Sensitivity Analysis

The sensitivity analysis option allows you to specify a range of values as a percentage for one or more input variables to investigate how sensitive an output metric is to variations in the input variables' values. Examples of sensitivity analyses include:

•	Determining the sensitivity of the levelized cost of energy to different capital cost components.

•	Comparing the sensitivity of the levelized cost of energy to capital cost and financial assumptions.

Configuring sensitivity analyses makes it possible to plot tornado graphs showing the range of an output metric values for one or more sensitivity variables.

Note. Solar Advisor calculates results for each sensitivity variable independently. In some analyses, this may cause misleading results. This is especially true when the sensitivity variable is a performance input variable rather than a cost or financial input variable. For example, for CSP trough systems with storage, varying the thermal storage capacity independently of the tank heat loss variable to examine how sensitive the system's electrical output is to storage capacity would not accurately account for the expected increase in heat loss for larger storage systems. Similarly, for photovoltaic systems, varying the number of modules per string independently of the inverter type or number of inverters might result in inaccurate system output calculations if the inverter is improperly sized for a number of modules within the range specified for the sensitivity analysis.

To display the sensitivity simulation setup options:

1.	On the Main window, click Configure Simulations to view the Configure Simulation page.

2.	On the Configure Simulations page, click Sensitivity to display the Parametric simulation setup options.

SS_ConfigureSimulations-SensitivityClick

3.	Click Add Sensitivity Simulation to add a set of sensitivity simulation setup options. You can add as many sensitivity simulations as your analysis requires.

Click Remove Simulation to delete a simulation option.

Click Clear All to remove all simulation options from the case.

Contents

►	Page Reference describes the sensitivity simulation setup options.

►	Setting up a Sensitivity Analysis describes the steps for defining sensitivity variables.

►	Sample Sensitivity Results shows examples of tornado graphs that can be created using sensitivity analyses.

Page Reference

The Analysis Setup options allow you to choose an output metric, add and remove variables from the list of sensitivity variables, assign values to and edit sensitivity variables, and assign ranges to each sensitivity variable.

SS_Sensitivity-Overview

Analysis Setup

Select an output metric	Choose an output metric for the sensitivity analysis. This metric will appear on tornado graphs in the results.
Add	Add an input variable to the sensitivity variables list.
Edit	Assign a "custom" variation range to the variable highlighted in the sensitivity variables list. Solar Advisor assigns the default range to all sensitivity variables that do not have a different custom range. Solar Advisor indicates the custom range in parentheses next to the variable's name in the sensitivity variable list.
Remove	Remove a variable from the sensitivity variables list.
+/- Variation on inputs	The default range applied to all sensitivity variables that do not have a different custom range. For a range value of 10 %, Solar Advisor would calculate the range of values of an input variable between 10 % below and 10 % above the variable's value on the input page.

Setting up a Sensitivity Analysis

Once you have added a sensitivity simulation, you must add one or more sensitivity variables to the simulation.

After setting up the optimization, click the Run All Simulations button, or click Run All Simulations on the Case menu to run the optimization and any other enabled simulations.

To set up a sensitivity analysis:

1.	Display the sensitivity simulation setup options as described above.

2.	Click Add to choose variables to which you want to assign a variation range from a list of available input variables. Solar Advisor adds the variables to the sensitivity variables list.

3.	If you want to use a variation range value other than the default value displayed below the sensitivity variables list, click Edit to assign a custom range value.

Check Enable this simulation to include the sensitivity analysis in simulation runs. You can save the sensitivity simulation setup options and exclude the analysis from simulations by clearing the checkbox. Clearing the checkbox allows you to shorten simulation run times without losing the setup configuration.

SS_Parametrics-Enable

Sample Sensitivity Analysis Results

The following tornado graphs were created by setting up sensitivity analyses. You can use these examples to better understand how to use parametric analysis to create useful graphs.

The following graph shows how sensitive a CSP trough project's levelized cost of energy is to four capital cost categories. To create the graph, the following four variables were defined as sensitivity variables using the default variation range of 10 %: Power plant cost, solar field cost, HTF system cost, and storage system cost:

SS_Sensitivity-CapitalCostTornado

The next graph shows shows how sensitive the levelized cost of energy is to selected capital cost categories compared to selected financial assumptions for a CSP trough system. The solar field cost, loan rate, and PPA escalation rate were defined as sensitivity variables with a 10 % variation range. how the first year annual electric output depends on both the array tilt and azimuth. The tilt variable was assigned the same values as the previous graph, and the azimuth variable was assigned values between -90 and 90 degrees west of south in increments of 15 degrees:

SS_Sensitivity-CapitalVsFinancialTornado