Introduction to Engineering

Transcription

1 Introduction to Engineering Lecture 36: Alternate Energy Sources Approximate Runtime: 38 minutes Copyright Baylor University Introduction Steven Eisenbarth, Ph.D. Associate Dean of Engineering and Computer Science Baylor University Copyright Baylor University 006 Alternative Energy Sources Alternative energy refers to any type of energy which is not derived from fossil fuels. Significant alternative energy sources: Bioenergy Nuclear Solar Wind Geothermal Hydroelectric Ocean Current H Fuel Cells Copyright Baylor University

2 Global Energy Production by Fuel Type from: copyrighted by the OECD/IEA, September 006. Copyright Baylor University Basic Building Blocks of the Universe Basic building blocks of matter Electrons, muon, and tau Neutrinos (one corresponding to electron, muon, and tau) Quarks (six types; up and down most common) Four fundamental forces of nature: Electromagnetic (photons) Strong Nuclear (gluons) Weak Nuclear (W+, W-, Z) Gravitation (Higgs boson?) Copyright Baylor University What is Energy? Broad definition: The ability to do work. Comes in a wide variety of forms, for example: Nuclear Energy Chemical Energy Electrical Energy Thermal Energy Radiant Energy Potential energy a reservoir from which energy can be extracted. Copyright Baylor University 006 6

3 Energy s Manifestations Energy related to movement of matter: Kinetic Energy: where m is mass and v = velocity of the mass. Kinetic Energy of Rotation: where I is the moment of inertial and ω is the angular velocity. 1 E = mv 1 E = Iω Thermal Energy: where k is the Boltzmann constant and T is absolute temperature. 3 E = kt Copyright Baylor University Energy s Manifestations Energy related to position: Gravitational Potential Energy: Where m is mass, g is the acceleration due to local gravity at the earth s surface, and h is height. E = mgh Gravitational Potential Energy: Where E is energy, G is the gravitational constant, m and M are the two masses, and r is the distance between the masses center of gravity. GmM E = r Copyright Baylor University Energy s Manifestations Energy related to position: Electrostatic Potential Energy: Where q and Q are electric charges, r is the distance between the charges, and ε 0 is the permittivity of free space. E = qq 4πε 0 r Magnetostatic Potential Energy: Where μ is the magnetic dipole moment an B is the magnetic field strength. (This is a scalar product of two vector quantities.) E = μ Β Copyright Baylor University

4 Energy s Manifestations Energy related to nature of matter: Radiant Energy (photons): Where h is Planck s constant, and ν is frequency. E = hv Rest Mass Energy: Where m = mass and c is the speed of light. E = mc Chemical Energy: related to the chemical bonds between atoms within a molecule. No simple formula, primarily electrostatic in nature. Copyright Baylor University Energy s Manifestations Energy related to nature of matter: Nuclear Energy (fusion): The result of strong and weak nuclear forces that bind nuclear particles. E = mc Nuclear Energy (fission): The result of strong and weak nuclear forces that bind nuclear particles. E = mc Copyright Baylor University Energy s Manifestations Potential energy related to elastic properties of materials. Elastic potential energy of a compressed spring: Where k is the force constant and x is the displacement from mechanical equilibrium. 1 E = kx Copyright Baylor University

5 Energy Conversion Efficiency Energy Conversion Efficiency = (Energy Input / Energy Output) * 100. Energy Input Energy Conversion Process Usable Energy Output Energy Lost Copyright Baylor University Combustible Renewables Bio-energy refers to any type of energy derived from bio-mass. Bio-energy energy derived from the Sun which is stored within biomass Biomass includes: Agriculture and forest wastes Public wastes Animal wastes Bio-energy is considered a renewable energy because its production and use operate in a cycle. Copyright Baylor University Bio-Energy Production Overall Photosynthesis reaction: 6H O + 6CO + light --> C 6 H 1 O 6 + 6O Organic fuels are produced via the photosynthesis of sunlight. Water and Oxygen is used by Chlorophyll to convert sunlight to NADPH and ATP. Cell respiration converts water, CO, NADPH and ATP to sugar with O as a bi-product. Energy associated with the forming or breaking of chemical bonds. Figure from: abee/biobk/biobookps.html Copyright Baylor University

6 Energy Crops Energy crops are bioengineered to grow bigger and faster than regular crops making them useless for any other type of application. Energy crops include plants, trees and other vegetation which are processed for energy. Copyright Baylor University Other Biomass Agriculture and forest waste may be used to create fuels instead of allowing to it decompose. Public wastes that can be used as biomass include paper, trimmed grass, landfill gas, etc. Animal wastes, obtained mainly from farm animals, can be used for bio-energy production. In some remote locations it is used as a cooking fuel. All of these different forms of biomass may be used for electric energy production. Copyright Baylor University Bio-Energy Conversion Biomass may be used traditionally to produce heat which can provide heating and cooking energy. Alternatively, biomass can be transformed into liquid fuels such as ethanol, bio-diesel, and methanol. These liquid fuels may be used in conjunction with other fuels to create a high-energy-content fuels. These liquid fuels produce lower levels of pollutants than traditional fossil fuels. Copyright Baylor University

7 Bio-Energy Conversion Direct Firing Method: biomass is taken as a solid and fired to produce hot gases. The hot gases are passed through a heat exchanger which boils water to produce steam which powers turbinedriven generators. Co-Firing Method: biomass is combined with coal and used as feed to a existing coal-fired power plant. Bio-mass can represent 1 to 15% of total energy output. From: Copyright Baylor University Bio-Energy Conversion (Gasification) Bio-mass Oxygen Oxygen Partial Oxidation Gasifier H, CO, CO Power Generation or Syn-gas Production 850º C, 1/3 O Ash Copyright Baylor University Bio-Energy Conversion Anaerobic Digestion: This method uses biomass such as manure and solid waste. The biomass is broken down with bacteria to release methane which is then used as a fuel for gas engines powering generators. k4.htm Copyright Baylor University

8 Bio-Energy s Future Advantages Good way of recycling waste. May be less expensive than energy derived from fossil fuels. Positive impact on environment. Disadvantages Hard to keep a huge amount of waste at all time. Release and burning of methane causes greenhouse gases. Without proper management bio-energy plants can pollute the environment. Future plans involving bio-energy include drilling into landfills and capturing methane instead of letting it escape to the atmosphere. Copyright Baylor University 006 Nuclear Energy Production Copyright Baylor University Nuclear Power Plants within U.S. From: Copyright Baylor University

9 Nuclear Power Plants Worldwide From: Copyright Baylor University Nuclear Reaction The most common nuclear fuel is U-35. The nuclear fission process starts when U-35 atoms absorbs slow neutrons to become U-36. U-36 is unstable and breaks apart releasing two fission products and three fast neutrons. The mass of the fragments and released neutrons is about 0.1% less than original U-36 mass. This mass has been converted to kinetic energy. A moderator slows the released neutrons so that a chain-reaction can be sustained. From: Copyright Baylor University Pressurized Water Reactor (PWR) In a Pressurized Water Reactor, water heated by the nuclear fuel is kept in a primary closed loop. The pressure raises the boiling point of the water in the loop. The primary-loop water passed through heat exchangers which transfers heat from the water in the primary loop to the water in the secondary loop which boils creating steam which powers turbine generators. Copyright Baylor University

10 4/6/86 Chernobyl, Ukraine. Reactor No. 4 after fire/meltdown. 130,000 evacuated 1.5 M exposed to radioactive fallout 600,000 involved in clean-up Increased cancer rates Copyright Baylor University Nuclear Power s Future Advantages 1. More efficient than traditional fossil fuels.. Does not contribute to greenhouse effect. 3. Produces a small amount of waste. Disadvantages 1. Waste is extremely dangerous.. Accidents can be catastrophic 3. Can be used to create nuclear weapons. Future development of nuclear technology will involve releasing energy through fusion instead of fission. In fusion two nuclei would be joined to create a heavier one. Although it is already possible, it takes more energy than is released. Copyright Baylor University Summary Fundamental sources of energy Fundamental forces Mass Energy conversion efficiency (penalty) Alternative Energy Sources Bio-Mass Nuclear Power Copyright Baylor University