2.84 shown in figure p2.84 is cogeneration power plant operating in a thermodyna

Question

2.84 shown in figure p2.84 is cogeneration power plant operating in a thermodynamic cycle at steady state . the plant provides electricity to a community at rate of 80 MW. The energy discharged from the power plant by heat transfer is donated on figure by Q out. of this 70MW is provided to the cpmmunity for water heating and the reminder is discarded to the environment without use .The electricity is valued at $0.08 per KW .h. if the cycle thermal efficiency is 40%, determain the (a) rate energy is added by heat transfer .Q in MW, (B) ara energy is discarded to the environment. in MW and (c) value of the electricity generated, in $ per year.

Explanation / Answer

{Cycle Efficiency} ={Work Output}/{Heat Input}

Using standard definitions ofthermodynamic quantities,
and also Conservation of Energy for Item (b), we get:

(a): {Heat Input To Power Plant} =QIN =
= {Work Output}/{Cycle Efficiency}
= (80 MW)/(0.4)
= 200MW

(b): {Heat Discarded To Environment} =QOUT:Env =
= QIN - {ElectricPower Gen} - {Heat For WaterHeating}
= (200MW) - (80 MW) - (70MW)
= 50MW

(c): {Value Of Electric Power Generated In 1 Yr}= V =
= {Value Per Energy Unit}*{Electr Power Gen}*{Time: 1Yr}
= {$$ per kW*hr}*{Electr Power Gen in kW}*{1 Yrin hrs}
= {$0.08 per kW*hr}*{80.0e+3kW}*{(365)*(24) hrs}
=56.06e+6 Dollars

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