Physics 162 Winter The Big Picture We use a heck of a lot of energy We use a heck of a lot of energy primitive society used < 100 W of power per person primitive society used < 100 W of power per person our modern society burns 10,000 W per person our modern society burns 10,000 W per person surely not in our homes! Where is this energy going? surely not in our homes! Where is this energy going? Energy availability has enabled us to focus on higher-level issues as a society Energy availability has enabled us to focus on higher-level issues as a society art art Science Science entertainment entertainment home shopping network home shopping network

Physics 162 Winter Once upon a time… Long ago, almost all of our energy came from food (delivering muscle power), and almost all our energy went into securing food for ourselves Long ago, almost all of our energy came from food (delivering muscle power), and almost all our energy went into securing food for ourselves Enter the work animal, supplementing our muscle power and enabling larger-scale agriculture Enter the work animal, supplementing our muscle power and enabling larger-scale agriculture Later we burned wood to run boilers, trains Later we burned wood to run boilers, trains 150 years ago, muscular effort and firewood provided most of our energy—and today this is less than 1% of the story 150 years ago, muscular effort and firewood provided most of our energy—and today this is less than 1% of the story Today, more energy goes into growing/harvesting food than comes out of food! (is this bad news for biodiesel??) Today, more energy goes into growing/harvesting food than comes out of food! (is this bad news for biodiesel??)

Physics 162 Winter The Global Energy Scene Global energy production is about 400 QBtu/yr Global energy production is about 400 QBtu/yr a QBtu is a quadrillion Btu, or Btu a QBtu is a quadrillion Btu, or Btu so about 4  J per year so about 4  J per year U.S. share is about one fourth of this (100 QBtu or J) U.S. share is about one fourth of this (100 QBtu or J) J/yr = 3  W (do the calculation!) J/yr = 3  W (do the calculation!) divided by 300 million people (3  10 8 ) = 10 4 W per person (10 kW, as stated above) divided by 300 million people (3  10 8 ) = 10 4 W per person (10 kW, as stated above) We’ll talk about units next week. 1 Btu is the energy required to raise 1 pound of water by 1 o F. There are about 1000 Joules (J) in a Btu. A Watt (W) is a measure of power, or energy per unit time, and 1 W = 1 J/s. A 100 W light bulb uses 100 J of energy each second.

Physics 162 Winter The Great Energy Disparity 30,000 20,000 10, Energy equivalent barrels of oil per capita per year Gross Domestic Product (GDP): $ per capita Poland Cuba Ecuador India Italy U.K. Japan Switzerland Sweden Norway Iceland Germany Belgium Canada United States Many countries in the world lie in this quarter-circle!! 1989 data; Reproduced from Fig. 1.3, Ristinen and Kraushaar

Physics 162 Winter More Countries Fills in the gaps 1971 data Now on a Logarithmic Scale

Physics 162 Winter A note on graphs: log vs. linear Many graphs in the book are on logarithmic scales Many graphs in the book are on logarithmic scales This condenses wide-ranging information into a compact area This condenses wide-ranging information into a compact area Pay attention, because you could warp your intuition if you don’t appreciate the scale Pay attention, because you could warp your intuition if you don’t appreciate the scale Log scales work in factors of ten Log scales work in factors of ten A given vertical span represents a constant ratio (e.g., factor of ten, factor of two, etc.) A given vertical span represents a constant ratio (e.g., factor of ten, factor of two, etc.) An exponential increase looks like a straight line on a logarithmic scale An exponential increase looks like a straight line on a logarithmic scale

Physics 162 Winter Example Plots Exponential plot is curved on linear scale, and straight on a logarithmic scale

Physics 162 Winter Aside: Exponential Growth and the Rule of 70 (or 72) If some quantity, the price of oil say, increases by 10% per year, how many years does it take for the price to double? 10 years x 10%/year = 100% = doubled price: correct??? No, because the increase compounds (as in your savings account or, maybe more appropriately for today’s college student, on your credit card) Say the price of oil is $50/barrel this year and it increases by 10%/year. Prices in following years: 0$50 1$55 2$ $ $ $ $ $ $ Rule of 70 (or 72): Doubling time = 70 years/annual % growth rate

Physics 162 Winter Evolution of Energy Sources

Physics 162 Winter U.S. Consumption in 1996 SourceAmountQBtuPercent Joules Coal 1.00  10 9 tons %22.1 Natural Gas 21.9  ft %23.8 Petroleum 6.14  10 9 bbl %37.7 Nuclear 681  10 9 kWh %7.56 Renewables 695  10 9 kWh %7.80 Total %99.0

Physics 162 Winter The Fall of the Work Animal Used to rely completely on animals for transportation Used to rely completely on animals for transportation Trains entered the picture in the mid-1800s Trains entered the picture in the mid-1800s Cars entered the scene in a big way around 1920 Cars entered the scene in a big way around 1920 World has never been the same World has never been the same Work animal fell off the map around 1940 Work animal fell off the map around 1940 Today automotive is over 95% of the story Today automotive is over 95% of the story Average Horsepower/person in the US Year automotive work animal Nonautomotive inanimate

Physics 162 Winter How much does this cost us? Presently in the US we use the energy equivalent of ~60 barrels/year/person Presently in the US we use the energy equivalent of ~60 barrels/year/person 60 barrels/yr x 42 gallons/barrel x $2.80/gallon = $7056/year = $19.30/day = $19.30/day Total spent in US = $7056/year * 290,000,000 ~ $2T Total spent in US = $7056/year * 290,000,000 ~ $2T ~ 20% of US GDP This does not include the economic and social costs of ongoing instability in oil-producing regions of the world... This does not include the economic and social costs of ongoing instability in oil-producing regions of the world...

Physics 162 Winter U.S. Consumption vs. Production policy change

Physics 162 Winter Where is our energy produced, and of what flavor?

Physics 162 Winter Lessons Our energy use is completely dominated by fossil fuels, with only about 15% coming from nuclear and hydroelectric Our energy use is completely dominated by fossil fuels, with only about 15% coming from nuclear and hydroelectric hydroelectric is the only truly renewable resource of the two hydroelectric is the only truly renewable resource of the two Part of our enormous appetite is due to the expanse of our country: transportation is important Part of our enormous appetite is due to the expanse of our country: transportation is important Space heating is also an issue in a country where detached houses are the rule Space heating is also an issue in a country where detached houses are the rule Any industrial society (at our current scale) is going to have a large demand for energy Any industrial society (at our current scale) is going to have a large demand for energy Our use of energy is more efficient than it could be! Conservation measures since the 1970’s have allowed energy usage to increase more slowly than the growth of the GDP. Our use of energy is more efficient than it could be! Conservation measures since the 1970’s have allowed energy usage to increase more slowly than the growth of the GDP.

Physics 162 Winter Thanks to a lifestyle invented by your grandparents and perfected by your parents generation, we live in a special time and place… We use almost 100 times the average amount used by the world ( per person) We use almost 100 times the average amount used by the world ( per person) This phase has only lasted for the last century or so This phase has only lasted for the last century or so Most of our resources come from fossil fuels presently, and this has a short, finite lifetime and using it comes with potentially serious environmental consequences. Most of our resources come from fossil fuels presently, and this has a short, finite lifetime and using it comes with potentially serious environmental consequences year Fossil fuel usage Reproduced from Fig. 1.2, Ristinen and Kraushaar

Physics 162 Winter Global Energy: Where Does it Come From? Hydroelectric* then radiated away 2,000,000 Sun Abs. by Earth* Solar Direct* Wind* Geothermal Biomass (burning)* Nuclear Energy Natural Gas* Coal* Petroleum* Percent of Total Joules/yr Source * Ultimately derived from our sunCourtesy David Bodansky (UW)

Physics 162 Winter Gas costs less than Perrier ! What’s going on here? We spend about $19/day, or $7000/yr per person on energy in the U.S. We spend about $19/day, or $7000/yr per person on energy in the U.S. about 20% of GDP about 20% of GDP saves us much more than 20% of our time (labor-saving devices, transportation, etc.) saves us much more than 20% of our time (labor-saving devices, transportation, etc.) But we’re running through our fossil fuel resources at a phenomenal rate But we’re running through our fossil fuel resources at a phenomenal rate let’s see if this lasts even another hundred years! let’s see if this lasts even another hundred years! The ‘third world’ is increasing its use of energy resources as it tries to adopt your parents lifestyle The ‘third world’ is increasing its use of energy resources as it tries to adopt your parents lifestyle Our world will see a profound change in the next century as we adjust to a world without gasoline Our world will see a profound change in the next century as we adjust to a world without gasoline

Physics 162 Winter Still fuzzy on the concept of energy? Don’t worry—we’ll cover that in great detail in the coming weeks Don’t worry—we’ll cover that in great detail in the coming weeks Energy is defined as the capacity to do work Energy is defined as the capacity to do work But what is work? But what is work? we’ll get to this shortly we’ll get to this shortly At some level, I* don’t know what energy is: why there is such a thing, why it’s conserved, where it all came from, etc. At some level, I* don’t know what energy is: why there is such a thing, why it’s conserved, where it all came from, etc. these are deep and interesting questions that some physicists try to understand these are deep and interesting questions that some physicists try to understand Any questions???

Physics 162 Winter How about a question to work on right now? The Toyota Prius, one of the early and increasingly popular hybrid vehicles, has a base list price of about $22,000 in 2006, about $4000 of which pays for the electric motor, batteries, second drive train, etc. The feds say the average mileage is about 47 mpg. An approximately comparable non-hybrid Toyota called the Matrix averages about 33 mpg. Assume a Prius with a regular internal combustion engine would get the mileage of a Matrix. With gas costing about $3.00/gallon, how many miles would you have to drive before the savings on gasoline make up for the $4000 you had to pay to buy a hybrid?

Physics 162 Winter My answer.. To drive one mile with the Prius costs $3/gal = $0.064/mile $3/gal = $0.064/mile 47 miles/gal To drive one mile with the Matrix costs $3/gal = $0.091/mile $3/gal = $0.091/mile 33 miles/gal Every mile drive we save $ $0.064 = $0.027/mile on gas. To save $4000 we need to drive $4000/($0.027/mile) ~ 148,000 miles At 12,000 miles/year, that’s over 12 years. So, each year we recoup about $ of the initial $4000 investment.

Physics 162 Winter But wait, it’s worse than that... The Prius has two drive trains and a battery pack. Maintenance costs will likely be higher than for a conventional engine. There is not very good data on that yet. The lifetime of the NiH battery pack itself is an issue. Toyota now offers an 8-year warranty on the battery, with a current (dealer) replacement cost of about $3000. This should be included in the maintenance costs, too. At a rate of $ /year, that will consume most of the savings from higher gas mileage. It’s possible that a current model hybrid will never actually pay for itself - that it is impossible to recoup the initial investment plus ongoing maintenance costs. Toyota knows this and is trying to bring the cost of hybrid technology down. Market forces and economy of scale will make this happen (some). Federal subsidies also change the equation by lessening the burden on individuals by spreading the cost across all taxpayers. Is this a good investment?

Physics 162 Winter But what about CO 2 emissions and Global Warming? Hybrids make us feel good - very environmentally conscious - since they emit fewer greenhouse gases. But the cost of any modern contrivance is heavily dependent on the cost of energy: our lifestyle is very energy intensive. Since a hybrid costs more, it must take more energy to produce than a regular internal combustion engine. How many miles must one drive before this ‘environmental cost’ is recouped? I don’t think the data exist to answer this question very accurately: it depends on what fraction of the extra $4000 was spent on energy. If 25% of the added cost were energy, then you need to drive about 40,000 miles before the Prius become really ‘green’. It’s not really clear what all needs to be included. Should we include some fraction of the energy used by Toyota employees to get to work every day? It’s a tough question.