Potential of Single Axis Trackers Feb 7 2016

P O T E N T I A L O F

SINGLE AXIS HORIZONTALS O L A R T R A C K E R S

IN UTILITY-SCALE PROJECTS

Photo: Optimum Tracker, Garein 12MW

Contents

Acknowledgements 1List of Figures 1Abstract 1About the Authors 2Methodology 3Disclaimer 3Assessing 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 F igures

(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(c) The Triana Group, Inc. 2016

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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.

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Reed MacMi l lanReed 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 SinghKhushbu 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.


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MethodologyOur 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


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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’sGeneral 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.

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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.

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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

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Simplified Equation for Calculating the Benefit of a Solar Tracker (For the same site)

1. Calculate Productivity in kWh/hr. with Fixed Tiltsystem2. Calculate Productivity in kWh/hr. with Single AxisHorizontal 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 IntuitionThe 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(c) The Triana Group, Inc. 2016

TRACKINGEnergy 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.

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Figure 5: 3rd party Solar Power Purchase Agreementsas 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


SpecificationsInformation availablefor # 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.

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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 MainArchitectures

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

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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.


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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 toTechnical 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


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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%

Com

pany

Performance

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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

Com

pany

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+-

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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.


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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


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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:

[email protected]

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)

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Documents

Potential of Single Axis Trackers Feb 7 2016