Power Plant Builder

Build Block by Block


The block number can be defined along with the option to define module energization dates. These dates are only applicable if a construction energy prediction is required. In this scenario, the application will show how much energy will be produced by each block as they are energized. The AC and DC capacity will update automatically once the arrays are fully built behind the block.

Any additional blocks can be added by clicking Add Another (+). If details of a particular block needs to be reviewed or changed, clicking the tree-view displays a list of all blocks associated with the power plant, providing convenient navigation between blocks.

Key Terms

Block A collection of Arrays, usually sharing an energy meter
EditBlock Change preassigned block number from 1-100
ConstructionDates Staggers energization of blocks within a prediction


Add an array by clicking Add an Array (+) which enables the array tab.

The array number can be defined along with the array repeat count to show the quantity of a particular type of array contained in a block. Additionally the medium voltage transformer characteristics are associated with the array.

Any additional arrays, with different attributes, can be added by clicking Add Another (+).

If details of a particular array needs to be reviewed or changed, clicking the tree-view displays a list of all arrays associated with the respective block providing convenient navigation between arrays.

Key Terms

Array A collection of Inverters that share a MV transformer

Change preassigned array number from 1-100

HowMany Allows a single array to be repeated multiple times within a block. Helps to reduce nodal data storage and speed up prediction run time.


Transformer characteristics are added via the array tab and comprised of kVA rating, high side voltage, no-load loss and full-load loss.

There is a checkbox, for convenience, to match the total kVA of the inverters behind the respective transformer. Often, the transformer size is not determined until much later in the project phase so this feature allows a convenient way to pick a nominal size.

Key Terms

MatchTotalInverter Sets transformer rating to the total of the kVA ratings of all of the inverters included in that Array.


The electrical section of the array allows the user to account for AC wiring losses, data acquisition and auxiliary losses and shelter cooling losses.

Key Terms

ACCollection Meant to account for ohmic losses in the AC wiring between the Array and the Block.

Meant to account for parasitic losses due to the data acquisition system. Can also be used for general time-constant parasitic loss accounting.

HowMany Meant to account for HVAC or other cooling losses associated with sheltered inverters. Can also be used for general time-constant parasitic loss accounting.


Add an inverter by clicking Add an Inverter (+) which enables the inverter tab.

Select an inverter from the list view by searching for the desired make and model. Once selected, inverter setpoints and design derate requirements are added via the additional user entry fields. Also note the Temperature Adjusted kVA sizing of the inverter is determined using the cooling design temperature and the elevation and temperature derate curves if applicable, otherwise the 50°C kVA rating is used.

Any additional inverters, with different attributes, can be added by clicking Add Another (+).

If details of a particular inverter need to be reviewed or changed, clicking the tree-view displays a list of all inverters associated with the respective array providing convenient navigation between inverters.

Key Terms

EditInverterChange preassigned Inverter letter from A-Z

DC Field

Add a DC field by clicking Add a DC Field (+) which enables the DC field tab.

A DC field is defined by:

  1. Choosing an available module from the list view.
  2. Providing the electrical characteristics (planned module nameplate, modules in series, etc.)
  3. Defining losses (module quality, mismatch, LIDs and ohmic losses)
  4. Defining mounting structure details (mounting type, azimuth, module orientation, table size, etc.)

Advance settings and/or losses can be viewed by clicking their respective dropdowns. Any additional DC Fields, with different attributes, can be added by clicking Add Another (+).

If details of a particular DC field need to be reviewed or changed, clicking the tree-view displays a list of all DC fields associated with the respective inverter providing convenient navigation between DC fields.


Key Terms

DCEdit Change preassigned DC Field number from 1-100

Used when selected module file wattage is lower or higher than planned installation module wattage. The Planned fields will reflect the installation design counts based on Planned Module Rating rather than using the selected Module File. These fields are informational only and not used in the prediction engine.

Modules in Series The Suggested Range for Modules in Series is derived using the Voc and Vmp rating in the selected Module File and the Plant Design temperatures selected in the Environmental Conditions.
Module Quality Meant to account for deviations in module power from nameplate rating. Also sometimes used to account for DC Field losses not included elsewhere (i.e., DC Health or MPPT).
Mismatch Loss due to combining many modules in parallel and series that have slightly different maximum power points.
LID Light Induced Degradation – used to account for initial degradation in p-type silicon modules.
DC Wiring Accounts for ohmic losses in the DC cables and connectors of the DC Field. Defined at Standard Test Conditions.
Azimuth Solar azimuth angle is measured from north (N=0°, E=90°, S=180°, W=270°). For both Fixed Tilt and Tracker, due south is 180.
Row Spacing Post-to-post separation distance.
Modules High The number of module ranks in a table.
Collector Band Width The overall width of the modules in a table.
Ground Coverage Ratio Ground Coverage Ratio – the ratio of Collector Band Width to Row Spacing.

Object Shading

The object shading section affords users the ability to place near-field objects next to their PV array so that their shading impacts can be properly modeled. Users can create rectangular prisms that can potentially represent a near-field tree/tree line, building, power pole, or any number of other objects (multiple blocks could be used to construct a more complex object, if need be). Adding objects to the DC field can be achieved by either clicking the Add Objects button (located on the Objects tab of the DC Field page) or clicking the Advanced 3D Design button (located in the top right corner of either the Field tab or the Objects tab section of the DC Field page).

Once you launch the Advanced 3D Design tool, a ground object gets automatically added to lie underneath the PV array. The ground object will really only have an impact on shading losses in scenarios with high slope.

The object shading feature can only be utilized in tandem with the 3D shading algorithm (shading algorithms are located under the Field tab of the DC Field page in the Block Builder)

Once saved, the advanced editor can be accessed from any of the following places:

  1. Under the “Field” tab in the DC Field section of the prediction, the “Advanced 3D Design” button can be used to enter the editor

2. In the same section, under the “Objects” tab, the editor can be accessed when there are not yet objects added to the prediction:


Advanced 3D Design Editor

Below is the view when first entering the 3D Advanced Design editor. From this screen, you are able to add objects, adjust views zoom in and out, and enter the shade simulation panel:

In order to add a new object, click the “Add New Object” button in the left panel as shown in the above screen capture.

Adding and Editing Objects

The above will be shown upon clicking “Add New Object”

Key Terms

Object Label refers to the name of the object being created


Dimension running parallel to the DC field


Dimension from the bottom to the top of the object


Dimension running perpendicular to the DC field


Side of field on which the object is located (For northern hemisphere, North is Side 1 and numbers increase clockwise; for southern hemisphere, South is Side 1)


Distance between the object face closest to the field and the center of the PV table/row on the designated origin side.


Distance from the ground to the bottom of the object


Distance, measured parallel to the field, that the object is shifted away from the center of the given origin side of the DC field. (For sides 1 and 3, positive shift moves the object east; For sides 2 and 4, positive shift moves the object south; This is opposite in the southern hemisphere)


Toggles the slope of the object. When set to “ON” the object will match the angle of the slope. When toggled to “OFF” the object will retain it’s default angle


In order to exit the current object to return to the previous screen on the left panel, click the “x” to the right of “Shade Object Details”. This will allow the user to add more objects by clicking the “Add Object” text as shown below

Note that once an object is added, the ground object is also added to the left panel, which can be edited similarly to standard shade objects


Shade Simulation

The “Advanced 3D Design” feature includes the ability to visually simulate the shade of objects created at any given time of year. This can be accessed by selecting the “play” icon on the left panel, as shown below:

Upon clicking “Load Data” PlantPredict will load sun shade data into the advanced viewer

The sliders will allow you to adjust the sun position for any given data to be modeled on the DC Field in the Advanced 3D Design Viewer. Alternatively, the “Run” button will allow the user to observe the shadows cast by objects through the year. Specific dates can be input into the date field (Labelled “Sun Position”)


Build on the Map

Site Boundary

Add a site either by clicking Create Site Boundary in the upper right of the map or by clicking Upload KMZ above and to the left of the map.  Once created, shape the site to match your specifications by clicking and dragging the points on the Site Boundary.  If needed, click and hold to move the site relative to the map.

Following the improvements made to the “Build on the Map” functionality, a boundary can now be drawn rather than simply creating a boundary and resizing it. Clicking the “Draw Site Boundary” icon will allow a drawing tool to be used to create a more fluid shape for more complex site boundaries.

Constraints can be added, both linear and area, in order to better model environmental factors when creating a site prediction. More can be found on adding constraints in the respective section found further in the documentation.

The measuring tool can be used to measure an area without creating a boundary in order to better understand the distances or sizes of objects before placing a plant.

The outer line of the site boundary defines the total Buildable Area.  The inner line defines the setback distance between the boundary and the edge of the outermost DC tables.  The area within the inner line is the Array Area.  The difference between the Buildable Area and the Array Area can be controlled by changing the Setback value.

Key Terms

Upload KMZ file to Map Builder

Download KMZ File From Map Builder

Draw Site Boundary

Create Site Boundary

Create Linear Constraint

Create Area Constraint

Measuring Tool

Delete Selected Features


Inverter and Module Selection

Add an inverter by clicking Add Inverter and selecting an inverter from the list view.  The inverter can be changed by clicking Change Selection and selecting a different inverter.  Note that the DC:AC Ratio may change when the inverter is changed.

Add a module by clicking Add Module and selecting a module from the list view.  The module can be changed by clicking Change Selection and selecting a different module.  Note that differences in module dimension may cause the GCR to change when the module is changed.

Site Parameters

Build on the Map allows you to specify site parameters to see how much MWdc can fit within your boundary.

Note that the Maximum Desired DC value limits MWdc and MWac.  This can prevent the array area from being completely filled with DC tables if the site capacity is significantly greater than the Maximum Desired DC.

The primary building block of the map is the DC table, which is a group of modules mounted and electrically connected together on a single mounting structure. Changing Modules High and Modules Wide under Advanced Options will change the number of modules that fit on a single table and affect the pixel size which governs how densely the tables will fit in irregularly shaped boundaries. For example, the image on the left below is a small table size (12 modules per table) versus  the image on the right which is a large table size (300 modules per table).








The pane on the left will allow you to set the site parameters and can be collapsed for a full screen map view

Key Terms

Target DC or AC power output.


Ground Coverage Ratio – the ratio of Collector Band Width to Row Spacing.

Row Spacing – Distance between rows of DC tables.

Distance between the Site Boundary and the DC tables.


Determines if tables are fixed tilt or tracker.


Permanent angle position if using fixed tilt.


Minimum and maximum angles if using tracker.


Ratio of DC power capacity to AC power capacity.


The number of module ranks in a table.


The number of modules across a table.


Determines horizontal or vertical positioning of modules.


Solar azimuth angle is measured from north (N=0°, E=90°, S=180°, W=270°). For both Fixed Tilt and Tracker, due south is 180.

Map Display

After input of all required information, an “Update DC Capacity” button will appear in the upper-center part of the screen allowing the boundary to be populated with DC tables:

  • 0-15 Acres: Individual DC tables are displayed.
  • 15-50 Acres: Individual DC tables are displayed and 20ft roadways are included between quadrants.
  • 50-1500 Acre: Arrays are displayed with custom edges for irregular shapes but individual tables are not shown.
  • 1500+ Acres: Arrays are displayed without custom edges for irregular shapes.

Results – Key Terms

Estimated AC Output.


Estimated DC output.


Area Enclosed within the site boundary.


Area that can hold DC tables.


Maximum DC output when utilizing full array area.


The percent of the site capacity required to produce the maximum desired DC.


The build on the Map functionality now includes the ability to add layers to your plant.

Selecting and deselecting the checkbox next to the appropriate layer will turn it on or off on the map. The expanded section opened by clicking the plus sign will provide a legend outlining the layer that is displayed:



A new feature to the “Build on the Map” functionality includes the ability to select a parcel layer. A Parcel layer can be selected to provide more information on the area selected:



Constraints provide the ability to better model the DC field by allowing a user to include various objects created by the user. Constraints can be toggled on and off from the “Layers” menu.


Linear constraints can be created by selecting the “Create Linear Constraint” option on the right of the screen. A linear constraint allows the user to draw a straight line on the map


Area constraints are created in the same way as linear, only the user is able to draw the constraint using the polygon drawing tool



In order to better organize the constraints created, the option to name the constraints and change their color can be access by selecting the constraint. The setback for each constraint can also be modified from this view



Wetlands-vectors can be toggled from the “Layers” section with the added functionality of creating a constraint straight from the selected object on the map



This section of the prediction builder is devoted to parameters that affect the entire power plant following the AC collection of all the blocks.

At this point, HV transformers and transmission lines can be applied, if it is required to include their loss contribution.

Finally a system capacity limit can also be applied to ensure the PV plant output never exceeds the interconnection limit.

Key Terms

Plant Output LimitCurtailment limit (LGIA / SGIA) applied to the PV plant output, limiting all hours

Energy Storage System - PVS

Energy Storage System

PlantPredict offers modeling of AC-coupled storage systems; DC-coupled systems are currently not supported in PlantPredict. The section below describes the inputs and basic functionality of modeling these systems in PlantPredict. In many cases, the modeling requires calculating energy at a number of “nodes” within the storage system and so the diagram below may be a helpful reference when thinking about these systems and when referencing system nodal data.

Figure 1. Nodal reference diagram for PV+ Storage system


To add an energy storage system to your power plant, click the Add button corresponding to the Energy Storage System section under Power Plant Specifications. The system can be later deleted by clicking the Delete link, or updated by clicking the Update button.

An Energy Storage System is defined on the Energy Capacity tab by:

  1. Defining two of the three parameters:

a) Energy Capacity Nameplate

b) Energy Capacity Factor

c) Energy Capacity Usable

2. Providing degradation rates (calendar and cycling-dependent) of energy capacity and DC Roundtrip Efficiency

3. Providing efficiencies (DC Roundtrip Efficiency and Inverter) and losses (MV Transformer and HVAC)

4. Defining power ratings (Inverter Real Power and MV Transformer Power Rating)


An Energy Storage System Dispatch algorithm is defined on the Dispatch Algorithm tab by:

  1. Choosing an available Dispatch Algorithm, either predefined or the Custom option.

a. If the Custom option is selected:

i. the template Custom dispatch file can be downloaded

ii. charging and discharging times must be identified

iii. the fraction of inverter rated capacity (at the input to the MV transformer) desired to be charged or discharged (dispatch will be limited to the available capacity of the system) must be defined, for each index corresponding to the time steps in the prediction weather file

iv. the Custom dispatch file must be uploaded

v. skip Step 2

  1. Identifying the desired dispatch hours in the Target Period table. The selected hours will direct the algorithm to target output at the interconnect capacity during those hours.

The ESS is always assumed to be at a full State of Charge during the first time interval of the prediction.

The system input values should be carefully considered, as they are dependent on the storage technology being modeled.


Key Terms

 The total storage nameplate DC energy capacity.

The percent of the nameplate DC energy capacity that is usable energy capacity.


The initial total storage usable DC energy capacity. This is the energy capacity within the usable State of Charge window.


The percent of the initial usable DC energy capacity by which  the usable DC energy capacity decreases over time, linearly.


The percent of the initial usable DC energy capacity that the usable DC energy capacity decreases as a function of cumulative storage cycles.


Initial ratio of stored energy to input energy for the storage system.


The percent of the initial DC Roundtrip Efficiency by which  the DC Roundtrip Efficiency decreases over time, linearly.


The percent of the initial DC Roundtrip Efficiency by which  the DC Roundtrip Efficiency decreases as a function of cumulative storage cycles.


The total active power capacity setpoint of the storage inverters.


Ratio of output power to input power of the storage inverters.


The total kVA rating of the storage MV transformers. Often assumed to be the same as the Inverter Real Power rating, for simplicity.


The energy consumption of storage MV transformer equipment as a percent of MV transformer rating, defined for the no-load operation of the transformers.


The energy consumption of storage MV transformer equipment as a percent of MV transformer rating, defined for the full load operation of the transformers.


The energy consumption due to HVAC per MWh of storage nameplate DC energy capacity.


The energy consumption due to HVAC per MW of DC power input or output at the ESS.


The Interconnect Excess charging algorithm charges all energy generated by the PV that exceeds the Power Output Limit (set under the System menu item), except during target period hours.


The Energy Available charging algorithm charges all energy generated by the PV system until the storage is at full usable State of Charge.


The Custom dispatch algorithm allows the user to define a charge and discharge target profile. The dispatch will be limited to the available capacity of the system. The file must contain indexes that correspond to the number of time steps in the prediction weather file.


File format for the Custom dispatch:

  • First row contains column headers. Each following row contains the consecutive value.
  • Column A header: Index

– Incremental index corresponding to each timestep in the weather file, beginning with 1.

  • Column B header: Command

– Field can be blank, Discharge, or Charge, as desired.

  • Column C header: Inverter Capacity Fraction
    • The proportion of total ESS inverter capacity to be transferred to or from the storage, at the Low Voltage AC (node 3) point on the Energy Storage System, in standard number format.


Note that a command to discharge energy that results in the total discharged and PV generated power exceeding the interconnection capacity is followed but causes the excess energy to be clipped.


Upload the file containing the Custom dispatch algorithm.

Boxes checked in the Dispatch Table are target period hours, and those that are not checked are not. The storage system will discharge only during checked hours. It will discharge at the maximum amount up to the stored energy, the power allowed by the inverter power capacity, and the power allowed to meet the interconnect capacity that exceeds the PV capacity.

Bifacial Modules

*There is a general shortage of utility-scale field validation of bifacial prediction models in industry and this model is no different. Unlike the core monofacial PlantPredict models, this new bifacial performance model has not been validated and benchmarked at scale against measured data.

Module File

The module tiles will now display facility of the module


Within the module file, the user can define 1) Faciality, and if the module is bifacial, 2) Bifaciality Factor and 3) Transmission Factor

The “backside mismatch” loss can be defined in the Modeling Defaults section of the module file


Company Defaults

The “Bifacial Structure Shading” loss can be defined in the company defaults.


Power Plant Builder

Choosing a bifacial module…

Bifacial losses in the DC field. Note these are not present if a mono-facial module is present.



Bifacial loss factors in the results section.

Indication of bifacial module.

Bifacial module losses in block section of results.


Comparing Predictions

Bifacial loss factors using the “Compare Predictions” function