal). Since the Monocrystalline silicon is pure and defect
free, the efficiency of cell will be higher. 2.In polycrystalline
solar cell, liquid silicon is used as raw material and
polycrystalline silicon was obtained followed by solidification
process. The materials contain various crystalline sizes. Hence,
the efficiency of this type of cell is less than Monocrystalline
cell. Types of Solar cell
Slide 19
PH 0101 Unit-5 Lecture-219 3. Amorphous silicon was obtained by
depositing silicon film on the substrate like glass plate. The
layer thickness amounts to less than 1m the thickness of a human
hair for comparison is 50-100 m. The efficiency of amorphous cells
is much lower than that of the other two cell types. As a result,
they are used mainly in low power equipment, such as watches and
pocket calculators, or as facade elements.
Slide 20
PH 0101 Unit-5 Lecture-220 Comparison of Types of solar cell
MaterialEfficiency (%) Monocrystalline silicon14-17 Polycrystalline
silicon13-15 Amorphous silicon5-7
Slide 21
PH 0101 Unit-5 Lecture-221 Advantage, disadvantage and
application of Solar cell Advantage 1.It is clean and non-polluting
2.It is a renewable energy 3.Solar cells do not produce noise and
they are totally silent. 4.They require very little maintenance
5.They are long lasting sources of energy which can be used almost
anywhere 6.They have long life time 7.There are no fuel costs or
fuel supply problems
Slide 22
PH 0101 Unit-5 Lecture-222 Disadvantage 1.Solar power cant be
obtained in night time 2.Solar cells (or) solar panels are very
expensive 3.Energy has not be stored in batteries 4.Air pollution
and whether can affect the production of electricity 5.They need
large are of land to produce more efficient power supply
Slide 23
WIND POWER What is it? How does it work? Efficiency
Slide 24
WIND POWER - What is it? All renewable energy (except tidal and
geothermal power), ultimately comes from the sun The earth receives
2 x 10 17 watts of power (per hour) from the sun About 2 percent of
this energy is converted to wind energy Differential heating of the
earths surface and atmosphere induces vertical and horizontal air
currents that are affected by the earths rotation and contours of
the land WIND. ~ e.g.: Land Sea Breeze Cycle
Slide 25
Wind is slowed by the surface roughness and obstacles. A wind
turbine obtains its power input by converting the force of the wind
into a torque (turning force) acting on the rotor blades. The
amount of energy which the wind transfers to the rotor depends on
the density of the air, the rotor area, and the wind speed. The
kinetic energy of a moving body is proportional to its weight. In
other words, the "heavier" the air, the more energy is received by
the turbine.
Slide 26
KidWind Project | www.kidwind.org
Slide 27
LARGE TURBINES: Able to deliver electricity at lower cost than
smaller turbines, because foundation costs, planning costs, etc.
are independent of size. Well-suited for offshore wind plants. In
areas where it is difficult to find sites, one large turbine on a
tall tower uses the wind extremely efficiently.
Slide 28
SMALL TURBINES: Local electrical grids may not be able to
handle the large electrical output from a large turbine, so smaller
turbines may be more suitable. High costs for foundations for large
turbines may not be economical in some areas. Landscape
considerations
Slide 29
Wind Turbines: Number of Blades Most common design is the
three-bladed turbine. The most important reason is the stability of
the turbine. A rotor with an odd number of rotor blades (and at
least three blades) can be considered to be similar to a disc when
calculating the dynamic properties of the machine. A rotor with an
even number of blades will give stability problems for a machine
with a stiff structure.
Slide 30
Wind power generators convert wind energy (mechanical energy)
to electrical energy. The generator is attached at one end to the
wind turbine, which provides the mechanical energy. At the other
end, the generator is connected to the electrical grid. The
generator needs to have a cooling system to make sure there is no
overheating.
Slide 31
*No other factor is more important to the amount of power
available in the wind than the speed of the wind The power in wind
is proportional to the cubic wind speed ( v^3 ). 20% increase in
wind speed means 73% more power Doubling wind speed means 8 times
more power WHY? ~ Kinetic energy of an air mass is proportional to
v^2 ~ Amount of air mass moving past a given point is proportional
to wind velocity (v)
Slide 32
Calculation of Wind Power Power in the wind Effect of air
density, Effect of swept area, A Effect of wind speed, V R Swept
Area: A = R 2 Area of the circle swept by the rotor (m 2 ). Power
in the Wind = AV 3
Slide 33
Environmental benefits No emissions No fuel needed Distributed
power Remote locations
Slide 34
Limitations of Wind Power Power density is very low. Needs a
very large number of wind mills to produce modest amounts of power.
Cost. Environmental costs. material and maintenance costs. Noise,
birds and appearance. Cannot meet large scale and transportation
energy needs.
Slide 35
The Future of Wind Energy Future of wind energy can be bright
if government policies subsidize and encourage its use. Technology
improvements unlikely to have a major impact. Can become cost
competitive for electricity generation if fossil energy costs
skyrocket.
Slide 36
Ocean Energy Thermal energy-OTEC(Ocean Thermal Electric
Conversion) Mechanical energy From tides From waves
Slide 37
Wave Facts: Waves are caused by a number of forces, i.e. wind,
gravitational pull from the sun and moon, changes in atmospheric
pressure, earthquakes etc. Waves created by wind are the most
common waves. Unequal heating of the Earths surface generates wind,
and wind blowing over water generates waves. Wave energy is an
irregular and oscillating low-frequency energy source that must be
converted to a 50-Hertz frequency before it can be added to the
electric utility grid. Mechanical energy-From waves
Slide 38
Three Basic Kinds of Systems Offshore (so your dealing with
swell energy not breaking waves) Near Shore (maximum wave
amplitude) Embedded devices (built into shoreline to receive
breaking wave but energy loss is occurring while the wave is
breaking)
Slide 39
3 basic systems for ocean wave energy devices 1. Channel
systems that funnel waves into reservoirs 2. Float systems that
drive hydraulic pumps 3. Oscillating water column systems that use
waves to compress air within a container mechanical power either
directly activates a generator, or transfers to a working fluid,
water or air, which then drives a turbine/generator
Slide 40
Wave Power Designs Wave Surge or Focusing Devices-Channel
System These shoreline devices, also called "tapered channel"
systems, rely on a shore-mounted structure to channel and
concentrate the waves, driving them into an elevated reservoir.
These focusing surge devices are sizable barriers that channel
large waves to increase wave height for redirection into elevated
reservoirs. Wave Surge or Focusing Devices
Slide 41
Floats or Pitching Devices Floats or Pitching Devices These
devices generate electricity from the bobbing or pitching action of
a floating object. The object can be mounted to a floating raft or
to a device fixed on the ocean floor.
Slide 42
17-42 Oscillating Water Columns (OWC) Oscillating Water Columns
(OWC) These devices generate electricity from the wave-driven rise
and fall of water in a cylindrical shaft. The rising and falling
water column drives air into and out of the top of the shaft,
powering an air-driven turbine.
Slide 43
-Advantages and Disadvantages- Advantages The energy is free no
fuel needed, no waste produced Not expensive to operate and
maintain Can produce a great deal of energy Disadvantages Depends
on the waves sometimes youll get loads of energy, sometimes almost
nothing Needs a suitable site, where waves are consistently strong
Some designs are noisy. But then again, so are waves, so any noise
is unlikely to be a problem Must be able to withstand
Slide 44
Tidal Power Tidal power generators derive their energy from
movement of the tides. Has potential for generation of very large
amounts of electricity, or can be used in smaller scale.
Slide 45
Tides The interaction of the Moon and the Earth results in the
oceans bulging out towards the Moon (Lunar Tide). The suns
gravitational field pulls as well (Solar Tide) As the Sun and Moon
are not in fixed positions in the celestial sphere, but change
position with respect to each other, their influence on the tidal
range (difference between low and high tide) is also effected. If
the Moon and the Sun are in the same plane as the Earth, the tidal
range is the superposition of the range due to the lunar and solar
tides. This results in the maximum tidal range (spring tides). If
they are at right angles to each other, lower tidal differences are
experienced resulting in neap tides.
Slide 46
How do tides changing = Electricity? As usual, the electricity
is provided by spinning turbines. Two types of tidal energy can be
extracted: kinetic energy of currents between ebbing (tide going
out) and surging tides(tide coming in) and potential energy from
the difference in height (or head) between high and low tides. The
potential energy contained in a volume of water is E = xMg where x
is the height of the tide, M is the mass of water and g is the
acceleration due to gravity.
Slide 47
1.) Tidal Barrage Two types: Single basin system Double-basin
system Utilize potential energy Tidal barrages are typically dams
built across an estuary or bay. consist of turbines, sluice gates,
embankments, and ship locks. Basin
Slide 48
Slide 49
Single basin system- Ebb generation: During flood tide basin is
filled and sluice gates are closed, trapping water. Gates are kept
closed until the tide has ebbed sufficiently and thus turbines
start spinning and generating electricity. Flood generation: The
basin is filled through the turbine which generate at flood tide.
Two way generation: Sluice gates and turbines are closed until near
the end of the flood tide when water is allowed to flow through the
turbines into the basin creating electricity. At the point where
the hydrostatic head is insufficient for power generation the
sluice gates are opened and kept open until high tide when they are
closed. When the tide outside the barrage has dropped sufficiently
water is allowed to flow out of the basin through the turbines
again creating electricity.
Slide 50
Double-basin system There are two basins, but it operates
similar to en ebb generation, single-basin system. The only
difference is a proportion of the electricity is used to pump water
into the second basin allowing storage.
Slide 51
Ocean Thermal Energy Conversion Ocean thermal energy conversion
(OTEC) is a method for generating electricity which uses the
temperature difference that exists between deep and shallow
waters
Slide 52
The ocean stores thermal energy Each day, the tropical oceans
absorb an amount of solar radiation equal to the heat content of
250 billion barrels of oil The oceans surface is warmer than deep
water -Ocean thermal energy conversion (OTEC) is based on this
gradient in temperature -Closed cycle approach = warm surface water
evaporates chemicals, which spin turbines -Open cycle approach =
warm surface water is evaporated in a vacuum and its steam turns
turbines -Costs remain high and no facility is commercially
operational 17-52
Slide 53
OTEC: What is it? Thermal energy- form of energy that manifests
itself as an increase of temp. Thermal energy- form of energy that
manifests itself as an increase of temp. Method for generating
electricity. Method for generating electricity. Runs a heat engine-
a physical device that converts thermal energy to mechanical output
Runs a heat engine- a physical device that converts thermal energy
to mechanical output Uses temp. difference that exists b/w deep
& shallow waters. Uses temp. difference that exists b/w deep
& shallow waters. Temperature difference between warm surface
water and cold deep water must be >20C (36F) for OTEC system to
produce significant power. Temperature difference between warm
surface water and cold deep water must be >20C (36F) for OTEC
system to produce significant power.
Slide 54
Ocean Thermal Energy Conversion (OTEC) Ocean Thermal Energy
Conversion produces electricity from the natural thermal gradient
of the ocean, using the heat stored in warm surface water to create
steam to drive a turbine, while pumping cold, deep water to the
surface to re- condense the steam. Ocean Thermal Energy Conversion
produces electricity from the natural thermal gradient of the
ocean, using the heat stored in warm surface water to create steam
to drive a turbine, while pumping cold, deep water to the surface
to re- condense the steam.
Slide 55
Closed Cycle OTEC In closed-cycle OTEC, warm seawater heats a
working fluid, such as ammonia, with a low boiling point, such as
ammonia, which flows through a heat exchanger (evaporator). The
ammonia vapor expands at moderate pressures turning a turbine,
which drives a generator which produces energy.
Slide 56
OTEC: Closed Cycle The vapor is then condensed in another heat
exchanger (condenser) by the cold, deep-ocean water running through
a cold water pipe. The working fluid (ammonia) is then cycled back
through the system, being continuously recycled.
Slide 57
Ocean Thermal Energy Conversion (OTEC)
Slide 58
Open Cycle OTEC In an open-cycle OTEC plant, warm seawater from
the surface is the working fluid that is pumped into a vacuum
chamber where it is flash- evaporated to produce steam at an
absolute pressure of about 2.4 kilopascals (kPa). The resulting
steam expands through a low-pressure turbine that is hooked up to a
generator to produce electricity. The steam that exits the turbine
is condensed by cold, deep-ocean water, which is returned to the
environment. If a surface condenser is used, the condensed steam
remains separated from the cold ocean water and can be collected as
a ready source of desalinated water for commercial, domestic or
agricultural use.
Slide 59
OTEC Open Cycle System In an open-cycle plant, the warm water,
after being vaporized, can be re-condensed and separated from the
cold seawater, leaving behind the salt and providing a source of
desalinated water fresh enough for municipal or agricultural use.
In an open-cycle plant, the warm water, after being vaporized, can
be re-condensed and separated from the cold seawater, leaving
behind the salt and providing a source of desalinated water fresh
enough for municipal or agricultural use.
Slide 60
OTEC Hybrid Cycle System Hybrid plants, combining benefits of
the two systems, would use closed-cycle generation combined with a
second-stage flash evaporator to desalinate water.
Slide 61
OTEC limited applications Very costly Limited suitable sites
cant justify for electricity must also desalinize, sustain
aquaculture, etc
Slide 62
Geothermal Energy
Slide 63
Sources of Earths Internal Energy 70% comes from the decay of
radioactive nuclei with long half lives that are embedded within
the Earth Some energy is from residual heat left over from Earths
formation. The rest of the energy comes from meteorite impacts.
Geothermal energy Renewable energy is generated from deep within
the Earth Radioactive decay of elements under extremely high
pressures deep inside the planet generates heat -This heat rises
through magma, fissures, and cracks Geothermal power plants use
heated water and steam for direct heating and generating
electricity
Slide 64
Different Geothermal Energy Sources 1.Hydrothermal resources:
a)Hot Water Reservoirs: As the name implies these are reservoirs of
hot underground water. There is a large amount of them in the US,
but they are more suited for space heating than for electricity
production. b)Natural Stem Reservoirs: In this case a hole dug into
the ground can cause steam to come to the surface. This type of
resource is rare in the US.
Slide 65
2.Geopressured Reservoirs: In this type of reserve, brine
completely saturated with natural gas in stored under pressure from
the weight of overlying rock. This type of resource can be used for
both heat and for natural gas. Normal Geothermal Gradient: At any
place on the planet, there is a normal temperature gradient of +30
0 C per km dug into the earth. Therefore, if one digs 20,000 feet
the temperature will be about 190 0 C above the surface
temperature. This difference will be enough to produce electricity.
However, no useful and economical technology has been developed to
extracted this large source of energy. 3.Molten Magma: No
technology exists to tap into the heat reserves stored in magma.
The best sources for this in the US are in Alaska and Hawaii.
Slide 66
4.Hot Dry Rock: This type of condition exists in 5% of the US.
It is similar to Normal Geothermal Gradient, but the gradient is 40
0 C/km dug underground. The simplest models have one injection well
and two production wells. Pressurized cold water is sent down the
injection well where the hot rocks heat the water up. Then
pressurized water of temperatures greater than 200 0 F is brought
to the surface and passed near a liquid with a lower boiling
temperature, such as an organic liquid like butane. The ensuing
steam turns the turbines. Then, the cool water is again injected to
be heated. This system does not produce any emissions. US
geothermal industries are making plans to commercialize this new
technology.
Slide 67
Geothermal energy is renewable in principle But if a geothermal
plant uses heated water faster than groundwater is recharged, the
plant will run out of water -Operators have begun injecting
municipal wastewater into the ground to replenish the supply
17-67
Slide 68
We can harness geothermal energy for heating and electricity
Geothermal ground source heat pumps (GSHPs) use thermal energy from
near-surface sources of earth and water -The pumps heat buildings
in the winter by transferring heat from the ground into buildings
-In the summer, heat is transferred through underground pipes from
the building into the ground -Highly efficient, because heat is
simply moved 17-68
Slide 69
Use of geothermal power is growing Currently, geothermal energy
provides less than 0.5% of the total energy used worldwide -It
provides more power than solar and wind combined -But much less
than hydropower and biomass Commercially viable only in British
Columbia In the right setting, geothermal power can be among the
cheapest electricity to generate 17-69
Slide 70
Geothermal power has benefits and limitations Benefits:
-Reduces emissions -It does emit very small amounts of gases
Limitations: -May not be sustainable, as CO 2 can be released
-Water is laced with salts and minerals that corrode equipment and
pollute the air -Limited to areas where the energy can be trapped
17-70
Slide 71
Biomass Biomass is a renewable energy source that is derived
from living or recently living organisms. Biomass includes
biological material, not organic material like coal. Energy derived
from biomass is mostly used to generate electricity or to produce
heat. Thermal energy is extracted by means of combustion,
torrefaction, pyrolysis, and gasification. Biomass can be
chemically and biochemically treated to convert it to a energy-rich
fuel.
Slide 72
72 Biomass Resources Energy Crops Woody crops Agricultural
crops Waste Products Wood residues Temperate crop wastes Tropical
crop wastes Animal wastes Municipal Solid Waste (MSW) Commercial
and industrial wastes
http://www.eere.energy.gov/RE/bio_resources.html
Slide 73
Slide 74
Conversion Technologies A wide variety of technologies is
deployed for energy production from biomass Production of heat,
electricity and transport fuels is possible through a portfolio of
technologies
Slide 75
Conversion technologies: power and heat Digestion : Biogas is
released with the digestion of organic material Combustion: Because
heat releases with the combustion of biomass, electricity can be
aroused using a steam turbine Gasification: high heating of organic
material, releases biogas Production of bio-oils
Slide 76
Conversion technologies: biofuels for the transport Sector
Extraction and production of esters from oilseeds Fermentation:
production of ethanol Methanol, hydrogen and hydrocarbons via
Gasification
BIOMASS AND CARBON EMMISIONS Biomass emits carbon dioxide when
it naturally decays and when it is used as an energy source Living
biomass in plants and trees absorbs carbon dioxide from the
atmosphere through photosynthesis Biomass causes a closed cycle
with no net emissions of greenhouse gases
Slide 79
GEOGRAPHIC AREAS Comes from the forest Can also come from plant
and animal waste Wood and waste can be found virtually anywhere
Transportation costs
Slide 80
Introduction: What is Biodiesel? A diesel fuel replacement
produced from vegetable oils or animal fats through the chemical
process of transesterification Mono-alkyl esters Biodiesel can be
used in any diesel motor in any percent from 0-100% with little or
no modifications to the engine
Slide 81
Why make biodiesel? Diesel fuel injectors are not designed for
viscous fuels like vegetable oil Glycerin (thick) Biodiesel
Slide 82
The Chemistry of Biodiesel All fats and oils consist of
triglycerides Glycerol/glycerine = alcohol 3 fatty acid chains (FA)
Transesterification describes the reaction where glycerol is
replaced with a lighter and less viscous alcohol e.g. Methanol or
ethanol A catalyst (KOH or NaOH) is needed to break the glycerol-FA
bonds
Slide 83
Transesterification (the biodiesel reaction) Fatty Acid Chain
Glycerol Methanol (or Ethanol) One triglyceride molecule is
converted into three mono alkyl ester (biodiesel) molecules
Biodiesel Triglyceride
Slide 84
Vegetable Oil as Feedstocks Oil-seed crops are the focus for
biodiesel production expansion Currently higher market values for
competing uses constrain utilization of crops for biodiesel
production Most oil-seed crops produce both a marketable oil and
meal Seeds must be crushed to extract oil The meal often has higher
market value than the oil
Slide 85
Soybeans Primary source for biodiesel production in U.S.
Approximately 2 billion gallons of oil produced annually
Canola/Rapeseed Rapeseed is a member of the mustard family Canola
is a variety of rapeseed bred to have low levels of erucic acid and
glucosinolates (both of which are undesireable for human
consumption) Good oil yield
Slide 86
Sunflowers Wide geographical range for production Market value
is high for edible oil and seeds, birdseeds Second largest
biodiesel feedstock in the EU Camelina Camelina sativa is a member
of mustard family Summer annual crop suited to grow in semi-arid
climates and northern U.S.
Slide 87
Advantages of Biodiesel Biodegradable Non-toxic Favorable
Emissions Profile Renewable Carbon Neutrality Requires no engine
modifications (except replacing some fuel lines on older engines).
Can be blended in any proportion with petroleum diesel fuel. Can be
made from waste restaurant oils and animal fats
Slide 88
Disadvantages of biodiesel Lower Energy Content 8% fewer BTUs
per gallon, but also higher cetane #, lubricity, etc. Poor cold
weather performance This can be mitigated by blending with diesel
fuel or with additives, or using low gel point feedstocks such as
rapeseed/canola. Stability Concerns Biodiesel is less oxidatively
stable than petroleum diesel fuel. Old fuel can become acidic and
form sediments and varnish. Additives can prevent this. Scalability
Current feedstock technology limits large scalability
Slide 89
Fuel Cells
Slide 90
PEM Fuel Cell
Slide 91
Parts of a Fuel Cell Anode Negative post of the fuel cell.
Conducts the electrons that are freed from the hydrogen molecules
so that they can be used in an external circuit. Etched channels
disperse hydrogen gas over the surface of catalyst. Cathode
Positive post of the fuel cell Etched channels distribute oxygen to
the surface of the catalyst. Conducts electrons back from the
external circuit to the catalyst Recombine with the hydrogen ions
and oxygen to form water. Electrolyte Proton exchange membrane.
Specially treated material, only conducts positively charged ions.
Membrane blocks electrons. Catalyst Special material that
facilitates reaction of oxygen and hydrogen Usually platinum powder
very thinly coated onto carbon paper or cloth. Rough & porous
maximizes surface area exposed to hydrogen or oxygen The
platinum-coated side of the catalyst faces the PEM.
Slide 92
Fuel Cell Operation Pressurized hydrogen gas (H 2 ) enters cell
on anode side. Gas is forced through catalyst by pressure. When H 2
molecule comes contacts platinum catalyst, it splits into two H+
ions and two electrons (e-). Electrons are conducted through the
anode Make their way through the external circuit (doing useful
work such as turning a motor) and return to the cathode side of the
fuel cell. On the cathode side, oxygen gas (O 2 ) is forced through
the catalyst Forms two oxygen atoms, each with a strong negative
charge. Negative charge attracts the two H+ ions through the
membrane, Combine with an oxygen atom and two electrons from the
external circuit to form a water molecule (H 2 O).
Fuel Cell Energy Exchange
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/electrol.html
Slide 95
PEM Fuel Cell Schematic
Slide 96
Hydrogen Fuel Cell Efficiency 40% efficiency converting
methanol to hydrogen in reformer 80% of hydrogen energy content
converted to electrical energy 80% efficiency for inverter/motor
Converts electrical to mechanical energy Overall efficiency of
24-32%
Slide 97
Auto Power Efficiency Comparison Technology System Efficiency
Fuel Cell24-32% Electric Battery26% Gasoline Engine20%
http://www.howstuffworks.com/fuel-cell.htm/printable
Slide 98
Other Types of Fuel Cells Alkaline fuel cell (AFC) This is one
of the oldest designs. It has been used in the U.S. space program
since the 1960s. The AFC is very susceptible to contamination, so
it requires pure hydrogen and oxygen. It is also very expensive, so
this type of fuel cell is unlikely to be commercialized.space
Phosphoric-acid fuel cell (PAFC) The phosphoric-acid fuel cell has
potential for use in small stationary power- generation systems. It
operates at a higher temperature than PEM fuel cells, so it has a
longer warm-up time. This makes it unsuitable for use in cars.
Solid oxide fuel cell (SOFC) These fuel cells are best suited for
large-scale stationary power generators that could provide
electricity for factories or towns. This type of fuel cell operates
at very high temperatures (around 1,832 F, 1,000 C). This high
temperature makes reliability a problem, but it also has an
advantage: The steam produced by the fuel cell can be channeled
into turbines to generate more electricity. This improves the
overall efficiency of the system. Molten carbonate fuel cell (MCFC)
These fuel cells are also best suited for large stationary power
generators. They operate at 1,112 F (600 C), so they also generate
steam that can be used to generate more power. They have a lower
operating temperature than the SOFC, which means they don't need
such exotic materials. This makes the design a little less
expensive.
http://www.howstuffworks.com/fuel-cell.htm/printable
Slide 99
Advantages/Disadvantages of Fuel Cells Advantages Water is the
only discharge (pure H 2 ) Disadvantages CO 2 discharged with
methanol reform Little more efficient than alternatives Technology
currently expensive Many design issues still in progress Hydrogen
often created using dirty energy (e.g., coal) Pure hydrogen is
difficult to handle Refilling stations, storage tanks,
Slide 100
What is a Gas Hydrate? A gas hydrate is a crystalline solid;
its building blocks consist of a gas molecule surrounded by a cage
of water molecules. It is similar to ice, except that the
crystalline structure is stabilized by the guest gas molecule
within the cage of water molecules. Suitable gases are: carbon
dioxide, hydrogen sulfide, and several low-carbon-number
hydrocarbons. Most gas hydrates, however are Methane Hydrates.
Slide 101
What are Methane Hydrates? Methane Hydrates are one example of
clathrates Clathrates are compounds which consist of a cage
structure, in which a gas molecule is trapped inside a cage of
water molecules Methane (CH 4 ) is trapped in Water (H 2 O) forming
an ICE
Slide 102
1 m 3 of hydrate -> ~170 m 3 methane gas (STP) Grey=carbon
Green=hydrogen in CH 4 Red = oxygen White= hydrogen in H 2 O
Slide 103
Hydrate Samples Gas hydrates in sea-floor mounds Here methane
gas is actively dissociating from a hydrate mound. Gas hydrate can
occur as nodules, laminae, or veins within sediment.
Slide 104
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Slide 106
Gas Hydrate on the Sea floor Beasties!
Slide 107
Origin of natural methane Bacterial degradation of organic
matter in low-oxygen environments within sediments Thermal
degradation of organic matter, dominantly in petroleum (e.g., Gulf
of Mexico)
Slide 108
Where do clathrates occur? How much clathrate is there? Methane
and water must be available (organic matter: produced by biota; in
oceans: close to continents) Clathrate must be stable (ice): cold
and/or high pressure High latitudes (permafrost) In medium deep sea
sediments (300-2000 m)
Slide 109
How much hydrate is there? Estimates vary widely: globally
600,000 to 2,000,000 Tcf (trillion cubic feet) 1 Tcf ~ 1
quadrillion Btu (quad) World energy use (2000): about 375-400 Quad
= 500 Tcf hydrate gas per year US gas hydrates: estimated at about
100,000 to 600,000 Tcf Gas hydrates abundant in oil-poor countries
(Japan, India)
Slide 110
Slide 111
Why are CH 4 Hydrates a good energy resource The gas is held in
a crystal structure, therefore gas molecules are more densely
packed than in conventional or other unconventional gas traps.
Hydrate forms as cement in the pore spaces of sediment and has the
capacity to fill sediment pore space and reduce permeability. CH 4
- hydrate-cemented strata thereby act as seals for trapped free gas
Production of gas from hydrate-sealed traps may be an easy way to
extract hydrate gas because the reduction of pressure caused by
production can initiate a breakdown of hydrates and a recharging of
the trap with gas
Slide 112
A Proposed Method For the gas production from hydrates and the
seabed stability after the production, we proposed a new concept.
The figure illustrates the molecular mining method by means of CO2
injection in order to extract CH4 from gas hydrate reservoirs. The
concept is composed of three steps as follows; 1) injection of hot
sea water into the hydrate layer to dissociate the hydrates, 2)
produce gas from the hydrate, 3) inject CO2 to form carbon dioxide
hydrate with residual water to hold the sea bed stable
Slide 113
CH 4 Hydrates and Climate Change Methane is a very effective
greenhouse gas. It is ten times more potent than carbon dioxide.
There is increasing evidence that points to the periodic massive
release of methane into the atmosphere over geological timescales.
Are these enormous releases of methane a cause or an effect of
global climate change?
Slide 114
Global warming may cause hydrate destabilization through a rise
in ocean bottom water temperatures. The increased methane content
in the atmosphere in turn would be expected to accelerate warming,
causing further dissociation, potentially resulting in run away
global warming. Sea level rise, however, during warm periods may
act to stabilize hydrates by increasing hydrostatic pressure,
thereby acting as a check on warming. Hydrate dissociation may act
as a check on glaciations, whereby reduced sea levels may cause
seafloor hydrate dissociation, releasing methane and warming the
climate.
Slide 115
CH 4 Hydrates and the Atmosphere An important aspect of methane
hydrates and their affect on climate change is their potential to
enter the atmosphere Methane concentration in seawater is observed
to decrease by 98% between a depth of 300m and the sea surface as a
result of microbial oxidation. The flux of methane into the
atmosphere is thus lowered 50-fold (Mienert et al., 1998) However
during catastrophic events such as largescale sediment slumping
much higher proportions of methane would be released.
Slide 116
The Future of Methane Hydrates Worldwide gas production in the
next 30-50 years Areas with unique economic and/or political
motivations could see substantial production within 5-10 years We
need to better understand the mechanisms of hydrate disassociation
and its role in global warming, either as an accelerator or and
inhibitor
Slide 117
Slide 118
Carbon Dioxide Emission: 24 billion tons per year
Slide 119
CARBON CAPTURE AND STORAGE Carbon capture and storage is mostly
used to describe methods for removing CO 2 emissions from large
stationary sources, such as electricity generation and some
industrial processes, and storing it away from the atmosphere.
Slide 120
Slide 121
Carbon Capture Technology Post- combustion capture React the
flue gas with chemicals that absorb CO 2 and then heat the
chemicals to release CO 2. NOTE: Flue gas : Mixture of nitrogen,
water vapor and 15 % of Carbon dioxide.
Slide 122
Carbon Capture Technology Pre- combustion capture Remove carbon
before combustion. By gasifying the coal through the reaction with
more oxygen, it is possible to a mix of mostly CO 2 and
hydrogen.
Slide 123
Carbon Capture Technology Oxy-fuel combustion Use pure oxygen
to support the fossil fuel combustion. The flue gas is then mostly
CO 2 and water making it to separate easily.
Slide 124
Transportation Many point sources of captured CO 2 would not be
close to geological or oceanic storage facilities. In these cases,
transportation would be required. The main form of transportation
pipeline. Shipping
Slide 125
CO2 storage Various forms have been conceived for permanent
storage of CO2. These forms include gaseous storage in various deep
geological formations (including saline formations and exhausted
gas fields), liquid storage in the ocean, and solid storage by
reaction of CO2 with metal oxides to produce stable
carbonatesoxidescarbonates
Oceanic Storage Two storage mechanism has been proposed
Dissolving CO 2 at mid-depth. Injecting the CO 2 at depths in
excess of 3 km, where it would form lakes of liquid CO 2. Bellow 3
km liquid CO 2 would be denser than sea water and would sink to the
ocean floor.
Slide 129
Carbon Storage Concerns CCS technologies actually require a lot
of energy to implement and run transporting captured CO 2 by truck
or ship, require fuel. Creating a CCS-enabled power plant also
requires a lot of money. What happens if the carbon dioxide leaks
out underground? We can't really answer this question. Because the
process is so new, we don't know its long-term effects. Slow
leakage would lead to climate changing. Sudden catastrophic leakage
is dangerous, and causes asphyxiation. The more CO 2 an ocean
surface absorbs, the more acidic it becomes, higher water acidity
adversely affects marine life.
Slide 130
What might Carbon Capture and Storage look like? The diagram is
from a BP news release from the abandoned Miller project, UK North
Sea, which is no longer available online.
Slide 131
FutureGen FutureGen is a public-private partnership to build a
first-of-its-kind coal- fueled, near-zero emissions power plant. It
will use cutting-edge technologies to generate electricity while
capturing and permanently storing carbon dioxide deep beneath the
earth. The plant will also produce hydrogen and byproducts for
possible use by other
Slide 132
132 the "forever fuel" that we can never run out of HYDROGEN
Water + energy hydrogen + oxygen Hydrogen + oxygen water +
energy
Slide 133
133 Hydrogen is ~75% of the known universe Hydrogen is ~75% of
the known universe On earth, its not an energy source like oil or
coal Only an energy carrier like electricity or gasoline Only an
energy carrier like electricity or gasoline a form of energy,
derived from a source, that can be a form of energy, derived from a
source, that can be moved around moved around The most versatile
energy carrier - Can be made from any source and used for any - Can
be made from any source and used for any service service - Readily
stored in large amounts - Readily stored in large amounts Why is
hydrogen so important?
Slide 134
Sources of Hydrogen Sources that Hydrogen can be extracted
from: Natural Gas, Water, Coal, Gasoline, Methanol, Biomass Other
sources being researched include the uses of solar energy,
photosynthesis, decomposition, and fuel cells themselves can
tri-generate electricity, heat, and hydrogen.
Slide 135
135 Is it safe?: A primer on Hydrogen safety All fuels are
hazardous, but All fuels are hazardous, but Hydrogen is comparably
or less so, but Hydrogen is comparably or less so, but different:
different: Clear flame cant sear you at a distance; no smoke smoke
Hard to make explode; cant explode in free air; burns first air;
burns first 22 less explosive power Rises, doesnt puddle Hindenburg
myth (1937) nobody was killed Hindenburg myth (1937) nobody was
killed by hydrogen fire by hydrogen fire Completely unrelated to
hydrogen bombs
Slide 136
136 Where Does Hydrogen Come From? 95% of hydrogen is currently
produced by steam reforming Partial Oxidation Steam Reforming
Electrolysis Thermochemical Fossil Fuels Water Biomass currently
most energy efficient requires improvements not cost effective
requires high temperatures Gasification Microbial
requiresimprovements slowkinetics
Slide 137
Hydrogen carries energy Most of the energy we use today94%
comes from fossil fuels Fossil fuels are oil, coal, and natural gas
and have developed over thousands of years from decomposing
prehistoric plants and animalssince these plants and animals no
longer exist, making new fossil fuels cannot happen. Only 6% of the
energy we use comes from renewable energy sources But people want
to use more renewable energy. It is usually cleaner and can be
replenished in a short period of time compared to fossil fuels. The
problem is that renewable energy sourceslike solar and windcant
produce energy all the time The sun doesnt always shine. The wind
doesnt always blow. Sometimes the sun and wind provide more energy
than we need at that moment. Hydrogen can store and carry the
energy until its needed and can be moved to where its needed.
Slide 138
Why are Energy Carriers good? Every day, we use more energy,
mostly coal, to make electricity. Electricity is an energy carrier.
Energy carriers can store, move, and deliver energy to consumers.
We convert energy source like coal and natural gas to electricity
because it is easier for us to move and use. Electricity gives us
light, heat, hot water, cold food, TVs, and computers. Life would
be really hard if we had to burn the coal, split the atoms, or
build our own dams. Energy carriers make life easier. Hydrogen is
an energy carrier like electricity. It can be used in places where
its hard to use electricity. Electricity requires wires and poles,
like you see along the highway and in your neighborhood, to be
delivered to a home. Hydrogen can be shipped by a pipeline or
produced at the home directly.
Slide 139
How does Hydrogen turn into useable Electricity? Hydrogen
cannot directly make the lights turn on, the water run, or the heat
work. It must be converted into electricity. This happens in a fuel
cell. This is a real live fuel cell The only waste product is
water
Slide 140
Uses for Hydrogen Energy NASA uses hydrogen as an energy
carrier; it has used hydrogen for years in the space program.
Hydrogen fuel lifts the space shuttle into orbit. Hydrogen fuel
cells power the shuttles electrical systems. The only by-product is
pure water, which the crew uses as drinking water. Hydrogen fuel
cells are very efficient, but expensive to build. Small fuel cells
can power electric cars. An engine that burns pure hydrogen
produces almost no pollution. It will probably be many years,
though, before you can walk into a car dealer and drive away in a
hydrogen-powered car.
Slide 141
141 HYDROGEN IN TRANSPORTATION
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142
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Options for Storing Hydrogen Today
Slide 144
HYDROGEN STORAGE OPTIONS HYBRID TANKS LIQUID HYDROGEN
COMPRESSED GAS PHYSICAL STORAGE Molecular H 2 REVERSIBLE
Slide 145
Compressed Storage Prototype vehicle tanks developed Efficient
high-volume manufacturing processes needed Less expensive materials
desired carbon fiber binder Evaluation of engineering factors
related to safety required understanding of failure processes
Slide 146
Liquid Storage Prototype vehicle tanks developed Reduced mass
and especially volume needed Reduced cost and development of
high-volume production processes needed Extend dormancy (time to
start of boil off loss) without increasing cost, mass, volume
Improve energy efficiency of liquefaction
Slide 147
Hybrid Physical Storage Compressed H 2 @ cryogenic temperatures
H 2 density increases at lower temperatures further density
increase possible through use of adsorbents opportunity for new
materials The best of both worlds, or the worst ?? Concepts under
development
Slide 148
HYDROGEN STORAGE OPTIONS REVERSIBLE HYBRID TANKS LIQUID
HYDROGEN COMPRESSED GAS PHYSICAL STORAGE Molecular H 2 REVERSIBLE
CHEMICAL STORAGE Dissociative H 2 2 H COMPLEX METAL HYDRIDES
CONVENTIONAL METAL HYDRIDES LIGHT ELEMENT SYSTEMS NON-REVERSIBLE
REFORMED FUEL DECOMPOSED FUEL HYDROLYZED FUEL
Slide 149
Non-reversible On-board Storage On-board reforming of fuels has
been rejected as a source of hydrogen because of packaging and cost
energy station reforming to provide compressed hydrogen is still a
viable option Hydrolysis hydrides suffer from high heat rejection
on- board and large energy requirements for recycle On-board
decomposition of specialty fuels is a real option need desirable
recycle process engineering for minimum cost and ease of use
Slide 150
Reversible On-board Storage Reversible, solid state, on-board
storage is the ultimate goal for automotive applications Accurate,
fast computational techniques needed to scan new formulations and
new classes of hydrides Thermodynamics of hydride systems can be
tuned to improve system performance storage capacity temperature of
hydrogen release kinetics/speed of hydrogen refueling Catalysts and
additives may also improve storage characteristics
Slide 151
The Future of Hydrogen Before hydrogen becomes a significant
fuel energy picture, many new systems must be built. We will need
systems to make hydrogen, store it, and move it. We will need
pipelines and economical fuel cells. And consumers will need the
technology and the education to use it.