Example 2: Independent parametric with linkage |  |  |  |

| This topic describes SAM 3.0 and has not been revised for SAM 2009 Beta. You may find useful information, especially if you are new to SAM, but some of the information may be inconsistent with the new version.

This example illustrates the use of the linkage parametric group, which is useful for parametric analyses involving one or more variables whose value depends on that of other variables. This example also demonstrates how to define a non-numeric variable as a parametric variable. It is based on the second case in the sample file Parametrics Examples.sam.

What would the annual output of a residential photovoltaic system be in different locations, assuming that the array tilt angle for each location is equal to the location's latitude? To answer the question, we will compare the annual output of a system for three locations by linking the numeric variable Tilt, expressed in degrees, with the text variable, Location, expressed as a place name.

Note. If you did not follow the procedure in Example 1: Independent Parametric, you can start with the file Parametrics Examples.sam, which should be in the Solar Advisor folder (C:\SAM\Samples by default).

Link the independent parametric variable Tilt to Climate:

1. | Open the file that you created in Example 1 (or the sample file Parametrics Examples.sam).

2. | Create a copy of the Example 1 - Independent case: right-click the Residential Flat Plate System tab, click Duplicate on the shortcut menu.

3. | Rename the new case to "Example 2 - Independent with Linkage" Right-click the case tab and click Rename on the shortcut menu.

4. | On the Case menu, click Define Parametrics to open the Define Parametric window, or on the Array page, right-click the Tilt variable box.

5. | In the Tilt Input Type window click Parametrics and then click .

6. | In the Define Parametric window, under Linkages, click Add Variable.

7. | In the Add Variable window, click Tilt and Location. (Scroll up to the Climate section to find the Location variable.)

8. | Click OK to return to the Define Parametric window.

The Climate and Tilt variable names should appear in the Linkage 1 box, and all four buttons (Add Variable, Delete Variable, Edit Linkage, Delete Linkage) should be active.

9. | Click Edit Linkage to open the Edit Linked Group window.

Notice that the climate variable values appear in the Edit Linked Group window in drop-down boxes because they are non-numeric values. Solar Advisor has assigned CO Boulder.tm2 to each of the seven Module Tilt values that we created in Example 1 because we have not yet assigned values to the Climate variable.

For this example, we are going to use only three locations, Boulder, Seattle, and Newark.

10. | Use the arrow in each of the first three rows of Location column, to select CO Boulder.tm2, WA Seattle.tm2, and NJ Newark.tm2.

11. | Type a new value in the Tilt column for each location: CO Boulder 40, WA Seattle 48, and NJ Newark 41.

12. | Click the box in the first column of the Boulder row to set CO Boulder as the base value.

13. | Use the Delete key to delete the remaining rows. You may need to delete each cell in the table individually. If necessary, you can use the Insert key to add a row.

14. | Click OK three times to close all of the parametric windows and return to the Array page.

So far, we have defined a linked parametric group, and assigned it two variables, Location and Tilt. The Location variable is also defined as an independent parametric variable. In the next procedure, we will run the simulation to create a set of results for each of the values.

Run the simulation and view results:

1. | Click Run Analysis.

2. | If the Inverter Size Issue window appears, click Run All. The message indicates that the inverter's rated capacity is slightly less than the array's rated capacity, which for the purposes of this exercise, is not a problem.

3. | In the Information window, note that the number of TRNSYS simulations is equal to the number of linked parametric variables. Solar Advisor will perform a complete simulation for each of the three locations we specified.

4. | Click Yes to start the simulations. When Solar Advisor finishes calculations, the Results Summary page appears.

5. | In the Graphs list, click *Annual Output Vs Location.

6. | Save the file.

The graph shows the annual output predicted for the three locations at tilt equals latitude.

Notes: You can also use sliders to examine results for the three locations. For example, you could add a slider for the Location variable to the Cashflow graph to explore the cash flow for each location. See Sliders for more information.