Predictions

Prediction Overview

This dashboard view of a prediction serves two purposes. It guides the user through creating a prediction by sectioning off core areas so the user can dive in and out of different aspects of the prediction. It also pulls out summary data from each main section to help the user understand what has been completed in each area of the prediction.

Environmental Conditions

This section of the prediction is focused on environmental data that will be used in conjunction with the energy prediction.

On the Weather tab, a weather file can be selected, compared, or downloaded.

 

Power Plant Builder

To enter power plant specific parameters, click the Start button for the corresponding attribute (Blocks & Arrays or System).

 

The Blocks & Arrays attribute section is designed to work dynamically, providing the means to quickly scale up or down a particular block type with any combination of subsystem components (e.g. mounting orientation, module type, inverter type, etc.). There are two ways to build out your Blocks & Arrays:

  1. The “Build on the Map” option defines a system using input for site boundary, inverter, module, and site parameters (e.g. MWdc, row spacing, tracker or fixed tilt, module orientation, etc.). This is the best option for users who don’t already have a site layout and want to estimate about how much PV will fit on a specific plot of land.
  2. The “Build Block by Block” option defines a system in a more traditional manner, by defining what equipment is on site, starting with a block and defining components all the way to the DC field. An exploded view is available by clicking the icon to the left of the block tab. This option is typically most useful to users who have a layoutor a basic idea of the electrical system they’d like to build.

Users can start in the Build on the Map feature and then move into the Block Builder but it is not currently possible to switch from Block Builder into the Build on the Map feature. This functionality is a planned future improvement.

HELP VIDEO Power Plant Builder

Simulation Settings

The Simulation Settings menu is where a user can define which models and algorithms they’d like to use in their energy prediction.

 

HELP VIDEO Simulation Settings

Environmental Conditions

Weather File Selection

The user can select a weather file for use in the prediction by clicking the title of the file. Once the user selects a file, the associated map icon will show where the weather is located, relative to the project location.

Typically, the closer the weather file is to the site location, the more representative the dataset will be to actual site conditions. A summary of each file can also be viewed along with a more detailed comparison of up to six files.

If there are no files present or the desired file is not found, the user can download or import a file by using the Add Additional Weather File feature.

HELP VIDEO Weather Selection

Key Terms

Compare Allows user to compare up to six weather files.

Weather File Upload Guide

The selection of a weather file is one of the first steps in running a prediction. PlantPredict can handle weather files of almost any granularity, from 60 minutes down to single minute granularity. PlantPredict can also handle many different weather file formats:

  • Meteonorm
  • SolarGIS
  • 3Tier/Vaisala
  • AWS
  • Clean Power Research
  • NSRDB
  • Solar Prospector
  • NREL TMY3
  • EPW

In addition to the file formats above, any reasonable excel workbook or CSV file can be uploaded and formatted during the upload process.

 

Step-by-step Process

The user can start uploading their own weather file either from 1) the weather component library, or 2) from within a prediction. In either case, the use will be taken to the following screen:

 

From here, the following steps describe how to upload the desired weather file:

  1. Click on “upload your own weather file” and select the desired file

  2. Define Locality

3. Set Parameters– These values are not required. However, it is highly encouraged to fill in these values for informational purposes

 

4. Format Data – The “meat and potatoes” of the weather file upload. Some items to note:

a) The table on the right shows all the data from the uploaded file. This step aims to trim out unwanted information not needed for the final PlantPredict weather file

b) The section on the left with “Variables” and “Timestamp” tabs contains 1) all potential variables that can be included in a PlantPredict weather file, and 2) inputs required to define the timestamps associated with the data

i) Using the “Variables” tab in the column on the left, the user first selects which variables are to be included in the PlantPredict weather file by using the check boxes. After the checkbox is selected, the user then selects in which column that variable exists in the imported file by using the drop down menu.

ii) “Header Rows to Skip” indicates how many header rows in included in the excel file. These are not to be included in the final PlantPredict weather file and are thus to be skipped

 

iii) Timestamps are not currently able to be read from columns in an imported file. Instead, when defining the parameters on the “Timestamp” tab, the user indicates 1) the Start Date and 2) the Interval Duration. The application then automatically extrapolates the end date of the file. Additionally, the user can toggle on whether to include a leap day(s) in the timestamp definition or not.

c) As a note – the minimum required data series for a PlantPredict weather file is irradience (GHI or POAI) and Temperature.

 5) Quality Check – Here the user can review all the data uploaded before the PlantPredict whether file is created. Users can also visualize how the weather data compares to the clear sky model which is especially useful for detecting timeshifts in the data. A handy data shifting feature is available for cases where a timeshift does exist to avoid having to start the process over.

 

FAQ’s, Tips and Tricks, and Troubleshooting

  • Imported files may contain neither blanks nor NULLS. If the weather file contains blanks or NULLS, fill in “0” for that entry prior to importing (the excel function “=COUNTBLANK()” can be very useful here)
  • It’s extremely easy for measured excel files to unintentionally have duplicate or missing data entries. These situations are especially tricky because an error won’t be thrown upon upload. A good way to identify this problem is to compare the projected End Date in the “Format Data” step of the upload process to the final timestamp in the excel file. If they do not match, that means there are either missing entries or extra entries in the original excel file, and the user should investigate further
  • If variables that affect spectral correction (relative humidity, dewpoint temperature, precipitable water) are not included, then spectral calculations will not be included in  predictions where this weather file is used
  • If the upload is erroring out on the first step, the application is having an issue parsing the file. Check to make sure all headers are correct and contain the correct type of information. Additionally, simplifying the imported file can many times allow for the upload to continue – one easy way of simplifying is to remove all or all-but-one header rows

Monthly Parameters

Clicking the Parameters tab will display a screen depicting monthly albedo & soiling factors, plant design temperature characteristics and horizon scene (if applicable).

All fields are editable to accommodate user defined prediction specifics such as a monthly soiling profile. An annual value is also permissible and can be entered by selecting Annual Override. The spectral profile is an override field; if no spectral input data is included with the weather file or if an alternate spectral profile is desired, the user may override with monthly loss factors.

To override, click the Spectral Override button and enter the desired monthly or annual spectral adjustment(s).

HELP VIDEO Parameters Selection

Key Terms

Spectral If no spectral input data is included with the weather file or if an alternate spectral profile is desired, enter monthly values to be used in the prediction.

Annual Locks monthly inputs and sets all monthly values to the value entered.

Plant Design Temperature

By default, the nearest ASHRAE station is used to provide default design temperatures for the site. The site design temperatures are used to recommend proper series string counts on the DC Field and to size the KVA of the inverter if an elevation and temperature derate profile is applicable.

These temperatures can be overridden to accommodate custom design temperatures.

Key Terms

Override Removes reference to default ASHRAE station temperatures and allows user defined design temperatures.

Horizon Scene

A horizon scene can be added to account for any far shading effects on the system. Clicking the Add (+) button will display an empty field for azimuth and elevation angle of the horizon point.

Repeat this process until the desired number of horizon points are added.

Power Plant Builder

Build Block by Block

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

Array

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
EditArray

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

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.

Electrical

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.
EditArray

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.

Inverter

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.

HELP VIDEO DC Field

Key Terms

DCEdit Change preassigned DC Field number from 1-100
ModuleRating

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.

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.

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 the map.
Draw 1000ft×1000ft site boundary on map.

Zoom in.

Zoom out.

Delete selected site.

Download site as a KMZ file.

 

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).

 

 

 

 

 

 

 

 

Key Terms

Target DC power output.

 

Ground Coverage Ratio – the ratio of Collector Band Width to 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 changing any value, clicking the Refresh Display button will update the map view of the site and the prediction values in the bar above the map.  The detail of the site in the map changes with the total array area as follows:

  • 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.

System

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.

 

Results

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

 

Simulation Settings

The final section before running the prediction defines the Model Choices for use in the prediction. Here, a timeframe that matches the chosen weather file can be selected if the user decides to run the prediction for a shorter timeframe than the default.

The Uncertainty Analysis menu and Advanced Model choices are viewable by clicking their respective dropdowns. Up to 4 alternative P-value results can be included in the uncertainty analysis of the prediction.

HELP VIDEO Simulation Settings

Uncertainty Analysis

The error analysis menu allows for the selection of multiple P-values or entry of a custom P-value to be displayed. A single custom uncertainty setting can be entered if you desire to override the application defaults.

Advanced Model Choices

The advanced model choice menu allows for selection of additional models such as direct -shading and diffuse shading models. Available options are depicted in their respective drop downs. There are also additional toggles to disable spectral and soiling.

Batch Predictions

Building a Batch of prediction variations – or just a “Batch” prediction – allows the user to run up to 350 predictions with a single click of the button by defining basic prediction inputs and varying up to two variables. This is extremely useful because it displays graphically the exact combination of parameters that gives a prediction the highest energy yield.

 

How To Create a Batch Prediction

  1. After creating a project, click “New Prediction”
  2. Choose the option for a “Batch prediction”

 

3. This brings up the Batch Prediction parameter page. On the left half of the screen, the user can fill in weather, module, and inverter data. Additionally, parameters such as max capacity, tilt angle, and azimuth can be populated.

On the right half of the screen, four variables are listed. These are the variables that can be chosen to be iterated from a start value to a finish value by a user-defined step. For example, Azimuth can be defined as moving from 100 degrees to 200 degrees in steps of 10 degrees. Currently, you can only choose up to two variables to vary.

 

4. After all parameters are defined, click “Run Prediction” in the top right. PlantPredict will then start to run a prediction for each iteration defined in the Batch prediction. The calculation can take a few minutes because of the large number or predictions being run.

 

5. The result of a Batch Prediction is twofold – first, a graphical heat map of predictions, where the z-axis consists of energy produced, and the x- and y-axis consist of the chosen variables to iterate. Second, the full list of predictions run in the Batch Prediction along the right side of the results screen. By default, these are sorted in descending order based on energy produced, so the highest-yield prediction is listed first. To create a single block builder prediction with any of the predictions along the right side of the results page, simply click “clone” next to the desired prediction.

 

6. Finally, the results of a Batch Prediction can be exported but clicking the “Export” button in the top right. Keep in mind that the exported results will include all child predictions from within a Batch Prediction.