Renewable energy

Primary renewable energy sources

wind

sunlight

falling water (hydropower)

earths heat (geothermal)

oceans tides and waves

biomass

General Challenges

renewables are diffuse (spread out) and intermittent,

technology needed to harvest (concentrate),

infrastructure (currently non renewable energy provides 84% of energy)

General Benefits

far fewer environmental impacts,

infinite energy source (from the human lifetime perspective)

Four General Categories of Challenges

New technologies, Economies of scale, Externalized costs, Limited consumer knowledge/choice

Wind Energy

Driven by the sun ( actually a type of solar energy),

Kinetic energy from wind collected by wind turbines,

Wind power just over 1% of global energy,

Fastest growing renewable

Wind Advantages

No fuel, no pollution

Economic

Domestic

CO2 free

Wind Disadvantages

Intermittent

Aesthetics

Impacts to wildlife (often exaggerated)

Passive Solar Energy

uses solar energy without mechanical devices

- natural lighting and heating

Active Solar Energy

- Uses mechanical devices

- solar panels (Photovoltaic PV)

- Solar water heater

- concentrating solar power system

- solar farms

Solar Advantages

- Widely available; panels can be installed anywhere

- few environmental costs; no CO2, other greenhouse gases, or air pollution

Solar Disadvantages

- Currently high up-front costs

- Manufacturing uses considerable energy an some hazardous materials

- intermittent

- regional

Biomass energy

Energy contained in wood and other plant matter

Derived from solar energy (photosynthesis)

can be burned to produce energy (wood, charcoal, crop residue, ethanol, biodiesel)

Biomass Advantages

- Many are carbon neutral (does not increase atmospheric CO2 overtime)

- Emits less nitrogen and sulfur than fossil fuels

- evenly distributed

Biomass disadvantages

- Impacts food supply

- inefficient choice of fuel crops

- land clearing

- additional energy needed to harvest, lowering return on investment

Hydropower

constantly supplied by hydrologic cycle (which is also powered by the sun),

Most abundantly used renewable energy use (38-39%),

mainly used for electricity generation

impoundment

dams creating a reservoir

run of river (hydropower)

diverting a portion of the river

Hydropower Advantages

fuel and pollution free,

relatively inexpensive to run, the plants

also provides flood control and water storage,

continuous electricity

hydropower disadvantages

Loss of land,

ecosystem disruption, high

initial cost

Future development of hydropower

⅕ of global potential hydropower already being used

new dams considered too costly to build (financially, socially, environmentally)

many existing dams being upgraded

Ocean Energy

takes advantage of tides, waves, and temperature differences

Tidal Power

driven by moon, turbines turned as tides enter and leave bays

wave power

uses kinetic energy of waves

Ocean Thermal Energy Conversion (OTEC)

experimental process

ocean energy advantages

fuel and pollution free

ocean energy disadvantages

ecosystem disruption,

limited geographically,

not yet cost-competitive (very expensive up front)

Geothermal

uses heat energy from earth's interior, harnessed in four ways

dry-steam power plants

uses steam from ground water

flash-steam power plants

pumps up hot ground water and converts it to steam

binary-cycle power plants

pump warm water to heat a different liquid with a lower boiling point, then uses that steam

ground-source heat pumps (GSHP)

used to heat/ cool buildings

Geothermal Advantages

reliable and relatively inexpensive,

mostly pollution free

Geothermal disadvantages

may release gases trapped in the ground to the atmosphere,

can be overused (the amount of hot water is limited),

start-up cost high,

regional