Environmental Effects of Energy Production and Use.ppt

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1、Environmental Effects of Energy Production and Use,Effects of fossil fuel production Effects of fossil fuel combustion “Acid rain“ CFC emissions from HVAC equipment Stratospheric ozone depletion Global Warming/The “Greenhouse Effect“ Energy conservation as a pollution and greenhouse gas reduction st

2、rategy,Effects of Fossil Fuel Production,Fossil fuels are produced by mining or drilling. Considerable environmental damage results from mining and drilling. Surface (“strip“) mining for coal often results in vegetation loss, stream and soil acidification, road damage, etc. Underground mining is ext

3、remely hazardous, and old mines sometime catch fire and burn for years/decades, causing surface subsidence and damage.,Abandoned coal strip mine pit near Brookwood, Alabama on Hwy 216,Fuel Production Effects (Contd),Drilling for petroleum and natural gas often results in release of briny water onto

4、surface and into streams causing damage to the stream life and sometimes rendering the water unfit for human consumption (even after ordinary treatment). Petroleum refining to produce gasoline, kerosene, jet fuel, diesel oil, fuel oil, etc. often results in the release of carcinogenic and ecological

5、ly damaging hydrocarbons into the environment. Most fossil fuel extraction technologies are themselves fairly energy intensive.,Fossil fuel processing has environmental consequences,Effects of Fossil Fuel Combustion,Fossil fuels are hydrocarbons containing traces of nitrogen, sulfur and other elemen

6、ts. Typical combustion reaction: CwHxOzNaSb + O2 + N2 CO2+ CO + H2O + NOx + SO2 + HC + Only H2O is essentially benevolent. CO and many HCs are toxic to humans. NOx and SO2 combine with rainwater to form nitric and sulfuric acids, i.e., “acid rain“. CO2 is the primary culprit in global warming, but o

7、ther gases are important.,Important Combustion Processes,The three most important combustion processes for energy production are natural gas flames for heating furnaces and water heaters, boiler flames, and internal combustion engine flames. Burning natural gas for heating produces some NOx, signifi

8、cant CO2 (but less than coal or oil). Boiler combustion of coal and fuel oil for industrial and electric power produces significant quantities of CO2, NOx and SO2,Combustion Processes (Contd),Because boiler flames are at relatively low temperature (compared to IC engines), most NOx is formed from ox

9、idation of fuel nitrogen. IC engine flames are very hot, which leads to dissociation of N2 and O2, thus, most NOx in engines is formed from the oxidation of nitrogen introduced with the combustion air. IC engines are also significant producers of CO2, CO (spark-ignited), SO2 (diesel) and hydrocarbon

10、s.,CFC from HVAC Equipment,Refrigerators, air conditioners and heat pumps have used chlorofluorocarbons (CFCs) as their working fluids (refrigerants). CFCs at normal conditions are extremely inert, stable and non-toxic. Their use leads to good equipment efficiency and safety. Because they are so ine

11、rt, CFCs are not destroyed in the lower atmosphere and eventually rise to the upper atmosphere (stratosphere).,CFC Problem,UV light in the stratosphere breaks down the CFC molecule, releasing chlorine ions. The Cl- ion attacks ozone (O3) molecules, converting them to O2 and O. The Cl- ions are relea

12、sed after breaking down an O3 molecule, and both the O and the Cl- are free to attack other O3 molecules. Release of CFCs has already caused significant stratospheric ozone depletion, particularly in the South and North Polar regions.,Stratospheric Ozone Depletion,Ozone is a good absorber of solar u

13、ltraviolet radiation, and depletion of upper atmosphere ozone results in increased surface levels of UV radiation. Increased levels of UV at the surface enhance global warming, but more importantly, can result to increased human skin cancer and plant damage.,The ozone hole at its peak in 2003 over A

14、ntarctica,Ozone Depletion (Contd),The Montreal Protocols, signed in 1987, called for a 50% reduction in the most damaging CFCS (including R-11 and R-12) by 2000. Because of new findings of polar ozone depletion and scientific demonstration of its cause, the London Montreal Protocol meeting of 1990 r

15、aised the cutback to 100%, and the Copenhagen meeting of 1992 moved the deadline to 1996.,Ozone Depletion (Contd),Hydrochlorofluorocarbons (CHFCs), such as R-22, are scheduled for phaseout by 2020 by the 1992 agreement (maybe 2010 or 2012 now). The ozone depletion index of R-22 (home air conditioner

16、s and heat pumps is about 0.05, where R-12 has an ODI of 1.0 The discoverers of the ozone depletion link to stratospheric ozone received the Nobel Prize in chemistry in 1995.,Global Warming,Glass is selective.,A Greenhouse.,Sunlight at = 0.5 m mostly passes through the glass Re-emitted radiant energ

17、y from the 300 K interior is at 0.5 m The glass is opaque to this infrared wavelength, so re-emitted energy cannot radiate away The greenhouse warms up,Principal Greenhouse Gases,CO2- (55% greenhouse effect)- Primarily from combustion of carbon-containing fuels (fossil fuels). CFCs- 24 % of warming

18、(R-11 and R-12: 17% and other CFCs: 7%). From HVAC equipment, foams, chip manufacturing, etc. (e.g., lens blower and asthma inhaler) “Developing” nations have 10 yr setback on Montreal Protocols- some problems with black market R-12, etc.,Greenhouse Gases (Contd),Methane- (15% of warming) Some “natu

19、ral” biological emissions, such as ruminant animal flatulence and “releases” from termites, but these are enhanced by mans activities (farming, logging). Some sources are purely manmade, such as unburned methane in natural gas combustion and gas line leaks (huge leaks in Russia). Compared to a CO2 m

20、olecule, one CH4 molecule has 25 times the global warming potential (GWP) and one R-12 molecule has 21,000 times the GWP!,Mans agricultural and logging activities result in enhanced emissions of greenhouse gas from natural sources. Ruminant and termite “emissions” are significant sources of CO2,Gree

21、nhouse Gases (Contd),Nitrous oxide (6% of warming)- From combustion and natural sources. With the exception of the CFCs, there has been little worldwide agreement on how to reduce greenhouse gases, including the most recent Kyoto Conference in 12/97. Industrialized countries w/ 20% of population acc

22、ount for 75% of greenhouse gas emissions. The U.S. accounts for 20% of the worlds manmade CO2 emissions.,How Can Global Warming Be Reduced?,Increased energy efficiency. This is simplest and most cost-effective. Substitution of natural gas for coal and oil (short term, limited supplies). Reforestation and reduction of deforestation. Safe nuclear power (fission). Alternative renewable energy: OTEC, wind, solar thermal, solar photovoltaic, biofuels. Hydrogen transportation fuel (needs research). Fusion power (needs development). Other alternatives?,