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Combined cycle combinations and advantages

Short answer

Possible combinations include gas turbine-steam turbine, diesel/gas engine-steam, MHD-steam, thermionic/thermoelectric-steam, nuclear gas-cooled reactor-steam, binary vapour (mercury-steam), and steam-organic Rankine. Advantages are 50-60% efficiency, lower fuel cost and CO2, low capital cost, quick start, less cooling water and space, and lower emissions.

What are the possible combinations of combined cycle power plants? Point out the advantages of combined cycles.

Possible combinations

A combined cycle couples a high-temperature topping cycle with a low-temperature bottoming cycle. Possible combinations:

  1. Gas turbine - steam turbine (Brayton-Rankine), the most common.
  2. Diesel/gas engine - steam turbine (engine exhaust raises steam).
  3. MHD (magnetohydrodynamic) generator - steam plant.
  4. Thermionic - steam and thermoelectric - steam plants.
  5. Nuclear (gas-cooled reactor) - steam / gas turbine plant.
  6. Binary vapour cycle, e.g. mercury - steam.
  7. Steam - organic Rankine cycle (low-temperature bottoming).

Advantages of combined cycles

  • High overall efficiency (50-60%), so lower fuel cost and lower CO2 per kWh.
  • Low capital cost per kW and short construction time.
  • Quick start and good load-following.
  • Less cooling water and less space than a steam plant of the same rating.
  • Lower emissions (clean fuels) and flexibility for cogeneration.

✓ Answer checked by Claude Opus 5.5 (high effort)

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