ch. 12 renewable energy. why? ff limited supply ff: global warming, air pollution, acid rain, oil...

CH. 12

RENEWABLE ENERGY

PASSIVE SOLAR HEATING

BUILDING PLACEMENT,MATERIAL, AND DESIGN ex: LARGE SOUTH-FACING WINDOWS (N. Hemisphere) WITH GOOD INSULATION; HEAT MOVES BY CONVECTION

Prevent heat loss at nightAttract heat in day

ACTIVE SOLAR

SOLAR

PROS CONS

No air pollutantsLittle maintenance

Not all areas get enough reliable sun

High start-up costs

INCENTIVES: tax break or rebate for installation

New technology should lower costs

Can be incorporated into building materials

Roofing shinglesTileWindow glass

Photovoltaic Solar Cells

windFastest

growing alt.

Costly to build, loud, bird flight patterns

No pollution, muliple use land

19% world

HYDROGEN FUEL CELLSSPLIT H2O

(photovoltaic cells or wind); requires energy; needs to be cheaper

No Sox, no CO2, some Nox (N + O + heat)

Hydrogen powered cars

Hydrogen as a Fuel Source-Electrolysis

HYDROELECTRIC

No pollutantsThermal pollutionDams rivers destruction of habitats, people uprootedSiltingSalmonWater loss due to evaporationFlood control (also, channels, identify flood prone areas, levees, wetlands intact)Breeding for disease vectors (mosquitoes & snails): malaria and

schistosomiasisMany rivers in US protected under Wild and Scenic Rivers Act

CASE STUDY: THREE GORGES DAM, CHINA

Small scale hydroelectricNo dams - no reduced salmon populations, no

reduced silt/nutrients down streamso no reservoir – no flooding of ecosystem

upstream, no excessive water evaporation, no water-borne disease vectors

Less river flow (less snow melt) in summer = less energy in summer

BIOMASSAny carbon-based, biologically derived fuel source

(wood, manure, charcoal, biogas – biodiesel, ethanol)½ of renewable in US; 3% of all US energyCommon plants – corn/sugarcane.Modern carbon vs fossil carbon+: could use wastes, reduce ff use, offset CO2 by

planting trees, no SOx-: requires land/water/ff to grow, competes with

growing food, take crops waste from soil, deforestation, ethanol = less energy content

Biogas (like methane) produced using a biogas digester (right pH, moisture) for bacteria

Or liquid (biodiesel, ethanol) for engines.Gasoline + ethanol = gasohol

BRAZIL

Ocean waves

Ocean Thermal Energy (OTEC)futureTemperature gradients between top and

bottom (from sun)Top water pumped (takes energy) into

power plant to boil liquid (ammonia) to create steam and drive a turbine.

Renewable, but not direct/indirect solar

TIDAL GEOTHERMAL

POPULAR IN ICELAND; US MAKES MOST

ENERGY CONSERVATION and EFFICIENCY

Reduce emissions, buy time, save energy for laterEnergy consumption greatest in HDC, but quickly

growing in LDC as standard of living increasesEfficient appliances (Energy Star)Efficient vehiclesFlorescent lightbulbs use 25% energy of

incandescent bulbs2001 refrigerator 75% less energy than 1970s (save

$135 per yr)

Efficiency calculationsPercent efficiency = Output/input (100%)

that is….o (Useful energy produced/total energy inputted)

Saving Energy at Home

THE ROLE OF RENEWABLE ENRGY CONSUMPTION IN THE NATION’S ENERGY SUPPLY, 2004 AND 2009.

2009

2004

ENERGY AND VEHICLES2/3 OF US PETROLEUM USAGE IS FOR

TRANPORTATION

3% US; primary transportation for othersBuses, trolleys, trains, subways – carry

more

MASS TRANSIT