Choosing the right rating of power plant

[electpower]

When the natural resources permit to build a Power plant with a total generation capacity of 800 MW. What factors determine the rating of the power plant, when I have to choose between 2 x 400 MW and 1 x 800 MW ?

 

[cranky108]

Choose the name plate values. That is what the manufacturer will stant behind, and so should you.

 

[wayne440]

A single 800 MW unit means when that unit is down for any reason, your plant capacity is 0 MW.

Having 2 400 MW units would under some conditions allow one unit to remain operational while the other was down for whatever reason. Your plant might still be capable of 400 MW, which is generally considerably better than 0 MW.

Your boss will still be jumping up and down over the outage, but perhaps not as high.

 

[ScottyUK]

Efficiency and capital cost: both will generally weigh in favour of the larger single machine. Wayne's points are very valid for a real-world plant.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[bacon4life]

Does your natural resource get wasted or saved when the plant is not running? For example some hydro plants must keep at least one generator running or spill water to maintain stream flows.

 

[rcw retired EE]

What type of power plant? Solar, hydro, gas turbine simple cycle, gas turbine combined cycle, bio-fuel boiler with steam turbine, photo-voltaic or wind turbine?

It sounds like it is hydro. One large turbine will probably have different efficiency curves than two smaller units. Based on the expected daily and seasonal stream flow data you could analyze which combination will provide more MWH over the life of the plant. Compare that with the capital cost estimates and factor in the concerns about reliability and security to get some answers (or more questions.)

 

[electpower]

It is a real time Power plant, Coal fired.

 

[rmw]

"What factors determine the .....?"

Well, for one, your power sales agreements. As pointed out, if you lose one big unit (and that is easy enough to do with a coal fired unit) you lose all your ability to sell power and meet the requirements of your contract. Same for when you are down for maintenance.

Another is your local grid and the importance of this unit on the grid. If this is the principal unit on the grid (or you are islanded) I'd recommend the two unit approach.

There is so much we don't know about your real needs that it is hard to hazard a guess.

rmw