P110_2008_Week_3

P110_2008_Week_3 - Conservation of Energy If only...

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Conservation of Energy If only conservative forces act (e.g. only gravity), then Mechanical Energy is constant: KE i + PE i = KE f + PE f
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ITAIPU (Brazil/Paraguay) http://www.solar.coppe.ufrj.br/itaipu.html 12.6 GW capacity
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ITAIPU (Brazil/Paraguay) 18 turbines, each producing roughly 715 MW 12.9 GW total output! (700 m 3 /s, effective height ~110m for each turbine) http://www.solar.coppe.ufrj.br/itaipu.html
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Residential Electric Power Bill $145.6/1948 kWh = $0.0747/kWh Avg. Power: 1948kWh/31day.24h/day = 2.6 kW.
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Commercial Power Costs Energy cost estimates for a project out at IUCF: use (i.e. energy) charge: $3105/(360hr*575kW)=$0.0147/kWh peak use (i.e. maximum power demand) charge: $13.11/kW Why is this different from the residential calculation?
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DVB: Energy can be neither created nor destroyed; It can only be changed from one form to another First Law of Thermodynamics (generalized energy conservation) Quantify: W + Q = PE + KE + TE Work+Heat exchanged= Change in (PE, KE and Thermal E) The rub, as we shall see, is that not all forms of energy are equally useful. In particular, thermal Energy is very easy to produce, but difficult to use.
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Energy Conversions (Table 2.2) Automatically Happens! digestion thermal A key question to consider is with what EFFICIENCY can each of these Conversions be accomplished (Useful energy output/ total energy input)
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Efficiency Efficiency = (useful E transferred)/(total E input) Device Transfer effected Efficiency
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P110_2008_Week_3 - Conservation of Energy If only...

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