GCR and Land Area for PV Systems

I am confused about how SAM and the user determines the footprint of a fixed PV module array. For example my test array has 90 (1 x 1.6 meter) modules in 6 modules per string and 15 strings in parallel. The GCR is 0.3 and the Estimated Module Overall Land use is 146.8 square meters. However with a 0.3 GCR this is not possible I think. Does SAM provide a quick analysis of footprint based on a desired array size or do you need to calculate this manually and run your own spacing calculations? Thanks for any help you can provide.
SAM's module area and GCR inputs help you account for some of the system's land requirements, but you need to do a more complete calculation outside of SAM.
In SAM 2014.11.24, for the detailed photovoltaic model, the "Total module area" shown toward the bottom of the System Design page is the product of the module area from the Module page and number of modules in the array. That value does not depend on the GCR. The "Land area" shown on the System Costs page is an estimate of the land area occupied by the modules based on this total module area and the GCR: Land area (acre) = module area (m2) / GCR x 0.0002471 acre/m2. You can use that land area estimate to assign a cost in $/acre that scales with the module area. You can also assign other land costs as a percentage of direct cost, $/Wdc, or fixed dollare amount.
In your example, the module area is approximately 1.6 m2, and for 90 modules, the total module area is approximately 90 x 1.6 = 144 m2. I assume that by "Estimated Module Overall Land use" you mean the "Total module area" from the System Design page.
Best regards,

Paul.

Thank you. It would be great if a future state code improvement could optimize array footprint as a function of self shading and sun path throughout the year. Fixed and tracking. It would be great if SAM also provided off the shelf tracking and racking options as well for the cost models.
Andy

Dear Andy,

Thank you for the suggestions. By "array footprint," do you mean the area occupied by the array? What terms would you like SAM to use to describe the array footprint? Also, could you explain more what you mean by off-the-shelf tracking and racking options?

Best regards,
Paul.

Paul,

For Array footprint I mean the physical area for an non shaded ground mount array including modules, area lost to self-shading, and possibly maintenance area required per code or by racking specification. Factors to describe and determine footprint would include: locale sun path input; worst case solar azimuth and elevation inputs; module type input; module orientation input; module stacking input; modules in a row input; module row number input; fixed, single axis, dual axis, or azimuth axis tracking input. A next step might even be to include a database of commercial racking and tracking systems to help define the physical footprint. Also, I realize these costs are in BOS Direct Capital Cost but a commercial database with a little more transparency would be helpful.

Question while I am on a roll. It would be great to see the cost change when working in DC Subarrays "System Design". I believe one achieves improved IRR, NPV, and Payback results with more energy production without the cost of improved tracking. So, is there a reason why the two are not connected since I believe you have the $/Wdc capacity data for the various tracking systems. Maybe I am missing something.

Thanks for the discussion.

Andy

Hi Andy,

For the photovoltaic models, there is not a cost category on the System Costs page that changes with the tracking option on the System Design page. That means that when you change the tracking option on the System Design page, you should also change whatever cost category you decide to use to represent tracking equipment costs (including maintenance costs, if any).

As you note, on the System Costs page, you can specify capital costs in dollars per DC Watt of array nameplate capacity, so those costs would scale with the nameplate capacity you specify on the System Design page.

Best regards,
Paul.