SAM_HOMER_setup_notes.md

Key inputs in SAM and HOMER to compare them:

SAM (Grid Outage):

• Create a Detailed PV-Battery, Residential Owner case.
• Select a weather file
• Used the Simple Efficiency Module Model (defaults) and the Inverter Datasheet model (max power 100 W, DC voltages 1-40 Vdc, night power consumption 0 W) [figure]
• System Design: enabled "Estimate Subarray 1 configuration", desired dc:ac ratio = 1.
• Battery desired bank power = 30 kW (max PV array size to be tested).
• Enable the Grid Outage option:
  • Set the Critical load percent of electric load to 100%
  • Edit the grid outage time series to be 1 in every time step
    • (TIP: In the Edit Array window, select "Copy", then paste the array of "0" values into a spreadsheet. Chnage the first value to "1" and double-click the "fill handle" in the bottom right of the cell, or press Ctrl+Shift+↓ then Ctrl+D)
• Use the parametric tool to vary battery capacity (20, 40, 60, 80, 100 kWh) and PV size (5, 10, 15, 20, 25, 30 kWdc) and to output unmet critical load.
  • To quickly setup the inputs to model all combinations, use the Quick setup... option, add Desired bank capacity (kWh) and Desired array size (kW), and use the variable editor to define the range of values.
  • For the parametric output, use Critical load unmet perentage (year 1) (%)
• TIP: for faster run times, set the Analysis period to 1 year in the Financial Parameters tab. Note that this ignores degradation, and many financial metrics will not be useful.
• Exporting results: Use the Export > Save as CSV option in the parametric tool

SAM (Grid Target)

Repeat the same steps as for the grid outage case, but instead of enabling the Grid Outage option, modify the battery dispatch an parametric outputs as described below. (TIP: Duplicate the case if you modified a lot of inputs and want to save some time).

• Under Battery Dispatch:
  • Set Minimum state of charge to 10% (or whatever yo uset the Battery Discharge Limit During Grid Outage to, if you modifed the default 10%)
  • Set the storage dispatch to Input grid power targets
  • Select Edit values... for Monthly grid power targets and set all months to "0"
• Use parametric outputs Electricity load total in each yeah (kWh) and Annual energy imported from grid (kWh).
• After exporting parametric results, calculate unmet load in each year as the ratio of the two annual values.

HOMER:

• Add a primary load, PV, Converter, and Battery
• Import solar resource (GHI), ambient temperature, and load datafiles
  • First copy/export these from SAM's weather file (GHI and temperature) and electric load.
  • Create separate text files for each variable, where values for each timestep are in a new row (no header or time stamps)
  • Save GHI and temperature files with .txt extension and load with .dmd
• For PV: enable temperature effects, set slope to 20 deg (or whatever tilt you used in SAM) and derate factor to 90% (i.e., 10% losses, roughly what SAM's default losses are), considering the same range of PV sizes as SAM (5-30 kW). Cost data may be required as well.
• For the battery: create a new battery, 10 V, 1000 Ah (10 kWh), with a flat capacity curve and 10% minimum SoC (roughly approximating Li-ion NMC in SAM in 10 kWh blocks), considering same sizes as SAM (2-10 batteries for 20-100 kWh).
• For the converter: set the capacity to be greater than or equal to peak PV capacity, and charge and discharge efficiency to match SAM values (96%)
• Under Constraints, set the maximum annual capacity shortage to 100%
• Exporting results:
  • After hitting Calculate, view Optimization Results > Details..., right click, and select Export Table..., then save the .CSV file.
  • Use Unmet Load (in kWh/yr) divided by annual load to calculate unmet load fraction.