Bifacial Gains: How much will bifacial modules add to solar tracker value? We are about to find out

Soltec

Soltec is testing for all bifacial tracking variables at its new evaluation center in Livermore, Calif.

We are on the verge of the bifacial solar tracker era. Projects are being quoted with many starting to break ground later this year and early 2019.

Only two issues remain in the way of serious wide-spread adoption. First is the price of bifacial modules, which sits at about 30 cents a watt on average right now. The premium price makes sense because the market hasn’t formed yet, and it won’t form until there are bankable production estimates for the technology. That would be issue No. 2: the data set for bifacial tracker performance is incomplete, but this is about to change in a hurry.

Several big-time partnerships between tracker companies, module companies and PV research and testing labs have formed within the last year to understand this new bifacial module + PV tracker paradigm, test theories and build a complete data set on bifacial tracker production.

“This is a fundamentally different paradigm than before because the tracker and module are all intertwined with the site conditions in a way they weren’t before,” says Ron Corio, founder and CIO of Array Technologies.

Multiple approaches

The splashiest of these partnerships is Spain-based single-axis tracking supplier Soltec teaming with the National Renewable Energy Labs (NREL), Black and Veatch and RETC to build BiTEC, the world’s first evaluation center specialized in bifacial trackers, in Livermore, Calif. We visited the facility in July, and the site has a variety of configurations structured to isolate and measure any site or system design effect, such as:

  • Albedo
  • Terrain surface
  • Types of bifacial technology (from Hanwha-QCells, Jinko, Canadian Solar, LG and more)
  • GCR
  • Pitch
  • String design
  • 2x modules in portrait versus 1x.

One variable not changed throughout the field is tracker height, with all 2x configurations standing at 7.71 ft (with 1x configuration trackers at a height of 4.43 ft). The reason is Soltec’s preliminary electric performance measures over bifacial modules reveal a short-circuit current difference of over 2.3 percent between 1x and 2x trackers, meaning that height has a significant influence over the energy output of bifacial panels. The capture of diffuse irradiance below and around the tracker is increased with height, while the shadow cast on the ground is softened.

Array Technologies is taking a different approach. Also working with a U.S. national laboratory, Array is mapping the backside irradiance at a half cell resolution as well as testing various configurations at string level. Array’s testing is focused primarily on the module tracker interaction, varying module mounting techniques as well as testing module design variance. An important objective of this testing is to validate ray tracing simulation programs which will aid in the accurate modeling of bifacial performance in site-specific applications.

“We are working closely with the module manufacturers in a way we’ve never done before for exactly that reason,” Corio says. “When you design the module and the tracker as one system, you get a better result.”

In a comparative one year test, conducted in 2017, Array saw a 9 to 10 percent yearly gain for bifacial over monofacial at the same test site.

Array Technologies

Array Technologies already sees a 9 to 10 percent gain in bifacial tracking performance.

The difference in Soltec and Array’s testing approaches is in line with the difference in their tracking approaches — Soltec uses distributed tracker rows and Array supplys centralized drive. All of the performance gains reported will need to be considered within the already established LCOE of each tracker design.

Example: The torque tube impact is an early point of differentiation depending on who you ask. The Soltec testing team has seen the shadow from the torque tube in a 1x configuration hurting irradiance harvest in a way it does not when positioned in a 2x configuration, so its SF7 tracker includes an intentional gap between modules at the torque tube location that avoids shadowing on the backside of the module. Preliminary measurements have shown that up to 38 percent of reflected light does not reach the center of the bifacial modules compared to the edge due to the torque tube shadow of the 1x configuration. Array is quantifying the impact of the torque tube to harvestable rear side irradiance and testing modules with design characteristics that may use the torque tube as a performance advantage. All of Array’s test data will be compiled in an LCOE comparison.

The difference in testing isn’t really the point. The Lawrence Berkley National Lab noted during the Market Trends panel at Intersolar that the cost premium associated with tracker projects is all but gone with 79 percent of newly installed capacity being trackers. When all of this testing is done, the choice will still be the same centralized or distributed tracker decision its always been, just with these new bifacial performance gains to plug into the equation.

— Solar Builder magazine

Details on Soltec’s new solar tracker wind-load analysis method

Soltec tracker

Soltec, already dedicating itself to bifacial tracker research, now presents Dy-WIND, an innovative method for comprehensive dynamic analysis in tracker wind-design developed with engineering consultancy Rowan Williams Davies & Irwin Inc (RWDI). Soltec decided to undertake this project after several studies have shown that certain wind-design code standards applied to solar trackers are insufficient for reliability because they do not consider the second order effects produced by the action of wind on the tracker.

Matthew T. L. Browne, Technical Director at RWDI, said: “the hybrid experimental-numerical approach developed through working with Soltec accurately estimates tracker behavior under the action of wind in multi-row arrays and allows flexibility in the design process that is generally not practical through full aeroelastic model testing.”

RWDI already has the expertise and wind tunnels that use stereolithography technology, integrated data acquisition, storage and processing systems, computer-aided drafting and a broad base of specialized instrumentation. Some of the most notable projects in which the firm has participated are the Petronas Towers in Malaysia, the Burj Khalifa skyscraper in Dubai or the Messina Strait Bridge in Italy.

sb-econference-web-post

— Solar Builder magazine

Total clean energy disruption is here and three other takeaways from Intersolar 2018

Starting with the opening keynote presentations on through the innovations on the expo floor, Intersolar 2018 was all about disruption. Yes, even those of you already succeeding in solar today, if you’re not careful, you could be disrupted too. Here’s what jumped out at us in San Francisco last week.

1. Total clean energy disruption is coming, and it’s bigger than you think it is.

Intersolar 2018 coverage (53)

Keynote speaker Tony Seba was the disruption tone setter. For those unfamiliar, Seba is a Silicon Valley entrepreneur, an instructor in Entrepreneurship, Disruption and Clean Energy at Stanford’s Continuing Studies Program and author of Clean Disruption of Energy and Transportation. His work focuses on clean energy, entrepreneurship and market disruption of the world’s major industries, such as energy, transportation, infrastructure, finance and manufacturing.

Yea, it’s a lot, but luckily he summarized it all in his presentation to kick off Intersolar. He makes the case that energy storage, EVs, ride-sharing and autonomous vehicles are on a path to converge very soon, and that the convergence of technology and business models in such a way is always the heart of true disruption.

“Every single technology has been adopted as an S curve. It is never a line,” Seba said. Consider the fact that cars replaced the horse and buggy in a mere 10-year span – and that’s in the days of, well, horse and buggy. His research shows how the tipping point for disruption has always led to a sharp S-curve trajectory, which is only getting sharper in our current time. “S curves are accelerating. It takes months or a year or two. More like J curves now. But yet there are still just straight lines in projections.”

Fast forwarding to the end scenario he lays out (which he originally laid out four years ago, and is right on track) is a world with little to no car ownership because of how much more economic sense it will make to “Uber” everywhere via fleets of automated ride services. This scenario upends much of our modern infrastructure — an abundance of storage on the grid, no use for parking lots, etc. I can’t really do it justice, so I’d recommend watching the full presentation for way more details.

The takeaway I’d like to highlight for the solar industry though is how winners of a disruption are rarely incumbents. Seba points to Kodak as a quick example. Kodak invented digital photography, had its best year ever, and then was basically out of business in under 10 years. Yes, despite that constant steep S curve, projection systems and experts and thought leaders are never prepared when that disruption hits. Companies you’ve never heard of are already ramping up to own the automated driving fleet space and random companies like Dyson are taking educated stabs in the dark at launching their own line of EVs.

For clean energy, the technology and economics are already there, it’s just a matter of a few other chess pieces moving into place, or dots connecting, or whatever other game analogy you’d like to use. If you smell what Seba is cooking, make your plans for this new world now.

2. You should try and win this funding competition.

Intersolar 2018 coverage (42)

Did that disruption talk get you excited, or get the gears turning on the next big idea? Well, hurry and tell the Department of Energy about it and you might get hooked up with a network of people to help implement it, along with some cash.

The DOE’s American Made Challenge Solar Prize competition is awarding $3 million in prizes as well as support from the DOE’s U.S,-based network to help grow, build business plans, prototypes and funding sources for labs and innovators. Additional cash prizes are then awarded to the most viable concepts.

“What role does DOE want to have? To focus on early stage research and forge strong partnerships with the private sector,” said Elaine Ulrich, Senior Advisor, Solar Energy Technologies Office, Energy Efficiency and Renewable Energy, Department of Energy. “We know this is the cornerstone of our success, so a new way we speed innovation is through prize competitions.”

And speed it, it does. This isn’t a laborious grant application process, but a series of contests. Record a 90 second video with a strong pitch and answer four questions: What’s the problem? What’s the solution? Who is on the team? What’s the plan?

The field will be winnowed to about 20 to 40 winners (for a max of $50,000 each) to about 12 after the proof of concept stage (an and additional $200,000 possible), until finally two winners will emerge with $500,000 to launch company.

“Within six months, you could have $750,000 in cash and $150,000 in facility vouchers and tapped into a full network,” Ulrich said. “This is just the first, of hopefully many of these contests.”

Oct. 5 is the submission deadline.

3. Yes, there is still new ground to break in ground-mounted solar.

We saw and heard about several design changes in ground-mounted solar that can forge new paths in underserved segments or take over/grow established segments. We can’t talk about all of them right now (stay tuned for Solar Power International), but here are a few to note.

AP Alternatives Ready Rack

AP Alternatives Ready Rack.

AP Alternatives‘ Ready Rack mounting hardware is designed for both large utility-scale projects and small commercial projects. The small helical anchors and quick install cross bracing make the simple system robust even for high wind zones.

What we liked: This system is nimbly installed with an attachment that fits on a skid steer, which opens up the 20 to 100-kW market up much more for small solar contractors to grow and scale their business.

Soltec bifacial tracking

Live at the Soltec Bifacial testing facility.

We will have more on this topic in our Sept./Oct. issue, but just know that the industry is very focused on finding true, objective results for bifacial modules deployed in various tracker combinations. The price point on bifacial modules may not make sense for wide deployment just yet, but when it does, highly bankable systems from Soltec and Array Technologies, to name two, will be at the ready. Soltec has built a testing ground and is working with NREL and Black and Veatch to gather a complete data set on the harvest of bifacial modules on solar trackers.

Alion tracker

Alion Energy tracker.

This Alion Energy tracker is definitely not for all sites – it has a very specific value proposition for tough and dusty terrains by incorporating a self-cleaning function. There is a lot of concrete needed to install this system, but you could picture it opening up new sites in remote, harsh desert landscapes because of how often its panels could be cleaned with an automated system that uses much less water and no labor.

4. Solar + storage value is much clearer on both the large and small scale.

SolArk

You’ll want to check out the Sol-Ark inverter.

On the small-scale side, we saw the most efficient solar + storage inverter on the market, and it isn’t from SolarEdge or Tesla but from little-known Sol-Ark. We explain DC transformerless architecture in greater detail in our Sept./Oct. print issue, but the quick story is this inverter is able to maintain an impressively high efficiency – both peak and consistent – in battery and grid tied scenarios.

On the large-scale side, more and more storage is being built into projects. First Solar recently signed a project contract for 150 MW of storage, for example. The key stat came from Joachim Seel, Scientific Engineering Associate at the Electricity Markets and Policy Group, Lawrence Berkeley National Laboratory, U.S.: At least six PPAs this year have featured PV-plus-long-duration storage that do not seem to be priced at a prohibitive premium to PV only.

Oh yeah, that reminds me of one more quote from Seba’s presentation: “At some point soon solar-plus-batteries will be cheaper than transmission,” Seba stated. Insert thinky emoji here.

— Solar Builder magazine

Tracking Trackers: We look at what’s new with these seven solar trackers

What are you looking for in a tracker? Longer rows with fewer spans? A two-up bifacial module setup? A simple central drive configuration with reliable bearings? More self-powered options? There are a lot of trackers in the segment, and we wanted to highlight some of the cool, innovative features outside of the market share leaders that reduce costs, ease installation or improve reliability.

Arctech

arctech

Three tracker styles to match every solar site

Arctech offers three tracker designs: The Arctracker Pro is its centralized tracker with push-pull design that is the best for flat land. The SkySmart is a single-row design with two modules in portrait that has fewer posts and is perfect for bifacial modules, and the SkyLine is a single-row design with one module in portrait.
Arctech makes the majority of its products with the support of two enormous factories, with a third on the way in 2019, to better control costs and quality.

Key hardware

  • All of Arctech’s trackers have its new D-shaped torque tube that adds stability and saves material.
  • Single-row trackers are powered from the string rather than from the batteries.
  • A beefy bearing was recently added that can handle a 20 percent N-S slope and stop the translation of weight.

Software

“Most of what we are doing is ensuring interfaces to client’s SCADA systems,” says Guy Rong, president of Arctech Solar. “We have a number of alarms in the rare case something happens to the system. Beyond this we are building software to create more accuracy on a row-by-row basis. We will announce when this is available.”

Case study

A 172-MW project in Telangana, India, had three main challenges that were solved by the design of the Arctracker Pro.

Challenge 1: Rough terrain and uneven slope. Solution: Arctech took advantage of special linkage and different post lengths to offset land contour variations and, at the same time, keep the high density of PV modules in available land and maintain high energy yield. Moreover, tracker sizes were specially designed to make best use of corner areas of land.

Challenge 2: High wind. Solution: Arctech Solar reinforced the tracking system by adding 25 percent more dampers to ensure stability and reliability of general operation and avoid damages caused by strong wind.

Challenge 3: Installation within timeline. Solutions: Installing 172 MW at a single site within the timeline was a challenging task for the EPC. In India, it’s not always easy to find skilled man power in remote areas. To solve these issues, the Arctech engineering team collaborated with the EPC to finalize installation phases well before shipping. Posts were shipped first to make sure the civil work started early while Arctech’s project managers gave tutorials on demo tracker installation so that all teams could start work simultaneously.

Nclave

nclave

Recently acquired by TrinaSolar, this international tracker has beefed up its design

Spain-based Nclave keeps on expanding. Founded 12 years ago by the Clavijo Family, it integrated with MFV in 2017. Nclave has installed over 2.5 GW worldwide. Earlier this year, the company teamed up with Trina Solar, a Chinese supplier of global solutions for the solar sector, to be a part of its TrinaPro utility-scale solution, which eventually led Trina to acquire a controlling interest in Nclave.

Structure

Nclave has developed and patented a module mounting design, the Nclave Clamp, that reduces assembly time of modules by more than 75 percent with as low as 50 manhours per MW. It also lessens the weight of the material by more than 30 percent. It includes UL-compliant integrated grounding features and has been load tested to UL and IEC standards.

Nclave separates the tracker assembly from the module assembly process to ease installation. The registered purlin allows the system to be pre-assembled on the tracker so modules can be installed with only a nut driver. Installers get rid of dedicated hardware for module installation (no more clips, bolts or rivets) as the U-bolt brackets secure module, purlin and clamp all together with just two nuts: a sandwich-like concept.

Software

The Nclave tracker controller is part of smart PV solution TrinaPro. The tracker controller is connected with the inverter in order to boost energy yield production: the optimized matching among components and the “Edge Computing” algorithm integration of TrinaPro can improve system stability with higher power generation.
The controller is empowered with a smart O&M system on a cloud platform that analyzes and processes data to optimize the system’s operation model and ensure the system runs smoothly and efficiently.

Solar FlexRack

solar flexrack

We featured this in more detail right here.

Tough, reliable, and cost-competitive, Solar FlexRack introduces their new, advanced TDP 2.0 Solar Tracker for commercial and utility-scale ground mount solar installations. The TDP 2.0 Tracker’s new BalanceTrac design offers more modules per row (up to 90), a rotational range of up to 110° and is compatible with 1,000V and 1,500V crystalline and thin film modules. This solution allows for shorter piles and lower per-unit fixed costs for balance of system savings. The combination of complete project support services and this next-generation technology enables solar power plants to increase energy yield while significantly reducing project risks. The results are cost savings across your solar project budget.

Soltec

soltec

Smartly designed structure offers slick wire management

Soltec, a manufacturer and supplier of single-axis solar trackers and related services, has installed its trackers all over the globe for more than a decade now, but the company says 2017 was its best year so far, showing over 200 percent revenue growth. The strategic move to the United States in 2015 has coincided with additional market share in 2017, amid market uncertainties and strong competition.

Structure

The DC Harness StringRunner wire management solution is a proprietary standardized component of Soltec’s SF7 tracker. It performs the functions of combining fused PV source circuits and cabling a homerun trunk circuit, all enclosed within the tracker torque tube, to a DC power switch for off-take. It eliminates the traditional fused combiner box and other cable management materials and controls the power output of eight trackers typically around 240 kW.

Soltec says the cost benefits come from the reduction of materials and related operations in manufacturing, power plant design, purchasing, supply and installation. The net cost benefit is a 30 to 35 percent reduction of installed first-cost compared to the traditional exposed installation of bundled copper wire circuits with a traditional combiner box. Installation labor is reduced by 75 percent thanks to less material and fewer manual operations including wire connections.

There are yield-gain benefits too with a reduction of IR cable losses, reliable low-resistance connections and factory dimensioned trunk cable sizing. The elimination of cable-management backside shading increases tracker compatibility with bifacial module technology.

Software

Comparative tracker yield-gain elements are both standard and site-dependent. Principal to site-dependence is asymmetric backtracking control to modify tracking position in the case that terrain irregularities cause inter-row shading in morning and afternoon hours, a case that is avoidable on flat terrain.

Soltec’s TeamTrack asymmetric backtracking control solution achieves both yield-gain and cost reduction benefits in tracker technology, achieving up to 6 percent yield-gain over the alternative of standard tracking on irregular terrain, and enabling cost reduction of earth-grading on contours and steps. The TeamTrack differs from other backtracking solutions that incorporate an auxiliary PV module and feedback response mechanisms that can add cost and vulnerability by instead performing the task straightforward with programmed operation and robust tracker position control.

The TeamTrack control algorithm works with NREL sun position data versus programmed constants of local irregularities (that never change) to calculate and execute backtracking movements and avoid inter-row shading. TeamTrack is part of comprehensive tracker positioning control that includes sensing and response to cloud cover, snow cover, standing water level and wind regime.

Schletter

schletter

New tracker product with self-locking mechanism now available

Although the U.S. arm of Schletter filed for bankruptcy, the Germany-based headquarters is still chugging along. At this year’s Intersolar Europe, Schletter Group presented its new tracking system.

Hardware

The core feature of the new Schletter tracker is that it combines the stability of a fixed mounting system with the additional yields of a tracking system. This is achieved by the drive concept: While most other tracking systems use hydraulic dampers or similar supporting structures to mitigate the vibrations and torsional forces caused by the wind, this Schletter system features a drive system with a self-locking mechanism. Each post locks as soon as the row has stopped moving. This newly-developed and soon to be patented drive system fully eliminates vibrations over the entire row which can be caused by wind. Therefore the system, while at rest, has the properties and durability of a fixed mounting system and is designed to withstand wind speeds of up to 161 mph. It thus completely avoids the dangerous galloping effect.

The second feature that stands out is its efficiency, achieved through its large wing-span and ground cover ratio. Each row can be up to 393-ft long and is driven by one centrally located motor. At 13 ft in width, each row is wide enough to hold either two panels oriented vertically or four horizontally, thus up to 574 sq yds of solar array can be installed per row and motor. This allows operators to make optimal use of the available land and a ground cover ratio of more than 50 percent can be achieved.

Software

The tracker has a rotational range of 60 degrees and is controlled through wireless technology, which completely obviates expensive wiring for both power supply and communication. The motor and the control systems are selfpowered by a dedicated PV panel in each row with a battery pack. To make O&M easier, mechanical connections between the rows have been deliberately avoided. This allows unhampered vehicle access between the rows, for instance during servicing and maintenance work.

GP JOULE

gp joule

GP JOULE’s single-axis tracker passes 20-year reliability test

The PHLEGON single-axis tracker from GP JOULE Canada Corp. passed a series of accelerated life-cycle tests conducted by the Southern Alberta Institute of Technology (SAIT) in Calgary. The Institute’s Green Building Technology Lab and Demonstration Centre confirmed PHLEGON’s long-term reliability within a wide range of environmental conditions and proved its performance in extreme northern climates. SAIT’s Accelerated Life Test Report shows that GP JOULE’s active tracking technology provides proven results in the Northern Canadian and U.S. markets where fixed-tilt PV has been dominant.

SAIT cycled PHLEGON’s mechanical components continuously 7,305 times over a 19-day period to simulate two decades of functionality. PHLEGON initially underwent the tests without environmental factors, and then went through another round that simulated extreme conditions including grit, freezing rain and sleet. The test included a deep freeze below -20C, confirming sensitive components function under extreme temperatures. “Freeze-thaw” tests mimicked the effects of spring and fall on the tracker, flooding moving parts with water before immediately exposing them to below-zero temperatures. The actuator, responsible for controlling and rotating the solar panels, completed both the mechanical and environmental rounds of testing — essentially 40 years without failure.

“GP JOULE wanted SAIT to test two things. First, how the system will operate in Alberta’s climate and second, what the cost of operating and maintaining the PHLEGON over a 20-year lifespan will be,” says Tom Jackman, SAIT’s principal investigator. “Our testing protocol introduced freezing conditions that were not considered in their original test plan, resulting in substantial ice buildup and additional weight. All components tested without failure.”

SunLink

SunLink Tracker

Updates strengthen the TechTrack design

SunLink’s single-axis tracker TechTrack is one of the quickest mounting systems to install, largely due to the simplicity of every component designed to eliminate inefficiencies and optimize energy production. The company is responding to the current environment, with customers looking for faster installation to keep up with their volume of solar projects and ultimately reduce field labor and associated installation costs, with some tweaks to its tracker design.

Hardware

One change is a new bearing and pivot design that arrives on site preassembled. The new and improved bearing design provides enough room in the stabilizer stroke (SunLink active damper) so that the system no longer needs to be rotated. Instead, the stabilizer mount position can be set from a measurement, saving substantial installation time. And with the preassembled bearings, installation crews can immediately install the component, saving valuable time in avoiding additional assembly of multiple parts in the field.

An additional design benefit enables drop-in torque tubes, eliminating the requirement for specialized jack equipment. SunLink also improved the durability of its pivot and bearing to withstand the rigors of construction crew handling on the project site.

“Another way we’re is reducing installation time is by revisiting our slew arm,” says Kate Trono, SVP of product, SunLink. “With a more streamlined design, we’ve eliminated the need for multiple or expensive custom tools and install kits that can sometimes add another $10,000 to a project. Our redesigned slew arm can be installed with standard tools, reducing the number of components, labor time and additional expenses.”

Feature enhancements like these may seem like small improvements, but the pay-off is big when you consider the reduction in labor, installation time and reducing your overall solar project cost.

— Solar Builder magazine

Soltec 2x solar tracker testing reveals notable bifacial gains

SF7 Soltec Bluxome party

As we reported a few weeks ago, Soltec, a manufacturer and supplier of single-axis solar trackers, is performing field tests at BiTEC, world’s first evaluation center specialized in bifacial trackers. Among those tests, the company is comparing bifacial production of 1x configuration solar trackers versus Soltec’s SF7 Bifacial, a 2x configuration tracker.

Early results

Soltec’s SF7 trackers have a standard height of 7.71 ft (2.35 m), while 1x-configuration trackers have a height of 4.43 ft (1.35 m). Preliminary electric performance measures over bifacial modules reveal a short-circuit current difference of over 2.3 percent between 1x and 2x trackers, meaning that height has a significant influence over the energy output of bifacial panels. The capture of diffuse irradiance below and around the tracker is increased with height, while the shadow casted on the ground is softened.

RELATED: Podcast: How NEXTracker ‘decapitated the duck’ with its new solar-plus-storage tracker design

In addition, SF7 includes an intentional gap between modules at the torque tube location that avoids shadowing on the backside of the module. With 1x trackers, on the contrary, the torque tube casts a shadow regardless of whether it has a round shape or quadrangular. Preliminary measurements have shown that up to 38 percent of reflected light does not reach the center of the bifacial modules compared to the edge due to the torque tube shadow of the 1x configuration.

BiTEC will be officially inaugurated on July 9 in Livermore, California. This center counts on the collaboration of the main of bifacial modules manufacturers and American organizations specialized in renewable energy such as NREL or RETC.

— Solar Builder magazine