can solar tracking algorithms alone provide the …...6 pv magazine webinar 14.5gw gpm, a dnv gl...

PV MAGAZINE WEBINAR1

CONFIDENTIAL UNDER ARRAY TECHNOLOGIES MNDA1

Can so lar t rack ing

a lgor i thms a lone

prov ide the so lut ion to

min imize energy losses

on d i f f icu l t ter ra in?Presented by:

Array Technologies & DNV GL


900+ Utility-Scale

Projects Worldwide

17+ GW Awarded

or Installed Globally

Installations in

25+ Countries

30 YEARS OF EXPERIENCE

30 GW YEARS OF OPERATION

OUR EXPERIENCE YOUR ADVANTAGE

1992 2004 2011 2013 2017 2019Ron Corio

purchases the

Wattsun

Corporation and

forms Array

Technologies, Inc.

Array Technologies begins

shipping trackers to utility-

scale projects across

Europe and Asia, including

a 5.7 MW site in South

Korea.

DuraTrack® HZ’s terrain

flexibility wins over fixed-

tilt for 20 MW site located

in Arizona, avoiding

grading and maximizing

land occupancy.

Array Technologies

ships DuraTrack® HZ

tracker to a 265 MW

in California, the

largest tracked thin

film project in the

world, at the time.

Array expands

globally and opens

offices in Europe,

Central and South

America, and

Australia.

Array celebrates 30

years of solar

innovation

1989 1996 2006 2012 2015 2018

Helium Balloon Tracker

built for Steve Fossett’s

first Around the World

attempt.

360 degree tracker

purchased by the

Canadian Government for

use in the Arctic Circle.

DuraTrack® HZ

installed in largest

utility-scale solar

project in the US, a 6

MW site located in

Alamosa, CO.

1 GW Shipment

Milestone

surpassed.

DuraTrack® HZ v3 is

launched and ships to its first

utility-scale site, Tranquility

256 MW.

Array introduces

SmarTrack™ optimization

software to boost power

production.

Ron Corio develops

first solar tracker for

the Wattsun

concentrator

module.


900+ Utility-Scale Projects in over 25 countries

30 GW Years of Operation

We have become obsessed with even the smallest detail in solar tracking, ensuring our customers get maximum

results from their investment. That includes achieving nearly 100 percent uptime and the lowest cost of energy

and maintenance in the industry.

ENGINEERED SIMPLICITY

99.996%

UPTIME

7%

LOWER LCOE

31%

LOWER LIFETIME O&M


Developing PV on Difficult Terrain

A significant portion

of project

development is

happening in the

southeastern United

States where the

topology tends to be

hilly or undulating


Broad and deep expertise in solar projects

FEASIBILITY ENGINEERING & DEVELOPMENT CONSTRUCTION & COMMISSIONING OPERATION

❯ Feasibility studies

❯ Utility grid integration

❯ Environmental permitting

❯ Component technology reviews

❯ Component qualification testing

❯ Type and component certification of PV

inverters

❯ Due diligence / Independent engineering

❯ Owner’s engineering

❯ Energy assessment

❯ Pre-construction engineering

❯ Interconnection support

❯ Project certification

❯ Due diligence/ Independent engineering

❯ Owner's engineering

❯ Construction oversight

❯ System testing and inspection

❯ Project certification and grid code compliance

❯ Declaration of conformity

❯ Module batch testing


❯ Performance validation

❯ Resource and energy forecasting

❯ Existing asset consulting, inspections and decommissioning

❯ Refinancing and mergers and acquisitions advisory services

❯ Forensic investigations

❯ Monitoring, control and asset management


*Our testing, certification and advisory services are independent from each other


14.5GWGPM, a DNV GL company, manages 14.5GW

of solar PV plants, which includes 25 mega-

plants of over 100MW each

6000+We have supported over 6,000 solarprojects worldwide from residential to utility

scale

2016DNV GL acquires GreenPowerMonitor (GPM),

a global solar monitoring company, founded

in 2006 in Barcelona, Spain

*Our testing, certification and advisory services are independent from each other

>20We have more than 20 years’ experience in

the solar industry helping investors, project

developers, system owners, utilities and

equipment manufacturers

PV MAGAZINE WEBINAR7 7

What energy/shading losses

are associated with sloped

and hilly terrain?

• North/South slopes

• East/West row-to-row shading

• Undulating, non-uniform

• Uniform, mono-sloping planes

• Backtracking

• It, too, is a loss mechanism of sorts, but

losses will usually be worse without

backtracking


How does uneven terrain affect tracking PV?

Slopes in the N-S direction have

about the same impact as with

fixed-tilt arrays.

Annual energy gains or losses of

0% to ±2% are typical.

NS


Analyzing W-E slopes

Slopes in the W-E direction can cause significant shading

losses, say, 0% to 5%, and the modeling is not easy.


DNV GL’s

method to

characterize

energy loss on

sloped terrain

• Characterize W-E slope undulations on a % root means square (RMS) basis

• Establish a link between shading loss and row spacing

• Establish a link between shading loss and diffuse fraction


Sample tracking PV system on rolling terrain


Measuring slopes: Use a microscope or fish-eye?

75%

slope?


Microscope, fish-eye, satellite? 75% or 0%?

5 m


Back to the basics: Undulating terrain geometry

1. 2. 3. 4.

5.


Typical methods for minimizing

shading on any kind of terrain,

sloping or flat

• GCR, where low densities are less

vulnerable to shading

• Backtracking, where beneficial


Ground cover ratio (GCR)

Row spacing/GCR – Shading from undulations is like the

shading near sunrise/sunset from adjacent rows on flat land.

GCR % daytime hours

backtracked

Apparent “slope” to next row on a mid-spring or summer morning or

afternoon (4/15 7:20 a.m.)

30% 21% 29% (16°)

40% 29% 42% (22°)

50% 39% 57% (30°)


Backtracking reduces shade losses

Near sunrise, a tracker at its range limit of

52° would be heavily shaded, so it needs to

backtrack a lot, to a tilt of just 9°, to avoid

shadows. ↓

Backtracking = no shadows

No backtracking = shadows


DNV GL’s recommended strategies to minimize

energy losses on sloping terrain

1. Shade-tolerant half-cut modules

2. Spot grading

3. Pile height reveals

4. A.M./P.M. custom backtracking slope settings

5. Custom power tuning software


Half-cut modules, a fall afternoon in Wichita


Grading + pile height reveals = less shading

0

5

10

15

20

25

0 100 200 300 400 500 600 700 800 900 1000

Ve

rtic

al h

eig

ht,

m

Horizontal distance from western end of array, m

Terrain height, m vs. horizontal ground distance, m, for original 10% RMS slope and post-graded 5% RMS slope


Side view of grading and post height reveals

10

12

14

16

18

20

22

24

375 380 385 390 395 400 405 410 415 420 425

Ve

rtic

al h

eig

ht

of

arra

y, m

West to East horizontal distance, m

IRREGULAR TERRAIN SOLUTIONSRaw black line slope is 10% RMS, with black posts hovering 1.5 m

above. After 1% grading, green slope is just 5% RMS.

After varying post heights to their limits, red slope is 4% RMS.

Raw Smoothed Posts ModPostHeights

0

5

10

15

20

25

0 100 200 300 400 500 600 700 800 900 1000

Ve

rtic

al h

eig

ht,

m

Horizontal distance from western end of array, m

Terrain height, m vs. horizontal ground distance, m, for original 10% RMS slope and post-graded 5% RMS slope

The combination of spot

grading and utilizing pile reveal

heights created tracking

monoplanes to effectively

eliminate inter-row shading.


Custom backtracking slope settings

A.M./P.M. custom backtracking slope settings – on uniform, mono-sloping planes, tracker controllers can be programmed to tighten backtracking in the morning and loosen it in the afternoon, or vice versa, depending on the direction. Shading is eliminated, and the remaining incidence angle losses are minor compared to flat ground performance.

1-axis tracker, morning view to north

blue are actual trackers, brown is the ghost equivalent of an imaginary row on level ground

The principle here is to find the spacing on level

ground for which the same critical shade R = row width

angle, alpha, is seen.

alpha,critical = shade angle, deg.

S = true row spacing

GS = ground slope, degrees

S' = apparent row spacing on level ground

USER'S INPUTS RESULTS

2 R, m GCR = R/S 0.400 base case GCR based on user inputs for R and S

5 S, m GCR' = R/S' 0.491 -0.9 m, reduced spacing

52 T, deg. GCR" = R/S" 0.298 1.7 m, increased spacing

10 GS, %

1-axis tracker, afternoon view to north

blue are actual trackers, brown is the ghost equivalent of the lower tracker on level ground

The principle here is to find the spacing on level

ground for which the same critical shade

angle, alpha, is seen.

S"=apparent spacing, lvl gnd

S=true spacing on sloped gnd


Shading energy loss table(typical ≈2% diffuse shading loss not included.)

↓W-E Slope 40% GCR

Diffuse Frac. →0.3

AZ,NV

0.4

TX,GA

0.5

NY,WI

2% 1% 0.5% 0.5%

5% 2% 1.5% 1.5%

10% 4% 3.5% 3%

15% 6% 5% 4%

20% 7.5% 7% 5%

25% 10% 8.5% 7%


DNV GL’s recommended strategies to minimize

energy losses on sloping terrain

1. Shade-tolerant half-cut modules

2. Spot grading

3. Pile height reveals

4. A.M./P.M. custom backtracking slope settings

5. Custom tracking software


Maximizing energy harvest on challenging terrain

Executing a game plan for

attacking energy losses

and maximizing energy on

hilly and sloped terrain.


Proven keys to success

• A well-designed and properly constructed site pays dividends in energy yield.

• There is no single solution or quick fix. Diligence is required at each phase of design

and construction.

• Several approaches are available to maximize energy yield. Designers should utilize

them all.

• Understand that the effectiveness of tracking optimizations decreases as site terrain

slopes increase.

• You cannot backtrack your way out of a hole. Don’t put your solar panel in one.


Strategic attack plan to maximize energy yield on

challenging terrain

Plan Overview:

1. Choose a module architecture with shading response suitable for the final site design.

2. Take advantage of existing terrain sloping toward the equator.

3. Execute spot grading and pile reveal heights to create tracking monoplanes, regardless of tracker architecture.

4. Choose quality modules, inverters, trackers, and other BOS with best in class proven uptime, demonstrated reliability, and lowest operations and maintenance.

5. Employ tracking optimizations, manual or automated.


Consider the PV module choice

1. If the site design has some rows with possible shading loss effects, consider the module technology choice.

2. Choose a module type with shading response suitable for the physical characteristics of the intended final site construction.

• 72 cell crystalline or polycrystalline modules

• 144 half-cell crystalline or polycrystalline modules

• Thin-film linear shading response modules


Utilize the maximum tilt toward the equator allowed by the tracker and EPC capabilities

• 0 degree tilt = 0% slope

• 8 degree tilt 14% slope

• 15 degree tilt 27% slope

✓ An 8-degree tilt can add ~2-4% more energy

✓ A 15-degree tilt can add ~ 4-6% more energy

Utilize terrain sloped toward the equator

15°/27%

8°/14%


Utilize spot grading to create tracking mono-planes

1% Site grading

can produce a

2% improvement

in energy yield

Before spot grading

After spot grading

Modules now create a mono-plane


Utilize pile reveal heights to create tracking

mono-planes

Pile reveal height refers to the amount of pile above grade.

Utilizing a few pile reveal heights in the east–west and/or

north-south direction will minimize row to row shading losses.


Example: Spot grading and pile reveal heights creating

tracking mono-planes


Test Case

• Eastern, USA

• RMS slopes greater than +/- 20% in locations

• Flat ground less than 15% of site

• Ground cover ratio predetermined at high 30% range

• Diffuse light fraction low 40% range

Site details


Modeling results at each step

No. Use Case Details

Tracking /

Backtracking Settings

Loss

From

Baseline

Effect

of

Change

BaselineTracker on flat ground

72 Cell PV ModulesStandard tracking

1Actual Site

TerrainTracker installed on existing terrain Standard tracking

2 Half-cell Modules Tracker installed on existing terrain Standard tracking

3Grading and Pile

Reveal HeightsTrackers as monoplanes Standard tracking

4Backtracking

Optimized

E-W Slope Adjustments

Backtracking Algorithm Software

Manually or automatically

optimized backtracking

0.0% 0.0%

5.7% - 5.7%

4.3% + 1.4%

2.1% + 2.2%

1.6% +0.5%


Summary

Plan of Attack to maximize energy on sites with hilly and sloped terrain:

1. Spot grading and pile reveal heights to create tracking mono-planes can have the largest impact

2. Choice of PV module architecture can dramatically reduce row to row shading losses

3. Taking advantage of existing terrain sloping toward the equator can increase energy yield and decrease grading needs

4. Utilizing proven and reliable components will increase uptime

5. Tracking optimization software should be the last consideration


CONFIDENTIAL UNDER ARRAY TECHNOLOGIES MNDA36

Can solar tracking

algorithms alone provide the

solution to minimize energy

losses on difficult terrain?

can solar tracking algorithms alone provide the …...6 pv magazine webinar 14.5gw gpm, a dnv gl...

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