Lookup

Syntax

Lookup(Method, Branch:Variable, IV1, DV1, IV2, DV2, IV3, DV3, ..., IVn, DVn)

Note: the independent value parameters (IV1, IV2) must be listed in ascending order of value. 

Description

Calculates a value based on the value of an independent branch:variable reference and a lookup table containing values for both the independent and dependent variables.  Two methods are supported. The Linear method calculates a result by doing linear interpolation between the values in the lookup table. The Step method assumes discrete (step-wise) changes in the independent and dependent values.

As an example, consider the linear method for the independent variable reference (ILV) having a range of alternative values.

If ILV <= IV1 then

Result = DV 1

If ILV >= IVn then

Result = DVn

if ILV lies between IV1 and IV2 then an interpolation is used to calculate the dependent value result as follows:

(

Imagine that the unit capital cost of wind power will decrease from its current price of 200 $/kW  to 150$/kW once the installed capacity reaches 3000 MW, but will go no lower than 100$/kW, even if capacity increases above 10000 MW. The current capacity is 1000 MW. Hence for the capital cost variable, you could enter a lookup function that refers to the installed capacity of wind:

Lookup(Linear, Capacity, 1000, 200, 3000, 150, 10000, 100)

Based on this function, when capacity reaches 2000 MW the capital cost will be 175 $/kW.  Similarly, when the capacity reaches 6500 MW, the capital cost will be 125 $/kW.