PV Pointer: How to optimize PV system structural design for environmental hazards

snow-covered solar panels

According to a recent study by SolarPower Europe, new solar photovoltaic (PV) capacity installed worldwide in 2016 reached more than 76 gigawatts. This was largely due to dramatic growth led by the United States and China, with both countries almost doubling the amount of solar added from 2015. Globally there is now more than 305 GW of solar capacity, and with the increase of solar projects around the world, different climates, topography and other geographic considerations are making design for the environment increasingly important to ensure the integrity of the system over its lifetime.

PV plants are subject to a multitude of threats from the physical environment over the span of their lifetime. These threats must be taken into consideration during structural design in order to mitigate the risk to the system. With PV plants now being installed all over the world, the applicable risks will vary greatly depending on the geographic location. Therefore, the design of each plant must be thoroughly evaluated for its unique set of potential environmental hazards.

Environmental Loads

The first decision to make in determining the environmental loads on a plant is to identify the appropriate risk category for the plant. Building codes around the world use this categorization to determine the probability of occurrence of the design loads, or in other words, how extreme the design loads are. More critical solar project facilities can be designed for a higher risk category, and therefore, for loads with a lower probability of occurrence and a larger magnitude. For example, a rooftop system at a hospital that is required to remain operational after a design level event will be designed to higher loading conditions than a utility-scale facility behind a fence that is not supplying critical power to the grid.

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Evaluating Different Types of Environmental Loads

When designing a PV plant, the environmental loads that usually first come to mind are wind and snow loads. However, certain architectures or geographical locations will necessitate consideration of seismic, ice or thermal loads as well.

Due to the large surface area and low weight of PV arrays, wind loads are often the most critical environmental forces. Consideration must be taken for both the potential wind magnitude at the site as well as surrounding topographic features that may amplify or weaken the wind as it approaches the PV plant. In many designs, wind tunnel test data is used to most accurately predict the resulting loads on a particular architecture. More accurate prediction of the wind loads allows for optimized structures that still meet the desired levels of performance and reliability.

Snow is another common critical design load on many PV plants. Rooftop and fixed-tilt ground-mounted systems are particularly vulnerable due to the relatively shallow slope of the modules. In addition to the snow’s weight on the tables, the designer must consider snow accumulation between tables, drifting and the potential need for an elevated system to allow for snow shedding. Tracker systems allow for some mitigation of the snow loads by tracking to maximum tilt to shed a large portion of the snow.

Seismic loads are less discussed in the solar industry, but they can be a significant concern in locations with high snow load and moderate to high seismic risk. Since the snow weight is considered part of the seismic mass, the resulting loads can be significant as snow accumulates (force = mass x acceleration). Many PV plants use wide flange post sections which have significantly lower strengths in one direction than the other. As earthquakes act in all directions, this is a vulnerability that needs to be expressly accounted for in design.

Ice, temperature and flooding are additional environmental risks that need to be examined for PV plants in some locations. Ice can add weight to a table and can be a concern for freezing up moving parts. Temperature becomes a concern with systems like trackers where there are long continuous members such as torque tubes. Thermal swings such as those found in desert climates can cause enough expansion or contraction of the steel along a row to result in non-trivial forces on the system. Finally, systems in floodplains must take the expected flood levels into account in the architecture and evaluate whether to design an elevated system.

Designing for these potential load effects helps to mitigate the risk to a PV plant from environmental hazards, thus increasing the overall reliability of the system throughout its lifetime and providing better value to the plant owner.

Lauren Busby Ahsler is a structural engineering manager at SunLink. She works on project engineering as well as tracker product development for SunLink.

— Solar Builder magazine

SunLink reports 150 percent growth in total MW shipped in 2017

sunlink racking

SunLink Corp. surpassed more than two gigawatts (GW) of total installed solar projects by the end of 2017. With more than 150 percent year-over-year growth in total megawatts shipped, SunLink increased its fixed-tilt market share by over 4x amid an overall industry decline in the utility ground mount market. The company grew TechTrack, its most technologically advanced solution, by 5x.

“SunLink continued to demonstrate its engineering prowess by taking on some of the industry’s most challenging solar projects in 2017. Customers continued to depend on SunLink to deliver the industry’s most flexible and dependable fixed-tilt mounting solution backed by our deep engineering expertise,” said Michael Maulick, president and CEO of SunLink. “We are especially pleased with the continued traction we’re making in the tracker market. It’s clear that our most innovative customers are responding positively to our intelligent tracker for optimal power density, energy generation and measurable reductions in total project costs.”

During 2017, SunLink’s GeoPro showed significant gains in new geographic markets. SunLink recorded 2,400 percent growth in fixed-tilt projects installed in the Midwest, stimulated by large project deployments in high-growth solar states such as Minnesota. Projects in the Southeast region also grew by 142 percent with local utilities expanding their clean energy mix in states such as Florida and Georgia. The Southeast was particularly challenging last year due to numerous hurricanes, high winds and other environmental factors that made GeoPro the go-to solution.

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Engineered to withstand high wind speeds of more than 150 mph, SunLink’s GeoPro installations weathered the most challenging environmental conditions this past hurricane season in high impact areas such as Florida.

On the tracker front, SunLink’s TechTrack continued to make strides with a five-fold increase in installations over the previous year. In 2017, select sites had the capability to monitor and control tracker performance via Vertex, SunLink’s tracker intelligence platform, providing real-time smart data captured by IoT sensors. For the first time, SunLink was able to show geospatial tracker performance data at the granularity of an individual row.

What’s coming in 2018

In 2018, SunLink will continue to focus on implementing the latest cloud and IoT technologies to make increasingly more intelligent trackers. New features focused on providing additional data analytics as well as firmware improvements to enable data capture from various sources will provide customers with even greater ability to maximize energy production while lowering installation, O&M costs and return-on-investment.

— Solar Builder magazine

Close the Gap: How to revive lagging large-scale PV project performance

Alencon’s SPOT X2 DC-to-DC optimizer

Alencon’s SPOT X2 DC-to-DC optimizer can boost utility-scale PV plant performance.

A completed PV project is like a splashy free agent sports signing. Everyone is all pumped up at the ribbon cutting or press conference, but if it underperforms and misses expectations, that goodwill is gone. Live up to that contract or get booed.

In a world where new utility-scale projects might slow down (a possible understatement if tariffs are placed on module and cell imports), optimizing current portfolios is crucial, not just for each project to hit its targets, but to continue to prove solar as a worthy investment and distributed resource.

Closing Performance Gaps

With more than a decade of hardcore O&M industry experience, there is a greater reservoir of institutional knowledge both out in the field and in plant operation management. For example, MaxGen is a U.S.-centric O&M provider focused on utility and C&I sites that manages a large team of licensed, professional technicians throughout the country, hitting about 5,000 different sites a year for corrective (CM) and preventive maintenance (PM).

As part of its business model, the company will take over portfolios of assets to monitor — some of which are underperforming. According to Mark McLanahan, CEO of MaxGen, assets are usually underperforming because of one or more of these reasons:

  1. The site is not in good physical condition because of poor vegetation management or erosion or general site management. Consider this a reminder to keep O&M in mind when designing a project because it is often the largest expense over the life of the project. “Handling stuff like vegetation management and module washing can be the biggest expense by far if you’re not careful,” McLanahan says.
  2. Poor PM records, which often means PM hasn’t been done. “That’s a problem because you have to perform PM to maintain warranties of inverters, combiners and modules,” McLanahan says. “We have seen many cases where service to date is either not verified or there’s no record.”
    This is where PowerFactors comes in handy. PowerFactors is an energy operations management software platform that MaxGen has been using since 2016 to integrate all the monitoring, alarm management, work order creation and management, dispatch and reporting for all the operations, and preventive and corrective maintenance tasks in its scope of work with its customers. Also, contract requirements can be programmed into the system. For example, Power Purchase Agreements in California often require instant notification of large drops in capacity and failure to do this will incur penalties. Auto-notifications can be routed to the right places in those events with the right rules plugged into the software. This enables fewer operators to manage more projects with greater complexity.
  3. The site data acquisition system simply hasn’t been mapped properly, which undermines the data quality of the entire project and leads to maintenance misdirection. There’s an outage on inverter A; a dispatched technician heads to inverter B because it’s mapped as inverter A. The issue isn’t discovered, and so on. McLanahan estimates that MaxGen encounters this in 20 to 30 percent of the underperforming sites it takes over.
    “It’s a data quality issue,” he says. “With solar, you have to study performance at the low level, not just the revenue meter, to make decisions on performance. You have to look at inverters or combiners or at the main circuit. If the mapping is no good, you’re wasting time.”

Once the site is remapped and the PM is up to date, annual maintenance and CM plans are put in place to build it back to baseline performance using better data. From there, more advanced decisions can be made. Data can be studied for factors such as ground coverage ratios, tracker angles, performance anomalies at the combiner level and similarity-based modeling to help identify additional opportunities. MaxGen has boosted a number of utility-scale projects 2 to 5 percent on the performance side using this systematic process.

“With consistency, you’ll see 1 to 3 percent improvement right off the bat just with low-hanging fruit,” McLanahan says. “Compare the combiners on a relative basis on performance and just look at last month. That sets the corrective maintenance for the next week. Once you have accomplished all the PM tasks, have good data access and capture the low hanging fruit, you can move up the lost energy priority list and tackle the things that are above the baseline to increase production and revenue even further.”

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Retrofitting or Repowering?

Traditionally, the two options for a lagging PV site to hit its expected performance target are: 1) boosting its actuals, or 2) lowering the expected numbers.

“Once a project has been reviewed to ensure all the basics are correct, we can focus on boosting output to outperform proforma expectations. Part of this process sometimes includes resetting the baseline based on correcting performance assumptions made before the plant was built,” McLanahan says.

Obviously no one wants the latter, but overestimates happen frequently during the high-stakes, quick turn-time bidding process via incorrect assumptions regarding soiling, degradation, line losses, etc.

But, what if there was a way to still overachieve from the original estimates? This is the proposition presented by large-scale, DC-to-DC optimizers just now coming onto the market as part of a retrofitting strategy. The Alencon SPOT X2 is one such optimizer that has been recast in a manner to make it easier to minimize the soft costs — such as labor and ancillary installation materials — associated with PV retrofits. Minimizing installation costs is key to achieving the highest rate of return on PV retrofits, and retrofitting a PV plant with Alencon’s SPOT can significantly increase PV yield by introducing more granular MPPT while at the same time improving safety and decreasing on-going O&M costs.

“With a number of PV assets now changing hands as PV plants get older and PV fleets get consolidated, we are seeing a great deal of interest in retrofitting PV plants to improve energy yield. The SPOT X2 makes performing larger commercial and industrial or utility scale PV retrofits much easier than ever before,” says Hanan Fishman, president of Alencon Systems.

Now, retrofitting a large-scale PV system with new equipment is a tough sell because the profit margins are thinner and ROI is tighter than new construction (plus the downtime that must be factored in), but going this route with an experienced team could prove valuable. Energy and electrical systems specialty firm ProtoGen, for example, has executed a number of retrofit projects and incorporated Alencon’s SPOT DC optimizer at the string level to minimize those retrofit costs because it’s as close to a plug-and-play PV retrofit solution as possible.

“The key to pulling off a PV retrofit in a cost and time effective manner is to think in terms of 80 percent planning and 20 percent execution,” Fishman says. “In our experience, if you can maintain that proportionality, you should be able to set a similar target for your percentage of hard costs to soft costs.

Here’s a checklist Alencon suggests using if you are considering a retrofit for a large-scale PV project:

  1. How much is the equipment going to cost?
  2. Have I considered all the elements of ROI that go into the project including production incentives and potential tax credits like accelerated depreciation?
  3. What sort of engineering analysis will I need for the project? Structural? Electrical? Anything else?
  4. Will the work require a permit? If so, who is the AHJ? What do they need to approve the project (i.e. stamped and sealed drawings or just a statement of work)?
  5. What sort of certifications will be needed for the equipment being installed (i.e. UL or NEC)?

Bottom Line

The true bottom line in PV system performance, from initial projections to 30 years in the future, is customer service. People need to make the correct assumptions, perform all O&M tasks correctly and use data analysis to their advantage while being as proactive as possible. As more data is gathered and algorithms are perfected, “trend events” will be the next frontier for improving performance.

“These don’t show up as a discrete one-time energy loss but as small events that happen continuously over time, and if you don’t look for them you won’t see them,” McLanahan says. So, maybe one inverter is coming on and offline in mere seconds. “If you look at the curve, you won’t see it, but if you look at the trend, there’s something wrong with that inverter, and it will likely break down at some point.”

That curve is a nice visual to end on. Just plan to stay ahead of it.


 

Speaking of data…

Chris Crowell and Kate Trono, VP of Products for SunLink

Craving some more nerdy solar data talk? You’ll want to check out our new podcast — Solar Builder Buzz — in which we grab a beer with people smarter than us to discuss the solar industry. In Episode 2, we sit down with Kate Trono, VP of Products for SunLink, and pick her brain on the value of data in the solar industry and just where the industry is going (and should be going) from here. We maybe also discuss Sci-Fi.

Listen to the pocast here.


 

Take a quick peek

Measure launched new turnkey solutions for solar facility owners

Measure launched new turnkey solutions for solar facility owners, asset managers and O&M contractors that include drone-based site overview and maintenance, site shading and terrain analysis, thermal inverter scans, tracker misalignment detection and vegetation management. On a site generating 21 MW, for example, Measure can complete an inspection in seven hours instead of weeks, freeing employees and contractors for higher-value activities while also lowering inspection costs. The lower cost also makes it possible to perform more frequent inspections that can detect problems in a timely manner.

Maximum revenue capture for larger plants may not be inspected in a single visit and potentially leave some issues or faults unidentified. Measure’s launch customer was able to avoid a potential revenue loss through an inspection that discovered over 200 malfunctioning panels on a new solar farm.

— Solar Builder magazine

PV Pointer: Why mass-customized solutions win in utility-scale solar

SunLink

SunLink started designing solar mounting systems in 2004 when the concept of commercial rooftop solar was novel. The first systems were custom designed for the particular application because everything was new. Needless to say these first arrays were inordinately expensive by today’s standards, but the success of those installations helped pave the way for a booming distributed energy economy.

The early rooftop systems were engineered as a single structure where every solar module was linked together, efficiently distributing wind loads. In fact, SunLink’s name was inspired by the structural links holding the system together, which is how our Precision system still works.

Solar, however, is relentlessly cost competitive. Smaller installations can’t absorb the soft cost of custom engineering. At the same time, no two solar projects are the same, which on the surface mandates custom engineering. Mass customization can make customization at scale cost effective.

What is mass customization?

I often use Legos to describe mass customization. The Legos are standard, but you can configure the blocks to build whatever you want. Here are a few examples of this approach working in utility solar.

Take a single-axis tracker. The tracker needs to be engineered for a wide range of environmental conditions and any row length (since string length varies by project and space constraints require partial rows). This could lead to countless combinations of torque tube lengths and thicknesses. In a mass customized solution, a half dozen or so standard torque tubes are configured to meet the unique needs of the project. Limiting the number of parts greatly increases supply chain and engineering efficiency.

Similarly, the number of foundations can be increased to boost load capacity without designing a new part. Cleverly designed module mounting hardware accommodates the most common PV modules with no changes. The unique nature of solar sites is designed into products so that manufacturers can respond to opportunities quickly, cost-effectively, and with a fully-vetted solution. SunLink’s TechTrack dynamic stabilization feature is an example, which is a new tool for efficiently configuring resistance to wind loads.

Innovative manufacturers are moving beyond traditional racking and into software and services. In doing so the focus shifts from catering to the unique needs of the project to the unique needs of the customer, yet the benefits of mass customization remain.

PV Pointers: How dynamic systems increase the value of a solar project

As an example, SunLink recently launched product packages to complement its mounting systems. What differentiates the product packages is that they integrate hardware, software and services to serve a customer’s specific needs. The TechTrack Standard Package, Cold Weather Package and Pro Package allow for standardized solutions for common needs while giving the customer choice in what to pay for.

The product packages are analogous to the options available when buying a car. Paint color, drivetrain and interior options cater to different customers, but all are built from the base model car.

Mass customization also guides the development of software. Different modules are implemented depending on whether the user is an O&M provider, an EPC or a developer. The best systems are highly flexible with provisions to connect to a wide variety of data monitoring systems, device types, SCADA implementations, etc., because inverters, trackers, storage systems and other intelligent hardware are constantly changing, as are the requirements of the utility and the ISO.

Modern communication protocols are critical to strong yet flexible systems. Modbus, developed in the late ’70s and early ’80s, is still the most common protocol for energy devices and SCADA systems. It should be no surprise, however, that a 30-year-old protocol isn’t up to the task of two-way communication between thousands of modern intelligent devices and numerous software services. Worse still, many software packages have limited ability to communicate with other applications. If you want to look at the performance of a solar portfolio but have several data monitoring systems, you may be forced to print reports from each system and manually input the data into a spreadsheet. This is a failure of technology.

In tech, RESTful API enables efficient, flexible communication between devices and services and allows developers to build applications leveraging other applications. We’re now seeing APIs used in inverters, trackers, data monitoring systems and initiatives like Orange Button for bankability data to unlock new value in the energy industry.

Mass-customized solutions win in utility solar because they drive down cost while accommodating the needs of the project and customer. The next time you are looking at the design of a solar plant, or anything else for that matter, I encourage you to consider what’s led the products to be standardized, customized or mass customized.

As Director of Project Management, Patrick Keelin helps define SunLink’s next generation of products and services. His focus includes dynamic tracker design, IoT and the role technology plays in R&D, design and long-term solar project economics.

— Solar Builder magazine

SunLink is the top energy company on Deloitte list of fastest growing tech companies

SunLink

The Deloitte Technology Fast 500, a ranking of the 500 fastest growing technology, media, telecommunications, life sciences and energy tech companies in North America, listed SunLink Corp. as the fastest growing energy technology company. SunLink grew 226 percent during the period identified.

“The Deloitte 2017 North America Technology Fast 500 winners underscore the impact of technological innovation and world class customer service in driving growth, in a fiercely competitive environment,” said Sandra Shirai, vice chairman, Deloitte Consulting LLP and U.S. technology, media and telecommunications leader. “These companies are on the cutting edge and are transforming the way we do business. We extend our sincere congratulations to all the winners for achieving remarkable growth while delivering new services and experiences for their customers.”

“It’s gratifying to see the market responding to the vision we set three years ago to transform and move the renewables and energy tech sector forward,” said Michael Maulick, SunLink president and chief executive officer. “Our evolution from a respected engineering powerhouse to a full-scope solar energy solutions company now utilizes the latest in IoT, big data and hybrid cloud technology to enhance the value of our clients’ projects. We’re proud to join the other innovators on this distinguished list who are thinking bigger and bolder to make a profound impact on their respective industries.”

SunLink previously ranked fifth as the Technology Fast 500 Energy Tech award winner for 2016. Overall, 2017 Technology Fast 500 companies achieved revenue growth ranging from 135 percent to 59,093 percent from 2013 to 2016, with a median growth of 380 percent.

— Solar Builder magazine