CAES Max Ratio Column
This optional column is used as part of the Compressed Air Energy Storage (CAES) logic, and it forces a certain combination of compressed air and thermal generation from the unit in the actual dispatch.
To activate the CAES logic, a unit needs the following characteristics:
- It is a storage type resource unit based on the primary fuel (i.e. the Fuel Type begins with STO or PS)
- The resource has a valid Second Fuel
- The resource references a valid Storage ID, and that row in the Storage table has a valid entry in the optional column CAES Min Ratio
This column, along with the CAES Min Ratio column, governs the portion of the output which must come from the thermal part of the plant. Valid entries are between 0 and 1 and Aurora will add constraints using the following formula:
CAES Min Ratio <= y/(x+y) <= CAES Max Ratio
- where y is the thermal output without the additional compressed air,
- and x is the incremental output gained from compressed air (in MWh), such that the total MWh output is x + y.
- In the above equation, the total x + y will also be limited by the overall capability of the plant (calculated in the normal way) and x will be limited by the storage generating limit of Capability * Generation Availability.
If a unit always runs at a constant mix of compressed air and thermal fuel usage, then set the CAES Min Ratio = CAES Max Ratio. For example, if a unit is operated in this way such that the amount of fuel needed is 1/3 that of the what the same thermal plant would use without the compressed air addition, the CAES Min Ratio and CAES Max Ratio would both be set to 1/3.
For CAES resources, the reported Storage_Contents, Stored_MWh, Generation_MWh, and Output_MWH_Primary outputs will be based only on the compressed air portion of the plant. The Output_MWH_Secondary and Seconday_Fuel_Usage will be based on the thermal portion of the plant. The Full_Load_Heat_Rate and Full_Load_Cost values will be reported based on the CAES Min Ratio, and the Net_Heat_Rate and Net_Cost will be based on the actual combined operation of the plant in the time period.
NOTE: A few characteristics to note: CAES units cannot be Must Run or Non Cycling. They cannot have resource segments (via UBB columns or heat rate definition). And finally, Start Up Costs can be used but they won’t affect dispatch decisions.
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.
CAES Max Ratio Column