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PSTL 1163: Physics by Inquiry Environmental connections

PSTL 1163: Physics by Inquiry Environmental connections. Unit 1: Environmental impacts of electricity generation Day 4: The Greenhouse effect and carbon. Interesting points from stupidity article Stupidity is a bad word to use, use curiosity

jeremy-pitts
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PSTL 1163: Physics by Inquiry Environmental connections

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  1. PSTL 1163: Physics by InquiryEnvironmental connections Unit 1: Environmental impacts of electricity generation Day 4: The Greenhouse effect and carbon

  2. Interesting points from stupidity article • Stupidity is a bad word to use, use curiosity • School puts to strong an emphasis on the correct answers • School is not research science.

  3. Key questions • What is the Greenhouse Effect and how does it work? • What are some methods under consideration for reducing the amount of greenhouse gases emitted into the atmosphere?

  4. Greenhouse Effect: Basic ideas • The amount of energy a body emits depends on its temperature (a hot stove emits more energy than a cold one). (Stefan-Boltzmann law P = sT4) • Because it is hot, the sun emits energy and some of this falls on the Earth. About half is visible (“light”) and ultraviolet (UV) radiation. About half is infrared (IR) radiation, AKA heat. • Because it is warm, the Earth emits energy, mostly in the form of IR radiation. http://theglassblog.files.wordpress.com/2011/02/solar-spectrum1.jpg

  5. Greenhouse Effect: Basic ideas • “Greenhouse gases” (GHG) in the Earth’s atmosphere do almost nothing to visible and UV radiation, it passes right through, keeping going in the same direction it was before. • GHG absorb a lot of IR radiation. This radiation is then re-reradiated evenly in all directions. • The more such gases there are, the larger the fraction of IR radiation they absorb and re-radiate. http://scienceofdoom.com/2009/11/28/co2-an-insignificant-trace-gas-part-one/

  6. (Very) simplified climate model 1 • No atmosphere: • The Earth absorbs energy from the sun Iin (UV + visible + IR) • The Earth radiates energy Iout (IR). If the Earth is to stay the same temperature, Iin = Iout.Temperature of the Earth can be calculated from Iout. Iin Iout Earth

  7. (Very) simplified climate model 2 • Atmosphere (low GHG): • The Earth absorbs energy from the sun Iin (UV + visible + IR) • The Earth radiates energy Iout (IR). • Half of this energy (1/2 Iout) is absorbed by atmosphere. • Half of the absorbed energy (1/4 Iout) is re-radiated away from the Earth and half (1/4 Iout) is re-radiated toward the Earth. Equilibrium condition: Iin = (1/2 + 1/4) Iout.Temperature of the Earth can be calculated from Iout = 4/3 Iin. Iin Iout Iout 1/2 Iout 1/4 Iout 1/2 Iout 1/2 Iout 1/4 Iout 1/4 Iout Earth

  8. (Very) simplified climate model 3 • Atmosphere (high GHG): • The Earth absorbs energy from the sun Iin (UV + visible + IR) • The Earth radiates energy Iout (IR). • Two-thirds of this energy (2/3 Iout) is absorbed by atmosphere. • Half of the absorbed energy (1/3 Iout) is re-radiated away from the Earth and half (1/3 Iout) is re-radiated toward the Earth. Equilibrium condition: Iin = (1/3 + 1/3) Iout.Temperature of the Earth can be calculated from Iout = 3/2 Iin. Iin Iout Iout 1/3 Iout 1/3 Iout 2/3 Iout 2/3 Iout 1/3 Iout 1/3 Iout Earth

  9. Comparing the models • Iin is about the same for all 3 cases (GHG don’t affect visible and UV.) If Iin = 1000: • No atmosphere: Iout = Iin = 1000 • Low GHG atmosphere, Iout = 4/3 Iin = 1333 • High GHG atmosphere Iout = 3/2 Iin = 1500 • Iout is higher for high GHG atmosphere. Higher emission means high Earth temperature. With more greenhouses gases as an insulating “blanket” around the Earth, the Earth has to be hotter in order to radiate more, so that the energy output matches the energy input.

  10. What are greenhouse gases? • Major ones include: • Water vapor H2O • Carbon dioxide CO2 • Nitrous oxide NO2 • Ozone O3 • Methane CH4 • Chlorofluorocarbons (CFCs) • Not all have equivalent effects • Lifetime in atmosphere and other factors make methane and CFCs much more effective than CO2. • Of the ones we can do something about, CO2 and CH4 contribute the most to the Greenhouse Effect.

  11. Technology: Carbon sequestration • Clean coal technologies: • Underground Coal Gasification: Instead of mining coal as rocks, convert it to a gas underground, then bring it to the surface. Resulting product has less S, N, and ash. • Next Generation Coal Gasification: Bring coal to the surface as rocks, then turn it into gas to clean it before use. • Post-Combustion Capture: Scrub the combustion gases resulting from the burning of coal to eliminate undesirable components • Geological sequestration: Bury the captured CO2 recovered from burned coal to keep it out of the atmosphere.

  12. Technology: Carbon sequestration • No one method is sufficient to achieve necessary reductions in CO2 emissions. • All methods reduce net efficiency of generating electricity from coal, raising the price of electricity from coal. • Federal regulation of CO2 emissions could spur investment and innovation in such technologies, bringing the price down.

  13. Economics: Carbon tax • Taxes can be levied based on: • Carbon content of fuels used • Carbon content of emissions from generating plants • Amount of energy generated, with or without consideration of energy source • Considerations: • What is the money collected through the tax used for? • Is this a regressive tax? (disproportionally impacting low income earners) • Will companies simply move to locations with low or no taxes?

  14. Economics: Cap and trade • The amount of undesirable emissions is capped by issuing a limited number of permits allowing some amount of pollution. Companies that do not have enough permits to cover their emissions may (1) buy or trade for more on the open market, (2) reduce their emissions to correspond to the permits they have, or (3) pay fines for emitting more pollution than they are allowed, whichever is most cost-effective. • It is not yet clear which is better, a tax or a cap and trade system. Both have advantages and disadvantages.

  15. Key questions • What is the Greenhouse Effect and how does it work? • What are some methods under consideration for reducing the amount of greenhouse gases emitted into the atmosphere?

  16. For next time: • See Environment assignment 4 on Moodle page (Electricity in the real world.) You will do some research to find out the answer to one of the following questions: • Why do most 2-pronged electric plugs have one blade wider than the other? • Why do some electric plugs have 3 prongs? What is the function of the 3rd prong? • Physiologically, how does electricity kill? Which is more dangerous, high voltage or high current? • Caution: Misinformation alert!

  17. What are some questions you have about electricity? • Which way does the current flow? • What is the difference between current and voltage? • Why do other countries have a different voltage? • How does a two way switch work? • Does it matter which end is positive and which is negative? • How do transformers work? • How does lightning work? • How do you record sprites? • Is wireless charging possible? • Is a Tesla coil possible? • How is there electricity in your body? • What is the current in the human body?

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