Topic 7summary due: Wednesday, October 10

Describe the costs and benefits of two forms

of alternative/renewable energy.

historical sources of energy muscle fire - wood & charcoal animal wind water steam

wood coal petroleum

current sources of energy (worldwide use) overall

oil - 35% coal - 29% natural gas – 24% nuclear – 5% Biomass - ? hydro - 6% Geothermal, wind, etc. – 1%

Chapter 20: Sustainable Energy

Conservation

utilization efficiencies standard conservation techniques public transportation cars: engine & use efficiency homes industry

energy conversion efficiencies (fig p. 448) fuel energy = useful energy + waste heat low percent useful energy yields can be improved efficiency table does not account for cost of

pollution negawatt programs cogeneration

solar vast resource passive solar heat active solar heat high temp

mirrors focus energy large and small scale

photovoltaic sun’s energy separates electrons from atoms and

moves them across a one-way barrier need energy storage

biomass

sources crop residue & energy crops wood dung methane (source – digesters) alcohol (fuel and oxygenator) peat

advantages renewable accessible use waste material

disadvantages open fires - very wasteful pollutes combustion efficiency fuel wood shortages

hydropower

pro very efficient no chemical

pollution readily available

in many areas water supply

control flood control navigation recreation

con blocks free flow siltation seepage water temp big dams are not

efficient destroys habitat

alternatives low-head run of the river micro-hydro (home

use)

wind pro

clean readily available

con ugly hurt birds takes up space (less per watt than conventional)

wind farms getting wind energy to users (map p. 466) home use

geothermal

examples electricity generation heat pumps (p. 467)

effects clean use up the resource depends on geothermal gradient

ocean

tidal need high tidal range incoming and out going

wave - difficult to harness ocean thermal electric conversion

Demand Matching

Big issue with alternatives Production & availability does not

always meet demand.

Chart p. 467