The Ramp Cost column is used to specify a charge, typically in $/MW, associated with a unit ramping up or down.  Here are a few details on how the value is applied:

• No cost is applied in the very first dispatch of the simulation since the previous hour’s output is unknown.

• The cost is the same for increasing the output and decreasing the output.  The total cost accumulated in a given hour is equal to:

 [Input Ramp Cost] * | Last Hour Output – This Hour Output |.

• However, the input is currency/MW and is not really per hour, but rather if the unit moves up or down 1 MW in any length of time this charge is applied per MW.  For example, when running sub-hourly if the units goes from 10 to 30 MW in a 5 minute increment, that will be the same charge as when running hourly and also increasing by 20 MW in the hour.  

• The Ramp Cost cannot be used on storage units.

• The value cannot be negative, as Aurora puts a minimum value of 0 on the charge.

For reporting, the costs will be included in the Variable_OM_Cost_Aux2 column of the Resource output table.

A special note regarding Study Period sampling and impacts on Reporting:

If the simulation is not running all hours, Aurora will scale down the reported value on the hourly level so that when it scales up the values the total cost is approximately correct.  For example, suppose that in an hourly study:

• a unit goes from 0 to 10, 20, 30, ... 230, 240 MW throughout the 24 hours of the day,

• and that the charge is $10 per MW,

• then the total charge for the day is 10*(|0-10| + |10-20| + ... + |230-240|) = 10*240 = 2400.

Now suppose that the same study is run every other hour:

• the unit has output that goes from 0 the previous day to 20, 40, 60, ... 240 MW in the 12 dispatch hours of the day

• Now the total charge for the day is 10*(|0-20| + |20-40| + ... + |220-240|) = 10*(20*12) = 2400.  

In this case, the output reporting roll-up function would multiply this final value by 2 for the total cost for the OutputDay reporting since only half of the hours were sampled.  Thus, for OutputHour reporting, the "hourly" value is divided by 2 for more precise reporting.  

 NOTE: If the FUEL reference is specified for this variable the value in the Fuel Table will be applied.

 NOTE: Inputs can be specified for any time period (annual, monthly, weekly, hourly or sub-hourly). For information on how to specify a time series for a variable, see Entering a Time Series.