Ground coverage ratio

I am trying to model a PV-integrated geomembrane (flexible thin film cells) on a capped landfill. I would like to be able to draw comparisons with a rack-mounted system using crystalline cells. It seems one of the important factors will be the capacity (in kW) that can be installed for each technology on the available land area.
I have an estimate of 150kWdc/acre for the PV geomembrane which I believe works out to 0.58 for a ground coverage ratio.

From other posts I understand that Packing Factor is not considered in energy calculations so I will have to adjust GCR.
My problem is that if I choose Fixed array in the PV Subarray area, the ground coverage ratio is greyed out and set at 0.3 as the default.
I cannot adjust it unless I choose 1-axis tracking, which this system most certainly is not.

?

Hello,

SAM's primary purpose is to estimate the electrical output of a renewable energy system, and to calculate financial metrics based on the cost of installing and operating the system and the value of the electricity it produces. SAM assumes that there is sufficient land area or roof space for the system you are modeling.

For your comparison, you will need to determine the system capacity and land cost for each scenario outside of SAM, and use those assumptions to determine what values to use for the SAM inputs.

Also, SAM assumes that the array (or each subarray) is flat and oriented in the same direction, which might not accurately represent the photovoltaic geomembrane.

In SAM 2014.1.14 and earlier, the photovoltaic model only uses the GCR input to estimate the possible reduction in incident radiation due to self-shading of rows of modules in an array with 1-axis tracking. That's why the GCR input is disabled for other tracking options. The packing factor is an input to the financial model that SAM uses to estimate the land cost for cash flow calculations.

In the next version of SAM, due out for release within the next couple of weeks, SAM uses the GCR for the land area estimate as well as the self-shading losses, and we've removed the land packing factor input to minimize confusion.

Best regards,
Paul.

Thank you, that makes sense.

I think the update to use GCR for land area estimates will be a nice improvement. It will help with practical decision-making about feasible system capacity given a limited area.