Primary Fuel Limit Column
Column Type = Text
The Primary Fuel Limit column is used for Traditional Commitment to specify a use limit for the primary fuel of a resource. This column also works for Commitment Optimization when the value is set to 0. If you choose Commitment Optimization, this column will only work if the value is null or zero (0).
Fuel limits are entered in mmBtu units. To specify an unlimited use of the fuel, enter "UNL" in this data field.
NOTE: While the fuel limit can be specified for any time period (annual, monthly, weekly, daily, hourly, sub-hourly) it is applied hourly based on monthly fuel usage using the following formula: Unit capability for the hour = (fuel limit as input - fuel usage so far for the month) / heat rate.
If a Primary fuel limit is applied the Second fuel is used when the Primary fuel limit is reached, regardless of which is more economical.
NOTE: If the value is zero (0), the limit applied is zero (0). If the value is null (no value), a fuel limit is not specified for the resource.
The limit can be input and can change on a period basis (any time period down to sub-hourly). For the purposes of the example below, the current hours limit will be used for the comparison. In the model, however, it is compared to the fuel usage so far in the month (not the current hours fuel usage).
Example:
Hourly fuel limits input as follows (hourly fuel usage is also shown):
Hour Limit Usage Cumulative Fuel
Usage For Month
1 90 50 50
2 50 10 60
3 75 5 65
4 45 20 85
5 100
Capability limits from fuel usage are then as follows (divided by heat rate):
1 90
2 50-50=0
3 75-60=15
4 45-65=0
5 100-85=15
NOTE: For information on how to specify a time series for a variable, see Entering a Time Series.
Primary Fuel Limit Column