Coming%20up:

1
Coming up

• Quiz Friday EFP chapters 9,13,15(minus section
  on Hydrogen)
• Test 2 Monday, October 29

2
US Geothermal Resources
3
Advantages

• Geothermal power requires no fuel, is emissions
  free and is not susceptible to fluctuations in
  fuel cost.
• geothermal power stations dont rely on transient
  sources of energy (wind, sun)
• It is considered to be sustainable because the
  heat extraction is small compared to the size of
  the heat reservoir.
• individual wells may need to recover, geothermal
  heat is inexhaustible and is replenished from
  greater depths. The long-term sustainability of
  geothermal energy production has been
  demonstrated at the Lardarello field in Italy
  since 1913, at the Wairakei field in New Zealand
  since 1958, and at The Geysers field in
  California since 1960.
• However, there has been a decrease in output
  noted at The Geysers
• Geothermal has minimal land use requirements

4
Disadvantages

• The geothermal fluid is corrosive and, worse, is
  at a low temperature compared to steam from
  boilers, this limits the efficiency of heat
  engines in extracting useful energy during the
  generation of electricity. Much of the heat
  energy is lost, but could be used for
  co-generation purposes
• Construction of the power plants can adversely
  affect land stability in the surrounding region.
  This is mainly a concern with Enhanced Geothermal
  Systems, where water is injected into hot dry
  rock where no water was before.
• Dry steam and flash steam power plants also emit
  low levels of carbon dioxide, nitric oxide, and
  sulphur, although at roughly 5 of the levels
  emitted by fossil fuel power plants. However,
  geothermal plants can be built with
  emissions-controlling systems that can inject
  these substances back into the earth, thereby
  reducing carbon emissions to less than 0.1 of
  those from fossil fuel power plants.
• Hot water from geothermal sources will contain
  trace amounts of dangerous elements such as
  mercury, arsenic, and antimony which, if disposed
  of into rivers, can render their water unsafe to
  drink.
• Locations may eventually cool down

5
Biomass

• Plant matter grown to generate electricity or
  produce biofuel
• Examples trash such as dead trees and branches,
  yard clippings and wood chips, plant or animal
  matter used for production of fibers, chemicals
  or heat.
• Biomass may also include biodegradable wastes
  that can be burnt as fuel.
• It excludes organic material which has been
  transformed by geological processes into
  substances such as coal or petroleum.

6
Energy from Biomass

• Comes initially from the sun
• Solar energy is stored as chemical energy in the
  plants
• This chemical energy is released when the biomass
  is burned or converted to another fuel that is
  burned.
• Process starts with the conversion of sunlight to
  chemical energy in the plant we call this
  photosynthesis

7
Review of Photosynthesis

• Plant takes in water and carbon dioxide. The
  energy in visible light excites atoms in the
  water and carbon dioxide which allows bonding to
  take place. As a result, compounds with hydrogen,
  carbon and oxygen are formed (called
  carbohydrates), along with oxygen and water.
• The simplest carbohydrate formed is sugar, and
  these compounds are the plants fuel.

8
Biomass

• About 30 of the energy in the incident sunlight
  is stored in biomass.
• Not a new idea, remember way back in the semester
  when we looked at sources of energy production in
  the US? Wood was a primary source of energy until
  1880.
• If you look at the average crop yield for all the
  harvested land in the US, you find that nearly
  all our energy needs could be furnished from
  biomass.

9
Municipal Waste

• Our solid waste (garbage) needs a home-we
  normally put it in a landfill (polite name for a
  dump!)
• Landfill sites are diminishing for a variety of
  reasons, but our waste production is increasing.
• Unfriendly to the environment
• Can contaminate groundwater
• Nasty smell
• Harbor diseases and disease carrying rodents
• Can contain toxic chemicals
• Emit methane (produced in the decay of organic
  materials and is not only toxic, but a greenhouse
  gas)

10
Municipal waste

• This waste has energy stored in it, which can be
  released of the waste is burned.
• Energy produced is modest, but this solves
  another environmental problem.
• Plants are expensive to construct and maintain,
  most cities do not have the money to get one
  started. Rely on private investors or companies

11
Creating Fuel from Biomass

• Ethanol common form of alcohol, it is an
  oxygenated hydrocarbon (a hydrocarbon with oxygen
  added).
• Also known as ethyl alcohol, pure alcohol, grain
  alcohol, or drinking alcohol,
• volatile, flammable, colorless liquid.
• type of alcohol found in alcoholic beverages and
  in modern thermometers.
• Fermentation of sugar to ethanol is one of the
  earliest organic reactions employed by humanity

12
Ethanol

• Usually produced from corn, though other grains
  can be used. (Brazil is a major user of Ethanol,
  and uses sugar cane to produce their ethanol)
• Entire plant is ground up and mixed with water.
• Cooked to convert starch to sugars via enzymatic
  action.
• Sugars are converted to alcohol via fermentation.
• Distillation removes the rest of the material
  from the alcohol.

13
Ethanol as a Fuel additive

• Ethanol increases the oxygen content of gasoline,
  and leads to more complete combustion and reduces
  CO2 emissions.
• Mixtures are defined by E, where is the
  percent of ethanol in the fuel.
• So E100 is 100 ethanol
• E10 (10 ethanol) is a particular type of mixture
  called gashol most cars can run on this with no
  adverse effects
• Current gasoline engines cannot run on pure
  ethanol since to maximize its energy conversion
  efficiency, higher compression ratios are needed,
  which wont work for gasoline engines.

14
Debate rages

• Will it really solve all our problems?
• Is it cheaper? Government tariffs and lower
  mileage
• Is it cost effective?
• What about the issue of using a food source
  (corn) for fuel?-note current research has made
  progress on a second generation of ethanol made
  from the non-edible parts of plants
• Potential damage to engine components with high
  ethanol content(gt E15) fuels(engines run hotter).

15
Methane from Biomass

• Methane makes up 85 of the natural gas extracted
  from the ground.
• In the presence of water and absence of oxygen,
  organic material will ferment naturally.
• Such organic materials include
• Crops
• Agricultural waste (animal or vegetable)
• Waste from lumber mills
• waste from breweries
• Algae
• Sludge from sewage treatment plants
• Municipal waste
• Fermentation by bacteria in the absence of oxygen
  is called anaerobic fermentation

16
Methane from Biomass

• Same heating value as natural gas
• High conversion efficiency(50-70 of the useful
  energy is converted)
• High cost
• Useful in systems that can generate their own
  power - for example sewage plants

17
Biodiesel

• Diesel fuel made from vegetable oil, recycled
  cooking grease or oil and animal fat
• Used as a fuel additive, designate the same way
  we designate ethanol fuels-i.e B where is the
  amount of biodiesel in the diesel fuel.
• B20 widely used in trucks and school buses

18
Nuclear Energy

• Nuclear Fission - the splitting of two atoms
• Nuclear fusion the combining of 2 atoms
• Both processes release energy

19
Atomic structure

• Atoms are composed of protons , neutrons and
  electrons discovered in the 1930s
• Protons positively charged
• q1.60217648710-19 C
• m1.67262158 10-27 kg
• Neutrons no charge
• m1.6749 x 10-27 kg
• Electron negative charge
• q -1.60217648710-19 C
• m 9.1093821510-31 kg

20
Atomic structure

• Protons and neutrons make up the nucleus
• Electrons orbit the nucleus at specific distances
  known as energy levels
• Atomic number number of protonsZ
• Atomic mass number A Z N, where N is the
  number of neutrons
• Atomic mass total mass of the electrons,
  protons and neutrons
• Atomic weight the ratio of the average mass of
  an atom to 1/12 of the mass of an atom of
  carbon-12.
• Ion if an atom loses or gains an electron and
  has a net charge
• Isotope-atom has the same number of protons but
  different number of neutrons

21
Atomic Structure

• Atoms are held together by forces
• There are four forces in nature
• Gravity -force between masses
• Electrostatic forces-like charges repel, unlike
  charges attract
• Strong nuclear force - causes an attraction
  between protons and neutrons
• Weak nuclear force causes protons to transform
  into neutrons and neutrons in to protons

22
Atomic Structure

• In atoms, the electrostatic force is holding the
  electrons to the nucleus, since the electrons are
  negatively charged and the protons are positively
  charged.
• The protons in the nucleus are being pushed apart
  by the electrostatic force since they have the
  same charge, but the strong nuclear force
  overcomes this repulsion on the atomic size
  scales and holds the protons together.

23
Fission

• In the late 1930s, it was discovered that if a
  uranium nucleus was bombarded by neutrons, it
  absorbed the neutron and became an unstable
  isotope of uranium, which then spilt into 2
  separate atoms (Krypton and Barium) and emitted
  more neutrons and gamma rays

24
Is mass conserved?

• Now the mass of the fission products plus the
  excess neutron should equal the mass of the
  initial incident neutron and the uranium. But it
  doesnt.
• Where did the mass go?
• Well, remember E mc2 - mass cannot be created
  or destroyed, only converted to and from energy,
  so the missing mass must be converted into energy.

25
How much energy

• 200 MeV is released per fission event
• The fission of 1 g of uranium or plutonium per
  day liberates about 1 MW.
• This is the energy equivalent of 3 tons of coal
  or about 600 gallons of fuel oil per day
• No CO2 emissions!
• Vastly superior in terms of energy per amount of
  fuel