Energy costs vary greatly with energy source: coal @ $25.00/ton, gasoline @ a pu
ID: 785526 • Letter: E
Question
Energy costs vary greatly with energy source: coal @ $25.00/ton, gasoline @ a pump price of $2.00/gal, and electricity @ $0.1000/kWhr. Conventional practice is to put these on a common basis by expressing them in $ GJ-1. [ A gigajoule is approximately 106 (Btu).] For this purpose, assume gross heating values of 29 MJ kg-1 for coal and 37 GJ m-3 for gasoline.
(a) Rank order the three energy sources with respect to energy cost in $ GJ-1.
(b) Explain the large disparity in the numerical results pf Part (a). Discuss the advantages and disadvantages of the three energy sources.
Explanation / Answer
(a) energy cost in $ GJ^-1
Coal = 0.025/(0.029 *10^-3) = 862.06 $ GJ^-1
gasoline = 2*37/(0.00378541*37) = 528.54 $ GJ^-1 (convertion from gallon to m^3)
electricity = 0.100/(1*3 412.14163/10^6) = 29.307 $ GJ^-1 (converting kwh to btu then to GJ)
from ascending order
electricity<gasoline<coal
(b)
electricity is made from other renewable resources like water , wind etc
gasoline has more enrgy content than other so it overcomes the cost
Coal is readily available, but is coastly......gasoline has to be purified....electricity can be made from renewable sources hence eco friendly and cheap
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