Presentation on theme: "ME 416/516 Environmental Effects of Energy Production and Use Effects of fossil fuel production Effects of fossil fuel combustion "Acid rain" CFC."— Presentation transcript:
ME 416/516 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 strategy
ME 416/516 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 extremely hazardous, and old mines sometime catch fire and burn for years/decades, causing surface subsidence and damage.
ME 416/516 Abandoned coal strip mine pit near Brookwood, Alabama on Hwy 216
ME 416/516 Fuel Production Effects (Cont’d) Drilling for petroleum and natural gas often results in release of briny water onto 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 ecologically damaging hydrocarbons into the environment. Most fossil fuel extraction technologies are themselves fairly energy intensive.
ME 416/516 Fossil fuel processing has environmental consequences…
ME 416/516 Effects of Fossil Fuel Combustion Fossil fuels are hydrocarbons containing traces of nitrogen, sulfur and other elements. Typical combustion reaction: C w H x O z N a S b + O 2 + N 2 CO 2 + CO + H 2 O + NO x + SO 2 + HC + … Only H 2 O is essentially benevolent... CO and many HC's are toxic to humans. NO x and SO 2 combine with rainwater to form nitric and sulfuric acids, i.e., "acid rain". CO 2 is the primary culprit in global warming, but other gases are important.
ME 416/516 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 NO x, significant CO 2 (but less than coal or oil). Boiler combustion of coal and fuel oil for industrial and electric power produces significant quantities of CO 2, NO x and SO 2
ME 416/516 Combustion Processes (Cont’d) Because boiler flames are at relatively low temperature (compared to IC engines), most NO x is formed from oxidation of fuel nitrogen. IC engine flames are very hot, which leads to dissociation of N 2 and O 2, thus, most NO x in engines is formed from the oxidation of nitrogen introduced with the combustion air. IC engines are also significant producers of CO 2, CO (spark-ignited), SO 2 (diesel) and hydrocarbons.
ME 416/516 CFC from HVAC Equipment Refrigerators, air conditioners and heat pumps have used chlorofluorocarbons (CFC's) as their working fluids (refrigerants). CFC's at normal conditions are extremely inert, stable and non-toxic. Their use leads to good equipment efficiency and safety. Because they are so inert, CFC's are not destroyed in the lower atmosphere and eventually rise to the upper atmosphere (stratosphere).
ME 416/516 CFC Problem UV light in the stratosphere breaks down the CFC molecule, releasing chlorine ions. The Cl - ion attacks ozone (O 3 ) molecules, converting them to O 2 and O. The Cl - ions are released after breaking down an O 3 molecule, and both the O and the Cl - are free to attack other O 3 molecules. Release of CFCs has already caused significant stratospheric ozone depletion, particularly in the South and North Polar regions.
ME 416/516 Stratospheric Ozone Depletion Ozone is a good absorber of solar ultraviolet 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 Antarctica
ME 416/516 Ozone Depletion (Cont’d) The Montreal Protocols, signed in 1987, called for a 50% reduction in the most damaging CFC'S (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 raised the cutback to 100%, and the Copenhagen meeting of 1992 moved the deadline to 1996.
ME 416/516 Ozone Depletion (Cont’d) Hydrochlorofluorocarbons (CHFC's), 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 conditioners 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.
ME 416/516 A Greenhouse... Sunlight at = 0.5 m mostly passes through the glass Re-emitted radiant energy 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
ME 416/516 Principal Greenhouse Gases CO 2 - (55% greenhouse effect)- Primarily from combustion of carbon-containing fuels (fossil fuels). CFCs- 24 % of warming (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.
ME 416/516 Greenhouse Gases (Cont’d) Methane- (15% of warming) – Some “natural” biological emissions, such as ruminant animal flatulence and “releases” from termites, but these are enhanced by man’s 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 CO 2 molecule, one CH 4 molecule has 25 times the global warming potential (GWP) and one R-12 molecule has 21,000 times the GWP!
ME 416/516 Man’s agricultural and logging activities result in enhanced emissions of greenhouse gas from natural sources. Ruminant and termite “emissions” are significant sources of CO 2
ME 416/516 Greenhouse Gases (Cont’d) 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 account for 75% of greenhouse gas emissions. The U.S. accounts for 20% of the world's manmade CO 2 emissions.
ME 416/516 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???