S4-S6 Flashcards
Renewable energy vs Nonrenewable energy
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.
Renewable Energy towards Sustainable Development
- 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
Types of Energy Sources
- HYDROELECTRIC POWER
- WIND ENERGY
- BIOMASS ENERGY
- MARINE
ENERGY - SOLAR
ENERGY - GEOTHERMAL
ENERGY
Hydroelectric Power
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.
Why is hydroelectric power an
indirect form of
solar energy
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.
power yield of hydroelectric power
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.
why is hydroelectric power far from perfect
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.
environmental problems of hydroelectric power
- 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
World’s largest hydropower dam
Three Gorges Dam - 2335 m long, 181 m high
Wind energy
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.
wind flow
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.
how can wind be exploited to make electricity
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
Wind power capacity
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.
The world electricity output
could be produced
from wind
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.
why size and speed
matters in wind energy
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.
The cubic dependence of energy on wind speed is the result of two factors
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.
Wind energy sites need to be picked on potential derived power.
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.
Earth’s Most Eligible Bachelorettes for wind energy
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.
Environmetal Issues of wind energy
- Energy payback,
while existent, is
the least for any
electric power source - Perceived visual
unsightliness - Construction of
windmills at remote sites
requires destructive infrastructure
Biomass: energy from plants and animals
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.
low conversion rate of biomass
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.
Biomass sources
- 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
How biomass works
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.
Pyrolytic Production: Bio-oil
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.
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.
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.
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.
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.
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.
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.
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.
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.
Production of Geothermal Energy
- dry steam power plant - Hot steam from underground is piped directly into turbines, which powers the generator.
- 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.
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.
Environmetal Problems of geothermal energy
- Large quantity
of hydrogen
sulfide gas are
released - Corrosion of
equipments - Water pollution
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.
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).
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.
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
Disadvantages of Solar Cells
- It is direct
current (dc)
rather than
alternating
current (ac) - Costly
- Cannot collect
energy during night time and
cloudy days
Advantages of Solar Cells
- The availability in sunny
locations - Much cheaper
than extending
power grid lines - Can be installed
in piecemeal
rather as one
large project
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.
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.
