S4-S6 Flashcards
1
Q
Renewable energy vs Nonrenewable energy
A
Renewable:
- energy that will not run out and
whose capture and use do not
result in the direct emission of
greenhouse gases or other
pollutants.
- energy derived from natural
sources that are replenished at a
higher rate than they are
consumed.
Nonrenewable:
- energy sources that exist in
finite quantities and cannot
be naturally replenished or
regenerated.
- a natural resource that
cannot be readily replaced
by natural means at a pace
quick enough to keep up
with consumption.
2
Q
Renewable Energy towards Sustainable Development
A
- Reduces greenhouse gas emissions (between 90 and 99% less greenhouse gases (GHGs) and produces 70 to 90% less pollutants.)
- Improves energy security
- Provides access to energy to communities
- Create jobs and stimulate economic growth
3
Q
Types of Energy Sources
A
- HYDROELECTRIC POWER
- WIND ENERGY
- BIOMASS ENERGY
- MARINE
ENERGY - SOLAR
ENERGY - GEOTHERMAL
ENERGY
4
Q
Hydroelectric Power
A
Of all the forms of renewable energy,
hydroelectric power is by far the most
important, with a capacity of about
1000GW.
Consists over 80% of renewable energy,
16% of global electric capacity, and 3% of
global commercial energy.
Although availability depends upon
seasonal rainfall patterns, it is still a more
reliable resource than solar or wind energy.
5
Q
Why is hydroelectric power an
indirect form of
solar energy
A
The Sun’s energy evaporates water from
bodies of water and transports the H₂O
molecules upward in the atmosphere.
Even after condensing to raindrops, they still
possess considerable potential energy from
their elevation.
This potential energy is harnessed by forcing
the downward-flowing water to turn turbines
and generate electricity.
6
Q
power yield of hydroelectric power
A
Most large-scale facilities use dams and
waterfalls where the water pressure - and
hence the power yield - is much greater.
In particular, the energy imparted to a turbine
is directly proportional not only to the volume
of the water but also to the height from which
it falls.
7
Q
why is hydroelectric power far from perfect
A
The construction cost of hydroelectric power
ranges from 1 to 5 million dollars per
megawatt capacity, depending on the size
and site of operation.
Changes in rainfall patterns, as well as the
melting of glaciers, resulting from climate
change could reduce the future capacity of
hydropower in some regions.
8
Q
environmental problems of hydroelectric power
A
- Displacement of
human
populations - Eutrophication
of water in
reservoirs - Release of
greenhouse
gases - Release of mercury
- Devastation to
fish populations - Buildup of silt
behind dams
9
Q
World’s largest hydropower dam
A
Three Gorges Dam - 2335 m long, 181 m high
10
Q
Wind energy
A
Winds are air flows that result from the
tendency of air masses that have
undergone different amounts of heating,
and that therefore have developed
unequal pressures, to equalize those
pressures.
Air flows from regions of high pressure to
those of low pressure. The heating of air
results directly or indirectly from the
absorption of sunlight.
About 1-2% of the Sun’s energy received on
the Earth is converted to wind energy.
11
Q
wind flow
A
Wind flows to reduce the temperature difference.
Polar areas receive less sunlight than do the
tropics. To reduce the resulting temperature
difference between tropical and polar regions
winds arise in the air as do currents in the
oceans. Warm air and water are carried
towards the poles, whereas cold air and water
are transported to the Equator.
12
Q
how can wind be exploited to make electricity
A
Wind energy systems operate the same way
as flowing water is used in hydroelectric
power plants.
The basic components of any wind energy
system are similar. Blades are connected to a
drive shaft, then a pump or generator that
collects the energy. If the wind energy is used
directly as a mechanical force to pump water
its called a windmill. If it converts wind energy
to electricity, its known as a wind turbine
13
Q
Wind power capacity
A
The global wind-power capacity in 2010 was
almost 200 GW, about 2.5% of worldwide
electricity capacity. As of 2010, China and the
United States had the greatest amounts of
installed capacity, with Germany, Spain,
and India following them in that order.
14
Q
The world electricity output
could be produced
from wind
A
A landmass the size of China would be
needed to satisfy world electricity demand
from wind alone.
However, the United States has the highest
potential for wind power if price were not
taken into account. About 90% of the U.S.
potential lies in the twelve states in the
Midwest, from North Dakota to Northern
Texas.
15
Q
why size and speed
matters in wind energy
A
The greater the velocity of the wind, the
greater the amount of energy a windmill can
produce. The energy yield from yield is
proportional to v³.
16
Q
The cubic dependence of energy on wind speed is the result of two factors
A
First, the kinetic energy of the motion of the
air mass in the direction of the wind is
proportional to the square of the air speed
since for any moving body, its kinetic energy
is (mv^2)/2.
Second, the amount of wind passing over the
blades per unit time increases linearly in
direct proportion to the wind speed.
17
Q
Wind energy sites need to be picked on potential derived power.
A
Geographical areas are classified into seven
classes of wind-power density, with class 7
having the highest potential. Ideal locations
are those having almost constant flow of
nonturbulent winds in all seasons. So
locations at less than 2km altitude with wind
speeds of at least 5 m/s or 18 kph are required
for a location to be economically feasible.
18
Q
Earth’s Most Eligible Bachelorettes for wind energy
A
The regions of high wind-power potential at
reasonable cost are the United States
Canada, South America, OECD Europe, and
the former U.S.S.R. Areas with lowest potential
are Africa, Eastern Europe, and Southeast
Asia. Within a given country, the best
locations are usually mountain passes, high-
altitude plains, and coastal areas. In general
wind speed increases somewhat with
altitude.
19
Q
Environmetal Issues of wind energy
A
- Energy payback,
while existent, is
the least for any
electric power source - Perceived visual
unsightliness - Construction of
windmills at remote sites
requires destructive infrastructure
20
Q
Biomass: energy from plants and animals
A
It was the world’s first energy source
and is still widely used in less-developed
countries but is phased out in favor of
fossil fuels and electricity.
The biomass produced by the worldwide
operation of photosynthesis constitutes a
form of solar energy.
Annual amount of energy generated is
about 55 EJ but the power density of
photosynthesis is too low to be used to
supply the majority of the world’s needs.
21
Q
low conversion rate of biomass
A
The efficiency of conversion of sunlight to
chemical energy by photosynthesis is very low,
no more than 1–2% even in the most productive
areas. At today’s consumption levels, the
amount of land required to supply the world’s
energy needs entirely by biomass equals that of
all agricultural land currently developed, which
constitutes more than 10% of Earth’s land
surface.
22
Q
Biomass sources
A
- Wood and wood processing waste -
firewood, wood pellets, lumber and
furniture sawdust and waste - Agricultural crops and waste materials
- corn, soybeans, sugarcane, and food
processing residues - Biogenic materials in solid waste -
paper products, cotton and wool
products, food wastes - Animal manure and human sewage
23
Q
How biomass works
A
1.Heat is created by burning coal, oil, natural gas, biomass trash
2. to boil water to make steam.
3. Steam turns the blades of huge turbines
4. which spin generators to create electricity.
5. A transformer increases the voltage to send electricity over
6. distribution lines. Then local transformers reduce the voltage..
7. for you to use.
24
Q
Pyrolytic Production: Bio-oil
A
The least sophisticated thermochemical
process for biomass utilization is pyrolysis. The
dried cellulosic biomass is heated at ambient
pressure in the absence of air to 300–600ᵒC. The
biomass substances decompose and rearrange
their atoms to form other compounds. The final
products of the process are a solid (charcoal),
noncondensable gases (methane, hydrogen
CO, CO₂) and bio-oil.
25
Bio-oil: What good
does it bring?
Although considered a biofuel, it has a fairly low
energy content since the original potential of
the biomass is split up between the solid
charcoal phase, the gases, and the liquid. Bio-
oil is not miscible with gasoline or diesel fuel.
Although it will combust and can be used as
heating oil, it is not suitable as a vehicular fuel
due to its corrosiveness, as well as its poor
energy content. It also slowly deteriorates over
time with exposure to air.
26
Synthesis Gas
The most widely used thermochemical method
is gasification. Here, the carbon-containing
material is subject to such high heat (700–
1000ᵒC) that it decomposes into the very stable
gases molecular hydrogen, and CO, along with
some residual tar which is cleaned out of the
reactor. The decomposed material usually is a
fossil fuel but it can also be biomass—e.g., low-
grade wood or crop wastes.
27
Syngas reaction
The gas mixture of H2 and CO is called synthesis gas, since it can be used as the versatile reactant from which many different organic compounds
can be created. Alternatively, it can be used as a gaseous fuel.
28
SynGas in the Fischer-Tropsch Synthesis
H2 + 2 CO -> CH2 + CO2
When used to create organic compounds, the synthesis gas is reacted under high pressure and temperature and in the presence of the specific catalyst
that will hold the molecules in the correct positions such that the desired
product is obtained. The hydrogen-to-carbon monoxide ratio in the synthesis
gas must correspond to that in the product for efficient reaction to occur. One important such reaction was used to produce synthetic gasoline.
29
Marine Energy
A renewable power source that is
harnessed from the natural movement
of water, including waves, tides, and
ocean currents.
Wave power and tidal power, sometimes
collectively known as marine energy.
It is estimated that about 20 EJ of power is
potentially recoverable annually from
waves and tides.
30
Tidal Wave
The source of the energy of tides is the
gravitational influence of the Sun and the Moon
on the water mass. Shallow seas surrounding
the ocean perimeters are the best locations for
tidal power.
Tides cause large masses of water to be lifted
and then lowered twice a day.
31
Wave Power
Wave power is generated by using the up-and-
down motion of water that results from waves,
which are caused by winds and thus are an indirect
form of solar energy.
The machines based upon an oscillating water
column consist of a chamber located just above the
water surface that contains trapped air.
32
Geothermal Energy
Geothermal energy is heat that
emanates from beneath the Earth’s
surface and results from the radioactive
decay of elements and from conduction
from the molten core of the Earth.
Though not solar-based, geothermal
energy is still another form of renewable
energy.
Useful in countries that have no fossil fuel
resources, and currently accounts for
slightly less than 0.1% of the world’s energy
supply.
33
Production of Geothermal Energy
1. dry steam power plant - Hot steam from underground is piped directly into turbines, which powers the generator.
2. flash steam power plant - Hot water from underground is pumped into a cooler temperature flash tank. The sudden change in temperature creates steam which powers the generator.
34
Geothermal Energy advantage
Geothermal energy's availability is 100% of the
time at a uniform rate. It can be used as
baseload power and need not be stored.
35
Environmetal Problems of geothermal energy
1. Large quantity
of hydrogen
sulfide gas are
released
2. Corrosion of
equipments
3. Water pollution
36
Direct Solar
Energy
The direct absorption of energy from
sunlight, and its subsequent conversion
to useful forms of energy such as
electricity.
Can occur by two mechanisms: Thermal
conversion and Photoconversion.
37
Types of Solar Energy
Low-Temperature Solar Energy
- An example of passive solar thermal
technology, in which the
systems do not use continuous additional
energy source to operate them.
Concentrated Solar Thermal Power
- Use mirrors to reflect and
concentrate sunlight
onto a receiver.
- The energy from the
concentrated sunlight heats
a high temperature fluid in the receiver.
Solar (PV) Cells
- Electricity can be produced
directly from solar energy
by the photoconversion mechanism.
Dye-Sensitized Solar Cells
- Is a solar photovoltaic that converts
sunlight into electrical
energy using a sensitizer
molecule (usually some dye
molecules).
38
Example of Concentrated Solar
Thermal Power
Solar Tower or Power Tower
- Consist of a tall tower topped with
a receiver onto which sunlight
from hundreds of sun-tracking
flat mirrors (“heliostats”) on the
ground are focused. The
substance in the receiver is
heated to a very high
temperature, and its thermal
energy is continuously removed
for use in an electric power plant.
Advantages of Solar Tower
- High heat capacity
- Wide temperature range
- Stability to decomposition
- Convenient and economical
supply source
Mixture of nitrate salts of sodium
and potassium. The lowest-melting point combination is called the
eutectic, with a composition of 46mol % NaNO3, (60% by mass) and
54% KNO3.
The liquid range of eutectic
mixture extends over more than
300 degrees.
Up to 18% of the sunlight
energy is converted to
electricity in tower systems.
By using large storage tanks,
excess hot liquid salt can be
stored during the day and
extracted at night when the
sun is not shining.
Storing heat is more efficient
and less expensive in general
than storing the equivalent
amount of energy as
electricity.
39
Thermochemical Application of Concentrated Solar Thermal Power
Another way to use the very-high-temperature
concentrated solar heat is to drive an endothermic
thermochemical process in order to produce a fuel such
as hydrogen.
Example: metal oxide to oxygen gas
40
Disadvantages of Solar Cells
1. It is direct
current (dc)
rather than
alternating
current (ac)
2. Costly
3. Cannot collect
energy during night time and
cloudy days
41
Advantages of Solar Cells
1. The availability in sunny
locations
2. Much cheaper
than extending
power grid lines
3. Can be installed
in piecemeal
rather as one
large project
42
Renewable
Energy
sources of clean, inexhaustible, and increasingly competitive energy.
they differ from fossil fuels principally in their
diversity, abundance, and potential for use anywhere on the planet.
produce neither greenhouse gases nor
polluting emissions.
43
WHAT ARE LITHIUM-ION BATTERIES?
most widely used power sources in the world
and are used to power smartphones, notebooks,
tablets, and many other devices that require a
reliable battery.
rechargeable energy storage devices that use
lithium as a core component in their chemistry.
have high energy density, making them
suitable for a wide range of applications,
including renewable energy storage.
44
Basics of Lithium-ion Battery
A battery is made up of an anode, cathode,
separator, electrolyte, and two current collectors
(positive and negative).
The anode and cathode store the lithium. The
electrolyte carries positively charged lithium ions
from the anode to the cathode and vice versa
through the separator.
The movement of the lithium ions creates free
electrons in the anode which creates a charge at
the positive current collector. The electrical
current then flows from the current collector
through a device being powered (cell phone,
computer, etc.) to the negative current collector.
The separator blocks the flow of electrons inside the
battery.
45
The Importance of Renewable Energy Conversion and
Storage
- Renewable energy sources like solar and
wind are intermittent, producing energy
inconsistently.
- Lithium-ion batteries help bridge the gap
by storing excess energy when it's available
and delivering it when needed.
46
Role of Li-ion battery in Solar Energy
Solar panels generate
electricity during the day,
but not at night or on
cloudy days.
Lithium-ion batteries store
surplus daytime energy for
use during nighttime or
low-production periods.
This enables homeowners
and businesses to rely more
on solar power.
47
Role of Li-ion battery in Wind Energy
Wind turbines produce
electricity when the wind
blows, which may not
coincide with peak demand
times.
Li-ion batteries store surplus
wind energy for use during
calm periods, ensuring a
steady power supply
48
Role of Li-ion battery in electricity generation
One of the well-known shortcomings
of solar and wind-power energy sources is their large variability in power
generation.
Batteries are used to store surplus power
when generation is
abundant for use or
to distribute power
when there is a
deficit.
The large capacity of batteries
to store energy can reduce the
maximum capacity needed by
power plants (and associated
construction costs), which are
designed to meet the
estimated peak demand during, say, a hot summer day
when the use of air
conditioners is above normal.
49
The importance of batteries in the
transportation
sector
As the battery energy density has soared and
prices have dropped, the Li-ion battery has
become the major source for the
electrification of various sizes of vehicles
such as bicycles, scooters, cars, buses,
trucks, and even ferries. Shipping and aviation
are also making electrification progress, though
at the very infant stage. Battery technology has
the potential for further becoming a great
enabler for sustainable transport.
50
Environmental Considerations of Li-ion batteries
While Li-ion batteries offer numerous
benefits, their production and
disposal can have environmental
impacts.
Recycling and sustainable sourcing of
materials are being addressed to
minimize these concerns.
51
FUEL CELLS
a clean, efficient, reliable, and quiet
source of power.
do not need to be periodically
recharged like batteries, but instead
continue to produce electricity as long as
a fuel source is provided.
52
Basics of Fuel Cell
composed of an anode, a
cathode, and an electrolyte
membrane.
a typical fuel cell works by passing
hydrogen through the anode of
a fuel cell and oxygen through
the cathode.
at the anode site, a catalyst splits
the hydrogen molecules into
electrons and protons. The
protons pass through the
porous electrolyte membrane,
while the electrons are forced
through a circuit, generating an
electric current and excess heat.
53
Types of Fuel Cell
1. POLYMER ELECTROLYTE
MEMBRANE FUEL CELLS
2. DIRECT-METHANOL
FUEL CELLS
3. ALKALINE
FUEL CELLS
4. PHOSPHORIC ACID
FUEL CELLS
5. MOLTEN CARBONATE
FUEL CELLS
6. SOLID OXIDE FUEL CELLS
54
POLYMER ELECTROLYTE MEMBRANE FUEL CELLS
also called proton exchange membrane fuel
cells, use a proton-conducting polymer
membrane as the electrolyte.
Hydrogen is typically used as the fuel.
These cells operate at relatively low
temperatures and can quickly vary their output
to meet shifting power demands.
the best candidates for powering automobiles.
due to their low operating temperature, they
cannot directly use hydrocarbon fuels, such as
natural gas, liquefied natural gas, or ethanol.
55
DIRECT-METHANOL FUEL CELLS
similar to the PEM cell in that it uses a
proton-conducting polymer membrane as
an electrolyte.
DMFCs use methanol directly on the anode,
which eliminates the need for a fuel
reformer.
are of interest for powering portable
electronic devices, such as laptop
computers and battery rechargers.
Methanol provides a higher energy
density than hydrogen, which makes it an
attractive fuel for portable devices.
56
ALKALINE FUEL CELLS
use an alkaline electrolyte such as
potassium hydroxide or an alkaline
membrane that conducts hydroxide ions
rather than protons.
Originally used by the National Aeronautics
and Space Administration (NASA) on space
missions.
57
PHOSPHORIC ACID FUEL CELLS
use a phosphoric acid electrolyte that
conducts protons held inside a porous
matrix and operates at about 200°C.
they are typically used in modules of 400
kW or greater and are used for stationary
power production in hotels, hospitals,
grocery stores, and office buildings, where
waste heat can also be used.
58
MOLTEN CARBONATE FUEL CELLS
use a molten carbonate salt immobilized in
a porous matrix that conducts carbonate
ions as their electrolyte.
they are already being used in a variety of
medium-to-large-scale stationary
applications, where their high efficiency
produces net energy savings.
their high-temperature operation
(approximately 600°C) enables them to
reform fuels such as natural gas and biogas
internally.
59
SOLID OXIDE FUEL CELLS
use a thin layer of ceramic as a solid
electrolyte that conducts oxide ions.
they are being developed for use in a
variety of stationary power applications,
as well as in auxiliary power devices for
heavy-duty trucks.
Operating at 700°C–1,000°C with zirconia-
based electrolytes, and as low as 500°C with
ceria-based electrolytes, these fuel cells can
internally reform natural gas and biogas
and can be combined with a gas turbine to
produce electrical efficiencies as high as
75%.
60
Efficiency of fuel cells
Fuel cells can operate at higher
efficiencies than combustion engines
and can convert the chemical energy in
the fuel directly to electrical energy with
efficiencies capable of exceeding 60%.
Fuel cells have lower or zero emissions
compared to combustion engines.
There also are no air pollutants that
create smog and cause health
problems at the point of operation.
Fuel cells are quiet during operation
as they have few moving parts.
61
CHALLENGES AND ONGOING RESEARCH of fuel cells
1. COST
Research, development,
and demonstration (RD&D)
focuses on the
development of low-cost
fuel cell stack and balance
of plant (BOP) components
and advanced high-volume
manufacturing approaches
to reduce overall system
cost.
2. PERFORMANCE
To improve fuel cell efficiency
and performance, RD&D
focuses on innovative
materials and integration
strategies.
3. DURABILITY
Fuel cell applications generally
require adequate performance
to be maintained over long
periods.
RD&D focuses on identifying
and understanding the fuel cell
degradation mechanisms and
developing materials and
strategies to mitigate their
effects.
62
Photovoltaic solar cells
Solar cells, also called
photovoltaic cells, convert
the energy of light into
electrical energy using the
photovoltaic effect.
Unlike batteries, solar
systems do not use
chemical reactions, nor do
they require fuel. In
addition, solar cells don’t
have moving parts like
electric generators.
Domestic solar systems
convert around 20% of the
sunlight they receive into
electricity, while more
expensive commercial
systems can convert up to
40%.
63
large formation of solar cells
arrays
64
small group of cells
solar panels
65
How do solar cells work?
1. Sunlight shines on the surface of the
cell
2. Energy is carried through the layers of
the cell as photons
3. The photons give their energy over to
electrons in the lower layer
4. The electrons use this energy to jump
back into the upper layer and escape into the circuit
5. The electrons flowing around the circuit
provide the power to a device
66
TYPES OF
SOLAR CELLS
1. CRYSTALLINE SILICON CELLS
2. THIN FILM SOLAR CELLS
3. THIRD GENERATION SOLAR CELLS
67
Crystalline Silicon Cells
Around 90% of solar cells are made from
crystalline silicon (c-Si) wafers which are
sliced from large ingots grown in
laboratories.
These ingots take up to a month to grow and
can take the form of single or multiple
crystals.
68
Types of Crystalline Silicon Cells
Mono - have a distinctive
appearance and are often
colored as well as tending to
have a cylindrical shape.
provide the highest levels of
efficiency.
Poly - do not need to be cut to
shape as the silicon is
melted and poured into
square molds.
Polycrystalline solar panels
are seen as being a mid-
range option both in terms
of price and efficiency.
69
WHY DO MONOCRYSTALLINE SOLAR CELLS
HAVE HIGHER EFFICIENCY THAN
POLYCRYSTALLINE SOLAR CELLS?
monocrystalline panels are cut from a single crystal of
silicon, which makes it easier for the highest amount of
electricity to move throughout the panel
70
Thin Film Solar Cells
around 100 times thinner.
made from amorphous silicon (a-Si), in which the atoms are
randomly arranged rather than in an ordered crystalline
structure.
can also be made from cadmium-telluride (Cd-Te), copper indium
gallium diselenide (CIGS), or organic PV materials.
these cells are produced by layering photovoltaics to create a
module and are the cheapest option for producing solar panels.
the cells can be laminated onto windows, skylights, roofing tiles,
and other substrates, including glass, metals, and polymers.
however, despite this flexibility, they are not as efficient as
regular crystalline silicon cells.
71
Third Generation Solar Cells
combine the best features of crystalline silicon
and thin-film solar cells to provide high
efficiency and improved practicality for
use.
they tend to be made from amorphous silicon,
organic polymers, or perovskite crystals and
feature multiple junctions made up of layers
of different semiconducting materials.
these cells have the potential to be cheaper,
more efficient, and more practical than
other types of cells, and be able to achieve
around 30% efficiency (with a perovskite-
silicon tandem solar cell).
72
Efficiency and
cost considerations of solar cells
Solar cells can only produce electricity based on the
light they receive and can process. Most cells convert just
10-20% of the energy they receive into electricity, with the
most efficient cell laboratory cells reaching around 45%
efficiency under perfect conditions.
The reason for this is that solar cells are optimized to only
capture photons from within a particular frequency band,
with those outside this band being wasted
73
Swanson's Law
the price of solar PV modules decreases by
about 20 percent for every doubling in global
solar capacity. The law is named after Richard
Swanson, founder of high-efficiency solar panel
manufacturer SunPower, and indicates a
phenomenon seen across many different
technologies: new industries face a major
learning curve, and as they improve, prices fall.
74
CHALLENGES and SOLUTIONS in integrating solar cells into the energy grid
challenges
1. Grid Compatibility
2. Transmission Lines
3. Power Quality
4. Inertia
5. Variable Sunshine
solutions
1. Better Predictions
2. Spread Out Solar Panels
3. Store Extra Energy
4. Change Electricity Usage Times
75
Environmental Concerns of solar cells
1. Land Impact
2. Chemical Use
76
WATER SPLITTING
Water is a simple chemical molecule made up of two
molecules of hydrogen and one molecule of oxygen.
Water is a remarkable substance with unique scientific
properties, such as its chemical composition (H2O),
universal solvent capabilities, density anomaly, and
cohesive/adhesive nature.
77
WHY WATER SPLITTING?
Hydrogen Production
Energy Storage
Green Hydrogen
Chemical Industry
Environmental Benefits
Oxygen Production
Space Exploration and more..
78
Water Splitting Methods
Main Type:
- Photocatalytic
Water Splitting
- Electrocatalytic
Water Splitting
Other Methods:
- Radiolysis
- Thermolysis
- Photobiological
Water Spilitiing
79
Photocatalytic Water Splitting
Photocatalytic water splitting is a process
that uses light energy, typically from
sunlight, to split water into hydrogen and
oxygen.
80
Electrocatalytic Water Splitting
Electrolysis is a method of water
splitting that uses electricity to drive the
chemical reaction.
81
Photocatalysis
It uses light energy to split water
into hydrogen and oxygen using a
semiconductor photocatalyst.
82
Photocatalysis MECHANISM
1. Photon Absorption - The photocatalyst material absorbs light (photons), usually from sunlight
2. Generation of Electron-Hole Pairs - The absorbed photons energize electrons in the photocatalyst, creating electron-hole pairs
3. Separation of Electron and Hole - These electron-hole pairs are separated within the photocatalyst, with electrons moving to the surface and holes remaining inside the material.
4. Reduction and Oxidation Reactions - Electrons at the surface engage in a reduction reaction, converting water into hydrogen gas. Meanwhile, holes participate in an oxidation reaction, turning water into oxygen gas.
5. Formation of Hydrogen and Oxygen - Hydrogen and oxygen gases are produced as a result of these reactions.
83
Photocatalytic Material
Titanium Dioxide (TiO2)
Zinc Oxide (ZnO)
Tungsten Trioxide (WO3)
Semiconductor Nanomaterials (e.g., CdS, CdTe, In2O3)
Graphitic Carbon Nitride (g-C3N4)
Hydrogenated Titanium Dioxide
Metal-Organic Frameworks (MOFs)
Perovskite Materials
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Electrocatalysis
Electrocatalytic water splitting is a process of using
electricity to split water into hydrogen and oxygen.
85
Hydrogen Fuel vs. Fossil Fuel
Hydrogen fuel:
Renewable or Natural Gas
Green & Clean
Fuel Cell Efficient
Special Storage
Renewable Potential
Growing Tech
Cost Varies
Fossil fuel:
Non-Renewable
Polluting & Warming
Lower Efficiency
Conventional Storage
Finite & Challenged
Global Infrastructure
Cost Competitive
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WHAT IS BIOMASS?
biomass refers to organic materials, primarily
plant and animal-based, that can be used as a
source of energy.
the term is generally understood to exclude coal,
oil, and other fossilized remnants of organisms, as
well as soils.
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BIOENERGY & BIOFUEL
bioenergy is a broader term that encompasses all
forms of energy derived from organic materials
such as plants and animals while biofuels are a
subset of bioenergy and specifically refers to
liquid or gaseous fuels made from organic
materials
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HOW TO CONVERT BIOMASS INTO BIOENERGY
1. direct combustion
2. thermochemical conversion
3. chemical conversion
4. biological conversion
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types of thermochemical conversion
1. Pyrolysis entails heating organic materials
to between 800° F and 900° F (400° C and
500° C) in the nearly complete absence of
free oxygen. Biomass pyrolysis produces
fuels such as charcoal, bio-oil, renewable
diesel, methane, and hydrogen.
2. Gasification entails heating organic
materials to between 1,400° F and 1,700 F
(800° C and 900° C) with injections of
controlled amounts of free oxygen or steam
into the vessel to produce a carbon
monoxide- and hydrogen-rich gas called
synthesis gas or syngas
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ADVANTAGES & DISADVANTAGES OF USING BIOMASS AS AN ALTERNATIVE SOURCE OF ENERGY
1. BIOMASS IS A RENEWABLE SOURCE
2. BIOMASS HELPS REDUCE WASTES
3. BIOMASS IS A RELIABLE SOURCE OF ELECTRICITY
4. BIOMASS REDUCES OVERRELIANCE TO FOSSIL FUELS
1. BIOMASS COSTS
2. BIOMASS SPACE REQUIREMENTS
3. BIOMASS ENVIRONMENTAL IMPACT
4. BIOMASS EFFECTIVITY
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ALGAE-BASED FUELS
Algae are sometimes grown to make algae
biofuels, which make up the third generation
of biofuels. Many types of algae can be used
and processed to become a biofuel. Biofuel is
a fuel made from living things, or the waste of
a living thing, also known as biomass. The algae
oils can be converted to biodiesel and the
remaining material can be used to create
bioethanol.
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ALGAE FOR BIOFUEL PRODUCTION
Algae are organisms that grow in aquatic environments and
use light and carbon dioxide (CO2) to create biomass. There
are two classifications of algae: macroalgae and microalgae.
Microalgae have long been recognized as potentially good
sources for biofuel production because of their relatively
high oil content and rapid biomass production. Microalgae
grow very quickly compared to terrestrial crops; the
practice of algal mass culture can be performed on non-
arable lands using non-potable saline water and waste
water. Thus, use of microalgae as an alternative biodiesel
biofuel feedstock is gaining increasing interest from
researchers, entrepreneurs, and the general public.
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MICROALGAE ADVANTAGES
An appealing characteristic of algae is its oil content, with
some strains consisting of over 50% triglycerides.
The yield of biodiesel from algae per square kilometer
could greatly exceed even that of tropical palm oil.
Unfortunately, achieving a high yield of triglyerides
requires the algae to be nutrient-deprived, which slows
their production.
Algae production does not begin with the huge carbon
deficit from clearing land for biodiesel or bioethanol
production that is required directly or indirectly.
The algae grow quickly; about 1% of sunlight is absorbed
and converted to biomass, which is small by comparison
to ~10–15% capture by solar cells, but the initial capital
costs are much less.
The water used in the bioreactor or ponds need not be
pure—wastewater can be used and may even be
advantageous if it contains some of the nutrients
required for algal growth (nitrogen and phosphorus).
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MICROALGAE DISADVANTAGES
A problem associated with the triglycerides derived from
algae is that they are polyunsaturated: their fatty acid
chains often contain four or more C double bond C bonds.
Other problems in algae systems are that in open
reactors many strains of algae are present, and that the
water tends to evaporate.
The capital cost is increased of setting up the system
since expensive metal support structures are used to hold
the tubes vertically.
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BIODIESEL
It is a fuel that produced from
vegetable oils, yellow grease,
used cooking oils, or animal fats.
It is a non-petroleum based
diesel fuel, made up of methyl or
ethyl esters of fatty acids
found in vegetable oils.
Biodiesel has become a
standardised term referring
exclusively to mono alkyl esters.
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PROPERTIES OF BIODIESEL
1. Biodiesel varies in colour from
golden to dark brown.
2. It has a high boiling point and
low vapour pressure.
3. The flash point of biodiesel is
130 ºC, which is significantly
higher than that of petro-diesel (64 ºC) or gasoline (-45 ºC)
4. Biodiesel gels at low
temperatures
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Sources of biodiesel
1. Plant oil
2. Algae
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USE OF BIODIESEL IN
MOTOR
VEHICLES
The fraction of biodiesel in diesel fuel is
designated by a B labeling system
B5 symbolizes diesel fuel containing 5% biodiesel
by volume, and B100 is pure biodiesel
Currently, the largest manufacturers and users
of biodiesel in the European Union are Germany
and France, who together account for about
half the totals.
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GREENHOUSE GAS AND AIR
POLLUTION EMISSIONS FROM
BIODIESEL
The use of methanol created from a fossil fuel makes biodiesel less than 100% renewable.
Biodiesel blends produce significantly fewer emissions of carbon monoxide, particulate matter (PM10), and hydrocarbons—including
polycyclic aromatic ones and those that promote photochemical smog
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Advantages and Disavantages of Biodiesel
Advantages of Biodiesel
- Biodiesel produces significantly fewer air pollutants, other than NO, due to its lower aromatic content and to better combustion efficiency resulting from the presence of oxygen in its molecular structure.
- Biodiesel has a significantly higher flash point so it is safer to handle.
- Biodiesel is a better lubricant, and reduces long-term engine wear.
- Biodiesel biodegrades faster (owing to its oxygen content, a point of enzyme attack) in freshwater and soil, and is much less toxic.
- Growth of plants for biofuel absorbs much of the COz subsequently emitted during its production and combustion; thus it reduces by about half the greenhouse gas emissions from diesel fuel combustion
Disadvantages of Biodiesel
- Biodiesel has a slightly lower energy content (about 7-9%, depending on feedstock), though this is partially offset by its superior combustion efficiency.
- Biodiesel is more viscous, though much less so than SVO, so its use in cold climate winters can be problematic
- Biodiesel undergoes degradation by reaction with air during long-term storage due to the presence of C C bonds in the original oils, which make the carbon chain more susceptible to oxidation.
- Biodiesel may attract water from atmospheric moisture owing to the presence of mono- and diglycerides not completely esterified by methanol. The water causes corrosion of the engine's fuel system, reduces the efficiency of combustion, can speed the gelling of the fluid at cool temperatures and accelerates the growth of fuel-plugging microbe colonies
- The CO2 reduction is more than offset for decades if new land must be cleared to grow the plants.
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AMMONIA AS BIODIESEL FUEL
Ammonia a combination of
nitrogen and
hydrogen, is a
primary industrial chemical that is the
least expensive
Green ammonia refers to
ammonia whose production is
100% renewable and carbon-free
Method: to use hydrogen from the
electrolysis of water using energy
from renewable sources and
nitrogen extracted from the air at
high temperatures under pressure
in the presence of a suitable
catalyst.
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production method of ammonia
Haber-Bosch process
400-450 deg C
200 atm
Iron catalyst
103
advantages of ammonia
1. Since ammonia doesn’t contain any molecular carbon,
during its combustion there are no CO2 emissions.
2. Currently produced in substantial volumes for the chemical
industry and distributable using existing infrastructure
3. Commonly transported as cargo, so issues around handling and carriage are already understood.
4. Ammonia is relatively easier to handle in terms of
temperature, as it is stored at around -33oC.
5. Low fire risk due to its relatively narrow flammability range, as
compared to other fuels.
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disadvantages of ammonia
1. Its toxicity. Being extremely soluble, even at extremely low
concentrations, ammonia can be absorbed by body fluids and
may cause severe chemical burns
2. Ammonia also poses enhanced corrosion risk of certain
metals such as copper, brass and zinc and various alloy
3. Ammonia burns much more slowly than other fuels and has
higher autoignition temperature than conventional fuel oil.
4. While carbon-free, ammonia contains nitrogen, and burning it will
result in nitrogen oxide (NOx) and nitrous oxide (N2O) emissions.
GHG impact of N2O emissions is nearly 300x greater than CO2.
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WHAT ARE CARBON
NEUTRAL
FUELS?
are synthetic fuels that are created as an
alternative to the liquid fuels typically
burned in internal combustion engines
is a term used to describe carbon-based fuels
that when burned will not increase carbon
dioxide (CO2) in the atmosphere.
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CARBON-NEUTRAL
ALTERNATIVE
FUELS
Biodiesel
Bioethanol
Methanol
Algae
Diesel Fuel From Water And CO2
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WHAT ARE CARBON NEGATIVE FUELS
This means the greenhouse gases (GHGs)
generated by its use are less than the GHGs
removed by its production when calculated
on a carbon dioxide-equivalent basis. For this
to happen, the carbon-negative fuel must
come from a feedstock that is currently
contributing to climate change.
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CARBON NEGATIVE FUELS
BIOENERGY WITH CARBON CAPTURE AND STORAGE
ALGAE-BASED BIOFUELS
DIRECT AIR CAPTURE WITH CARBON UTILIZATION
ENHANCED WEATHERING
