Renewable Energy

hydropower process

1. dam potential energy 2. concentrate in penstock 3. spin turbine 4. power generator

Renewable energy sources include

1. direct solar energy 2. indirect solar energy (wind, biomass, hydropower, ocean) 3. non-solar (geothermal, tidal) quickly competitive with fossil fuels and nuclear energy

Geothermal Energy process (non solar energy)

1. hot fluid pumped up from underground 2. used to generate steam in heat exchanger 3. steam turns turbine & generates electricity 4. steam is condensed & recirculated

Wind power uses mechanical energy to generate electricity

1. wind turns blades 2. drive shaft spins 3. spinning powers generator 4. electricity sent to cables

about 80% of global energy sources are nonrenewable

60% fossil fuels 20% nuclear energy

Biomass CONS

CO2 & pollutants released land & water required deforestation & desertification soil nutrient depletion already use faster than regeneration time

Geothermal energy CONS (non solar energy)

H2S emissions sinkholes water depletion

Active Solar Heating (ASH) (direct solar energy)

a system that harvests the sun's energy and uses pumps or fans to distribute the collected heat typically used to heat water 8% of energy consumed in U.S. is used to heat water easiest and cheapest solar source for average household ASH could supply large amount of U.S. energy demand

Passive solar heating (direct solar energy)

a system that harvests the sun's energy without using mechanical devices to distribute the collected heat no pumps or fans required because convection helps circulate the air

Solar thermal electric generation (direct solar energy)

a system that uses mirrors or lenses to concentrate the sun's energy onto a fluid that is used to generate electricity solar power towers

solar cells

a thin film of solid materials treated with metals so that it generates electricity (flow of electrons) when it absorbs solar energy

hydropower: fish ladders

allow migrating species to spawn

biomass (indirect solar energy)

chemical energy stored in the form of organic matter solar energy ---> chemical energy via photosynthesis & that chemical energy is stored in molecules of the plant oldest fuel primary energy source for 1/2 human population renewable, but not used sustainably

hydropower dam CONS

ecological disruption downstream (loss of sediment deposition, water source diversion, blocked fish migration ecological disruption in reservoir (habitat flooded, sediment build up) possible seismicity evaporation & salinity soil infertility electricity production declines/expires as sediment builds up displacement of people/loss of cultural resources safety/health issues

hydropower (indirect solar energy)

electric energy obtained from flowing or falling water most popular renewable energy for electricity production U.S. & hydropower: 10% of our energy is hydropower; we have 84,000 dams but only 2,200 are used for hydropower

wind energy (indirect solar energy)

electric energy obtained from winds caused by solar heating of the air world's fastest growing source of energy new wind turbines hardness wind efficiently

Ocean Energy - wave power (indirect solar energy)

electricity obtained from the movement of ocean waves

Renewable energy

energy from sources that are replenished over a short time or that are perpetually available

Sustainable energy

energy sources that are renewable and have a low environmental impact

Energy service companies

find ways for businesses to save energy and money money saved by the business is used to repay the energy services company

photovoltaic solar cells

good for household energy needs 2 pizza boxes = 5 lights, 1 radio, 1 TV not very cost effective: 20 cents per KWh vs. 5 cents (coal) can be most affordable option in remote areas able to function on rainy & cloudy days

hydropower: bypass systems

help fish avoid turbines

Three Gorges Dam, China

largest hydroelectric dam in the world 1.5 million people displaced

photovoltaics

method of converting sunlight directly into electricity using materials that readily absorb or give up electrons

solar power towers (direct solar energy)

mirrors follow the sun and concentrate solar energy onto a central tower

tidal energy PROS (non solar energy)

no CO2 no air pollutants reduced fossil fuel dependence

Wind Energy PROS

no CO2 no air pollutants reduced fossil fuel dependence cost competitive

hydropower dam PROS

no CO2 no air pollutants (sort of) reduced fossil fuel dependence flood control irrigation navigation commercial fishing recreation

Geothermal energy PROS (non solar energy)

no CO2 reduced fossil fuel dependence

direct solar energy

perpetually available, but availability varies with latitude, season, time of day, & cloud cover in U.S., solar radiation is greatest in SW

Solar cookers in LDCs (low developed countries) (direct solar energy)

reduce forestation, desertification, and air pollution associated with using firewood for cooking

Biomass PROS

reduces fossil fuel dependence often uses waste burns cleaner than coal, oil, diesel

tidal energy (non-solar energy)

renewable energy that relies on the ebb and flow of tides to generate electricity potential energy difference between low & high tide can be captured with: a dam across a bay OR a turbine similar to a wind turbine

Wind energy CONS

requires abundant winds bird & bat strikes NIMBY

tidal energy CONS (non solar energy)

species migrations erosion storm damage aesthetics

Energy savings / Conservation

the act of using less energy and increasing efficient use of sources "the greenest kilowatt is the one you never use" one CFL bulb in every U.S. home saves enough energy to light more than 3 million homes & prevents release of greenhouse gas emissions equivalent to 800,000 cars

geothermal energy (non solar energy)

the heat stored underground, contained in either rocks or fluids ex: geothermal power plant in Iceland

Could we use other dams for electricity?

traditional hydropower: only large dams with rapid flow provide enough energy new technology potential to harness power of large, slow-moving rivers & smaller, low flow streams without having to build any new dams

Hydropower dams...

trap silt, which decreases fertility in the river valley

Hydropower - Schistosomiasis

tropical disease caused by a parasitic worm reservoirs provide habitat for worm

geothermal heat pumps (GHPs)

use difference in temperature between surface and subsurface heat and cool buildings expensive installation EPA: one of the most efficient heating & cooling systems

ocean thermal energy conversion (OTEC) (indirect solar energy)

using ocean temperature gradients to produce electricity or cool buildings

wind energy (indirect solar energy)

wind energy is most profitable in large open areas (rural areas, ocean, islands, mountain passes, grasslands) great plains offers huge capacity for wind energy (ND, TX, KS could power entire U.S.) Texas is largest producer of wind power in U.S.