Table 1 The key parameters, WC, QSPE, and CF of CCGT plant.
Components of hybrid CCGT plant with desalination | Process-average temperatures | Actual work (Wa) or heat input (QH or Qa) (MW) | |
|---|---|---|---|
High-temperature reservoir, TH (K) | Low-temperature reservoir, TL (K) | ||
Gas Turbines (GT) mg = mass flowrate of combustion gases (kg/s) Cp = specific heat of gases (J/kg.K) Eff_GT = efficiency of GT (-) | 1750 | 911 | QH = 2000 (input energy to CCGT) WC, GT = QH*(1 – TL/TH) Wa, GT = mg*Cp*(Tin − Tout)*eff_GT |
HRSG (air side) mexh = combustion products flowrate = 2002.5 kg/s Cpexh = specific heat of exhaust  = 1.005(J/kg.K)mexh   = combustion products flowrate  = 2002.5 kg/s  Cpexh = specific heat of exhaust  = 1.005(J/kg.K) | 911 | 370 | QHRSG, airside = mexh(Cpexh)·(TH − TL)HRSC |
HRSG (steam side) Effectiveness (EHRSG = 0.862), Mass flowrate of steam = mS (kg/s) Actual work = Wa (MW) | hin (kJ/kg) | hout (kJ/kg) | mS = (QHRSG, air side)*(EHRSG)/ (hfg) Wa = mS*(hin – hout) |
Steam Turbines (bb = before bled steam, ab = after bled steam | |||
High pressure (HP) | 3514 | 3360 | Wa, HP = ms,HP*(hin – hout) |
Intermediate pressure (IP with reheat) | 3600 | 3490 | Before bled steam to TVC (vacuum) |
3490 | 3380 | Wa, IP = ms,IP*(hin – hout) | |
Low pressure (LP) | 3380 | 3090 | Wa, LP = ms,LP,bb*(hin – hout)bb + ms,LP,ab*(hin – hout)ab |
3090 | 2590 | ||
Total Wa, ST | Wa, ST = (Wa, HP + Wa, IP + Wa, LP) | ||
The work-driven turbines (GT and ST), the total consumption of standard primary energy (QSPE) is (1159.64 + 752.20) = 1911.84 MW (57.98% of GT + 37.61% of ST = 95.6% of the total QSPE supplied by the fossil fuel) The actual output in electricity (Wa) is (765.48 + 331.79) = 1097.27 MWelec., which the difference between the Carnot and actual work are the losses incurred in the turbines The conversion factor for work heat engine is defined as the ratio of QSPE to Wa, where the latter is the derived electricity that is normally measured by users, either in kWelec or kWhelec/m3. Note that the 1/CF differs from the first law efficiency as the apportioned QSPE for electricity generation is invoked, not the Qinput to CCGT | Actual electricity output is Wa, standard primary energy consumption, QSPE. The conversion factor of individual turbine is (CFelec) \(= \left( {\frac{{Q_{{\mathrm{SPE}}}}}{{W_{\mathrm{a}}}}} \right)\) As the electricity are combined from GT and ST, the weighted CF is CFelec, weighted = \(\left( {\frac{{Q_{{\mathrm{SPE,GT}}}, + Q_{{\mathrm{SPE}},\,{\mathrm{ST}}}}}{{W_{{\mathrm{a,GT}}} + W_{{\mathrm{a,ST}}}}}} \right)\) | ||
In a heat-driven desalination plant, low-pressure (LP) bled steam from LP-turbines is utilized as a heat source. Since MED, MED-TVC, HT-MED, and MEDAD are operating at different temperatures, hence separate CFth are calculated as shown below MED-TVC: To = 303 K, TH = 403 K, corresponding CFth = 0.299 MSF: To = 303 K, TH = 383 K, corresponding CFth = 0.252 MED: To = 303 K, TH = 338 K, corresponding CFth = 0.125 MEDAD and DCSEC cycles: To = 303 K, TH = 333 K, corresponding CFth = 0.109 | Actual heat input, Qa The conversion factor for the thermally driven process is (CFth) \(= \left( {\frac{{Q_{{\mathrm{SPE}}}}}{{Q_{\mathrm{a}}}}} \right) = \frac{{\left( {1 - \frac{{T_{\mathrm{o}}}}{{T_{\mathrm{H}}}}} \right)}}{{\left( {1 - \frac{{T_{\mathrm{o}}}}{{T_{{\mathrm{adia}}}}}} \right)}}\) | ||
