Appendix C: Adjustment of Capital Costs for Unit Size
The specific capital costs generally apply to plant that is close to the size of plant that has been quoted. Scaling factors are used to estimate the specific cost of plant of a different size. Capital costs tend to obey power laws in terms of relation to size.
An estimate of a different size of plant can be found by applying the following formula
C = Cknown x (Sknown / S)n
Where
C is the unknown cost
Cknown is the known cost
Sknown is the known size
S is the size for which the cost is to be calculated
n is the scaling factor
The following table C1 gives approximate capital cost scaling factors over a limited range, say ± 50%.
Table C1: Capital Cost Scaling Factors
| Technology | Scaling Factor "n" |
|---|
| Simple cycle gas turbine | 0.4 |
| Combined cycle gas turbine (CCGT) | 0.22 |
| Integrated gasification combined cycle (IGCC) | 0.28 |
| Pulverised coal fuel | 0.28 |
| Fluidised bed plant | 0.28 |
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