Energy Production & Consumption: Fossil Fuels, Nuclear, Renewables & Conservation - Prof. , Exams of Community Health

Download Energy Production & Consumption: Fossil Fuels, Nuclear, Renewables & Conservation - Prof. and more Exams Community Health in PDF only on Docsity! ENERGY Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Topics • Energy Sources and Uses • Fossil Fuels • Nuclear Power • Energy Conservation • Solar Energy • Fuel Cells • Biomass • Energy From the Earth’s Forces • What’s Our Energy Future? Worldwide Commercial Energy Production Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Wind, etc. Hydro 1% Nuclear 6% 6% Uses of Energy • Commercial uses of energy – Industry uses 38%; – Residential and commercial buildings use 36%; and, – Transportation uses 26%. Uses of Energy • Half of all energy in primary fuels is lost during conversion to more useful forms while being shipped or during use. – Nearly two-thirds of energy in coal being burned to generate electricity is lost during thermal conversion in the power plant. – Another 10% is lost during transmission and stepping down to household voltages. Per Capita Energy Use & GDP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. @ Qatar = 25,000 L E i - 20,000 So Ss & = 15,000 oe 5 3 United Arab Se iceland £2 o 10,000 |~“Bahrain a Finland Luxembourg 9 Canada @ We Gweden 2 5.000 Belgium @ Norway : Sloveniam U.K. mt me mg @ Japan mu Poland Denmark 0 a Malaysja | | 0 20,000 40,000 60,000 Per capita GDP $US. FOSSIL FUELS • Fossil fuels are organic chemicals created by living organisms that were buried in sediments millions of years ago and transformed to energy-rich compounds. • Because fossil fuels take so long to form, they are essentially nonrenewable resources.  __Coal_______  ___Oil______  Natural Gas Coal South and Central America 2% Oil Copyr ght The MeGraw-HIl Companies, Ins Permission required for reproduct er oF dieplay: Nigeria Africa and Middle East 6% 3.0% Libya 3.1% USA 2.7% Natural Gas Huseia Copy: ©The MeGrew-Hil Companies, Inc, Permission required for reprexkasion or cispay. Venezuela Asia Pacific 6.8% Atrica 7.7% North America south and Iran . 7.8% 4.2% Central America 11.4% Kuwely 4.1% Other/Europe Oil Extraction and Use • The countries of the Middle East control two- thirds of all proven-in-place oil reserves. Saudi Arabia has the most. • The U.S. has already used up about 40% of its original recoverable petroleum resource. • Oil combustion creates substantial air pollution. Oil Extraction and Use • Drilling causes soil and water pollution. • Often oil contains a high _sulfur level_. Sulfur is corrosive, thus the sulfur is stripped out before oil is shipped to market. • Oil is primarily used for transportation providing > 90% of transportation energy. • Resources and proven reserves for the year 2000 are 650 billion barrels (bbl). 800 bbl remain to be discovered or are currently not recoverable. Natural Gas Consumption •World’s third largest commercial fuel (23% of global energy used). •Produces half as much CO2 as equivalent amount of coal. •Most rapidly growing used energy source. NUCLEAR POWER • Nuclear power now produces only 7% of the U.S. energy supply. • Construction costs and safety concerns have made nuclear power much less attractive than was originally expected. – Electricity from nuclear power plants was about half the price of coal in 1970, but twice as much in 1990. Nuclear Reactors • The common fuel for nuclear reactors is U235 that occurs naturally (0.7%) as a radioactive isotope of uranium (U is 99% U238). • U235 is enriched to 3% concentration as it is processed into cylindrical pellets (1.5 cm long). The pellets are stacked in hollow metal rods (4 m long). • 100 rods are bundled together into a fuel assembly. Thousands of these fuel assemblies are bundled in the reactor core. Nuclear Reactors • When struck by neutrons, radioactive uranium atoms undergo nuclear fission, releasing energy and more neutrons. This result triggers a nuclear chain reaction. • This reaction is moderated in a power plant by neutron-absorbing cooling solution (Moderator). • Control Rods composed of neutron-absorbing material are inserted into spaces between fuel assemblies to control reaction rate. • Water or other coolant is circulated between the fuel rods to remove excess heat. Reactor Design Containment structure Steam Steam L- = Turbine generator Generator Pressurized water reactor | Condenser 1 | cm Fuel rods Hot water Radioactive Waste Management • Production of 1,000 tons of uranium fuel typically generates 100,000 tons of tailings and 3.5 million liters of liquid waste. – Now approximately 200 million tons of radioactive waste exists in piles around mines and processing plants in the U.S. Radioactive Waste Management • About 100,000 tons of low-level waste (clothing) and about 15,000 tons of high-level (spent-fuel) waste in the US. – For past 20 years, spent fuel assemblies have been stored in deep water-filled pools at the power plants. (designed to be temporary). – Many internal pools are now filled, and a number plants are storing nuclear waste in metal dry casks outside. ENERGY CONSERVATION – Most potential energy in fuel is lost as waste heat. – In response to 1970’s oil prices, average US automobile gas-mileage increased from 13 mpg in 1975 to 28.8 mpg in 1988. Falling fuel prices of the 1980’s, however, discouraged further conservation. Energy Conversion Efficiencies • Energy Efficiency is a measure of energy produced compared to energy consumed. – Household energy losses can be reduced by one-half to three-fourths by using better insulation, glass, protective covers, and general sealing procedures. Energy gains can be made by orienting homes to gain passive solar energy in the winter. SOLAR ENERGY • Photosynthesis • Passive solar heat is using absorptive structures with no moving parts to gather and hold heat. Greenhouse design • Active solar heat is when a system pumps a heat- absorbing medium through a collector, rather than passively collecting heat in a stationary object. Water heating consumes 15% of US domestic energy budget. Mean solar energy striking the upper atmosphere is 1,330 watts per square meter. The amount reaching the earth’s surface is 10,000 times > all commercial energy used annually. Until recently, this energy source has been too diffuse and low intensity to capitalize for electricity production. Photovoltaic Solar Energy • During the past 25 years, efficiency of energy capture by photovoltaic cells has increased from less than 1% of incident light to more than 10% in field conditions, and 75% in laboratory conditions. – Invention of amorphous silicon collectors has allowed production of lightweight, cheaper cells. Photovoltaic Solar Energy • Photovoltaic cells capture solar energy and convert it directly to electrical current by separating electrons from parent atoms and accelerating them across a one-way electrostatic barrier. – Bell Laboratories - 1954 • 1958 - $2,000 / watt • 1970 - $100 / watt • 2002 - $5 / watt Average Daily Solar Radiation Solar radiation units of the legend are langleys [a langley = 1 calorie/cm2 (3.69Btu/ft2)] •______Distributional Surcharges______ –Small charge levied on all utility customers to help finance research and development. •Renewable Portfolio –Mandate minimum percentage of energy from renewable sources. •__Green Pricing__________ –Allow utilities to profit from conservation programs and charge premium prices for energy from renewable sources. Promoting Renewable Energy FUEL CELLS • Fuel cells use ongoing electrochemical reactions to produce electrical current • Fuel cells provide direct-current electricity as long as supplied with ____________ and ________________. • Hydrogen is supplied as pure gas, or a reformer can be used to strip hydrogen from other fuels. • Fuel cells run on pure oxygen and hydrogen produce only drinkable water and radiant heat. • Reformer releases some pollutants, but far below conventional fuel levels. • Fuel cell efficiency is 40-45%. • Positive electrode (cathode) and negative electrode (anode) separated by electrolyte which allows charged atoms to pass, but is impermeable to electrons. Electrons pass through external circuit, and generate electrical current. FUEL CELLS Fuelwood Crisis in Less-Developed Countries • About 40% of the world’s population depends on firewood and charcoal as their primary energy source. • Supplies diminishing • Half of all wood harvested worldwide is used as fuel. Using Dung as Fuel • Where other fuel is in short supply, people often dry and burn animal dung. • When burned in open fires, 90% of potential heat and most of the nutrients are lost. • Using dung as fuel _deprives fields of nutrients and reduces crop production. • When cow dung is burned in open fires, 90% of the potential heat and most of the nutrients are lost. Using Methane As a Fuel Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Shredded a organic Gas to purification materials Gas meter or combustion K+ a —- Digester ==) effluent • Hydropower – By 1925, falling water generated 40% of world’s electric power. • Hydroelectric production capacity has grown 15-fold, but fossil fuel use has risen so rapidly that now hydroelectric only supplies one-quarter of electrical generation. • Total world hydropower potential estimated about 3 million MW. – Currently use about 10% of potential supply. • Energy derived from hydropower in 1994 was equivalent to 500 million tons of oil. Much of recent hydropower development is in very large dams. Hydropower Hydropower • Drawbacks to dams include: – Human Displacement – Ecosystem Destruction – Wildlife Losses – Large-Scale Flooding Due to Dam Failures – Sedimentation – Herbicide Contamination – Evaporative Losses – Nutrient Flow Retardation Wind Energy • Wind power - advantages and disadvantages • Wind farms - potential exists in Great Plains, along seacoasts and Eastern Washington