Renewable Energy

Nov 19

Wind Power

Wind Power

Vertical axis machine

Horizontal axis machine

Wind Power

Wind Power

• Winds arise from differential heating of the Earth’s surface on a local, regional, or worldwide scale.

• Global winds• Local winds

Wind Power

• Environmental Impacts– Visual impact– Electromagnetic interference: potential to

interfere with radio, tv, and radar signals and with microwave communication links

– Ecological impacts– Noise

Wave Power

• Water has a higher density than air, so has higher energy densities

• Have little effect on general flow of water around them

• Central issue: economics of harnessing power in harsh marine environments

• Need sites with regular waves

Wave Power

Wave Power• Onshore devices– Must be located in deep water areas adjacent to

coasts to avoid loss of energy through friction

Tapered channel wave energy converter

Wave Power• Offshore devices– Can produce more energy,

but at a higher cost– Passing waves force joints to

pump high-pressure oil through hydraulic motors

– Motors then drive the electrical generators to produce electricity

– Power is fed from the device via cable to the seabed, and then to shore

Pelamis sea snake

Tidal Power• The regular rise and fall of the tides

represents a shifting store of potential energy powered by the drag of the moon and sun

• Water collected at high tide and then drained through a water turbine to generate electricity or use of spin turbine

• The Earth experiences 2 tides a day, allowing tidal power dams to be filled every 12 hrs

• More tidal energy in Atlantic Ocean basin than Pacific

Tidal Power

Spin turbine Tidal dam

Small-Scale Hydropower

• Doesn’t have the environmental and social impacts of large-scale hydropower

• Can be used in areas where local geography doesn’t allow for large dams

• Plant sits on one side of the river• Little water is held back and diverted, so the

river is unaffected• Less powerful

Small-Scale Hydropower

Biomass• Fuel GJ/t• Grass (fresh-cut) 4• Domestic waste (as collected) 9• Straw (baled) 14• Sugar cane (air-dried stalks) 14• Wood (air-dried, 20% moisture) 15• Paper (stacked newspaper) 17• Commercial wastes ( UK average) 16• Dung (dried) 16• Calorific value of various biomass feedstocks [data from BOY96,p143].

Biomass

Geothermal• Derived from radioactive decay of isotopes

deep within the Earth or from heat left over from the original coalescence of matter that formed the Earth

• Heat accessed in 1 of 2 ways:– Hot dry rock technology – drill close to radioactive

sources– Wet rock technology – natural output of energy

higher because of presence of water

Geothermal

Wet-rock technology

Geothermal

• Environmental concerns– New boreholes would have to built every 10 years

as local heat is diminished– Dry-rock technology required water to be pumped

into the ground– Odors could be released– Land subsidence– Increased seismicity

Fast Breeders and Fusion

• Fast breeder reactors and fusion reactors use uranium more efficiently than thermal nuclear reactors

• These expand the world’s resource of uranium from 70 years to 9930 years

• They do this by producing more fissionable fuel than they use

• Also produce less radiation and radioactive waste