Energy. on this world and elsewhere. Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434)

Transcription

1 Energy on this world and elsewhere Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434) Course web site available at click on classes and find Physics or at Lecture #3 August 29, 2017

2 Announcements Starting Thursday (the 31st) I ll start keeping track of attendance. On the two class websites: - - Main website: you will find the slides from lectures 1 and 2, and shortly 3, in pdf form. On UVa Collab: The Character of Physical Law by Feynman will be in the resources folder. Homework for Thursday/Tuesday: - - Please read Chapter 1 from The Character of Physical Law. Also read Chapters 2 of the class notes (I m assuming you

3 U.S. renewable electricity generation by technology

4 End uses for energy Too many to begin listing individually! There is no one unique way to enumerate end uses. Residential Commercial Industrial Transportation Electricity Transportation Other It will become clear in a moment why I include the list on the left. I prefer thinking about things with categorizations more along the lines of the list on the right.

5 Getting the big picture Primary energy sources End uses

6 Energy Flow Unit of energy used above is the quad which is equal to BTU s - more on units shortly

7 Energy Flow b NGPL 2.61 Natural Gas Crude Oil Coal a Fossil Fuels Domestic Production d Supply Coal h Natural Gas Coal 1.53 g Other 2.57 Fossil j Fuels Exports 4.10 k Consumption Residential Commercial and Industrial l Nuclear 8.01 Renewables 6.56 c i Petroleum Crude Oil and Products Imports f Adjustments 2.18 Nuclear 8.01 c Renewables 6.82 Transportation e Other 4.74

8 Energy Intensity

9 Primary energy consumption by source and sector (2015, in quads) percent of sources percent of sectors petroleum (36%) transportation 27.6 (28%) natural gas (29%) industrial (22%) residential and commercial (11%) coal (16%) renewable energy (10%) nuclear electric power 8.3 (9%) source 9 < electric power (39%) sector

10 The energy infrastructure has a huge array of components on both the supply and the consumption ends.

11 Examples of energy infrastructure Railroads Mining operations Power plants Oil fields Pipelines Electrical power-line grids Natural-gas-line grids Vehicle fleet (cars, trucks, etc.) and much much more Some authors estimate 50 years will be necessary to truly change our energy infrastructure.

12 Example of energy infrastructure Transportation fleet Over 150,000,000 vehicles domestically. Typically less than 10% replaced per year. No more than a few percent are hybrids. Even something dynamic, like the automobile fleet, would take well over a decade to replace with new technology (maybe many decades).

13 Example of energy infrastructure Coal - Coal Mines - Railroads Power plants Transmission wires Local electrical distribution

14 Railroads From postcard dated September 20, In 1840 s, was the western-most station in Virginia. Today the station is gone, but the tracks still carry CSX trains carrying coal that also go through Charlottesville.

15 Coal-fired power plants in excess of 60 years old were only recently converted to natural gas Dominion Power s Bremo coal-fired power plant First two units (now retired) went into operation in Units 3 and 4 went into operation in 1950 and 1958 respectively. Also uses burners that minimize the emission of NO x s Produces 220 Megawatts using 2500 tons of coal daily (25 hoppers). Have been retrofitted with electrostatic precipitators to trap fly ash.

16 Estimates for fully replacing our energy infrastructure are around 50 years. The decisions we make today will in many cases take decades to have a full impact.

17 Distribution systems Energy Grids - - the Electric Grid the Gas grid: lighting (historically), heating, industrial processes, generating electricity Centralized distribution Solid fuels: coal, wood, other biomass Liquid fuels: gasoline, diesel, ethanol

18 The electric grid has some It decouples the primary energy sources from the end uses. The utility can switch from one primary energy source to another and the transition is invisible to the consumer. wonderful features: Nice example: VERY efficient generation of electricity using natural gas can be accomplished with a plug and play unit.

19 Dominion Power s Bremo power Station Stopped using coal in 2013 Units 3 and 4 were converted. Power now generated by gasfired combustion turbines. Reduced pollutants including CO 2

20 Diversity of primary energy sources for the production of electricity Other Oil Wind Other Nukes Nukes Coal Hydro Coal Hydro Natural gas Natural gas (Wind was 0.36% in 2004) (Wind was 4.4% in 2014) Taken from the website: although I checked 2005 (not shown) against EIA, and it agreed within 1%.

21 Energy flow into electricity

22 Energy flow into electricity Electric Utilities Petroleum 0.78 Coal Natural Gas 3.09 Nuclear Electric Power 7.49 Hydroelectric Power 2.56 Fossil Conversion Fuels Lossesa Plant Useb T&D 0.54 Losses 0.97 Energy Consumed To Generate Electricity Gross Generation of Electricity Net Generation of Electricity c Electricity Exports 0.05 Electric Utility Retail Sales Residential 4.07 Commercial 3.51 Industrial 3.64 Geothermal and Otherd 0.02 Electricity Imports 0.17 Sales to Electric Utilities 1.99 g Unaccounted fore 0.19 Otherf 0.38 Coal 2.79 Natural Gas 3.38 Petroleum 0.43 Nuclear 0.51 Hydropower 0.22 Otherh 1.00 Other 8.33 Nonutility Power Producers Energy Consumed To Generate Electricity 8.33 Conversion Losses 5.52 Gross Generation 2.81 Net Generation 2.67 a Plant Use 0.14 b Balancing Item 0.04 i Nonutility Power Producers Direct Use and Sales to End Users 0.71

23 The Physics of Energy

24 The Conservation of Energy Energy can neither be created nor destroyed, but can only be converted from one form to another.

25 Getting a concrete sense of human energy output Power = Energy Unit time = Joules second = Watts A person burns energy at the rate of about 100 Watts Athletes can maybe go to a few hundred watts output

26 The power we generate The power we consume American s per capita A person burns energy consumption is energy at the rate 100x100 Watts of about 100 Watts = 10 kilowatts The standard of living is closely coupled to per capita energy use. Pre-industrial societies were definitely energy constrained. Multiple authors have suggested that the historical quest to harness energy was a contributing factor to slavery.

27 Some things in nature do not change. Conservation Laws

28 Conservation of charge The total amount of charge in the universe (or some defined isolated space) does not change. Charge comes in positive and negative varieties. If it disappears from one place, it shows up somewhere else. Electrons are negative Protons are positive Neutrons, as the name suggests, are neutral.

29 Conservation of charge Particles can change into different particles, but the charge needs to go somewhere. In Beta Decay, depicted below, a neutron changes into a proton, emitting a W - that then turns into an electron. This is the type of reaction we detected with a geiger counter during one of our earlier classes. Feynman diagram for the weak decay of a neutron n p + e W - - Neutron decay note charge is conserved at each vertex νe

30 Conservation of angular momentum Kepler discovered that when planets orbit the sun, they... sweep out equal areas in equal times. This is another example of the conservation of angular momentum.

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