Session 11 - Renewables

• Biomass

• Geothermal

• Hydro

• Solar

• Ocean Based

• Wind

Renewable Sources

• Solar

• Gravitational

• Radioactive

All have a nuclear history

Attractiveness of Renewables

Generally:

• It’s abundant, available everywhere

• Does not deplete Earth’s resources

• Minimal environmental impact

Challenges

• Technological Challenges– Low capture efficiency– Low energy density– Lack of dispatchability– Environmental issues

• Integration Challenges– Small present contribution– High capital costs– Materials ramp up limitations– Storage, location vs. load, transmission lines– Output versus load requirements

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)

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)

Renewables - 2007

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

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