Renewable Energy Systems

Transcription

1 Renewable Energy Systems 1 Buchla, Kissell, Floyd

2 Chapter Outline Energy Sources 1 Buchla, Kissell, Floyd 1-1 FOSSIL FUELS: OIL, COAL AND NATURAL GAS 1-2 NUCLEAR ENERGY 1-3 THE SOLAR RESOURCE 1-4 THE WIND RESOURCE 1-5 GEOTHERMAL RESOURCES 1-6 HYDROELECTRIC RESOURCES 1-7 BIOMASS AND BIOFUEL RESOURCES

3 Fatman73/Fotolia 1-1 Fossil Fuels: oil, coal and natural gas Major fossil fuels are: Coal Petroleum Natural Gas All fossil fuels are considered to be non-renewable resources because they are being consumed at a much faster rate than they are replenished.

4 ( Source: Lawrence Livermore National Laboratory. Reproduced by permission.) 1-1 Fossil Fuels: oil, coal and natural gas 4

5 1-1 Fossil Fuels: oil, coal and natural gas Coal is a hydrocarbon that formed from ancient plant life that was buried and subjected to heat and pressure. It formed into a organic peat in a process called diagenesis. Types of coal: Heating value lignite subbituminous bituminous anthracite Moisture content

6 1-1 Fossil Fuels: oil, coal and natural gas Petroleum (oil) was formed from organic sediments in a two step-process: 1. Compaction and heat into a waxy material known as kerogen and a black tar-like material called bitumen. 2. Further chemical and physical change in a process called catagenesis.

7 1-1 Fossil Fuels: oil, coal and natural gas Natural gas is trapped underground in reservoirs. The primary constituent of natural gas is methane, the simplest hydrocarbon. The chemical formula for methane is CH 4. The chemical reaction that occurs in burning methane is: CH 2O CO 2H O Energy The equation shows that for one molecule of CH 4, two molecules of O 2 combine with it to form one molecule of CO 2 and two molecules of water.

8 1-1 Fossil Fuels: oil, coal and natural gas The relative weights of the reactants is just the molecular weight of each substance: Carbon = 12.0 g, Hydrogen = 1.0 g, Oxygen = 16.0 g Determine the molecular weights of the molecules in the reaction CH 2O CO 2H O Energy CH 4 = (1.0) = 16.0 O 2 = 2(16.0) = 32.0 CO 2 = (16.0) = 44.0 H 2 O = 2(1.0) = 18.0

9 1-1 Fossil Fuels: oil, coal and natural gas Determine the weight of CO 2 produced if one ton of methane is burned. The reaction is CH 2O CO 2H O Energy Start by putting the molecular weights below each reactant, and multiply each weight by the number of molecules shown in the equation. Set up a proportion with CH 4 on the left and CO 2 on the right. Solve for the weight of CO 2 : x = 2.75 tons

10 Leonid Ikan/Fotolia 1-1 Fossil Fuels: oil, coal and natural gas Environmental effects of fossil fuels are: Release of CO 2 and pollutants such as sulfur, arsenic, lead, and mercury Acidification of lakes and streams from sulfur dioxide Issues with obtaining fuels including spills and ash releases. 10

11 1-1 Fossil Fuels: oil, coal and natural gas Another environmental disaster that has not received much attention is coal seam fires. These underground fires have been started by both natural means and humans but are estimated to account for 3% of the world s industrial carbon emissions may come from these fires. One fire in India has been burning since 1916 and has consumed an estimated 37 million tons of coal. Fires like this have a huge impact on pollution, land subsidence, and destruction of wildlife habitat by Pearson Higher Education, Inc.

12 1-2 Nuclear Energy Nuclear energy accounts for about 8.7% of the world energy supply. Nuclear reactors derive power from the stored binding energy of the nucleus. Think of binding energy as the energy required to break apart the nucleus. 12

13 1-2 Nuclear Energy From the binding energy curve, there are two conclusions that can be drawn: 1. If a heavy nucleus is broken apart in a process called fission, the resulting nucleus will have a greater binding energy per nucleon. 2. If two light elements below iron are joined together in a process called fusion, the new nucleus will have greater binding energy per nucleon. 13

14 1-2 Nuclear Energy Currently, all reactors that produce useful energy use the fission process in which the release of neutrons keeps the process going in a chain reaction. 14

15 1-2 Nuclear Energy A basic pressurized water reactor (PWR) uses the standard Rankine cycle to convert heat energy to mechanical motion. 15

16 1-2 Nuclear Energy Fusion reactors offer promise for the future with unlimited fuel (from water) but have been notoriously difficult to build. There are two approaches to building a fusion reactor: 1. Inertial method in which pellets of fuel are dropped into container and compressed to ignition temperatures using lasers 2. Containment of a super hot plasma that has the reaction. To date the most successful An artist rendition of a Tokamak design is a large Tokamak reaction chamber 16 design.

17 1-2 Nuclear Energy The ITER Tokamak fusion reactor (Courtesy of ITER organization) 17

18 1-2 Nuclear Energy Environmental effects for all fission reactors include potential and actual accidents and radioactive waste disposal requiring very long term storage. Water can dissolve and transport radionuclides. By locating waste in zones well above the water table, water transport of waste can be avoided. A double walled container for transportation and storage has a canister with a basket assembly for spent fuel rods (end view). The canister is surrounded by a double-walled container. Source: NREL

19 1-3 The Solar Resource The solar spectrum includes a visible region and energy above and below the visible region. At the top of the atmosphere, the spectrum is: 19

20 1-3 The Solar Resource The solar constant (in W/m 2 )can be calculated from the sun s power out by applying the inverse square law. The solar constant is the energy per square meter per day at the outer edge of the atmosphere. The amount that reaches the earth s surface is less because some is absorbed and some is reflected. 20

21 1-3 The Solar Resource The radiation reaching the earth's surface is given in three different ways: 1. Global horizontal irradiance (GHI) is the total amount of shortwave radiation received on a horizontal surface 2. Direct normal irradiance (DNI) is the portion of GHI that comes in a straight line from the sun 3. Diffuse horizontal irradiance (DHI) is that portion of radiation that arrives at the surface from indirect paths. The GHI value includes both the direct and diffuse irradiance. Both direct radiation and diffuse irradiance is useful for solar applications like flat plate collectors, but only direct radiation can be focused using concentrating collectors. 21

22 Source: NREL 1-3 The Solar Resource A map of the average annual solar resource for the U.S.:

23 Source: Courtesy of 3TIER. 1-3 The Solar Resource A map of the average annual solar resource for the world: 23

24 Source: David Buchla 1-3 The Solar Resource Environmental effects of solar energy are: Manufacturing including certain hazardous materials Disposal of panels when life of the product is over Certain types of solar installations have water requirements Land use issues Effect on wildlife 24

25 1-4 The Wind Resource Global patterns of winds are driven by three primary air cells in each hemisphere: The tropical cell, the mid-latitude cell, and the polar cell. When the earth s rotation is taken into account, the winds are deflected by the Coriolis force that adds an east-west component to the movement of the air in the global air cells. In the U.S., the best wind resources are on the coasts, the Great Lakes and the Midwest as shown in the following slide: 25

26 Source: NREL 1-4 The Wind Resource 26

27 Source:3TIER 1-4 The Wind Resource A map of the wind resource for the world: 27

28 Source: NREL 1-4 The Wind Resource Offshore winds are generally higher because of the clear path free of buildings and land masses. The offshore resource is frequently near population centers, minimizing transmission issues. Some countries with the best offshore wind resources are the UK, Ireland, Italy, the Philippines, Japan, and parts of the United States.

29 Source: David Buchla 1-4 The Wind Resource Environmental issues: Land use and visual eyesore Structures may create hazard for small aircraft Noise Bird strikes Additional power line infrastructure

30 1-5 Geothermal Resources Geothermal is heat generated within the earth primarily from radioactive decay. The best resources are along tectonic boundaries where it can be used for driving steam generators and provide baseline power. 30

31 Source: NREL 1-5 Geothermal Resources Low quality geothermal heat is available in most parts of the world and can be used for geothermal heat pumps (GHP) to provide heat or air conditioning. These are systems that work on a basic refrigeration cycle using heat in the ground as a basic resource.

32 1-5 Geothermal Resources Plate tectonics is a geological theory that explains how the earth s surface moves and changes over time. The outer surface of the earth is divided into plates that form the lithosphere. The best spots for geothermal energy tend to be near plate boundaries.

33 Source: NREL 1-5 Geothermal Resources In the U.S., the best geothermal sites tend to be in the west as shown on the geothermal resource map.

34 Source: NREL 1-5 Geothermal Resources Environmental effects of Geothermal plants Low gaseous emissions including a small amount of CO 2 Can have high volume of water requirements Water injection into ground to replace ground water Very minor earthquakes ( micro-quakes ) 34 34

35 1-6 Hydroelectric Resources Hydroelectric resources broadly covers any source that converts the energy in moving or falling water into electricity. As such, the water is considered to be a prime mover. Water is used to generate electricity primarily by trapping it behind dams and releasing it to turn turbines as it is needed. Flowing water in rivers, streams, and tides are also used to a smaller extent. Source: 35

36 1-6 Hydroelectric Resources The location of hydroelectric power plants in the U.S. principally is in mountainous regions.

37 Source: NREL 1-6 Hydroelectric Resources In addition to large storage dams, there are dams used in rivers in systems called run of the river systems (ROR). In a few coastal locations, a tidal barrage dam is used to trap water from tides and generate power by releasing it through turbines. Ocean waves and natural current from tides have been used to generate power in some areas, but overall have been a small part of the energy mix.

38 1-6 Hydroelectric Resources There is a tremendous reservoir of low quality heat in the oceans. Warm surface waters can boil ammonia, which is condensed by deeper cold water to drive a turbine. This technology is called Ocean Thermal Energy Conversion (OTEC) and there is interest in developing the technology.

39 Source: David Buchla 1-6 Hydroelectric Resources Environmental issues with dams: Silting problems filling in reservoirs and depriving farmlands of the renewing effects of silt. Water quality and flow are affected Loss of fish habitat and upsetting natural migration patterns Loss of scenic and wild rivers and loss of useful land for reservoirs.

40 1-7 Biomass and Biofuel Resources Biomass fuels are fuels derived from organic matter and they comprise the largest segment of the renewable energy sector. Examples of biofuels are: wood chips waste from the paper industry agricultural waste organic and food waste various crops grown for fuels One use for biofuels is to cofire it with coal in electrical power stations to alleviate some of their CO 2 emissions.

41 Source: NREL 1-7 Biomass and Biofuel Resources For the U.S., the crop residue resource map is:

42 Poet Bio Refining 1-7 Biomass and Biofuel Resources Liquid biofuels include ethanol, produced from grains such as corn. An ethanol plant: An ethanol plant. Principle steps are:1) offloading 2) grinding 3) treatment with sulfuric acid to decompose into sugars 4) fermentation 5) storage of fuel Biodiesel is another biofuel made from vegetable oil, animal fat, or cooking grease that is combined with alcohol.

43 Source: NREL 1-7 Biomass and Biofuel Resources Environmental effects of energy crops: Reduced biodiversity and loss of wildlife habitat particularly as farmers plant more pristine lands for energy crops Increased water requirements for irrigation and processing, particularly with ethanol production Increased use of pesticides and fertilizers which has significantly increased nitrate levels in rivers and streams and affected drinking water Replacement of farmland that was used for food crops with production of ethanol. There are some positive benefits for growing certain biofuels, especially with switch grass and tree farming,

44 Selected Key Terms Biomass Catagenesis Diagenesis Diffuse horizontal irradiance Organic material that is commonly used for fuels for heating, power generation or making liquid fuels useful in transportation The cracking process that results in the conversion of kerogens into hydrocarbons including natural gas and oil. The process of converting constituents to a different product through application of heat and pressure. The portion of global horizontal irradiance that comes in a indirectly (scattered radiation) from the sun.

45 Selected Key Terms Direct normal irradiance Ethanol Kerogen Solar constant Tokamak The portion of global horizontal irradiance that comes in a straight line from the sun. The primary biofuel used as a gasoline additive and is a type of alcohol. A mixture of organic chemical that are part of the organic matter in sedimentary rocks. The power emitted by the sun that falls on 1 square meter. It is generally cited as 1368 W/m 2. A fusion reactor used by researchers to investigate properties of plasmas with the goal leading to a fusion energy reactor that can be used for electrical power generation.

46 true/false quiz 1. The primary use of coal is for industrial heat.

47 true/false quiz 2. The formation of coal into an organic peat is called diagenesis.

48 true/false quiz 3. Burning any fossil fuel releases CO 2.

49 true/false quiz 4. The major issue with nuclear power is the large amount of cooling water required.

50 true/false quiz 5. The fuel for future fusion reactors is CO 2.

51 true/false quiz 6. The solar spectrum refers only to visible light.

52 true/false quiz 7. The Coriolis force adds an east-west component to the movement of the air in the global air cells.

53 true/false quiz 8. Hydroelectric resources are concentrated in mountainous regions.

54 true/false quiz 9. Geothermal heat pumps cannot be used for cooling.

55 true/false quiz 10. Biomass burning can help electrical power stations to alleviate some of their CO 2 emissions

56 true/false quiz Answers: 1.F 2.T 3.T 4.F 5.F 6.F 7.T 8.T 9.F 10. T