Heat Rate at Minimum Column
Column Type = Text
This column is used to specify the heat rate to be used at a unit's minimum capacity (as indicated in the Minimum Capacity column). This column can be used for non cycling and must run units only (as indicated in the Non Cycling and Must Run columns). It can also be called "Minimum Capacity Heat Rate" or "Minimum Heat Rate".
When a heat rate at minimum is specified, and a minimum capacity exists for either a commitment unit or a must run unit, an incremental heat rate is calculated for the dispatchable segment above minimum capacity. It is calculated such that the unit average heat rate will equal the heat rate at full output (as specified in the Heat Rate column of the Resources table). (If the derived value for incremental heat rate is negative, warning messages are displayed and the plant full output average heat rate is used).
The incremental heat rate is treated as constant for all output levels between minimum and maximum capacity and is used only for commitment evaluation and in determination of the dispatch cost for the dispatchable segment. However, for true fuel usage and variable cost accounting reported in the Resource and Fuel Output Tables, the average or net heat rate will be reflected. Plant fuel use will increase linearly as its output increases between the minimum segment and full output and the plant’s net heat rate (fuel use/output) will be an inverse function of output.
The incremental heat rate is calculated as:
(Total Fuel Used Between Min Segment and Full Output) / (Total Output Between Min Segment and Full Output), or
Here Full Output does not include output from a UBB segment if applicable.
* By default, the net heat rate at full output is applied to the de-rated capability so that the heat rate is not penalized for maintenance or forced outage rates.
Heat Rate at Minimum
