Design Guide

PVB_DG_070618 pvbooster.com

Rooftop Tracker

Find DC Power Rating .......................................................................4

Find System PV Booster Yield .......................................................5

Find System Fixed Tilt Yield ............................................................6

PV Boost Percentage.........................................................................7

Steps

2 PVBooster Design GuideRooftop Tracker

Purpose of this DocumentPV Booster is the only rooftop tracker on the market, and for the first time brings the known

benefits of tracking to rooftop solar projects. This document guides you through steps to design

your PV Booster solar project using best practices. This includes generating rooftop layouts

and system outputs using standard industry tools, which provide you transparency when

proposing new projects to your clients.

The methodology used in this guide, models the yield (kWh/kWp) improvement percentage

provided from tracking compared to a fixed tilt system. Although modeling results may vary

from tool to tool, the incremental benefits among different PV systems designed within each tool

are proportional and consistent. This yield improvement over ordinary fixed racking is expressed

in percent – the PV Boost Percentage. NREL and PV Watts have been collecting this data for

decades and the benefits are well understood. To estimate the output of your PV Booster array

with confidence, users only need apply the PV Boost Percentage to the fixed tilt yield. The

following steps illustrate the steps to calculate PV Boost Percentage.

Begin your preliminary design as normal with the modification steps in this guide. See array planning and design assumptions on the following page.

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Module size

Roof coverage ratio

Panel to panelspacing

Row-to-row spacing

60 cell

.36

1.62ft

3.72ft

72 cell

.36

1.14ft

4.36ft

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Array Planning and Design AssumptionsBest Practice Recommendations and Guidelines

1 Specified GCR is recommended by Edisun, and was established by Edisun to optimize module density, kWh output, and installation ease and effectiveness.

PVBooster Design Guide

Homerun

• Tracker center support posts must attach to building roof joists.

• Trackers are installed/wired in series, strings of up to 36 units per string.

• Edisun recommends that PV and tracker string lengths (units per string) should match to share cable routing and conduit.

• Unlike the PV configuration, tracker strings are controlled at only one end of the string. As such, tracker control cable does not require home runs.

• Edisun recommends designing PV strings in U-shapes to minimize home runs, per the figure below.

Edisun recommends power optimizers and other premium products to reduce system losses

There is often a variety of preferences amongst system designers. Reduce shading, mismatch, and wiring losses by using high efficient products such as optimizers and PERC modules.

Row Spacing & Roof Coverage Ratios1

PV Watts Calculator

Soiling (%)

Shading (%)

Snow (%)

Mismatch (%)

Wiring (%)

Connections (%)

Light-inducedDegradation (%)

Nameplate Rating (%)

Age (%)

Availability (%)

Default Assumptions

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3

0

2

2

0.5

1.5

1

0

3

PV Booster Recommended Assumptions

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1

0

0

1

0.5

1.5

1

0

3

Rooftop Tracker

Find DC Power RatingHelioScope Field Segment Parameters

Azimuthshould be adjusted so modules are square with the building sections. The azimuth axis varies throughout the day and is programed to face due south no matter how the frame sits. This will maximize usable space.

Row Spacing should be 4.36’ to ensure no row-to-row shading, maximizing energy Boost.

Module Spacing should be 1.14’ which ensures the modules do not come in contact with each other as they track.

Frame Spacing should be 0’ which ensures the units do not come in contact with each other as they track.

Draw the field segment for the building as normal. The following field segment inputs will be used for PV Booster when designing projects on HelioScope.

Number of Modules2,635

DC Power Rating*1,054.0 kWp

Area159,915.2 ft2

GCR 0.39

DC Power Rating PV Booster Yield Fixed Tilt Yield PV Booster Yield Increase

INPUT OUTPUT

4 PVBooster Design Guide

Complete remaining sections as normal.

Note:

*You will need the DC Power Rating (kWp) as an input for PV Booster Yield Increase(step 4)

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Rooftop Tracker

Choose Solar Resource Data weather station as nornal and click “Go to system info.” The following system info input will be used to find PV Booster Yield Increase.

PV Booster Yield IncreaseDC Power Rating PV Booster Yield Fixed Tilt Yield

5 PVBooster Design Guide

Take the AC Energy (kWh) Annual total as shown above. This is your PV Booster Yield and will be used as an input for PV Booster Yield increase (step 4).

Note:If using Energy Toolbase, on section 4 click “+ Add PV” and choose PV Watts API Version 5. Pick preferred TMY Station. Follow instructions for PV Watts as described above.

Set DC Power Rating to 1 kWdc

Array Type should be “1-Axis Backtracking”

Set Tilt to match project site’s latitude 5-45°

Set Azimuth to 180°

Remaining Parameters should be the same as fixed-tilt parameters for comparison

Once Inputs are correct, click “Go to PVWatts results”

2 Find System PV Booster Yield PV Watts System Info Inputs

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Rooftop Tracker

PV Booster Yield Increase

Find System Fixed Tilt Yield PV Watts System Info Inputs

DC Power Rating PV Booster Yield Fixed Tilt Yield

6 PVBooster Design Guide

Take the AC Energy (kWh) Annual total as shown above. This is your Fixed Tilt Yield and will be used as an input for PV Booster Yield increase (step 4).

Note:If using Energy Toolbase, on section 4 click “+ Add PV” and choose PV Watts API Version 5. Pick preferred TMY Station. Follow instructions for PV Watts as described above.

Choose Solar Resource Data weather station as nornal and click “Go to system info.” The following system info input will be used to find PV Booster Yield Increase.

Set DC Power Rating to 1 kWdc

Array Type should be “Fixed (roof mount)”

Set Azimuth to 180°

Remaining Parameters should be the same as previous parameters for comparison

Once inputs are correct, click“Go to PVWatts results”

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Rooftop Tracker

DC Power Rating (kWp)From your helioScope layout

PV Booster Yield (kWh/kWp)From PV Watts output tool

Fixed Tilt Yield (kWh/kWp) From PVWatts output tool

PV Booster Yield IncreaseCalculation for PV Boost Percentage

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If using a production modelling tool other than PV Watts (PV Syst, PV Sol, etc.), take total AC energy delivered to the grid (kWh) and multiply it by PV Booster Yield Increase.

PV Booster Yield Increase (%)Divide PV Booster Yield by Fixed Tilt Yield

Use these values: To calculate:

DC Power Rating

1,054

PV Booster Yield

2,204

PV Booster Annual Output

2,323,016

Include your helioscope layout, DC Power Rating PV Booster Yield and PV Booster annual output for a compelling project proposal to your client.

kWp

kWh/kWp

kWh

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Rooftop Tracker7 PVBooster Design Guide

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PV Booster Yield IncreaseDC Power Rating PV Booster Yield Fixed Tilt Yield