Generator Start Cost
| Units: | $ |
| Mode: | Input Only |
| Multi-band: | True |
| Default Value: | 0 |
| Validation Rule: | ≥0 |
| Key Property: | No |
| Description: | Cost of starting a unit |
Generator Start Cost is the operations and maintenance cost associated with start up of a unit. The cost of starts is reported in the property Start & Shutdown Cost.
There are two components to the cost associated with unit start up:
- Start Cost
- Offtake at Start multiplied by Fuel Price
The total cost as seen by the optimization is the sum of these two components, thus the reported Unit Start Cost will reflect this.
If desired, the Start Cost can be modified by the Marginal Loss Factor by setting the Region MLF Adjusts Start Cost property.
Generators cool after being shut down, and this increases the cost of re-starting the units. The simulator models this cooling by using multi-band Start Cost in combination with Start Cost Time.
Example:
| Generator | Property | Band | Value | Units |
|---|---|---|---|---|
| Gen | Units | 1 | 1 | - |
| Gen | Max Capacity | 1 | 300 | MW |
| Gen | Min Stable Level | 1 | 150 | MW |
| Gen | Run Up Rate | 1 | 1.0 | MW/min. |
| Gen | Run Up Rate | 2 | 0.8 | MW/min. |
| Gen | Run Up Rate | 3 | 0.5 | MW/min. |
| Gen | Start Cost Time | 1 | 2 | hrs |
| Gen | Start Cost Time | 2 | 4 | hrs |
| Gen | Start Cost Time | 3 | 4 | hrs |
| Gen | Start Cost | 1 | 1000 | $ |
| Gen | Start Cost | 2 | 2500 | $ |
| Gen | Start Cost | 3 | 3000 | $ |
In this example the unit is:
- 'hot' for up to two hours after being shutdown and costs $1000 to start inside the two hours;
- 'warm' for a further four hours (i.e. up to six hours after being shutdown) and costs $2500 to start at the six hour point;
- 'cold' after it has cooled for a further four hours (i.e. 10 hours in total) and costs $3000 to start at the 10 hour point.
Note that start cost time is always the incremental number of hours between cooling states. It is not the total time the unit has been cooling. This is set up this way to make it easier to avoid the mistake of mis-ordering the cooling states. Also, the start cost varies linearly between cooling states as in the following illustration.
If no initial conditions are defined for a Generator, the start decision variable for the first horizon period will not be included in the objective function. This allows the optimization to assume a start occurred some time in the past and so it can have a free start at the start of t=0. If this is not desired, Initial Units Generating should be set to 0.
Note:
- For Irish SEM: When the Uplift Compatibility attribute is set to "Irish SEM" the start cost function is modeled as a step function, not the linear interpolation shown here.
- When Start Profile is defined in addition of Start Cost and Star Cost Time bands, the start cost function is modelled as a step function instead of the linear interpolation shown above.
See also: