Engineers discuss field test of PanelClaw’s new Panda Bear Ground Mount

Panel claw solar mounting

Preventing a Solar Slide

As solar energy becomes more popular in the marketplace, the technology continues to improve and become more cost effective. The rapid pace of development and highly competitive environment has incentivized solar companies to better understand how their products interact with the surrounding environment.

As an example, PanelClaw Inc. specializes in the development of commercial flat-roof and ballasted ground-mount solar equipment in North America. PanelClaw contacted Terracon to inquire about development of a full-scale field load testing program to evaluate the sliding resistance of its Panda Bear Ground Mount System.

The system is a ballasted mounting solution that is ideal for landfills, brownfields sites and other installations in which the ground cannot be penetrated. The structure sits on top of the ground with a mount that consists of a ballast pan, a post and a pre-assembled bracket that supports the solar panels.

The resistance to sliding for the ballast pans depends on several elements, including:

■ test pad material properties,
■ ballast pan configuration,
■ normal load applied to the ballast pan,
■ levelness of the test pad surface,
■ slope of the supporting surface and other factors.

PanelClaw provided Terracon with several ballast pans, which were modified to facilitate the sliding resistance testing, accomplished by attaching a load cell to a ballast pan, and then pulling the ballast pan horizontally using a hand crank winch, fastened to a metal beam anchored into the ground. The sliding distance was then measured along with corresponding loads required to force the ballast pans to slide.

Terracon worked closely with a local earthwork contractor that provided a test location, several test pad materials and initial preparation of the test pad surfaces.  Terracon performed the sliding resistance testing on test pads constructed of native dense grade (pit run) materials, 3/4-in. crushed rock, firm cohesive soils consisting of sandy lean clay and asphalt pavement.

RELATED: PV Pointers: Tips for mounting PV on a low-slope roof 

Before the sliding resistance testing process began, test pad materials were assessed for materials properties, compaction characteristics and assessed in the field following pad preparation for percent compaction and water content.

Terracon also worked closely with PanelClaw to fully understand how its initial analysis was performed when determining the contribution of sliding resistance to the ballast pan foundation capacities. Methods for applying factors of safety were also determined and added to this process.

Based on discussions with the client, Terracon elected to quantify the resistance to sliding for the ballast pans constructed on various subgrade materials using an alpha factor (a) for each of the test scenarios. The factor places a numerical value for quantifying the resistance of sliding between two different materials. For the purposes of our analysis, we defined the alpha factor as the ratio between the total normal force (including the ballast pan, paver blocks and sandbags) to the horizontal force applied to the ballast pan. PanelClaw indicated it would utilize the alpha factors calculated for the test scenarios at a total movement of 1/2 in.

There are numerous resources documenting frictional resistance between similar materials such as sheet pile design manuals, but Terracon was specifically requested to determine the sliding resistance for the actual ballast pans on various subgrade materials. The testing would account for the rivets penetrating the base of the ballast pans, openings manufactured in the base of the ballast pans and other considerations that a full-scale field load test would provide as compared to recreating the set up in a laboratory.

To provide additional resistance to sliding, PanelClaw uses shear pins on several of its products.  These shear pins are driven into the ground through pre-manufactured holes drilled through the ballast pans. A portion of the field load testing program was performed to obtain data regarding the contribution of shear pins to sliding resistance. Our testing provided PanelClaw with data that could be used for various subgrade materials when assigning additional capacity against sliding for ballast pans used with shear pins.

In the end, Terracon was able to work closely with PanelClaw and develop geotechnical parameters that were representative of its specific product. Terracon has also completed a similar testing program for a roof top solar system for PanelClaw involving various roofing materials at several locations across the United States.

Eric D. Bernhardt and James Cherry are in the geotech department at Terracon’s Fort Collins, Colo., office.

— Solar Builder magazine

PV Pointers: How to future-proof PV systems with a storage-ready inverter

You don’t need to install a battery (yet) to give solar customers a next-gen solar-plus-storage system.

Your customer wants reassurance

Solar-plus-storage is finally ready for mainstream adoption, thanks to technology enhancements in DC-coupled inverters and continued cost reductions in smart battery technology. Batteries with grid-tied PV will soon be the standard offering as customers recognize the benefits of storing local behind-the-meter energy. According to Bloomberg New Energy Finance, lithium-based smart batteries are poised to follow the same cost reduction curve as PV modules, crossing the $200/kWh threshold in the next several years.

Pika Energy“We are seeing strong demand for storage-ready grid-tied photovoltaic systems,” says Phil Coupe of ReVision Energy, a solar installer in northern New England. “Today’s battery options remind me of where PV was five to 10 years ago, when the technology was pretty good but retail pricing was out of reach for all but the wealthiest and most progressive consumers.”

ReVision Energy has been installing the Pika Energy Island inverter for clients in the Northeast to prepare them for the day when batteries are more cost-competitive.

The demand for these batteries will grow proportionately with the economic use cases for solar-plus-storage. Already, an increasing number of U.S. markets are introducing time-of-use billing, eliminating or reducing net energy metering, billing residential customers based on periods of peak usage, or, in parts of Hawaii, disallowing new PV permits entirely.

Meanwhile, you have customers dragging their feet with proposals for carefully designed and economically modeled PV installations. And the more they read about solar-hostile policies, the more they may worry that their state could be the next Nevada.

How do you reassure a customer with misgivings about the future of solar-friendly politics in his or her utility region? The answer lies in the inverter you offer.

You can learn all about this and more during the upcoming Solar Builder webinar “Future-ready solar Installations with the Pika Energy Island.” Register here.

Your customer wants a secure investment

By offering a hybrid PV inverter that can operate as a grid-tied “conventional” system, but which has built-in islanding and the capability of directly integrating a smart battery later, you’re giving your customer the reassurance of a future-proof of the investment.

“More and more, people are recognizing that storage costs are beginning to decline, and they want their solar energy system to be able to integrate batteries when the price point justifies the investment,” Coupe notes.
Sometimes, having that reassurance is all a customer needs to move forward with their wise decision to power their home with solar. And for you, that means your solar installations can continue, unimpeded by local policy rhetoric.

Your customer wants options

In addition to reassurance to offset customers’ doubts in uncertain policy markets, hybrid inverters with the innate ability to switch between grid-tied and islanding power can offer customers flexible operational modes for various states of use. For example, customers with such inverters can use them for grid-tied net metering today and have the option to add a battery tomorrow for clean backup power.

ReVision Energy’s customers will use their battery-integrated grid-tied systems for clean backup power during winter grid outages, and, if solar policy grows hostile toward net metering, those customers have a simple step toward recovering their investment.

By offering hybrid islanding inverters that feature the option of adding directly-coupled batteries in the future, installers like ReVision Energy are providing a differentiated option that protects the customer’s clean energy investment, helping solar buyers to feel smart and secure in their decision.

Chip Means is director of sales development at Pika Energy.

— Solar Builder magazine

How to optimize performance and profit through O&M monitoring

As the solar industry matures well past the early adopter stages, smart asset management and operations and maintenance (O&M) practices have increasingly become the focus of savvy solar plant owners and investors. Optimizing uptime has now become a critical foundation of ROI, and one of the keys to achieving optimized plant performance is a comprehensive data acquisition and monitoring system backed by an experienced O&M monitoring team.

Historically, O&M was often added to engineering, procurement and construction (EPC) contracts to sweeten the deal. Monitoring was heavily used during the commissioning and performance guarantee period but was not often maintained thereafter. Only egregious faults were captured, if at all, and failing but not yet dead components would usually be overlooked.

How times have changed.  Numerous tech advancements have increased the capability and granularity of O&M monitoring, including:

■ Device-level communication and alarms.
■ Calibration/configuration algorithms to ensure equipment is reporting accurately.
■ Real-time multiple model comparisons to actual performance (financial, operational, historical).
■ Application programming interface (API) tie-ins to computerized maintenance management systems (CMMS) for automated work-order generation.
■ Camera/sensor feedback for soiling, vegetation, snow and similar issues.
■ The use of multiple sensors and cameras for calibration verification and site security.

In today’s solar O&M marketplace, data drives data. That is, the more actionable data you can extract from systems, the more you learn about the “real-world” behavior of those systems, and the more proactive you can be in maintaining systems at their maximum performance.

Of course, an equally important part of the equation is to have a skilled team that can properly configure alerts and alarms, monitor system data, identify how real-world incidents impact performance and understand the balance between uptime and ROI.

The goal today is to accurately diagnose the problem and determine what equipment or parts are needed long before a technician arrives onsite. This capability can decrease system downtime, reduce the number of tech visits and increase the owner’s uptime and ROI.

There are many specific benefits that smart O&M monitoring backed by an expert O&M team can bring to system owners. For example:

■ Panel washing and vegetation abatement can be scheduled more timely.
■ Contractor compliance can be scrutinized more effectively, helping to answer what is for some a critical question: Did the subcontractor do what they said they would do?
■ Programmed alerts for the CMMS can generate automated work orders and make dispatch efforts more efficient.
As more solar plants enter the secondary market, the benefits garnered from ongoing, comprehensive monitoring takes on added value of its own. If the current asset owner can show prospective buyers in-depth operational and performance records, as well as real-time data metrics and modeled expectations based on real-world conditions, a successful sale is much more likely.

Think of it this way, are you more inclined to buy a used car from an owner who can provide a complete history of maintenance and work records or one whose operating and maintenance history is a mystery?
So, what does the future of solar O&M monitoring hold? Since the industry is driving toward more data and greater granularity, we can expect to see the development of further refined algorithms that can identify ever-more nuanced issues. We can expect to see improved real-time control and forecasting models, remote fault diagnostic and reset capabilities, RMA generation without the need for a field tech visit, greater CMMS and inventory management tie-in and more software automation built around prognostic/predictive tools.

Yet, despite the increasing levels of data finiteness, at the end of the day, there will also be an equally strong need for experienced O&M experts, since the best monitoring platforms truly are only as good as the people who set it up and are capable of performing the operations.

Bay4 Energy is an independent renewable energy service provider, with more than 30 years of asset performance and portfolio management experience.

— Solar Builder magazine

1,500-volt systems to trend in 2017: Here’s what you need to know


SolarBOS combiner

Large-scale solar projects are heading into yet another sea change: the 1,500-volt PV system (Vdc). The idea behind the voltage increase is the same now as it was during the move from 600 volts to 1,000 volts — further reduce installation costs and increase profitability by reducing the number of inverters and other BOS components required.

“But there is a difference this time,” notes TJ Kanczuzewski, president of Inovateus Solar located in South Bend, Ind. As a solar EPC and distributor, Inovateus Solar was one of the first solar companies to be introduced to 1,000 Vdc from 600 Vdc and has seen these types of technology transitions before. “Today’s 1,500 Vdc are more sophisticated systems than we’ve ever had before.”

Advanced Intelligence

Kanczuzewski relays his experience designing projects with Schneider Electric’s new Conext SmartGen 1,500-Vdc inverters, which can record and store operations and service history, as well as upload all of this data and self-diagnostics to the cloud.

“The Conext system also offers 30-year service life and a minimum of 15 years before the first major service,” he says. “So, this time, these systems are very intelligent as well as powerful.”

And this is just the beginning as all of your favorite inverter brands start to launch and ramp up production on their product lines. At the 2016 Solar Power International, Yaskawa-Solectria Solar, one of the most widely installed brands, pre-announced its 1,500-Vdc, utility-scale string inverter, the SLX 1500 line. These inverters will be available at various power levels and AC voltages, but adding in its Wireless Mesh network eliminates the need for communication wiring, reducing communications and BOS cost.

“In addition, the Wireless Mesh proves to simplify commissioning, has robust/secure networking, advanced grid functionality, superior asset management and improves response time,” says Natalie Holtgrefe, senior marketing manager for Yaskawa-Solectria Solar.

RELATED: How optimizers bridge the gap to 1,500-volt PV systems 

But is it safe?

Regardless of ancillary benefits, being an early adopter to such a step up in voltage carries risk.
“There is a lack of understanding in the industry concerning incident energy and arc flash risk. This is true for 1,000-Vdc systems and clearly becomes more important in 1,500-Vdc systems,” says SolarBOS CTO Coel Schumacher.

BOS equipment provides overcurrent protection and disconnecting means used for system operation and maintenance and must be accessible to personnel. Due to the nature of photovoltaic installations, there are a significant number of sources that aggregate in BOS equipment, and a series of devices are typically used to achieve this.

“While it is possible to isolate these devices, the long runs between them make it inconvenient as well as difficult to isolate a device by a means within line of sight,” Schumacher continues. “If the device is not completely isolated, portions of the equipment remain energized. This poses an arc flash risk and yet there is no consensus on how to evaluate that risk, much less how much risk there truly is.”

SolarBOS offers BOS equipment including combiners and recombiners with various options for circuit count, current ratings, OCPD and disconnecting means. On the AC side of the inverter, SolarBOS offers configurable switchgear that is necessary for string inverter implementation.

Yaskawa-Solectria Solar’s DISCOM 1500 string combiners offer various options that make design and safety easier for installers, including MC4/H4 connectorized wire whips, compression lug studs and heavy gauge bus bars.

Eaton, which has extensive experience in managing DC circuits in other high voltage DC environments such as battery storage systems, rail systems and steel mills, reminds us that the call for 1,500-volt safety extends to the equipment, too.

“At 1,500 Vdc, there is substantially higher voltage stress on the solar modules, which can make modules more susceptible to potential induced degradation (PID),” says John Vernacchia, segment manager for renewable energy at Eaton. “Only a few years ago, PID had a disastrous effect on many solar projects. As developers look at using this higher voltage technology, caution should be taken to use PID-resilient solar modules and to use grounded arrays. Past experience has shown that floating arrays are significantly more sensitive to PID due to the negative voltage bias placed on the solar modules.”

Eaton’s 1,500-Vdc inverters will employ a new proprietary DC design concept that replaces manual DC disconnects with DC contactors to improve both control and enhance operator safety.

Eaton’s 1,500-Vdc inverters will employ a new proprietary DC design concept that replaces manual DC disconnects with DC contactors to improve both control and enhance operator safety.

Reducing BOS costs

As dazzling as the new capabilities are, the potential BOS cost reductions are just as enticing for an industry constantly having to prove its economic worth. GTM Research estimates that overall project costs can be reduced by three to five percent by moving to 1,500-Vdc systems, realized mainly through reduced installation time and fewer components.

SolarBOS’s Schumacher says the 1,500-Vdc projects they’ve done are acting as flagship installations to prove the benefits of higher voltage systems. In general, he says, BOS equipment becomes more energy dense and cost effective at 1,500 Vdc.

“In addition 1,500-Vdc systems lend themselves to higher AC voltages [600 Vac or more], which helps to reduce AC conductor and switchgear cost,” Schumacher says.

Eaton developed its Crouse-Hinds series DC collection system, Sunnector, to reduce costs and installation time in these utility-scale solar projects. This system can help reduce labor and material costs by 15 percent on average, according to Vernacchia, in 5 MW and larger-scale, grid-tied solar projects that use fixed-tilt ground-mount racking designs.

A key here is using aluminum for long-distance runs, but still incorporating copper connections to the PV modules. This way contractors are able to use standard copper connectivity and tools, while project owners are able to reduce costs by taking advantage of lower cost aluminum wire.

Yaskawa-Solectria’s SLX 1500 line and Wireless Mesh network eliminates the need for communication wiring, reducing communications and BOS cost.

Yaskawa-Solectria’s SLX 1500 line and Wireless Mesh network eliminates the need for communication wiring, reducing communications and BOS cost.

So, where are we?

Holtgrefe says Yaskawa-Solectria Solar is seeing considerable demand for 1,500 Vdc in utility-scale projects. However, 95 percent of demand in the C&I space is still for 1,000-Vdc products. Her expectation is for the C&I space to move toward 1,500-Vdc systems at a slower rate of adoption than utility-scale.

“We’ll need to educate our customers about this new offering and help them understand the value,” Kanczuzewski says. “Code standards will need to be revised in some areas, and different utilities may have their own guidelines, so installers will need to make sure that 1,500 Vdc is compliant or show how 1,500 Vdc is becoming the new standard. We can always go back to 1,000-Vdc systems if our customers require it, but we hope we’ll be able to transition quickly.

“Inovateus went through the same type of customer education and standards review with the transition to 1,000 Vdc, but we expect that 1,500 Vdc will overcome any hurdles and become the norm within the next two to three years.”

Chris Crowell is the managing editor of Solar Builder.

— Solar Builder magazine

Q&A: Seaward talks solar data trends and its cool new gizmo


Solar Builder: What is the most important data analytics trend or innovation that installers should be paying attention to?

Mark Barron of Seaward Solar: Along with ensuring electrical safety on both new and existing installations, it’s also important to measure the actual system performance. Customers invest considerable funds into solar PV systems, and they need to have the confidence that the system is performing at its optimum capabilities.

Larger utility and commercial projects have always taken a more sophisticated view of effective operations and maintenance (O&M) activities to ensure that long-term performance levels associated with financial modeling and initial project investment decisions are maintained.

Now, residential solar installers are also increasingly adopting O&M strategies to protect asset values, meet warranty terms for new projects and monitor component performance at the end of existing warranty periods.

Against this background, periodic electrical testing is the proven method to establish the reasons for any identified underperformance and to enable the application of timely mitigation measures. In this respect, the absolute minimum testing that needs to be undertaken involves continuity measurements, open circuit voltage, short circuit current, insulation resistance and irradiance.

In addition, an assessment of the I-V curve of a PV cell or string during commissioning, or as part of the periodic inspection and testing of a system, can also help to verify that all the modules are healthy and performing at a consistent level in line with their specified parameters.

RELATED: How data can shift the energy market to solar 

SB: How does your PV210 in particular improve the typical electrical testing experience?

Barron: The PV210 is the first instrument to combine the required IEC62446 electrical safety tests for PV systems with I-V curve performance measurement capabilities. It’s portable, easy to use, fast and the most comprehensive test kit available today, eliminating the need for the engineer to carry lots of separate instruments and PC equipment around a site.

With an onboard memory, the test results can be downloaded to our PC software for further analysis and reporting. Three operating modes can give the test operator just the tests required for a particular site, or combine all possible tests with one press of the AUTO test button.

SB: Walk us through the workflow with the accompanying PVMobile app.

Barron: With some I-V curve tracers on the market, a laptop PC is required on site to convert the measured data into curve diagrams so that shapes can be determined and any system faults identified. The PV210 eliminates this need.

If the instrument detects a fault in a string, the results can be sent wirelessly to the Android PVMobile app to create high definition color displays of the I-V and power curves. This gives the engineer immediate visibility of the curves to then start the repair process to rectify the issue without having to leave the site and return after analyzing the data.

SB: How does this add to/enhance the experience?

Barron: There is considerable time savings in not having to download results to a PC to analyze faults and less equipment to carry to site (PC’s don’t like the intense heat that can be on solar farms, particularly in the United States). Simple and quick operation means spending less time on site in hot conditions.

Along with enabling immediate on site performance assessment and fault diagnosis, complete I-V curve and electrical test data can be stored in the PV210’s large onboard memory. Full test and measurement data can then be downloaded to a PC via USB connection for comprehensive system reports and full traceability records of system performance.

— Solar Builder magazine