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Sustainable Energy: Challenges and Solutions
STEM Scholars Lecture Series
California State University Sacramento
February 27, 2007
Sustainability
“Meeting the needs of the present without compromising the ability of future generations to meet their needs.”
Criteria for Sustainable Energy:
1. Fuel Supply not Depleted with Use
2. Properties of Earth/Atmosphere Unaltered
3. No Significant Social Injustices
Energy Supply
Hydro 3%
Nuclear 9%
Natural Gas 20%
Coal 24%
Petroleum 41%
Renewables 3%
320,000,000,000 Gallons of Petroleum
1,000,000,000 Tons of Coal
22,000,000,000,000 Cubic Feet Natural Gas
36% Imported (Petroleum and Natural Gas)
85% From Fossil Fuels
C8H18 + 12.5 (O2 + 3.76 N2)
8 CO2 + 9 H2O + 47 N2
1 kmol fuel 8 kmol CO2
1 kg fuel 3+ kg CO2
One 16 gallon tank 320 lbs CO2
U.S. CO2 Emissions = 6.5 Billion Tons
Worldwide CO2 = 30 Billion Tons
Combustion Products
Climate Change
Short Wavelength
High Energy
Long Wavelength, Low Energy
11 of Last 12 Years Rank Among the 12 of the Warmest Since 1850
Average Temperature Risen 1.5F Since 1900
Sea Levels Have Risen 7 inches in the Last Century
CO2
CO2
Climate Change
So it’s a Little Warmer, What’s the Big Deal?
1. Avg. Temp. to Increase 3 to 9 F by 2100 2. Oceans to Rise 7 to 31 Inches by 21003. More Frequent and Stronger Hurricanes4. Extreme Weather5. Ecosystems and Habitat Loss6. Glacier Retreat 7. Economic Impacts
Climate Change
February 17, 1993 February 21, 2000
Receding Snows of Mount Kilimanjaro, Tanzania, AfricaExpected to Be Gone By 2020
Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center
Fossil Fuel Sustainability
Depleting Fuel Reserves• Best Estimate: 40-80 years
• Undiscovered Reserves Uncertain• Proven Reserves Uncertain (OPEC)
• What is Certain?• Demand Increasing• Supply Decreasing
Atmospheric CO2 Concentration Increasing
Economic, National Security Issues
Renewable Technologies
Renewable Technologies• Direct Solar Thermal and PV• Indirect Solar
• Biomass• Wind• Wave
• Other Sources• Geothermal• Tidal
Active –Solar Collector, RooftopsPassive – Integrating Low Energy Design
Solar Thermal
Domestic Hot Water
Pools/Spas
Residential Space Heating
Adsorption Refrigeration
Industry/Processing
Solar Collectors
Water
Black Absorber(0-10C Rise)
Flat Plate Collector(0-50 C Rise)
Glass
Insulation
Evacuated Heat Pipe(10-100 C Rise)
Water
Focused Collector(50-150 C Rise)
Solar Photovoltaic
Antireflective Coating
n-type Semiconductor
p-type Semiconductor
Backing-+
+ +++---
Photons
Solar Summary
Benefits• Simplicity• Availability vs. Demand: Peak-Summer• Cost-effectiveness
Challenges• Intermittent and Little Availability in Winter• Energy, Cost of PV Cell Production
What’s Next?• Widespread Use• New PV Applications (Thin Film, Flexible)
Bioenergy
Biomass – All of the Earth’s Living MatterBiofuels – Fuels Derived from Biomass
CO2 Heat and ElectricityCO2Bioenergy
CO2 Low Temperature Heat
CO2
Respiration
Bioenergy
Traditional – Combustion of Raw Biomass“New” – Transform Properties (Liquid, Gas)
• Utilize Waste and Replace Fossil Fuels• Reduce Pollutant Emissions
Examples• Woody Crops – Forestry• Agricultural – Switch Grass, Corn, Oil Seeds• Wastes
• Agricultural (Rice Husks, Corn Shucks, etc)• Animal (Dairy, Sewage)• Commercial (Sawdust, Tires, Landfill Gas)
Abengoa Bioenergy Facility in York County, NebraskaEthanol Production Capacity: 50 Million Tons per Year
Biofuels: Ethanol
Benefits• Availability
• World’s Biomass Energy Storage 95 TW• World’s Energy Consumption 15 TW
• Existing Equipment, Infrastructure• Waste Utilization, Potentially Carbon Neutral• Scheduling Control
Challenges• Energy Balance and Economics• Improve “New” Biofuel Processes• Increase Production Capacity
Bioenergy Summary
The Aerofoil
Wind Energy
Wind Turbines• Lift and/or Drag Forces in Direction of
Rotation• Vertical or Horizontal Axis• Most Common: 3-Bladed, Horizontal Axis• Typical Efficiencies: 20-30%
Wind Energy
Wind Turbines or Bird Blenders?
Avian Deaths (U.S. per Year)• Wind Turbines: 30,000• Communications Towers: 40 Million • Pesticides: 67 Million • Vehicles: 70 Million• Cats: 100 Million• Utility Lines: 150 Million• Windows: 500 Million
Altamont: Location, Tower Design, Spacing
Benefits• Economical
• High Initial Investment• Low Maintenance, No Fuel Costs
• Minimal Air, Water, Land Pollution• Scalability (1 kW to 3 MW)• Many “Good” Locations
Challenges• Visual Pollution• Intermittency and Predictability
Wind Energy Summary
Wave EnergyWinds Turbulent Air Flow
Wind Flow on Upwind Wave Faces
Shear Stress on Surface of Water
Solar Radiation Wind Waves
Wave Size Factors1. Wind Speed2. Wind Duration3. Distance Over Which Wave Travels
Wave Energy
Pelamis (Sea Snake)
Hydraulic Rams Pump High Pressure Fluid
Accumulated Fluid Drives Turbines, Generators
A Few Other IdeasWhale Frog Dragon
Clam Swan
Wave Energy
Benefits• Waves = Concentrated Solar Energy• Demand in Phase with Availability (Winter)• Low/No Chemical Pollution• Low Visual Pollution (Offshore)• Large Potential Resource (Estimated 2 TW)
Challenges• Electricity Transmission• Immature Technology• Potential Shipping, Boating Accidents
Tidal Energy
Maximum Gravitational Force: High Tide
Gravitational Force• Proportional to Mass of Earth, Moon• Inversely Proportional to Distance Squared
Minimum Gravitational Force
Tidal Energy
Minimum Centrifugal Force
Centrifugal Force• Earth-Moon System• “Spinning Through Space”
Maximum Centrifugal Force: High Tide
Center of Mass
Tidal Energy
Ocean Reservoir
Flood Generation
Ocean Reservoir
Ebb Generation
h h
Large Generating Capacity (Many MW)Two Large 3.0 to 5.0 Hour Bursts per DayFour Smaller 1.5-3.0 Hour Bursts per Day
Tidal Energy
Benefits• Tremendous Electricity Generation Potential• No Green House Gas, Pollutant Emissions• Predictable
Challenges• Environmental Impact
• Modifying Water Levels Behind Dam• Less Variation, Affecting Birds and Fish
• Shipping, Boating• Tremendous Initial Cost• Intermittency
Independent of the SunRadioactive Isotopes, Gravitational Energy
Geothermal Energy
340 W/m2
Impermeable Rock
Impermeable Rock
Liquid Hot Magma
Water
0.05 W/m2
Impermeable Rock
Steam
Water
Hot Springs
Geothermal Plant
Many Possible Configurations
Geothermal Energy
Flash Chamber
Cooling Tower
Generator
Steam Turbine
Heating, Processing
Electricity to Grid
Geothermal Energy
One of twenty-one plants at the Geysers, Sonoma and Lake Counties, CAThe Geysers Provides 850 MW to Power about 750,000 Homes
Geothermal Energy
Benefits• No Intermittency• Low/Zero Pollutant Emissions
Challenges• Source Depleted (Energy Mining)
• 250:1 Use to Recharge Rate• Limited Sources
• High Quality Sources Tapped• Most Near Tectonic Plate Interfaces
• Better Utilize Low Quality Sources• Ground Source Heat Pump
How do we get Sustainable?
As Citizens• Reduce, Reuse, Recycle
• Drive a Fuel Efficient Car
• Don’t Drive (Telecommute, Public Trans)
• Make Your Home Energy Efficient• Insulation, Caulking and Door Seals• Tune Heater and Air Conditioner• High Efficiency Appliances and Lights• Install Renewables
• Plant Trees
How do we get Sustainable?
As Scientists, Engineers and Mathematicians• Traditional Technologies
• Efficient Gasoline and Diesel Vehicles• Cogeneration and Carbon Sequestration• Energy Efficiency and Management
• Research, Develop Emerging Technologies• New Biofuel Sources• Fuel Cells and Hydrogen• New Technologies and Applications
• Bring Sustainable Products to Market• Transparent, Cost Effective
Sacramento State Expertise
Solar Thermal• Solar Heating and Adsorption Refrigeration• Efficient Building Design
Biofuels and Combustion• Conversion of Biomass to Alcohol Fuels• Mesoscale and Distributed Power Systems• Ultra-Low Emissions Combustion
Stationary Power Fuel Cells• New Fuel Cell Types• Parametric Study and Computer Simulation
Clean Energy Center
Internal – Student Learning through ResearchExternal – Regional Clean Energy Growth
Mission: Contribute to Sustainable Energy in the Sacramento Region with Education and Research
Goals• Promote Collaboration within Sac State• Foster External Relationships• Facilitate External Funding and Publication• Create Authentic Learning Experiences• Provide Technical Expertise to Startups