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2/20/2015 Fire • Most modern fuels are substances we burn – Coal, gasoline, gas, oil, propane, charcoal, wood Chapter 4 Energy CHM 107 GCC • The rate we are burning them is not sustainable. Sustainability is more than just availability as we shall see. – These fuels are non renewable – They produce waste that has ill effects on our environment Energy Consumers • US top E consumer per person • US casual about E usage • 70% of US energy comes from fossil fuels – – – – Coal, oil, natural gas Burning them releases CO2, PM, CO, NOx and SOx Why are those gases a problem? Also produces Hg, mercury, in the ash 4.1 Burning Carbon Fuels NOx and SOx • Short hand ways to write – – – – NO and NO2 SO2 and SO3 Gases that cause acid rain Main pollutants • The media refers to them this way Powerplants • Powerplants use chemical energy stored in fossil fuels and burn them (combustion) to release the energy stored in their bonds. • They convert this chemical energy into heat then into kinetic energy then to electrical energy • Burning coal creates heat, which boils water that changes into steam that flows along pipes to the steam turbines which then turn in a magnetic field generating electricity. • The steam is then condensed back to liquid water which flows back to the furnace to be boiled again. This is about 42% efficient. 1 2/20/2015 Energy Burning Coal • Potential – stored energy – Chemical energy is stored in the bonds of fuel and foods • Kinetic energy – energy of motion – After digestion of food we can move • Combustion of coal converts potential energy to heat (boiling water) which turns into mechanical energy (turning turbines) which converts into electrical energy. Coal Power Plant Fossil Fuels • Where did fossil fuels get their energy? From the sun originally captured by plants • 6 CO2 + 6 H2O C6H12O6 + 6 O2 • Green plants capture sun energy via photosynthesis and produce glucose and oxygen gas. When they die they decompose partially getting buried under dirt. Temperature and pressure turns them into coal and oil and natural gas. • We will consume in a few centuries what took hundreds of millions of years to produce. 1st Law of Thermodynamics • Energy can not be created nor destroyed, only converted from one form to another • Forms include chemical, electrical, nuclear, mechanical, radiation, heat, friction, sound • Chemical energy = energy stored in bonds, chemical reactions like combustion releases this energy 2 2/20/2015 4.2 Energy Efficiency • Coal power plants are between 35-50% efficient. You lose heat between each step in the process. Car engines are only about 15% efficient! • How do we measure energy? – calorie (cal) – heat needed to raise one gram of water by one degree Celsius. – Joule (J) One heart beat is one J. Main Fuel Sources • • • • Up to 1880 the main source was wood Then coal became number one until 1950 Oil has been number one since 1950 Coal and oil are fossil fuels (so is natural gas) – Review – What are fossil fuels? Food Calories • Science measures energy in Joules or calories but food uses Calories which is really a kilocalorie or 1000 calories • There are 1000 calories in a Calorie • There are 4.184 Joules per calorie • How many calories are in a Snickers bar that contains 245 Calories? How many Joules? 4.3 Coal – Solid Fossil Fuel • Made up of C, H, O, N, S atoms • 85% is C, carbon • Typical coal plant uses 1.5 millions tons of coal per year • Formula: C135H96O9NS • Trace amount of Hg • Traces of arsenic • Traces of lead Types of Coal • • • • More oxygen means less energy per gram Lignite – lowest grade, similar to peat Sub-bituminous – medium grade Bituminous – higher grade, more pressure in its formation • Anthracite – highest grade, little left in US 3 2/20/2015 Problems with Coal Coal Mining – One Tough Job • Mining is dangerous – China had 4700 deaths in 2006 alone – Accidents in mines, black lung • Mining ruins the environment, erosion occurs • Groundwater exposed to mines becomes acidified and high in Fe and Al, which is bad for fish and human consumption. • Coal is dirty, makes soot, NOx, SOx, PM • Coal blackens buildings, costs money to restore • Coal has mercury concentrates in the ash • Coal burning produces CO2 a GHG (coal accounts for 40% of global CO2 emissions) Black lung Coal Train Just a Joke! What is good about coal? • Cheap • US has plenty of it (25% of the world’s supply) • What about clean coal? – Well that just means putting scrubbers on existing coal plants to help them remove pollutants from the smoke stacks. This should be done anyway. There is no new different better coal, same old coal. None of this addresses CO2 emissions. 4 2/20/2015 USA Has Lots of Coal Reserves Coal’s Future? • Between 1999 and 2009 – North America stayed about the same • But 214 new coal plants proposed, 1/3 refused, 1/3 in court, many can’t find funding – Europe decreased a bit – Africa increased a bit – Asia doubles its usage! Now using about 4x the amount of the US. 4.4 Petroleum – liquid fossil fuel Texas Landscaping • Easy to transport since flows, so more popular than coal, but way more expensive • Petroleum is 48 kJ/g vs high grade coal at 30 kJ/g • US does NOT have enough oil, so we import it – From where? Petroleum = crude oil Hydrocarbons - Alkanes • Petroleum must be refined • It is a mix of many hydrocarbons (1-60 C per molecule) – Compounds with Hydrogen and Carbon (H and C) – Simple hydrocarbons = Alkanes – all single covalent bonds between carbon atoms – Less sulfur than coal so less SOx • To separate the hydrocarbons you use distillation – Heat up the crude oil until it boils – Collect the vapors then condense back to liquid form – Smallest hydrocarbon boils off first, collect it first, and then so on – The more carbon atoms, the higher the boiling point 5 2/20/2015 Distillation Alkanes up to Octane Why do we care about Hydrocarbons? • Once in the gas phase, the vapors travel up the tower. Smaller mass compounds travel up the highest, larger mass compounds travel shorter distances up the tower. • Vapors are condensed back into liquid form at the different levels of the tower and collected. Petroleum Refinery Fossil Fuel; Petroleum “Addicted to Oil” One Barrel of Crude Oil 2009 • • • • • • 19.2 gal gasoline 10.0 gal diesel 3.8 gal jet fuel 1.7 gal heavy oil fuel 1.7 gal methane – butane 7.3 gal other (plastics, pharmaceuticals, fabrics, etc) • China is now the 2nd largest car market • Oil reserves will be depleted in 50-100 years • Shell’s CEO said “after 2015 easy access oil and gas will no longer keep up with demand.” • US Dept of Energy says that peak oil will occur between 2026 and 2047. 6 2/20/2015 Natural Gas Natural Gas = gas fossil fuel • • • • • • Gas Stove 90% methane, CH4, simple hydrocarbon Provides head for 2/3 homes in US Burns cleaner than coal or oil, less impurities No mercury ash produced Little NOx produced, almost no SO2 Makes less CO2 than oil or coal Fracking • Involves drilling down into shale that contains natural gas about 1-2 miles down • Water that contains a “cocktail” of substances is injected under pressure into the shale to create “cracks” into which the gas can flow to the surface for collection • Environmental impacts include the risks contaminating ground water, depleting fresh water, degrading air quality, potentially triggering earthquakes, noise pollution, surface pollution, and the consequential hazards to public health and the environment • The cocktail is usually chemicals that are not disclosed by the companies, sand, and water • Over one million “frac jobs” have been performed in the US 4.5 Heat vs. Temperature Temperature vs Heat • Temperature – kinetic every of atoms. Cold is atoms moving slowly, hot is atoms moving quickly. Does not depend on volume. • Heat – depends on volume. Heat is energy that flows from hot to cold. • A donut is 425 Calories. How many J is this? Recall that Cal = 1000 cal, cal = 4.184 J. Which has higher temperature? Which has more heat? 7 2/20/2015 Heats of Combustion Energy Changes • Heat given off when it burns. Reported in units of kJ/mol or kJ/gram. • Heat of combustion of methane is 802.3 kJ/mol. • Chemical reactions are either exothermic or endothermic • Exothermic = heat exiting CH4 + 2 O2 CO2 + 2 H2O + 802.3 kJ • Convert that to kJ/g using molar mass. – Heat is produced as a product of the reaction – Combustion produces heat – Reactant heat is higher than the product heat, thus heat released, the energy change is negative (goes down) • Endothermic = heat in – Heat is needed as a reactant in the reaction – Cold packs take in heat – Reactant heat is lower than the product heat, thus heat is absorbed, the energy change is positive (goes up) Exothermic • Recall a chemical reaction is • reactants g products • Reactant heat higher than product heat so heat is lost, heat exits, exothermic • Heat is produced • Ex: combustion, hot pack DH is negative 4.6 Energy changes in Molecules • Chemical reactions are when reactant molecule bonds are broken and the atoms rearrange into new different product molecules forming new product bonds • You should be able to tell which bonds are broken and which ones form • Example – H2 + Cl2 g 2 HCl + E – Is this reaction exothermic or endothermic? Endothermic • Recall a chemical reaction is • reactants g products • Reactant heat lower than product heat so heat is taken in, heat enters, endothermic • Heat is absorbed • Ex: photosynthesis must absorb sun’s energy, cold pack DH is negative We Need Fuel and Energy • US is about 5% of the world’s population, but uses 30% of the world’s energy. We are addicted to energy. Only Canada uses about the same per person as us. • The country using the most energy overall is China, but they also have the most people, and they use way less per person than us. • We average 16 tons of coal per person per year. Exothermic 8 2/20/2015 Electricity Consumption country Total MW population Per capita China 4,190,000,000 1.3 billion 364 US 3,741,485,000 298 million 1460 Europe 2,950,297,000 459 million 700 Japan 963,852,000 128 million 868 Russia 857,617,000 142 million 785 India 600,649,000 1.1 billion 51 Brazil 600,029,000 786 million 226 Canada 549,476,000 32 million 1410 2005 Data 4.7 Making Gasoline • Gasoline is hydrocarbons with 5-12 C atoms • These smaller hydrocarbons are in way more demand than those with 13 or more C atoms • Need a way to break larger hydrocarbons into smaller ones = Cracking – C16H34 g C8H18 + C8H16 – Is this balanced??? • Anyone remember leaded gasoline? Finally banned in US in 1996 by Clean Air Act A “Cracker” heats hydrocarbons to 400-450oC to crack them. Cracking • Thermal cracking involves very high temperatures. • Catalytic cracking involves using a catalyst at lower temperatures. • Octane is C8H18 and there are several isomers with this formula. (same formula, different structure) 9 2/20/2015 4.8 New Fuels • Coal can last another 150 years, but can’t be used in cars since it is not liquid. Cheap oil will run out in 30-50 years. We must change our ways whether we want to or not. Big money to be made in what replaces oil. • We can make synthetic oil from coal, but right now this is way too expensive. And it produces twice the amount of CO2. Why is this bad? Synthetic Gasoline • We can make it from coal (Fischer-Tropsch process) but it requires a catalyst. • A catalyst lowers the energy necessary to make a reaction proceed to products. And catalysts are not consumed during the reaction so they can be reused over and over and over. • South Africa synthesizes most of its gasoline this way. • However making gasoline from coal creates twice as much GHG as burning oil creates. This is bad news for the planet. 4.9 Ethanol Biofuel • Burning fossil fuels is not sustainable – we will run out of them eventually, we can’t grow them, and they cause harm to our lungs and the planet. • What are the options? One is to use biofuels which are renewable fuels made from plants. • Wood not viable, wood takes CO2 out of the air, we need more trees, not less. Also trees grow slow. • We can ferment corn to make ethanol. Corn grows quickly so is sustainable. Catalysts lower the energy required for a reaction to proceed forwards How to make Ethanol • How to ferment corn – Mix corn kernals and water – Use enzymes to break down the starch molecules into glucose – Yeast cells cause glucose to turn into ethanol – Distill and purify the ethanol • Often mixed with gasoline already = gasohol – Usually 10% ethanol – can be used in all cars – E85 is 85% ethanol – can be used in FFV (flex fuel vehicle). There are 6 million in the US now. 10 2/20/2015 Brazil • 4 million out of 13 million cars run on pure ethanol produced from fermenting sugar cane • The rest run on an ethanol / gas mix • You get less miles per gallon with ethanol however but the octane rating is higher. (The higher the octane rating, the smoother the fuel and less knocking) Ethanol Review • Mix of 90% gas and 10% ethanol can be used in all cars now • Must modify cars to run on 100% ethanol – Brazil has about 30% cars on ethanol • FFV (flex fuel vehicles) run on up to 85% ethanol (E85) and 15% gas, sold in Europe and US – – – – – – Few engine modifications Same performance levels, less mpg Produced since the 1980’s, you may have one and not know it Labeled on gas cap or fuel door Sweden has 1455 E85 stations, 1802 in US US has 8.3 million E85 cars Switch Grass Problems with Ethanol from Corn • • • • • Energy to make it is more than what we get from it More expensive than gasoline now Lower gas mileage Not enough land to grow that much corn Corn uses lots of fertilizers and pesticides, bad for water supply and soil. Transportation of these chemicals requires burning gasoline and emits CO2. • Corn degrades the soil. People are starving, corn could be used as food instead of fuel. • Many think switch grass is way better than corn as an ethanol source 4.10 Other Biofuels = Biomass Biomass • • • • Biodiesel Garbage Biogas Solar, wind, hydrogen and geothermal are renewable and alternative energy sources – Alternative energy means NOT fossil fuel – Renewable means produced quickly, readily available • Nuclear is alternative but not renewable because Uranium is not produced quickly 11 2/20/2015 Biodiesel • Increasing production, can be made by individual consumers • Made from vegetable oil, can get for free from restaurants • Can be used pure or mixed with gasoline in diesel engines How to Make Biodiesel – B20 means 80% diesel and 20% biodiesel • Non toxic and biodegradable • Releases more energy than required to make it (better than corn ethanol) How to make biodiesel • Vegetable oils contains triglycerides – React with methanol and NaOH (catalyst) – Produce 3 biodiesel molecules and glycerol waste – Glycerol can be sold to make a glycol Biodiesel • Does produce CO2 when burned, but is carbon neutral (the plant took in the CO2 first) Garbage as energy source • Cheap, there is lots of it, renewable, abundant • Solves 2 problems – What to do with trash – How to make energy • Burning trash leaves about 10% behind that goes to landfill • Can recover metals to reuse • Incinerator emissions below standard levels or regular incinerators • Japan and Germany are leaders in burning trash as fuel Biogas • Collect gas vapors from landfill and use to heat homes • Collect gas from sewage or manure on a farm to provide the heating for the farm • Good for small scale applications • 25 million users in rural China in 2008, expected to double this decade 12 2/20/2015 Conservation Biomass Cycle • Best way to control costs is still conservation – use less energy in the first place! • Oil will peak this century, costs will continue to rise, something must replace it • Recycling is key! One can recycled saves enough energy to run a TV for 3 hours • Drive fuel efficient cars – uses less fuel and saves money (2008 numbers) – Europe average 40 mpg – Japan average 45 mpg – US average 19.8 mpg Summary: Energy Sources 4.11 The Way Forward • • • • We will need more energy in the future 25% of energy is consumed by 5% (US) China and India are emerging economies Do we have enough energy for all people to live at NO US standard of living? • Must make smart choices. In US cars/trucks are 70% of oil usage and 1/5 CO2 emissions – our mpg is low, could improve here. • Mass transit – 47% of Japan’s travel vs only 6% of US travel • Our actions leave global footprints 13