While considering the cost you need to take care of the initial cost of the system and the running (or Operation and Maintenance) cost. You need to do your analysis taking into account the two costs as well as the life span and reliability of each system. When you model these costs you can then decide on which one to chose.

I may be able to help you if I have the details about each system.

So if cost is mater for a system then i need not to be bothered about the efficiency.

If the system in both situations abides by the minimum requirements of efficiency, then yes you assume efficiency is a constant factor and do not include in your calculations of the cost. However, if the efficiency is a factor (which in actual cases you have to worry about) then calculations is based on both factors.

I believe that the system's efficiency can be modeled in the running cost of the system so it can be converted to "cost" and you will optimize (or minimize) your total cost.

For example, if I have two generators:

Generator A has an initial cost of $1000 and 60% efficiency

Generator B has an initial cost of $500 but with 30% efficiency

If you assume that the lifespan of both generators is the same, and you neglect the inflation and other maintenance costs, then by simple calculations you can compare the total cost of A and that B.

If X is the running cost of A, then it will be 2X for B (modelling the efficiency - A is two times more efficient than B).

=> 1000 + X is to be compared with 500 + 2X to decide which is better.

(Note that I have simplified the calculations to one variable, but it can be done for more. You may need some sensitivity analysis later).

OK. However, sensitivity analysis should be done especially in a full fledged research work.

Excellent Michel.

Thanks a lot to both of you. really this will help me a lot for selection of better plant.

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