Renewable Energy Sources II: Alternatives Part IIChapter 5 SummaryRecall Renewable ResourcesRenewable Energy ConsumptionAnother look at available energy flowThe Renewable BudgetOutstanding Points from Fig. 5.1Energy Flow, continuedSlide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16BiomassPhotosynthesisPhotosynthetic efficiencyRealistic photosynthetic efficiencyiClicker QuestionSlide 22Slide 23Slide 24How much biomass is available?Ethanol from CornDoes Ethanol as a Fuel Make Sense?Ethanol, continuedSlide 29Food For ThoughtEthanol Issues, continuedSlide 32Slide 33Slide 34Slide 35Quantitative EthanolWhat does this amount of land look like?Take Home PointsOther Renewable ResourcesRenewable Resources ReviewGeothermal EnergySlide 42Tidal EnergyOcean Thermal Energy Conversion (OTEC)Slide 451Renewable Energy Sources II: Alternatives Part IILecture #11HNRS 228Energy and the Environment2Chapter 5 Summary•Hydroelectric Power•Wind Power•Ocean Thermal Energy Conversion•Biomass as Energy•Geothermal Energy•Tidal Energy•Wave Energy•Today’s Focus–Biomass–Others3Recall Renewable Resources•Renewable means anything that won’t be destroyed by using it–sunlight (the sun will rise again tomorrow)–biomass (grows again)–hydrological cycle (will rain again)–wind (sunlight on earth makes more)–ocean currents (driven by sun)–tidal motion (moon keeps on producing it)–geothermal (heat sources inside earth not used up fast)4Renewable Energy ConsumptionEnergy SourceQBtu (1994)Percent (1994)QBtu (2003)Percent (2003)Hydroelectric 3.037 3.43 2.779 2.83Geothermal 0.357 0.40 0.314 0.32Biomass 2.852 3.22 2.884 2.94Solar Energy 0.069 0.077 0.063 0.06Wind 0.036 0.040 0.108 0.11Total 6.351 7.18 6.15 6.35Another look at available energy flow•The flow of radiation (solar and thermal) was covered previously–earth is in an energy balance: energy in = energy out–30% reflected, 70% thermally re-radiated•Some of the incident energy is absorbed, but what exactly does this do?–much goes into heating the air/land–much goes into driving weather (rain, wind)–some goes into ocean currents–some goes into photosynthesis6The Renewable Budget7Outstanding Points from Fig. 5.1•Incident radiation is 1741015 W–this is 1370 W/m2 times area facing sun (R2)•30% directly reflected back to space–off clouds, air, land•47% goes into heating air, land, water•23% goes into evaporating water, precipitation, etc. (part of weather)•Adds to 100%, so we’re done–but wait! there’s more…8Energy Flow, continued•0.21% goes into wind, waves, convection, currents–note this is 100 times less than driving the water cycle–but this is the “other” aspect of weather•0.023% is stored as chemical energy in plants via photosynthesis–total is 401012 W; half in ocean (plankton)–humans are 6 billion times 100 W = 0.61012 W–this is 1.5% of bio-energy; 0.00034% of incident power•All of this (bio-activity, wind, weather, etc.) ends up creating heat and re-radiating to space–except some small amount of storage in fossil fuels9iClicker Question•With respects to energy, hydroelectric power represents–A remnant electric power from storms–B remnant water energy from chemical bonds–C remnant energy of chemical bonding–D remnant gravitational potential energy of precipitation–E a form of fictitious energy10iClicker Question•With respects to energy, hydroelectric power represents–A remnant electric power from storms–B remnant water energy from chemical bonds–C remnant energy of chemical bonding–D remnant gravitational potential energy of precipitation–E a form of fictitious energy11iClicker Question•What is true about hydroelectric power generation since 1950?–A It has always increased in MW produced–B It has always decreased in MW produced–C It has increased and decreased in total MW produced, but is now at a peak–D It has both increased and decreased in total MW produced–E The percentage of electric power produced by hydroelectric plants has generally increased over time12iClicker Question•What is true about hydroelectric power generation since 1950?–A It has always increased in MW produced–B It has always decreased in MW produced–C It has increased and decreased in total MW produced, but is now at a peak–D It has both increased and decreased in total MW produced–E The percentage of electric power produced by hydroelectric plants has generally increased over time13iClicker Question•What is about the maximum efficiency of energy generation using the wind?–A 20%–B 40%–C 60%–D 80%–E 100%14iClicker Question•What is about the maximum efficiency of energy generation using the wind?–A 20%–B 40%–C 60%–D 80%–E 100%15iClicker Question•Which state generates the most amount of electricity derived from wind power?–A Virginia–B Alaska–C Montana–D California–E Texas16iClicker Question•Which state generates the most amount of electricity derived from wind power?–A Virginia–B Alaska–C Montana–D California–E Texas17Biomass•Biomass is any living organism, plant, animal, etc.•401012 W out of the 174,0001012 W incident on the earth from the sun goes into photosynthesis–0.023%–this is the fuel for virtually all biological activity–half occurs in oceans•Compare this to global human power generation of 131012 W, or to 0.61012 W of human biological activity•Fossil fuels represent stored biomass energy18Photosynthesis•Typical carbohydrate (sugar) has molecular structure like: [CH2O]x, where x is some integer–refer to this as “unit block”: C6H12O6 (glucose) has x=6•Photosynthetic reaction: xCO2 + xH2O + light  [CH2O]x + xO21.47 g 0.6 g 16 kJ 1 g 1.07 g•Carbohydrate reaction (food consumption) is photosynthesis run backwards–16 kJ per gram is about 4 Calories per gram•Basically a “battery” for storing solar energy–usage just runs reaction backward (but energy instead of light)19Photosynthetic efficiency•Only 25% of the solar spectrum is useful to the photosynthetic process–uses both red and blue light (reflects green), doesn’t use IR or UV•70% of this light is actually absorbed by leaf•Only 35% of the absorbed light energy (in the useful wavelength bands) is stored as chemical energy–the rest is heat–akin to photovoltaic incomplete usage of photon energy•Net result is about 6%20Realistic photosynthetic