This document discusses renewable energy sources including biomass, geothermal, hydro, solar, ocean, and wind. It notes the attractiveness of renewables in being abundant, not depleting resources, and having minimal environmental impact. Challenges mentioned include low efficiency, density and dispatchability as well as integration challenges like costs, materials, transmission, and matching output to load. Conversion processes from various renewables to energy are outlined, including solar to electricity or heat and gravitational to kinetic. The document also discusses renewable energy levels in 2007 and policies like Minnesota's 25% renewable electricity goal by 2025 and parts of the US Energy Policy Act of 2005.

1. Session 11 - Renewables
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Biomass
Geothermal
Hydro
Solar
Ocean Based
Wind

2. Renewable Sources
• Solar
• Gravitational
• Radioactive
All have a nuclear history

3. Attractiveness of Renewables
Generally:
• It’s abundant, available everywhere
• Does not deplete Earth’s resources
• Minimal environmental impact

4. Challenges
• Technological Challenges
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Low capture efficiency
Low energy density
Lack of dispatchability
Environmental issues
• Integration Challenges
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Small present contribution
High capital costs
Materials ramp up limitations
Storage, location vs. load, transmission lines
Output versus load requirements

5. Overview of Conversion Processes
• Solar
– Photons to electricity (photoelectric effect)
– Electromagnetic wave to heat (absorption)
– Thermal expansion to kinetic
– Electromagnetic wave to chemical (photosyn.)
– EM wave to phase change, storage (hydro)

6. Overview of Conversion Processes
(continued)
• Gravitational
– Potential energy to Kinetic energy (hydro)
– Differential kinetic energies (ocean)
– Thermal energy from plates, magma
• Nuclear
– Nuclear to thermal (radioactive decay of K, U,
Th in Earth’s interior)

7. Renewables - 2007

8. Saturation
US Energy Consumption is ~ 100 Quads.
By 2050 with 2% annual growth: 230 Q
Scenario 1: No conservation, grow wind
and solar from levels of 0.4 Q in 2006 by
15% annually: 187 Q in 2050
Scenario 2: Conservation (1% growth),
grow wind and solar by 10% annually:
152 Q needed; 27 Q from renewables

9. Policy
• Minnesota’s Next Generation Renewable Energy
Objective of 2007:
– 25% of electrical energy must derive from renewable fuel by
2025 (30% for Xcel Energy)
• US Energy Policy Act of 2005
– Temporary tax breaks for biodiesel
– Breaks for closed-loop biomass, solar, wind, geothermal (closed
loop = grown exclusively for power production)
– Lesser breaks for open-looped biomass, landfill gas,
hydroelectric
• Minnesota Sustainable Forest Resources Act of 1995
– Provides for multiple uses of forests
– Directs Department of Natural Resources to monitor

10. Policy
• Minnesota’s Next Generation Renewable Energy
Objective of 2007:
– 25% of electrical energy must derive from renewable fuel by
2025 (30% for Xcel Energy)
• US Energy Policy Act of 2005
– Temporary tax breaks for biodiesel
– Breaks for closed-loop biomass, solar, wind, geothermal (closed
loop = grown exclusively for power production)
– Lesser breaks for open-looped biomass, landfill gas,
hydroelectric
• Minnesota Sustainable Forest Resources Act of 1995
– Provides for multiple uses of forests
– Directs Department of Natural Resources to monitor