Potential of Single Axis Trackers Feb 7 2016

P O T E N T I A L O F
SINGLE AXIS HORIZONTAL
S O L A R T R A C K E R S
IN UTILITY-SCALE PROJECTS
Photo: Optimum Tracker, Garein 12MW

Contents
Acknowledgements 1
List of Figures 1
Abstract 1
About the Authors 2
Methodology 3
Disclaimer 3
Assessing Trackers: Why The Solar Industry’s General Context Matters 4
Solar Energy Production Trends 4
Policies for Solar Power Production Drive Solar Tracker Usage 5
Importance of the Investment Tax Credit in Calculating Solar Trackers Benefits 6
Importance of the Time Of Day Charges for Solar Trackers 7
For Trackers Assessment, All States Are Not Equal 7
Benefits of Tracker Technology Within the Solar Industry’s General Context Drive Usage Growth 8
Comparing Trackers 9
The Single Axis Trend 9
Single Axis Trackers Main Architectures 9
Factoring the Site’s Terrain 10
Factoring the Site’s Irradiance 10
Factoring Tracking Algorithms 10
Assessment According to Technical Specifications 11
Factoring the supply chain 11
Factoring performance 12
Factoring wind tolerance 12
Operational Considerations While Assessing Trackers: Installation and O&M 14
Factoring upfront installation cost 14
Factoring the post-warranty phase 14
Factoring O&M costs 14
Factoring cost of parts vs. downtime cost 15
Factoring Maintenance Trade-Offs 15
Conclusion 16
Figure 1: How Utilities Offer Solar to Communities (p. 5)
Figure 2: NREL Internal Cost Model for PV Utility Costs by 2020 (p. 5)
Figure 3: Simplified Equation for Calculating Tracker Benefit (p. 7)
Figure 4: GTM Research’s To Track or Not To Track (p. 8)
Figure 5: 3rd party Solar Power Purchase Agreements as of 2015 (p. 8)
Figure 6: Additional Energy Output from Single Axis Tracker Compared with Fixed Tilt (p. 8)
Figure 7: Ganged Architecture (p. 9)
Figure 8: Distributed Architecture (p. 9)
Figure 9: Performance Gains Derived with Solar Trackers (p. 12)
Figure 10: Grounding, Stowing, and Backtracking Comparison (p. 13)
List of Figures
(c) The Triana Group, Inc. 2016

The authors would like to thank those who contributed to the
completion of this study, including companies that have responded
to our study and experts who agreed to be interviewed and took
the time to respond to our questions; they provided decades of
cumulative experience relevant to solar trackers, and their first-
hand knowledge helped shape the content of our research.
A special thank you goes out to Madyan De Welle and Wassim
Bendeddouche (Optimum Tracker), Rune Hansen (SPG Solar), Heidi
Larson (Leidos), Robert Dally (Con Edison Development), Jay Levin
(PSEG Solar Source), Christian Malye (Generale du Solaire), and
Valerie Blecua-Bodin, among others not mentioned by name, for
their valuable contributions.
Acknowledgements
The current solar market in the US is undergoing “pivotal” changes, augmenting the
potential for single axis trackers in utility-scale solar projects. Increased demand for solar
energy and favorable policies for solar energy production are driving the usage of
trackers in utility-scale solar plants and in large distributed generation projects in
order to harvest maximum solar energy and return on investment.
Solar trackers play an important role in providing additional energy to utilities when most
needed. The energy requirement from PV systems increases during late afternoon
especially during summer, in order to help reduce peak loading costs as homeowners
increase their energy consumption during this time, firing up appliances. Time-of-use
allows utility rates and charges to be assessed based on when the electricity is used
(i.e., day/night and seasonal rates).
However, one must keep in mind that all states are not the same and that policies and
regulations differ from state to state. Every state has its own renewable energy portfolio
and targets for solar energy and therefore state-specific context represents an
additional backdrop for solar trackers assessment in utility-scale projects. The
assessment of solar trackers should be performed not only on a state-by-state basis,
but also on a site-specific and project-specific basis.
Abstract
PAGE 1

The Triana Group is a New York based company located near Wall Street,
which works with international technology companies to introduce their
products to new markets. This study was sponsored by Optimum Tracker,
a company founded in 2009, with a line of innovative solar trackers for
utility-scale solar projects. Optimum Tracker contributed expertise but the
study was completed independently by The Triana Group.
The study was led by Reed MacMillan, MBA, with a research
team including Khushbu Singh, MBA, Crystelle Desnoyer, MIB, and
Jabril Bensedrine, Ph.D.
AbouttheAuthors
Reed MacMillan
Reed MacMillan has been an advisor to the Triana Group since 2013, where she has led market entry and
business integration projects for technology companies. Previously, while working for Science Applications
International Corporation (SAIC), a Fortune 500 company, she led efforts to win large federal contracts in IT,
valued above $200 million. Prior to this, as Training and Operations Manager, she oversaw enterprise
training and operations solutions for government agencies, overseeing global teams. During this project,
Ms. MacMillan stood up the operations team responsible for the 24×7 availability of multiple worldwide
systems. Throughout her career, she has achieved successful business outcomes by connecting people,
ideas, and business interests. She holds an MBA from the MIT.
Khushbu Singh
Khushbu Singh is a business development consultant with The Triana Group, Inc. With nearly five years of
professional experience in account management, corporate communication, and business consulting, she
has effectively managed projects from conception through productive completion across industries. She
holds a Masters of Marketing Management degree from Pace University in New York. Her past experience
includes positions in marketing and communications at the financial services firm Edelweiss and the global
marketing firm Ogilvy & Mather.

Methodology
Our methodology relied on interviews with industry experts with experience as
solar developers, system integrators, ﬁnanciers, tracker manufacturers, and
select customers who have used trackers for utility-scale solar projects.
Additional methods included participation at the leading solar conference, SPI
in Anaheim, CA in 2015; review of articles in industry publications available in
print and on the Internet documented at the end of this paper; companies’
websites and literature. Our team reached out to the companies mentioned in
this report to give the opportunity to provide feedback on our research.
The material presented in this white paper is based on publicly available information.
It is provided for informational purposes only. While every effort has been taken to
ensure the accuracy of this material, legislation, regulation, and market information
are subject to change and may no longer be accurate. The authors assume no
responsibility for errors or omissions, or for damages resulting from the use of the
information contained herein. This white paper is not intended to provide legal,
investment, technical or commercial advice and is for general informational
purposes only.
Disclaimer

It is a “pivotal” time in the solar market, resulting in increased use of
single axis trackers in utility scale solar projects.
Understanding this context is key to assessing the real opportunities in
using single axis horizontal trackers, and which tracker to choose. For
this reason, this study starts with a review of the solar industry’s general
business context.
Assessing Single Axis Trackers:
Why The Solar Industry’s
General Context Matters
Utility-scale PV is booming. In the US
for example (the largest market in the
world for trackers according to IHS),
solar energy production has grown
from 1.2 GW to an estimated 20 GW.
Solar Energy Industries Association
(SEIA) reported that nearly 4GW
went onto the grid in 2014, a 13%
increase over 2013. In total, 15
utility-scale installations with more
than 100MW were added to the grid
in 2014, with 28 MW as the average
size of these PV systems. In 2014, the
United States brought online as
much solar energy every three
weeks as it did in all of 2008.
One of the primary reasons that the
U.S. utilities continue to add solar into
their energy production portfolios is
the continued decline in the balance
of system (BOS) costs. BOS refers to
all components of a PV system other
than the modules, and because of
these declining costs, large-scale
systems are becoming competitive
with conventional power plants.
According to surveys conducted by
GTM research and SEI, the average
system price for non-tracking,
large-scale systems dropped in the
ﬁrst quarter of 2015 to 1.58 US
$/WDC, which is a 13 US$-ct
reduction over the ﬁrst quarter of
2014. In 2014, 32% of all new electric
generating capacity came from
solar, and the share in all new electric
generating capacity increased to
51% in Q1 of 2015.
One of the drivers for this increased
expansion into utility-scale invest-
ments was the potential expiration of
the ITC (recently extended). GTM
research says that the tax credit has
driven the project pipeline for
utility-scale plants to a record high of
nearly 15 GW for contracted projects
with signed PPA and more than 27
GW of announced projects at the
pre-contract stage.
SolarEnergy
ProductionTrends

The Solar Energy Technologies Office works to
accelerate the competitiveness of solar energy
by targeting cost reductions and supporting
increased solar deployment, making solar energy
resources affordable and accessible. Through its
SunShot Initiative, DOE supports efforts by private
companies, universities, and national laboratories
to drive down the cost of solar electricity to $0.06
per kWh, without incentives, by 2020 (depicted in
Figure 2: NREL Internal Cost Model for PV Utility
Costs by 2020.)
The SunShot Vision Study explores a future
in which the price of solar technologies declines
by about 75% between 2010 and 2020—in line
with the U.S. Department of Energy (DOE)
SunShot Initiative’s targets. These goals may
be partially hindered by 2014's anti-dumping
tariffs, which have driven module prices up.
IHS for example expects solar PV benchmark
capital costs to fall approximately 45% by 2030;
utility-scale solar PV benchmark capital costs
are anticipated to fall to US$1.21/WattDC by
2030 (nominal). Regardless, as a result of price
reductions, solar technologies are projected to
play an increasingly important role in meeting
electricity demand over the next 20–40 years,
satisfying roughly 14% of U.S. electricity demand
by 2030 and 27% by 2050. Solar trackers
contribute to achieving these production
targets.
PAGE 5
Figure 2: NREL Internal Cost Model for PV Utility Costs by 2020
In June of 2015, the Obama administration
announced a series of executive actions and
private sector initiatives in support of scaling up
solar. One key initiative, the National Community
Solar Partnership, seeks to unlock solar access to
the nearly 50% of households and businesses that
are renters or do not have adequate roof space to
install solar panels. Today there are more than 100
shared solar projects around the United States, with
a total capacity of more than 65 MW. Expanding
the market to those customers could result in
cumulative PV deployment growth of 5.5-to-11 GW
in the 2015-to-2020 period. Part of making this a
reality will come when utilities make energy from
solar sources available to these customers. The
U.S. Department of Energy’s National Research
Energy Laboratory’s (NREL) vision for the growth in
the utilities is depicted in Figure 1: How Utilities Offer
Solar to Communities.
Policies for Solar Power Production
Drive Solar Tracker Usage in the
US and Internationally
Figure 1: How Utilities Offer Solar to Communities

Importance of the Investment Tax
Credit in Calculating Solar Trackers
Benefits
One driver to the adoption has been the Investment
Tax Credit (ITC) for solar. This allows for owners of
photovoltaic systems to take a one-time tax credit
equivalent to 30% of qualified installed costs. The
commercial tax credit is reduced to 10% as of
January 1st, 2017.
In addition to the ITC, federal tax policy allows
businesses (but not individuals) to depreciate their
investments in solar projects on an accelerated basis.
For projects taking the ITC, the depreciable basis
must be reduced by half the value of the ITC. For
example, if the ITC equals 30% of project costs, then
the depreciable basis is reduced by 15%.
Provided below is a simplified equation for PV devel-
opment economics which demonstrate the gains
that can be obtained by adding trackers. Depending
on the site specifics, and the trackers selected, you
should be able to obtain between 12 – 30% additional
electricity by adding trackers. The simplified equation
below does not consider the additional gains possible
in areas where you can charge more during periods
of peak demand. Note also that the tax credit is
based on the entire cost of the project, so the tracker
expense is also offset by the same percentage.
It is important to note that even if the ITC subsidies
were reduced for utility-scale projects the relative
cost of the trackers compared with the gains they
deliver in productivity would result in making these
projects more feasible after the ITC. As more and
more states aim towards increasing solar in their
renewable portfolio standards and decreasing costs
of storing solar energy will result in increasing the
PAGE 6
Simplified Equation for Calculating the Benefit of a Solar
Tracker (For the same site)
1. Calculate Productivity in kWh/hr. with Fixed Tilt
system
2. Calculate Productivity in kWh/hr. with Single Axis
Horizontal Tracker.
3. Calculate costs per kWh/hr. of each system
(including O&M estimates, tax rebates, depreciation,
and other incentives, over the lifetime of the project.
4. Compare Lifetime Cost of Energy for Fixed Tilt vs.
with SAH Tracker.
The Intuition
The benefit of the increased electrical output or
productivity of the trackers should exceed the additional
cost incurred by adding the SAH Trackers.
Figure 3: Simplified Equation for Calculating Tracker Benefit
solar energy needs in the coming future and
making it possible for utilities to store the captured
energy to be used and sold later.
All these factors create a positive market conditions
for solar trackers to fulfill the ongoing needs for
development and capacity.

Importance of the Time of Day
Charges for Solar Trackers
The financial gains that can be obtained from the
use of trackers within a utility scale installation may
also depend on the ability to charge for time of day
(TOD) increases, something that is regulated at the
state level. Time of use (TOU) net metering employs
a specialized reversible smart (electric) meter that is
programmed to determine electricity usage any
time during the day. Time-of-use allows utility rates
and charges to be assessed based on when the
electricity was used (i.e., day/night and seasonal
rates). Utilities need energy from PV systems late in
the afternoon, especially during summer, to help
reduce peak loading costs as homeowners return
from work and fire up air conditioners, ovens,
televisions, etc. Solar trackers help provide
additional energy to utilities when they need it most.
That is reflected in some markets by the use of
TOD pricing. In Figure 3: Revenue Impacts of Fixed
Tilt Versus Tracking Systems, the times of year
when TOD premiums can be charged are
highlighted in yellow. This example comes from the
GTM Research’s Report Snapshot: To Track or Not
To Track, Part II.
For Trackers Assessment, All
States Are Not Equal
A key point for thinking about solar trackers in the
U.S. market is that in addition to the Federal policies
in place, each state must be researched thoroughly
in terms of its own regulatory environment or state
specific incentives.
Energy efficiency resource standards (EERS) are
state policies that require utilities to meet specific
targets for energy savings according to a set
schedule.
PAGE 7
TRACKING
Energy Poduction
(Kwh)
Revenue without
TOD ($)
Revenue with
TOD ($)
130,405
132,651
167,498
181,687
167,045
160,844
174,993
184,451
155,681
160,279
135,903
124,940
1,876,377 $187,638 $199,935
$13,041
$13,265
$16,750
$18,169
$16,705
$16,084
$17,499
$18,445
$15,568
$16,028
$13,590
$12,494
$16,028
$13,590
$12,494
$13,041
$13,265
$16,750
$20,349
$18,709
$18.015
$19.599
$20.659
$17.436
Figure 4: GTM Research’s To Track or Not To Track, Part II
EERS policies establish separate reduction
targets for electricity sales, peak electric demand
and/or natural gas consumption. In most cases,
utilities must achieve energy savings by devel-
oping demand-side management (DSM programs,
which typically provide financial incentives to
customers to install energy-efficient equipment.
Therefore, state-specific policies represent an
additional backdrop for solar trackers assessment
in utility-scale projects.
Every state has its own Technology roadmap
for the future and a research and development
path to full competitiveness of concentrating
solar power (CSP) with conventional power
generation technologies within a decade. Solar
trackers’ role in this equation varies depending
on each state’s roadmap.
The Database of State Incentives for
Renewable Energy (DSIRE), a comprehensive
source of information on incentives and policies
that support renewables and energy efficiency
in the United States, provides a map shown in
Figure 5: 3rd Party Solar Power Purchase
Agreements (PPA) as of 2015.

Figure 5: 3rd party Solar Power Purchase Agreements
as of 2015
Authorization for 3rd-party solar PV PPAs (Power
Purchase Agreements) usually lies in the definition
of a “utility” in state statutes and other
regulations. Thus, even though a state may have
authorized the use of 3rd-party PPAs, it does not
mean that these arrangements are allowed in every
jurisdiction.
In the 3rd party PPA model, developers can build
and own a PV system on a customer site, and sell
the power back to the customer. Depending on
whether the state allows these 3rd Party PPA
owners to act as a monopoly utility or as
competitive service suppliers according to state
definitions or state Public Utility Commission (PUC)
definitions, the third-party owners may also need to
be regulated by the state PUC. Though a 3rd-party
PPA provider may not be subject to the same
regulations as utilities, additional licensing
requirements may still apply. These regulatory
considerations have a direct impact on how the
electricity may be sold and will ultimately need to be
factored into the project development costs and
lifetime cost of energy (LCOE) and bankability
studies. The extra gains from trackers can be
considered especially beneficial in scenarios where
the vendors may charge time of day premiums.
Those considering adding trackers to obtain
such gains need to understand clearly if and
how this additional electricity can be billed and
how that impacts the bankability of the project.
The Benefits of Tracker
Technology Within the Solar
Industry’s General Context Drive
Usage Growth
Specifications
Information available
for # of companies
Range
Bankability
Cumulative projects
8
12
NA
Years in the Industry 8 2 to 25
81 MW - 3 GW
Presense across countries 12 1 - 12
Headquarters 12
- 2 in USA
- 5 in Spain
- 2 in France
- 1 in Germany
- 1 in Greece
- 1 in Canada
Figure 6: Additional Daily Energy Output from Single Axis
Tracker Compared with Fixed Tilt
For a utility-scale project, the main benefits of a
tracking system are the ability to reduce costs by
producing more energy per unit area by tracking
the sun. This not only reduces the lifetime cost of
energy (LCOE), but it extends the power production
curve to provide a smoother flow of energy from
dawn to dusk, as is shown in Figure 6: Additional
Energy Output from Single Axis Tracker Compared
to Fixed Tilt.

Within the world of single axis trackers there are
two architectures: ganged or distributed. Both
types rotate the modules using controllers and
motors, but differ in how many modules can be
controlled by each motor. The trade-offs between
these two architectures need to be factored in the
context of site speciﬁcs and project requirements.
Single Axis Trackers Main
Architectures
The Single Axis Trend
The September 2015 Power PV Tech magazine,
published an article titled “Motivation for single axis
solar trackers versus ﬁxed tilt” in which Matt Kisber
describes how the dramatic cost reduction of PV
modules is driving expanded use of the single axis
trackers (p.44). While both dual and single axis
trackers were used previously, dual axis trackers
have major disadvantages: they require more
acreage; they are more complex to implement; they
are less reliable and have more mechanical failures;
as a result, their overall economics is more
challenging.
For all of these bankability and technical reasons,
the majority of utility-scale tracker systems have
migrated to single axis trackers.
Comparing Trackers
Figure 7: Ganged Architecture
Figure 8: Distributed Architecture

Factoring the Site’s Terrain
For example, a ganged architecture is less flexible
in terms of configurability, whereas a distributed
architecture can maximize irregular site arrays.
When solar projects are on a level and open
terrain, larger and less flexible rectangular arrays
work fine. But, as less of such sites are available,
the distributed architecture systems of configura-
tion options make more sense, where a single
tracker unit can be installed in as little as 480
square feet. Valerie Blecua-Bodin highlights this
and adds that the flexibility of such tracking
systems will help enhance and optimize the ground
coverage ratio (GCR): This is important, because
"land control is always an issue (or at least is
sensitive) and impacts the project economics."
Factoring the Site’s Irradiance
In terms of the economics, (single axis horizontal
trackers can provide up to 35% of more power
generation compared to fixed tilt) trackers will make
more financial sense in regions that have a high
Global Horizontal Irradiance (GHI) and a relatively
low Diffuse Component (DHI) where the increased
output from the tracker can compensate for the
additional material and O&M costs. Areas with a
high GHI and a relatively low DHI are ideal for single
axis trackers. The annual GHI values for the desert
in the Southwestern US are on the order of
2100-2200 kWh/m2. By comparison the annual GHI
values for a Germany region are on the order of
11---1300 kWh/m2. Trackers are used in Germany
as well, but GHI and DHI are important when
considering a mounting system. The energy gain
from the tracker has to compensate for the
increased system costs relative to the fixed tilt
system; however, this is a moving equation since
trackers’ costs are decreasing rapidly.
Factoring Tracking Algorithms
Tracking algorithms both continue to improve and
also become more universally available. The NREL
tracking algorithms, which are publicly available,
are in use today by several of the major providers
of trackers. It is beyond the scope of this study to
consider the nature of and differences among
vendors’ algorithms. This information tends to be
proprietary in nature and is quite complex.
In an article titled, “A review of principle and
sun-tracking methods for maximizing solar
systems output” published in the Elsevier
Renewable and Sustainable Energy Reviews 13
(2009) 1800-1818, the authors review the different
sun tracking devices and compare both passive
and active trackers. They make the point that
trackers don't need to point directly at the sun to
be effective. In fact, they point out that if the aim is
off by 10 degrees, the output is still 98.5% of that of
the full-tracking maximum.
Most utility-scale operators monitor performance
ratios to detect their yields against their
projections, and are not in the business of
measuring the fine gains available from tweaked
algorithms. However, as the quality of the trackers'
algorithm is part of the reliability of solar tracking
systems, it has to be considered.

Factoring the supply chain
For example, if a motor is supposed to last 20
years, the technology assessment firm will examine the
components used to manufacture the motor, as well as
the number of manufacturers who can produce the part
and what the supply chain risk is, if there is only one
manufacturer of a specific component. When asked
about specific technical criteria, which might be most
significant in considering a solar tracker, Ms. Larson
iterated that context could vary tremendously.
In the next section, we compare leading solar tracker
manufacturers using publicly available information, taken
from product specification sheets and company websites.
The compiled list of tracker features provided here gives
you a basis by which to compare trackers that you are
evaluating. The characteristics must be assessed against
the specific project requirements and therefore our team
resists the urge to consider one tracker superior to
another. Each tracker has a set of features that may make
it suitable for one project vs. another.
Assessment According to
Technical Specifications
In looking at any solar tracker, a variety of
technical specifications can be evaluated
and considered in terms of suitability for a
project.
However, at the end of the day “It’s all in
the application of the technology,” says
Heidi Larson, the Director of Solar
Generation at Leidos. Leidos is one of the
top three firms in the US providing
independent technology assessment that
validate solar projects for Engineering,
Procurement, and Construction (EPC)
contractors and Project Developers.
Hence, benchmarking solar trackers is
irrelevant without considering each
project’s specific context.
Leidos is not hired to help optimize
designs, which is the job of the EPC, but
to ensure that the requirements for
systems work as planned and will last as
long as specified. Black and Veatch,
another leader in producing independent
assessments, also considers technical
and commercial factors. Questions you
can expect these firms to answer in their
assessments include:
Will the product perform as expected?
What is the quality of the product and materials?
What is the product’s durability and reliability?
How will performance change over time?
Can I trust the warranty to cover the expected
performance of the product?
“It’s all in the application of the technology”
Heidi Larson - Director of Solar Generation, Leidos.
“Nearly all tracker vendors claim that their products can deliver
significant gains on sloped terrains, which should be carefully
reviewed, since there are also losses that occur due to
shadowing.”
Christian Malye, the Chief Technical Officer for Generale du Solaire, developer of utility scale
projects

Factoring performance
The primary motivation for adding a
solar tracker into a site design is to
gather more energy – therefore these
energy gains are a good way to get a
sense of what is possible using a
tracker. In Figure 7: Solar Tracker Gains
Compared to Fixed Tilt, nearly all
vendors claim between 25 – 30%
gains. More importantly, nearly all
experts agree that the energy gain is
“site specific.” One developer we
spoke to, Christian Malye, the Chief
Technical Officer for Generale du
Solaire, a developer of utility-scale
projects, said “Nearly all tracker
vendors claim that their products can
deliver significant gains on sloped
terrains, which should be carefully
reviewed, since there are also losses
that occur due to shadowing.” While it
is possible to avoid shadowing, the
modules would need to be more
spread out, therefore costing more in
terms of the space required.
Each of these elements needs to be
considered alongside the other to
calculate the real performance gain of
adding a specific tracker.
Factoring wind tolerance
One of the areas where trackers seem to differ most is in their
wind tolerance. Heidi Larson gave the example of California or
Nevada projects needing wind tolerances for wind up to 110
mph whereas 90 mph in the Midwest might be adequate. She
also mentioned that every locality has their own specific
building codes that will dictate the wind speed requirements.
Thus, it is common for tracker manufacturers to be able to
engineer their trackers to withstand greater wind speeds by
increasing the size of their torque tubes, increasing strength by
adding more steel. Product literature may reference the
standard version of the product, but many companies can
address more demanding requirements.
In Figure 6: Grounding, Stowing, and Backtracking Comparison,
you will find a wide range in the wind tolerances among the
vendors from 37 miles per hour all the way up to 135 miles per
hour. Nearly all vendors also have the ability to engineer a
system specific to the site requirements for your site. Bear in
mind that each time they re-engineer the product, it will need to
be re-tested in a wind tunnel in order to be certified as
adhering to the necessary building codes and wind thresholds
required by that state and locality.
The table also shows the rotational angle, which can
be obtained by the trackers. The range here is between +-45°
and +-60°. The Elsevier article referenced previously also
compared gains obtained with different angles and
concluded that “It is clear that in tracking angles beyond
+-60° no considerable energy gain is obtained.”
In a session at the September SPI conference in Anaheim, CA,
David Banks, a wind-engineering consultant for solar
panels, said that the industry needed to move away from
compliance and toward performance, suggesting that gains
can be made that exceed standard building codes.
There are varying approaches to stowing and wind load. For
example, Array Technology engineers their trackers to
withstand the wind speed in any position, saying that even in
stow position there are harmonics that can compromise the
integrity of the structure.
Figure 9: Performance Gains Derived with Solar Trackers
Array Technologies
Ercam
Exosun
Gestamp Solar
Groupo Clavijo
Ideematec
Meca Solar
Mechatron
NextTracker
Optimum Tracker
Solar Flexrack
Soltec
Criteria
Energy Gain vs Fixed Tilt
Up to 25% Site Specific
Up to 35% Site Specific
Up to 25%
NA
NA
Up to 25%
Up to 30%
Up to 30%
NA
Up to 30%
NA
Up to 30%
Company
Performance

In discussing the importance of wind-tunnel
testing for the selection of a tracker, Robert
Dally, a veteran designer and developer of
utility-scale solar for global projects (24 - 55MW)
pointed out that, “In cases where the actual wind
tunnel test is not available, evaluators tend to
err on the conservative side and require
stronger materials, which will drive up costs.”
The table in Figure 8 also documents
whether backtracking is standard or
optimized. In an optimized scenario, a
backtracking algorithm takes into account the
sun's position, as well as panels spacing, size
and shape in the array to minimize shading
and maximize orthogonality, so that the
maximum amount of solar energy can be
harvested. The effect is more pronounced in
winter when solar angles are lower. The site's
topography will determine how important this
feature is for your project.
One key consideration for trackers is their wind
tolerance and design, which can be validated in
wind tunnel testing. Note that every time the
design changes, the wind-tunnel test needs to be
recreated.
Advances have continued in the calculation of
wind forces on tracker structures, which have been
aided by more wind-tunnel studies. These
studies are contributing to new approaches to
stowing trackers that reduce the forces on the
various structures. As discussed above, most
trackers can be constructed to achieve the
required levels of wind-resistance as determined by
the initial Independent Engineering (IE) assessments.
“In cases where the actual wind tunnel test
is not available, evaluators tend to err on the
conservative side and require stronger materials,
which will drive up costs”.
Robert Dally
Figure 10: Grounding, Stowing, and Backtracking Comparison
Speciﬁcations
Array Technologies
Ercam
Exosun
Gestamp Solar
Groupo Clavijo
Ideematic
Meca Solar
Mechatron
NextTracker
Optimum Tracker
Solar Flexrack
Soltec
Optimized
Optimized
Optimized
Optimized
Optimized
Optimized
Standard
Standard
Standard
Oprional
NA
NA
Company
Criteria
Rotational Angle Ground Coverage Ratio
Flexible 28% to 40%NA
25% to 56%
NA
NA
Flexible
NA
35% to 50%
33% to 55%
NA
Flexible
NA
NA
Backtracking
52o+-
55o+-
50o+-
NA
NA
60o+-45o
OR+-
45o+-
45o+-
45o+-
60o+-
50o+-
45o+-

However, other components require routine
maintenance and replacement. Aside from
O&M, operational expenditure will include
comprehensive insurance, administration costs,
salaries and labor wages. Since installations'
lifetime is between 20-30 years while product
warranties are between 5-15 years, there is a gap
to cover: the main concern for asset managers
is to understand how they will deal with the
product after initial warranties have expired.
Factoring O&M costs
With a 25-30 year lifetime of a PV power plant, it
is critical to accurately consider the O&M costs of
tracker design. Common failures modes of tracker
systems are motors, gearboxes, and controller
electronics. Architectures also impact these
costs, and which type of maintenance can
be expected.
While independent technical assessments are
critical for getting projects validated and funded, it
is also beneficial to listen to the veterans who
have been building these projects to learn
how they balance trade-offs such as
construction cost, productivity and O&M.
“After a while, everyone who has dealt with utility
scale PV has faced trackers stuck in one position
or another not producing at their optimum.”
A developer
Operational Considerations While
Assessing Trackers: Installation and
O&M
Factoring upfront installation cost
Upfront costs related to trackers installation
compared to fixed tilt are rapidly declining. As the
global utility-scale solar market continues to shift
from fixed tilt to tracker-based systems, trackers
are experiencing a steeper cost reduction rate
compared to fixed tilt systems.
At the same time, vendors differentiate themselves
with the services they provide during systems
installation and commissioning. For example,
several now offer certification programs in aspects
such as product installation, construction
management, commissioning, and operations and
maintenance. In some cases, services are
segmented into tiers. For project managers who
may find it difficult to hire qualified personnel, these
programs can help them train their own personnel.
Naturally, there are additional costs for these
services, some of which may show up in the
operational budget lines rather than the energy cost
calculations.
Factoring the post-warranty phase
O&M costs for solar PV are significantly lower than
other renewable energy technologies. They
depend on many factors, including project location
and surrounding environment. For example, a
site located in a dusty environment is likely to
require frequent cleaning of modules. It is difficult
to predict the O&M cost over the latter part of the 25
year design life as there are very few large scale
solar projects that have been generating for
sufficient time to have reached the end of
their design life. Modules are generally supplied
with performance guarantees for 25 - 30 years.

Factoring cost of parts vs. downtime cost
One of the most expensive parts for trackers is
their motor. As discussed earlier, some tracker
systems have a distributed architecture and
individual motors whereas others have a ganged
architecture with one motor powering the
movement of numerous modules. The relative costs
of these motors must be factored in, as well as
what amount of downtime can be anticipated when
one of them has failed. Downtime does not mean
that there is no production because even in
stow mode panels can produce energy.
The cost of motor replacement should not be
overly emphasized according to Robert Dally,
because motors are fairly easy to replace. Extra
costs can come from the grounds maintenance
required with a ganged architecture due to the
more narrow aisles, which can prevent trucks from
driving through. So, architecture and hardware
replacement must be considered alongside of the
costs the grounds maintenance for a specific
architecture.
A developer described the main issue
with trackers as follows: “After a while,
everyone who has dealt with utility-scale PV has
faced trackers stuck in one position or another
not producing at their optimum.” To illustrate the
kind of issues that can arise, he described having
to face a potential hurricane grade storm,
with the tracker stuck at a 50-degree angle
without the ability to be stowed.
Factoring Maintenance Trade-Offs
So, how are you going to ensure that your
trackers are providing the additional gains
anticipated?
In a training session on PV systems operations
and maintenance, the non-profit organization
Solar Energy International estimated the cost of
corrective maintenance as 3 times that of
preventive maintenance. They recommend a
minimum maintenance for each part of a PV
system. For trackers, they simply state:
“manufacture specific”, including lubrication and
wind-stow operation. They detail how to use the
Performance Ratio (PR) as an indicator of system
issues. In fact, by calculating the ratio of “actual
system energy yield divided by the ideal yield”,
you can identify component failures or even
problems in design or installation. Carefully moni-
toring the Data Acquisition System (DAS) should
enable you to isolate anomalies that need to be
investigated. This approach is relatively new. In the
past, banks wanted data on each row. Today, the
DAS is preferable, especially when you have
thousands of rows and might therefore have thou-
sands of data points to process to determine the
location of a problem. For example, sensors
installed on each tracker such as Optimum
Tracker’s real-time systems provide an alternative
to preventive vs. reactive maintenance trade-offs
by enabling pre-failure just-in time maintenance,
thus optimizing maintenance cost.
You may not realize the extent to which ground
maintenance or tracker cleaning can add consid-
erable operational expenses, but you do need to
build these costs into your financial models. A
developer of solar projects in France who uses
trackers said “Cleaning trackers is very
expensive, mostly because it requires you to stow
the trackers, during the time when they are
cleaned.”
“Cleaning tracker is very expensive, mostly because
it requires you to stow the tracker, while they are
cleaned.”
A developer of solar projects

There are many compelling reasons to add a single axis solar tracker into your PV project design,
with increased return on investment likely near the top of the list. For the right site, adding trackers can allow
capturing 30% additional energy. In some states, this can be further amortized since it is possible to charge
premiums for energy sold back to the grid during peak times.
There are quite a few vendors of trackers, some that have been in business for over 30 years while others
are relatively new to the industry and bring valuable innovations. Each vendor has elements of their design
which make them distinct in some way, yet differences such as whether the tracker has a certified training
program for technicians, its own power generation source, greater wind-tolerance, or greater configurability
will each be valued differently depending on the specifics of the project undertaken. Therefore, the site
itself will suggest which factors may be more significant, and will influence the bankability assessment or
other independent engineering report.
The good news is that many trackers today such as Optimum Tracker have been effectively configured to
meet site-specific requirements, have proven to generate financial gains, and have been designed with 30-
year operational horizons, reducing the chances that a tracker breakdown will result in system downtime.
Conclusion

For further information:
solar-technologies@trianagroup.com
www.trianagroup.com
1-646-417-8136

IHS (www.ihs.com)
SEIA: http://www.seia.org/research-resources/solar-industry-data
gtmresearch: PV Balance of Systems 2015: Technology Trends and Markets;
http://www.greentechmedia.com/research/report/pv-balance-of-systems-2015
gtmresearch: PV Balance of Systems 2015: Technology Trends and Markets;
http://www.greentechmedia.com/research/report/pv-balance-of-systems-2015
Fact Sheet: President Obama to Announce Historic Carbon Pollution Standards for Power Plants:
https://www.whitehouse.gov/the-press-office/2015/08/03/-
fact-sheet-president-obama-announce-historic-carbon-pollution-standards
Energy.GOV: Community and Shared Solar: http://energy.gov/eere/sunshot/community-and-shared-solar
Energy.gov: Sunshot Vision Study: http://energy.gov/eere/sunshot/sunshot-vision-study
gtm research: Report Snapshot: To Track or Not To Track, Part II: http://www.greentechmedia.com/articles/read/re-
port-snapshot-to-track-or-not-to-track-part-ii
DSIRE: http://www.dsireusa.org
Solar PV Project Financing: Regulatory and Legislative Challenges for Third-Party PPA System Owners, Katharine Kollins,
Duke University: http://www.nrel.gov/docs/fy10osti/46723.pdf
2015 Power PV Tech, Motivation for single axis solar trackers versus ﬁxed tilt Matt Kisber (p.44-47)
2015 Power PV Tech, Motivation for single axis solar trackers versus ﬁxed tilt Matt Kisber (p.44-47)
Endnotes
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Potential of Single Axis Trackers Feb 7 2016

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