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The Sustainable Energy Challenge


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This presentation is an introduction to the sustainable energy challenge. It gives an overview over fossil fuels, the laws of energy, energy efficiency and conservation, and renewable energy sources. The focus is on providing students with the scientific tools for understanding the magnitude of the challenge and analyzing potential solutions.

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The Sustainable Energy Challenge

  1. 1. The Sustainable Energy Challenge
  2. 2. Lecture Series in Sustainability Science by Toni Menninger MSc The Sustainable Energy Challenge
  3. 3. The Sustainable Energy Challenge 1. The Age of Fossil Fuels 2. Energy use in global perspective 3. The Sustainable Energy Challenge 4. Review: The Laws of Energy • The Law of Energy Conservation • Energy Transformations • The Second Law • Heat Engines • Conversion efficiency • Energy Return on Investment (EROI)
  4. 4. The Sustainable Energy Challenge 5. Energy Efficiency potentials • Systemic approaches • Individual approaches 6. Economic Considerations • External Costs of Energy • Energy Taxes • Energy Subsidies 7. Power sources • External Costs of Energy • Energy Taxes • Energy Subsidies 8. Conclusion: Does “Clean Energy” Exist?
  5. 5. The Sustainable Energy Challenge Oil rig explosion in Gulf of Mexico, April 20, 2010
  6. 6. The Sustainable Energy Challenge Mountaintop removal coal mining in West Virginia, 2003
  7. 7. The Sustainable Energy Challenge Fukushima nuclear disaster, March 2011
  8. 8. The Sustainable Energy Challenge
  9. 9. The Sustainable Energy Challenge
  10. 10. The Sustainable Energy Challenge
  11. 11. Fossil fuel combustion is the main cause of climate change and a main cause of air and water pollution and acid rain Mining and extraction of fossil fuels is ecologically and socially destructive: e. g. mountain top coal mining in the Appalachians, oil spills, coal mine accidents, oil rig explosions, social unrest (e. g. Nigeria), geopolitical instability (Iraq, Iran, Central Asia etc.), petro dictatorships in the Middle East... Fossil fuels are nonrenewable resources and their continued use is not sustainable. The Fossil Fuel Paradox: There is too much and not enough of it… More than enough to destabilize the climate system but not enough to preserve our current oil-dependent lifestyle much longer The Age of Fossil Fuels
  12. 12. Worldwide oil production is expected to peak in the near future. Although coal is still relatively abundant and “nonconventional” oil sources may increasingly be exploited, the era of “cheap oil” is probably over. Industrial civilization has been enabled by a “fossil fuel subsidy” - sunlight concentrated and stored in deposits of hydrocarbons that are relatively easily accessible, easy to transport, store, and use. The Age of Fossil Fuels
  13. 13. Oil discovery rate is declining (Hall and Day, American Scientist 2009) Peak Oil ?
  14. 14. Energy return on investment (EROI, EROEI) is declining (Hall and Day, American Scientist 2009 – required reading)
  15. 15. Petroleum Consumption by the numbers • Global supply 2010: 88 million barrels a day , or 32 billion barrels a year • Total US demand : 19 million barrels a day, or 7 billion barrels a year • The USGS estimates 5 – 16 billion barrels recoverable in the Arctic National Wildlife Refuge (ANWR) How long does that last?
  16. 16. Source: Tom Murphy Can we replace fossil fuels with renewables? The Sustainable Energy Challenge
  17. 17. The Sustainable Energy Challenge Can we meet the global energy need at US consumption level? Source: Tom Murphy
  18. 18. Energy use in global perspective Google public data explorer Total energy consumption per capita by US state
  19. 19. Energy use in global perspective Google public data explorer
  20. 20. Industrial civilization is based on fossil fuel energy Primary energy use in more and in less developed countries
  21. 21. Tropical deforestation accounted for 10 percent of global carbon dioxide emissions between 2000-2005 — a substantially smaller proportion than previously estimated — argues a new study published in Science. Read more at deforestation.html#7lxeme2XSOxrLXg0.99 Gross annual carbon emissions resulting from gross forest cover loss and peat drainage and burning between 2000 and 2006 in Giga Tons Carbon per year
  22. 22. Global Warming: what to do? ● Reduce greenhouse gas emissions (reduce fossil fuel use, stop deforestation) ● Enhance natural carbon absorption by soil and vegetation (reforestation, forest management, conservation tillage, biofuels from algae) ● Technically remove greenhouse gases from the atmosphere (“carbon sequestration”, “carbon capture and storage”) ● Try to counteract warming trend with artificial cooling (“geo-engineering”) ● Do nothing, hope for the best, try to adapt (“business as usual” (BAU))
  23. 23. “Stabilization wedges” proposed by Pacala and Socolow (Science, 2004)
  24. 24. “Stabilization wedges” proposed by Pacala and Socolow (Science, 2004) ● Wedges 1-4: Energy efficiency and conservation ● Wedge 5: Fuel shift from coal to gas ● Wedges 6-8: Carbon capture and storage (CCS) ● Wedge 9: Nuclear fission ● Wedges 10-13: Renewable energy ● Wedges 14-15: Forests and agricultural soils
  25. 25. Key to a sustainable energy future: large improvements in energy conservation and the transition to a “low-carbon” energy economy. The Sustainable Energy Challenge
  26. 26. The Sustainable Energy Challenge What is “clean”/ ”sustainable” energy? How do we define + measure “energy sustainability”?
  27. 27. Sustainable energy considerations • Energy efficiency • Availability, intermittency • Transport, storage • Environmental impact (pollution, biodiversity) • CO2 Emissions (based on Life Cycle Analysis) • Land use intensity • Material resource requirements • Energy return on energy investment (EROI) • Economic cost • Social acceptance • … … …
  28. 28. Sustainable energy considerations: Carbon emissions • Natural gas (methane) emits less pollution and less CO2 per unit of energy compared to coal. • But it is a potent greenhouse gas. Methane leakage might cause more harm than is avoided through fuel shift.
  29. 29. Sustainable energy considerations: Carbon emissions • Nuclear, wind, solar and hydro power generation do not emit CO2 during operation but indirect emissions from the life cycle must be taken into account. Results are contentious. World Nuclear Association Oxford Research Group
  30. 30. Land use intensity of selected power sources “Energy Sprawl or Energy Efficiency”, McDonald et al., PLOS One 2009
  31. 31. Review: The Laws of Energy • Energy is a physical entity that can be measured and quantified. • Energy (Work) is defined as a force (measured in N [Newton]) acting through a distance and measured in J [Joule]: 1J=1Nm • Power is a measure of energy flow over time, measured in W [Watt]: 1 W= 1J/s Required reading: Energy Literacy
  32. 32. Review: The Laws of Energy • A vehicle must expend mechanical energy to overcome the forces of friction and air resistance. • To climb stairs, you have to expend energy to overcome the gravitational force. The amount of gravitational energy is proportional to the weight of the body and the vertical height traveled. • Hydropower generation is proportional to the height of the dam and the mass of the water running through turbines.
  33. 33. Review: The Laws of Energy Different kinds of energy have been measured in different units (Btu, kWh, kcal) but they can all be converted into each other. • Mechanical energy (work) • Heat (Thermal) energy • Kinetic energy • Gravitational energy • Radiation • Chemical energy • Electric energy
  34. 34. Review: The Laws of Energy (The Laws of Thermodynamics) First Law (Law of energy conservation): Energy can be neither created nor destroyed, only transformed. The conversion efficiency is the percentage of “useful” energy efficiency= 𝑜𝑢𝑡𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑝𝑢𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 x 100
  35. 35. Review: Energy transformations
  36. 36. Review: The Laws of Energy Second Law of Thermodynamics (Law of entropy): • Heat energy flows spontaneously from higher to lower temperature but not the other way. • Heat cannot be completely converted to mechanical energy. The conversion efficiency of a heat engine cannot exceed the Carnot efficiency (1 − 𝑇𝐶/𝑇𝐻), the rest is lost as waste heat. • The entropy (“disorderliness”) of a closed system can only increase. High-grade (useful) energy is dispersed into low-grade (waste) energy. Decreasing entropy requires importing energy.
  37. 37. Review: Heat engines The energy conversion process from heat to mechanical energy taking place in a heat engine necessarily involves a loss of waste heat. Carnot's law states that the maximum conversion efficiency ( )that a heat engine can achieve depends on the difference between the absolute temperatures of the hot (TH) and the cold (TC) reservoir : Absolute temperature is measured in Kelvin. Tabs=Tcelsius+273.15
  38. 38. Implication of the Second Law Heat engines (combustion motor and thermal power plant) are inherently inefficient! A large part of the heat energy is lost, unless it can be made useful for heating (CHP – Combined Heat and Power) TH typically 350-550 ºC, about 600-800 K; TC about 25 ºC or 300 K. Optimal efficiency 50-60%, actual efficiency 15-40%.
  39. 39. Process Energy efficiency Theoretical limit Photosynthesis Up to 6% Muscle 15% - 25% Internal combustion engine 15% - 20% 55% (Carnot efficiency) Electric car up to 80% Thermal power plant 30% - 40% global average 32% ≈60% (Carnot efficiency, depends on temp.) Cogeneration (CHP) Up to 90% Hydropower plant 80% - 95% Wind turbine 15% - 35% 59% Photovoltaic cells 10% - 15% 35% (with caveats) Solar water heater 50% - 75% Electric heater 100% Gas or wood heating (modern) 75% - 95% Heat Pump COP (Coefficient of Performance) > 1 SEER (Seasonal Energy Efficiency Ratio) Conversion efficiency
  40. 40. Energy return on investment (EROI, EROEI) is declining (Hall and Day, American Scientist 2009 – required reading) EROI corn ethanol 1.3:1
  41. 41. EROI - Energy Return on Investment • The Energy Return on Investment (EROI/EROEI) is the energy cost of acquiring an energy resource. It is not the same as Energy Efficiency. • EROI is the ratio of the amount of usable energy acquired from a particular energy resource to the amount of energy expended to obtain that energy resource. Example: EROI = 4 means that each unit of energy invested yields 4 units of output. Conversely, net energy output is 75% of gross energy output. • An “energy resource” with an EROI < 1 is a net sink of energy.
  42. 42. Energy Efficiency potentials: systemic approaches ● Co-generation (Combined Heat and Power, CHP
  43. 43. Energy Efficiency potentials: systemic approaches ● Co-generation (Combined Heat and Power, CHP) ● “Smart Grid”: smooth out demand curve by giving incentives to consumers, efficiently controlling energy flow during peak demand. Reducing peak demand will significantly improve overall efficiency martGridIntroduction.htm
  44. 44. Energy Efficiency potentials: systemic approaches ● Co-generation (Combined Heat and Power, CHP) ● “Smart Grid” ● Transportation efficiency: Urban design to favor walkable, bikable neighborhoods, efficient mass transit, smaller cars, car- sharing, hybrid technology, replace short distance air travel by rail, efficient use of air travel capacity, move freight transport from truck to barge and rail UACDC: Visioning Rail Transit in NWA
  45. 45. Energy Efficiency potentials: individual approaches
  46. 46. Energy Efficiency potentials: individual approaches ● Building efficiency: building size, air-tightness, insulation, low-E windows, heat-recovery ventilation, passive solar design, reflective roof, efficient wood heating, geothermal heat pumps, solar water heating, roof PV cells, zero-energy buildings ● Most contractors oversize air conditioners and undersize air supply (at least 2 sqft per ton recommended) ● Appliances (inefficient: top-loader washer, oversized French door refrigerator with in-door ice dispenser) ● Lighting: efficient light bulbs, natural light and movement sensors in office + retail buildings ● Electronic devices: improved power control for computers, monitors, printers, TVs, even small devices like cell-phone chargers etc. can save energy; stand-by mode (“vampire energy loss”) is a huge energy drain
  47. 47. Energy Efficiency: economic considerations ● Investment in energy efficiency and conservation pays off ● “Conservation is the quickest, cheapest, most practical source of energy”- Jimmy Carter, 1977 Then why is there so little progress in energy efficiency? ● Up to recently, energy prices have been historically cheap, especially in North America. ● Economic incentives are effective. Businesses and consumers respond to increasing energy cost (e. g. increased US demand for transit, increased interest in home energy improvements) ● Energy policy should be consistent and predictable ● Energy or pollution taxes or similar mechanisms (e. g. cap and trade) provide consistent economic incentives for conservation.
  48. 48. Case study: “Progress” in automobile efficiency “Jevons’ Paradox” Technological progress that increases the efficiency with which a resource is used tends to increase (rather than decrease) the rate of consumption of that resource => Absent economic incentives, technology will not by itself promote conservation!
  49. 49. Economic incentives are effective! Prices change behavior Oil price
  50. 50. Economic incentives are effective! Prices change behavior High fuel taxes promote fuel conservation
  51. 51. Energy Efficiency: economic considerations ● Energy taxes are not a “drain” on the economy – they move resources from less to more energy efficient sectors. ● Revenues from energy taxes flow back into the domestic economy – money spent importing energy is lost from the domestic economy. ● Revenues from energy taxes can be redistributed to soften the impact on low-income groups, or used to create jobs, or invested in energy efficient infrastructure. ● Energy generation and use causes massive negative externalities (carbon emissions etc.). Taxes designed to compensate for a negative economic externality are known as Pigouvian taxes. Standard economic theory predicts that Pigouvian taxes increase economic efficiency. ● Difficulty: quantifying the externality ● Difficulty: energy intensive industries will go where energy taxes and regulations are least strict
  52. 52. Economic considerations: External costs of Energy Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use A report by the National Research Council’s Committee on Health, Environmental, and Other External Costs and Benefits of Energy Production and Consumption Freely available at
  53. 53. Economic considerations: energy taxes “Environmental taxes can play a central role in reducing the fiscal gap in the years to come. These are efficient taxes because they tax “bads” rather than “goods.” Environmental taxes have the unique feature of raising revenues, increasing economic efficiency, and improving the public health. (…) It is striking how the political dialogue in the US has ignored a policy that has so many desirable features. (…) Simply put, externality taxes are the best fiscal instrument to employ at this time, in this country, and given the fiscal constraints faced by the US.” Economist William D. Nordhaus
  54. 54. Energy Subsidies: “Black not Green” NYT, July 3, 2010: “oil production is among the most heavily subsidized businesses”
  55. 55. Power sources – a brief overview Coal ● Relatively abundant & cheap ● Biggest source of carbon emissions ● Emits many pollutants incl. Mercury, sulfur ● Coal mining often environmentally destructive – Mountaintop removal in Appalachia ● Carbon Capture and Storage (CCS) technically feasible method of minimizing carbon emissions but expensive and energy intensive
  56. 56. Power sources – a brief overview Natural Gas ● Less pollution, 40% less carbon emitted per unit of energy, potential as transportation fuel ● Problem of Methane leakage ● “Hydrofracking”, a relatively recent drilling technique, is controversial because of the use of toxic chemicals, high freshwater use, potential for watershed contamination, disposal of large amounts of fracking fluid, injection wells causing small earthquakes …
  57. 57. Power sources – a brief overview Nuclear fission power ● Uranium relatively abundant but not unlimited ● Low GHG emissions during operation, GHG emissions during construction and mining ● Uranium mining very “dirty”, huge environmental impact ● Socially contentious technology ● Investment cost of building new plants relatively high, protracted permit and construction process, huge delays and cost overruns universally observed ● Most existing plants are decades old, amortized and highly profitable but often fail to comply with modern safety standards. Operators tend to resist costly upgrades, have big economic incentives to continue operating unsafe plants. Whose interests do regulators protect?
  58. 58. Power sources – a brief overview Nuclear fission power ● Safety issues: Fukushima, Chernobyl, Three Mile Island only tip of the iceberg; there is a long list of incidents involving nuclear power plants. Incidents often lead to prolonged, expensive interruption of operation. ● Radioactive Tritium leaked from Yankee power plant in Vermont, 2010 ( ● Release of 18,000 liters of solution containing Uranium at Tricastin, France, in 2008 ● Nuclear power plants potential terrorist targets ● Nuclear proliferation concerns ● Waste disposal and decommissioning difficult if not unfeasible, costs generally not priced into electricity
  59. 59. Power sources – a brief overview Nuclear fission power Tchernobyl: more than 20 years after the disaster, the number of fatalities is still disputed. The lowest estimate – 56 direct deaths and 4000 long term cancer victims – was published by the IAEA, an organization constitutionally charged with promoting nuclear energy. Anti-nuclear groups estimate 50,000 potential fatal cancer incidents. Hundreds of thousands of workers (“liquidators”) came close to the reactor core during clean-up work. ● Selection of sites to look up on wikipedia: Sellafield, Mülheim- Kärlich_Nuclear_Power_Plant, Schacht_Asse_II, Tricastin_Nuclear_Power_Center, Olkiluoto_Nuclear_Power_Plant, Dounreay
  60. 60. Power sources – a brief overview
  61. 61. Power sources – a brief overview Wind ● Large wind farms economically competitive ● No fuel required, no GHG emissions during operation ● Low maintenance cost, but large upfront investment ● GHG emissions during construction ● Potential for ecological disruption, impact on birds and bats uncertain, high land use intensity per Megawatt (“Energy Sprawl or Energy Efficiency”, PLOS One 2009), ● Power output proportional to square of diameter and third power of wind velocity, transformation efficiency up to 35% (small scale turbines less efficient), intermittency and fluctuation of wind direction and velocity reduces efficiency further.
  62. 62. Power sources – a brief overview Wind ● Small and intermediate wind power units valuable for off-the grid, remote areas, developing countries but not a significant contribution to energy needs of developed countries.
  63. 63. Power sources – a brief overview Hydro power ● Very high conversion efficiency ● No pollution or GHG from operation ● Reservoirs can be used as energy storage ● Potential ecological disruption by large as well as small dams ● Loss of valuable farmland or wildlife habitat ● Large numbers of people relocated because of large dam projects ● Power disruption during drought ● Other issues with dams
  64. 64. Power sources – a brief overview Biofuels ● Potentially renewable, low-GHG energy source, potential alternative transportation fuel ● Many issues: - Land-use intensity - Water intensity - Energy inefficiency: very low EROI in some cases - Competition with food production - Deforestation for palm oil plantations in Tropics ● Different kinds of biofuels from different sources (e. g. algae, cellulosic biomass, recycled vegetable oil, sugar cane, corn): sustainability assessment different in each case ● Currently no plausible, sustainable large-scale source of biofuels Recommended readings: NGM; Thermodynamics of the Corn-Ethanol Biofuel Cycle; “Hunger Games”; Bioenergy – Chances and Limits
  65. 65. Power sources – a brief overview Solar Power ● Ideal, abundant, pollution free source of power ● Photovoltaics still expensive, manufacturing requires rare materials ● Maximum production during day time, when demand is highest ● Problems of predictability, reliability, storage ● Land use intensity less than wind but more than coal ● Solar water heating very efficient and cheap, mandatory in many Mediterranean countries, underused in US (why?) ● Many uses on many scales, including low-tech applications relevant to developing countries, off the grid use ● Immense potential, few draw-backs
  66. 66. Power sources: Solar Power The land area needed to produce 18 TW of electricity using 8% efficient photovoltaics, shown as black dots. Source: WikiMedia, Do the Math
  67. 67. Germany has promoted the installation of PV panels with subsidies. Good policy?
  68. 68. Power sources – a brief overview Conclusion: does “Clean Energy” exist? How would you implement a national (global?) energy policy promoting sustainability?
  69. 69. This presentation is part of the Lecture Series in Sustainability Science. © 4/2014 by Toni Menninger MSc. Use of this material for educational purposes with attribution permitted. Questions or comments please email Related lectures and problem sets available at • Growth in a Finite World: Sustainability and the Exponential Function • The Human Population Challenge • World Hunger and Food Security • Economics and Ecology • Exponential Growth, Doubling Time, and the Rule of 70 • Case Studies and Practice Problems for Sustainability Education: • Agricultural Productivity, Food Security, and Biofuels • Growth and Sustainability … and more to come! The Sustainable Energy Challenge