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Topic 7 summary 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
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Topic 7summarydue: 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%
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
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) hydropower
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