Constraint Table

Energy Min

Aurora seeks to honor a minimum MWh generation level across the month or year.

Energy Max

Specify an annual/monthly limit on the total energy which can be produced by the resources in the constraint set. The limits should be entered in megawatt hours (MWh).

Energy CF Min

Aurora puts a floor on the capacity factor of the resource over the year. This constraint is equivalent to using an Energy Min constraint but allows the expression of the constraint in terms of capacity factor instead of MWh.

Energy CF Max

Aurora limits the capacity factor of the resource over the year. This constraint is the same as limiting the actual energy but allows the expression of the constraint in terms of capacity factor instead of MWh.

LT Capacity Min

Aurora will seek to constrain the build decisions such that the total average nameplate capacity from the resources in the constraint which are online is greater than or equal to the input target. The Limit Type must be equal to Year, Year Cumulative, or Study for this constraint type.  

• With Limit Type = Year, Aurora adds a constraint for each year of the study putting a minimum on the total resource capacity with a begin year equal to that year.  

• With Limit Type = Year Cumulative, Aurora adds a constraint for each year of the study putting a minimum on the total resource capacity online in that year (whether its begin year is in that year or before).  

• With Limit Type = Study, Aurora adds one single constraint for the whole study horizon putting a minimum on the total average nameplate capacity online across all years.  

Note that Traditional LT Method is not allowed with this option.  If selected, the Mixed Integer Program, Chronological method will be used instead.

LT Capacity Max

Aurora will seek to constrain the build decisions such that the total average nameplate capacity from the resources in the constraint which are online is less than or equal to the input target.  The  Limit Type must be equal to Year, Year Cumulative, or Study for this constraint type.  

• With Limit Type = Year, Aurora adds a constraint for each year of the study limiting the total resource capacity with a begin year equal to that year.  

• With Limit Type = Year Cumulative, Aurora adds a constraint for each year of the study limiting the total resource capacity online in that year (whether its begin year is in that year or before).  

• With Limit Type = Study, Aurora adds one single constraint for the whole study horizon limiting the total average nameplate capacity online across all years.  

Note that Traditional LT Method is not allowed with this option. If selected, the Mixed Integer Program, Chronological method will be used instead.

LT Energy Min

Aurora will only honor the constraint in the LT decisions and not necessarily the dispatch.  It will ensure that enough energy is available from the resources that are built to meet the target, if possible.  This is particularly useful in modeling RPS build targets.  Note that the Limit Type must be equal to Year for this constraint type.

LT Energy Max

Aurora will only honor the constraint in the LT decisions and not necessarily the dispatch.  It will seek to limit the builds such that the expected energy from the resources in the constraint which are online is less than the input target each year.  Note that the Limit Type must be equal to Year for this constraint type.

LT Reserve Margin

Aurora will accept additional reserve margin target constraints, including at a monthly level.  This constraint can only be referenced by zones directly in the Constraint ID column of the Zone Definition table and Aurora will use the set of all zones referencing the constraint as the region over which the reserve margin target must be met.  

The Limit value is entered as a percent, just like it is for the pools and zones (e.g. 15 means that Peak Capacity/Peak Demand need to be at least 1.15), and any Firm Imports/Firm Exports will be summed across the zones that are within the constraint.  For this constraint, Aurora will use all resources in the defined zones and the total demand of all of the zones to determine the reserve margin values.  To put a reserve margin constraint on every month, then set the Limit Type = Month (and the Limit column can take a time series input).  To do an annual constraint that only looks at certain months in the year, use the Limit Definition column in conjunction with Limit Type = Year.  For example, specify a reserve margin target of 15% for all of the summer months and a second target of 15% for all of the winter months to ensure that both the winter and summer peaks are covered.

Emission

(e.g., tons, tonnes)

Emission Rate

(e.g., tons/MWh)

Emission limits are entered for a given Set ID and emission type, so there may be multiple rows with the same Set ID.  For example, limits may be placed on each of three emission types - such as carbon dioxide (CO2), sulfur dioxide (SO2) and oxides of nitrogen (NOx) - by entering three rows in the Constraint table.  The Item ID should match a value in the Name column of the Emission Rate table.  The rows are collected into the same constraint set by entering a common Set ID value for all three rows.  

The cost of producing the emissions is specified in the Emission Pricing column of the Constraint table and may reference a supply curve (see column description for more details).  Note that for any resources which reference an emission constraint in the Constraint table, the resource-level emission prices will be overridden by the emission price for the constraint.

Resource emissions and energy can be limited by referring to the relevant constraint set(s) in three different ways.  The relevant Set ID value from the Constraint table can be entered in the Constraint ID column of the:

• Resources, New Resources, Link or RMT tables - individual resources can be associated with a constraint set

NOTE: Pumped storage and demand curtailment units are not allowed.

• Resource Groups table - all resources in a resource group can be collectively associated with a constraint set

• Zone Definition table - all resources in a zone can be collectively associated with a constraint set

The Constraint ID column in these three tables may contain multiple constraint set references by entering several Set ID values separated by commas.  Thus resources may simultaneously participate in many constraint sets.

When using one of the mixed-integer program (MIP) methods in conjunction with annual emission targets specified in the Constraint table, Aurora adds explicit constraints in the LT solution to limit the builds of emitting units that contribute to the constraint.

Fuel Min

Fuel Max

Aurora puts a limit or minimum on the total fuel usage of all fuels which reference the Set ID in the Fuel Constraint ID column of the Fuels table.  All resources that utilize this fuel directly or indirectly (via a Reference Fuel) will participate in the constraint, and Aurora will properly distinguish between primary and secondary fuel types.  Fuel type constraints cannot be referenced directly by resources.

Link Flow Max

Link Flow Min

Aurora limits the total flow, in MWh, across a set of Zonal Links.  The links in the constraint are defined in two ways:

• Net Import Zones = a comma delimited list of zones. The net import into that set of zones will be limited by the constraint.

• Constraint ID column in the Link table = Set ID.  For each link that references the constraint set, Aurora will limit the directional flow on all specific links included.