Standardized Tracker File

[kurt-rhee]

Hey pvlib community,

A few people from different companies have separately reached out to me asking if I would be interested in working on a standardized tracker file that would mimic the purpose of existing PAN and OND file formats.

Is this something you would be interested in collaborating on?

[kurt-rhee]

Most of the useful information would likely be physical information to help in automatic layout tools, but some such as rotation limit, and possibly backtracking strategy might become useful for modeling as well.

[mikofski]

I think the SolarFarmer tracker specification file should do the trick (wink)

[kurt-rhee]

Hey @mikofski do you have a copy of the file I could look at? I checked here and couldn't find one. https://dnvgldocs.azureedge.net/SolarFarmer_Latest/UserGuide/UIChapters/DefineComponents/Trackers.html?q=tracker%20file

[AWABIE]

@kurt-rhee @mikofski As inspiration, this is what we currently use in PVComplete (JSON format) to allow users to share and save configurations (contains some extra info that would be removed for the .MNT file)
PVComplete_Config_file.zip
. This only focuses on structural info for layout fill, but I would propose to also include yield related inputs such as:

• Tracking angle limitations
• NS/EW slope limitations
• Pier height limitations
• Booleans (backtracking, terrain aware backtracking)
• Bifacial inputs (standards clearance heights and structural blocking factor)

[mikofski]

The mounting system specification for the SolarFarmer API might be useful. It's a single spec for both trackers and fixed. See the SolarFarmer User Guide: Web API > Endpoints > ModelChain endpoint > mountingTypeSpecifications and trackerSystems for a few extra parameters specific to trackers. There's also more info in the swagger docs but you need to be authenticated to see them. The relevant section is here:

"MountingTypeSpecification": {
  "type": "object",
  "description": "Contains the data relating to one design of rack",
  "additionalProperties": false,
  "required": [
    "isTracker",
    "numberOfModulesHigh",
    "modulesAreLandscape",
    "rackHeight",
    "ySpacingBetweenModules",
    "frameBottomWidth",
    "constantHeatTransferCoefficient",
    "convectiveHeatTransferCoefficient",
    "monthlySoilingLoss"
  ],
  "properties": {
    "isTracker": {
      "type": "boolean",
      "description": "True implies that this mounting type is a tracker\nFalse implies that this mounting type is a fixed tilt rack"
    },
    "numberOfModulesHigh": {
      "type": "integer",
      "description": "How many rows of modules can fit on the rack.",
      "format": "int32"
    },
    "numberOfModulesLong": {
      "type": "integer",
      "description": "How many modules are in each row on the rack.\nRequired for 3D calculations.  Not required for 2D calculations.",
      "format": "int32",
      "nullable": true
    },
    "modulesAreLandscape": {
      "type": "boolean",
      "description": "True if the modules are mounted on the rack in landscape orientation.\nFalse if the modules are mounted in portrait."
    },
    "rackHeight": {
      "type": "number",
      "description": "The total height of the rack, in meters.\nThis is not the vertical height, but the distance, in the plane of the modules, from the rack bottom edge to the top edge\nThis is the total measurement of the shading obstacle that the rack represents, so includes the frame.",
      "format": "double",
      "maximum": 10,
      "minimum": 0
    },
    "ySpacingBetweenModules": {
      "type": "number",
      "description": "The distance from the bottom edge of one module to the bottom edge of a module in the row above, in meters.\nIn portrait orientation, this should be equal to or just slightly greater than the module length.\nIn landscape orientation, this should be equal to or just slightly greater than the module width.\nIf there is just one row in the rack then this parameter is ignored, so can be set to zero.",
      "format": "double",
      "maximum": 5,
      "minimum": 0
    },
    "xSpacingBetweenModules": {
      "type": "number",
      "description": "The distance from the left edge of one module to the left of a neighbouring module in the same row, in meters.\nIn portrait orientation, this should be equal to or just slightly greater than the module width.\nIn landscape orientation, this should be equal to or just slightly greater than the module length.\nRequired for 3D calculations.  Not required for 2D calculations.",
      "format": "double",
      "maximum": 5,
      "minimum": 0,
      "nullable": true
    },
    "frameBottomWidth": {
      "type": "number",
      "description": "The distance from the bottom edge of the rack to the bottom edge of the bottom row of modules on the rack, in meters.\nTypically a small value, or zero.",
      "format": "double",
      "maximum": 0.1,
      "minimum": 0
    },
    "frameTopWidth": {
      "type": "number",
      "description": "The distance from the top edge of the rack to the top edge of the top row of modules on the rack, in meters.\nTypically a small value, or zero.\nRequired for 3D calculations.  Not required for 2D calculations.",
      "format": "double",
      "maximum": 0.1,
      "minimum": 0,
      "nullable": true
    },
    "frameEndWidth": {
      "type": "number",
      "description": "The distance from each end of the rack to the edge of the closest module, in meters.\nThis distance is considered the same for both ends.\nRequired for 3D calculations.  Not required for 2D calculations.\nTypically a small value, or zero.",
      "format": "double",
      "maximum": 0.1,
      "minimum": 0,
      "nullable": true
    },
    "constantHeatTransferCoefficient": {
      "type": "number",
      "description": "Thermal model parameter: the constant heat transfer coefficient, denoted U_c",
      "format": "double"
    },
    "convectiveHeatTransferCoefficient": {
      "type": "number",
      "description": "Thermal model parameter: the convective heat transfer coefficient, denoted U_v",
      "format": "double"
    },
    "monthlySoilingLoss": {
      "type": "array",
      "description": "The irradiance loss ratio due to soiling and snow. One value for each month of the year.\nA value would 0.01 would represent a loss of 1%.",
      "items": {
        "type": "number",
        "format": "double"
      }
    },
    "tilt": {
      "type": "number",
      "description": "The tilt angle in degrees\nRequired if not a tracker",
      "format": "double",
      "maximum": 90,
      "minimum": 0,
      "nullable": true
    },
    "heightOfLowestEdgeFromGround": {
      "type": "number",
      "description": "The height of the lowest edge of the rack to the ground, in meters.\nRequired if not a tracker",
      "format": "double",
      "maximum": 5,
      "minimum": 0,
      "nullable": true
    },
    "heightOfTrackerCenterFromGround": {
      "type": "number",
      "description": "The height of the tracker center from the ground, in meters.\n2D ONLY. For 3D models, this information is inferred from the z coordinate in each Tracker.NorthPoint and Tracker.SouthPoint\nWe assume that the trackers rotate around an axis that goes through\nthe plane of the modules, and this parameter specifies the height of that axis.",
      "format": "double",
      "nullable": true
    },
    "isBackTracking": {
      "type": "boolean",
      "description": "Deprecated. Moved to TrackerSystem\nTracker only\nIf set to true, the tracker system will back-track to avoid row-to-row shading.\nRequired if tracker",
      "nullable": true
    },
    "minRotation": {
      "type": "number",
      "description": "Deprecated. Moved to TrackerSystem\nTracker only\nThe minimum tracker rotation\nUnits: degrees\nRequired if tracker",
      "format": "double",
      "maximum": 0,
      "minimum": -90,
      "nullable": true
    },
    "maxRotation": {
      "type": "number",
      "description": "Deprecated. Moved to TrackerSystem\nTracker only\nThe maximum tracker rotation\nUnits: degrees\nRequired if tracker",
      "format": "double",
      "maximum": 90,
      "minimum": 0,
      "nullable": true
    },
    "transmissionFactor": {
      "type": "number",
      "description": "The transmission factor, or transparency factor.\nPositive value implies a gain. A gain is typical.\nIt is a fraction of 1. i.e. a value of 0.01 implies a 1% gain of back-irradiance\nThis accounts for the effect that some light passes through the racks and reaches the ground\nthereby increasing the ground reflected light that illuminates the back-side of the modules.\nThis is only taken into account for bifacial modules.",
      "format": "double",
      "maximum": 1,
      "minimum": 0,
      "nullable": true
    },
    "bifacialShadeLossFactor": {
      "type": "number",
      "description": "The bifacial shade factor.\nPositive value implies a loss. A loss is typical.\nIt is a fraction of 1. i.e. a value of 0.01 implies a 1% loss of back-irradiance.\nThis accounts for that fact that the rear of modules can be shaded by items such as junction boxes \nand cables.",
      "format": "double",
      "maximum": 1,
      "minimum": 0,
      "nullable": true
    },
    "bifacialMismatchLossFactor": {
      "type": "number",
      "description": "The bifacial mismatch loss factor.\nThis loss factor is applied to the back-irradiance to account for losses due to \nthe back irradiance being uneven across the module, so causing electrical mismatch.\nPositive value implies a loss. A loss is typical.\nIt is a fraction of 1. i.e. a value of 0.01 implies a 1% loss of back-irradiance.",
      "format": "double",
      "maximum": 1,
      "minimum": 0,
      "nullable": true
    }
  }
},
"TrackerSystem": {
  "type": "object",
  "description": "The data required for modeling a tracker system\nThese are the inputs to the tracker algorithm that is controlling\na set of trackers.",
  "additionalProperties": false,
  "required": [
    "systemPlaneAzimuth",
    "systemPlaneTilt",
    "rotationMinDeg",
    "rotationMaxDeg"
  ],
  "properties": {
    "systemPlaneAzimuth": {
      "type": "number",
      "description": "The azimuth of any tilt in the system plane. In degrees from North.\nThe system plane is an imagined plane that in which all the tracker torque tubes sit.\nIf the terrain is flat then it is typically a horizontal plane. In that case the tilt will be \nzero and the azimuth can take any value, it doesn't matter.\nIf the terrain is sloped, then typically the system plane will follow the slope of the underlying terrain.\nIf the terrain is undulating then typically the system plane will be an averaged slope over the array.\nIdeally all the trackers in the tracker system will be placed in the system plane, but when the terrain is undulating\nthis may not be achieved. The 3D model in SolarFarmer allows can model the individual trackers locations in 3D,\nso they can be placed off the system plane. In this case there may be row-to-row shading as the tracker algorithm\nwill not be correctly calculating the back-tracking.",
      "format": "double"
    },
    "systemPlaneTilt": {
      "type": "number",
      "description": "The tilt of the system plane, in degrees.\nFor example if the azimuth is 0 and the tilt is 10 then\nthe system plane will be tilted 10 degrees towards North.\nSee description of SystemPlaneAzimuth for more details.",
      "format": "double"
    },
    "trackerAzimuth": {
      "type": "number",
      "description": "The Azimuth of the trackers, in degrees.\nOptional in the 2D case as the azimuth from the Layout can be used.\nRequired for 3D models.",
      "format": "double",
      "nullable": true
    },
    "eastWestGCR": {
      "type": "number",
      "description": "East-West ground coverage ratio\nOptional in the 2D case as the GCR from the Layout can be used.\nRequired for 3D models.",
      "format": "double",
      "nullable": true
    },
    "rotationMinDeg": {
      "type": "number",
      "description": "Minimum tracker rotation angle in degrees\nThis is defined in the system plane, so \nthe RotationMinDeg and RotationMaxDeg are typically\nof the same magnitude even on an East-West slope.",
      "format": "double",
      "maximum": 0,
      "minimum": -90
    },
    "rotationMaxDeg": {
      "type": "number",
      "description": "Maximum tracker rotation angle in degrees\nThis is defined in the system plane, so \nthe RotationMinDeg and RotationMaxDeg are typically\nof the same magnitude even on an East-West slope.",
      "format": "double",
      "maximum": 90,
      "minimum": 0
    },
    "isBacktracking": {
      "type": "boolean",
      "description": "Is backtracking turned on for the tracker rotation algorithm?\nDefaults to true.",
      "nullable": true
    }
  }
}

The tracker and racking specs used by the desktop are similar, but in XML, I've converted them to JSON, but like I said above, I think the API mountingTypeSpec may be more useful. Zip of all three (desktop trackers, desktop fixed tilt, and api mounting spec's) are attached:
SolarFarmer_Specs.zip

note: MTHAG = minimum height above ground. I think it was supposed to be MHTAG, but I think there's a typo, oh well

[adriesse]

Would we call it the SUI format?? (French for tracker is suiveur.)

[AWABIE]

We might want to also include fixed tilt systems to not have too many file formats floating around.
In that case .MONT might be a good option (from Système de Montage)

[kurt-rhee]

I agree with this.

[cwhanse]

or .MNT for "mount" in English and "montage" in French?

[kurt-rhee]

^ even better

[AWABIE]

I think we have a winner