You down with CIP? How cast-in-place foundations add flexibility to a solar installation

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Flexibility is maybe not the first word that comes to mind when thinking about concrete blocks, but when planning your next ballast solar project, it should be considered.

Sure, the first concern when choosing your concrete foundations will likely be cost. How much will it cost to ship precast blocks to the site? Will it cost less to hire the necessary labor and bring a concrete truck on site for a cast-in-place (CIP) solution?

“Depending on where you are getting the concrete, the shipping numbers could be huge. It’s usually more cost effective for the truck to show up on site and then pour it that way,” says Nathan Knapp, design engineer at Solar FlexRack. “But regionally, you can have higher labor rates — New Jersey for instance — so yeah, if you’re paying a high union labor rate at the site versus paying a lower rate at the precast facility, it can pan out that precast is more effective even with the shipping.”

But the more intriguing consideration for us is that of flexibility, which mostly favors CIP — pouring foundations right there on site versus trucking in precast blocks from the manufacturer. Not having to move concrete blocks provides obvious convenience during the install, but the adjustability benefits go beyond that. Depending on the CIP system, you should be able to completely adjust the racking and line everything up prior to the modules arriving and prior to the concrete being poured.

RELATED: Mounting Challenges: Landfills, Brownfields, Water-Saturated Sites 

Also, consider the site itself — there is always something wonky about the field that was missed or unaccounted for in the original plans, such as subtle local grade changes. A precast foundation form, with its flat bottom, was not set with those in mind; a CIP solution can sit on grade and level the system.

Contractors have noted load rating concerns in landfills and other saturated sites that might not be able to handle a truck with precast blocks, a small crane needed to move said blocks or even a big cement truck needed for CIP foundations. As a work around in the latter case, according to Knapp, some contractors use a concrete buggy, which is a four-wheel machine with a dump bed that runs back and forth between the cement truck and the jobsite until the load of the truck is acceptable.

Every site and job have their own challenges, which is why a company like Solar FlexRack will provide both precast and CIP solutions. According to Greg Huzyak, PV Structures/Product Development Manager for Solar FlexRack, the company’s CIP solution adds more flexibility as the CIP forms are roll-formed channel sections that are manufactured to create custom ballasts of virtually any size and nest for optimized shipping. After arriving on site, the forms are quickly folded, assembled and ready for concrete.

Filling the CIP blocks is streamlined too with internal bracing that doubles as reinforcement during the pour, eliminating the need for additional rebar or external supports. Huzyak notes that they are always filled to the top to avoid water filling the excess space on top.

When specing that next landfill PV job, just be sure to consider all of your options in terms of price, installation speed and flexibility.

— Solar Builder magazine

How to add flexibility to your solar cable management strategy

snake tray cable management

Back in 2010, Snake Tray decided to install a PV system on its own roof. At that point, Snake Tray had been a manufacturer of trays for other industries for many years, with no ties to the solar industry. But after seeing a PV system installation up close, owner Roger Jette believed their trays would be a perfect solution for commercial rooftop cable management.

Tray is an open-air solution. Installers typically meet electrical code compliance by stringing cables through conduits, which protect them from harsh environmental conditions like temperature fluctuations and direct UV. Would the tray be up to code?

The tray most certainly was up to code, but most of the solar industry wouldn’t have guessed so.

“In 2008, there was a significant code change that said you do not need to just use conduit for solar panels anymore,” according to Eric Sadler, engineering sales manager for Solar Snake Tray. “It explicitly permitted exposed wiring methods, and consequently, we started telling our customers that this method is easier, faster and you can do this right now.”

Since then, it has been about shifting perceptions for Snake Tray ­— a shift that seems to be happening. The company’s solar business grew steadily from that first self-install, and now solar pathways are the company’s largest portion of business, with a focus on both commercial rooftop and utility scale. The code was even amended further in 2014 to explicitly allow cable trays.

Cable tray value

Traditional conduit requires cables to be sized larger, which can add cost. Snake Tray’s patented open design allows the cables to be securely managed while allowing for better airflow so cables can operate at higher capacity. Trays connect together with a single connector for a 15-second bonded attachment tray-to-tray.

The tray system costs more than a conduit, but Sadler says the value of the tray lies in its install speed, design flexibility and long-term accessibility.

“We are about labor savings and ease of installation,” he says. “You have pairs of wires coming off of every string, and in order to do it the old way, you had to T into the conduit and pull the cable. Snake Tray is an open tray, so you can start anywhere in the tray without having to T off.”

Bending conduit requires  planning and a tool; whereas trays can be bent using your hands and knees. After forming to the necessary shape, the tray is simply attached to the mounting system via Tek screws or bolts. Built-in mounting rings allow for a variety of mounting options.

“Between the ease of aggregating the strings and the ease of making the turns, it just is so much faster,” Sadler says. “Our rule of thumb is Snake Tray takes approximately 60 percent of the time it would have taken to do a job using the traditional methods.”

Those estimates can vary a bit above or below that mark depending on how the tray needs to be mounted. When the racking allows regular attachment, the value can be better.

“As racking evolves, we have to come up with more clever ways to attach the tray. That applies to both rooftop and utility,” Sadler says. “Everyone wants cost down as far as possible, and the racking manufacturers come up with more clever designs to get panels in place. And we evolve with them.”

Open-air Strategy

The open-air style of the tray provides great value in the wide open spaces of a utility-scale installation. Typically, cables are buried under ground in those applications, which means digging trenches. The gains in speed and efficiency with a tray vs. a trench solution are obvious, but a secondary advantage is how the exposed cable is now much more accessible for maintenance purposes for the life of the system.

However, many installers still prefer the standard, underground method for both cable protection and safety code reasons. Sadler believes both concerns aren’t really an issue. On the exposure side, the cables are often positioned underneath the panels, and they are UV-rated.

“They might fade in color, but they won’t degrade with UV exposure,” Sadler says.

As for the code, solar projects are to be made “not readily accessible,” which could mean up on a rooftop or perhaps behind a fence in the middle of the desert where only authorized personnel have access. This is how exposed wire methods meet the criteria, which at least means utility-scale installers shouldn’t shy away from the newer cable management method for either code or functionality-related reasons.

“For utility scale, we have solutions for fixed mounted and tracker plants, and we’ve become good at managing the string cables that come off all the panels, as well as the feeder cables, whether AC or DC, depending on if a company decides to use more inverters or combiners boxes,” Sadler says.

Solar Snake Tray applications

Trays can form to the necessary shapes by simply bending them with your hands or knees.

Trays can form to the necessary shapes by simply bending them with your hands or knees.

Below are the main Solar Snake Tray applications (with talks of a residential rooftop option coming down the road ­— stay tuned). The majority of these are made from a recycled steel that’s pregalvanized in the production line and then fabricated by bending, cutting and welding, and then finally treated with an industrial-strength powder coat finish.

There is a stainless steel option for high salinity environments like Hawaii.

• Rooftop commercial. The standard solar Snake Tray.
• Car ports. A lighter-duty solar Snake Tray to fix to carport, which is complemented nicely with the Snake Tray ice guard.
• Fixed-mount utility scale. A solar Snake Tray that attaches to the racking system.
• Single-axis tracker utility scale. The biggest cable management challenge is the single-axis tracker. Snake Tray offers a messenger wire supported option that gets strung from the first poll to the last poll of any given solar plant, and the tray hangs from the wire.

Chris Crowell is managing editor of Solar Builder.

— Solar Builder magazine

Spotlight on: Microinverters

SMA_Sunny_Multigate_USSMA America’s Sunny Boy system

SMA America microinverters have a focus on reliability, monitoring and ease of installation

For modular PV systems, SMA America’s new Sunny Boy 240, in combination with the Sunny Multigate, is an ideal solution. As a result of its modular design, systems equipped with the Sunny Boy 240-US, the Sunny Multigate-US and the Sunny Multigate XT can be realigned and upgraded at any time — for structural modifications, capacity expansion or financial circumstances. The Sunny Multigate XT is specifically designed for outdoor use and is a robust, turnkey component with up to four preinstalled Multigate devices.

The Sunny Boy 240-US microinverter eliminates the need to bring extra grounding conductors or grounding devices in contact with the enclosure during installation, a feature that saves time and money and complies with UL 1741 certification for inverter electrical grounding. A unique thermal design concept keeps the system running smoothly even under harsh rooftop conditions.

The Sunny Multigate-US is the link between the microinverter and the power distribution grid and provides an electrical interface to the main service panel, networking support for panel-level monitoring and diagnostics. It allows for fewer components to be exposed to heat stress under the module, which leads to an improvement in communication reliability.

The Sunny Boy 240-US features a variety of DC plug-in options, including MC4 and Tyco, and AC wiring is made easy with preassembled plugs and connection cables. The turnkey setup of SMA’s Sunny Boy is designed for maximum flexibility and simplicity.

For more information, visit www.sma-america.com.

Enphase-S-SeriesEnphase M215 to C250 series

Reliable components to match a variety of residential and commercial installs

Enphase microinverters combine reliable components with a distributed architecture that makes for a more resilient system vs. a string inverter setup for certain applications.

The Enphase M250 microinverter delivers increased energy harvest and reduces design and installation complexity with its all-AC approach. With the M250, the DC circuit is isolated and insulated from ground, so no ground electrode conductor is required for the microinverter. It can be used in residential or commercial installations.

The Enphase C250 microinverter increases overall energy harvest and system availability along with substantial reductions in material and labor costs. Used with a transformer, the C250 microinverter system meets the needs of medium and large commercial installations where power distribution is 277 V/480 WYE or medium voltage. With support for both 60- and 72-cell modules, the system provides a flexible, operationally efficient and cost-effective solution across all commercial project segments.

The Enphase M215 microinverter with integrated ground delivers increased energy harvest and reduces design and installation complexity with its all-AC approach. With the advanced M215, the DC circuit is isolated and insulated from ground. Its primary use is residential.

Each of these integrate seamlessly with the Engage Cable, the Envoy Communications Gateway and Enlighten, Enphase’s monitoring and analysis software. Coming soon is the Enphase Energy Management System, which will offer a next-generation, smart grid-ready Enphase microinverter, plug-and-play storage, advanced control capabilities and load management.

For more information, visit www.enphase.com.

APS-YC500APS America’s YC series

An increase in power allows for maximizing efficiency
The APS microinverter solar solutions combine highly efficient power inversion with a user-friendly monitoring interface to bring you reliable, intelligent energy.

The APS flagship microinverter product is YC500A — a grid-tied microinverter with intelligent networking and monitoring systems with a focus on maximum efficiency. The YC500A handles up to 310-W modules with negligible clipping, delivering 250W AC per module with dual MPPT. Half the inverters and half the installation can mean real cost savings for residential and commercial customers.

The APS YC1000 is a true three-phase solar microinverter, handling commercial grid voltages of 208, 277 V/480 with 900-W maximum output, ZigBee communication and an integrated ground. Each YC1000 supports up to four solar modules.

The microinverter products are then tied to the APS Communicator, an energy communication unit (ECU), that is an information gateway. It collects and transfers module performance data in real time, providing comprehensive monitoring and control over each individual module, optimizing performance of the solar array. With the APS Monitor, monitoring takes place around the clock through any web-enabled device. This web-based software detects and alerts the user to any performance issues.

Visit www.apsamerica.com for more information.

— Solar Builder magazine

Beyond the rooftop: How offsite PPAs change the game for solar professionals

offsite-PPA-maryland-5---cut-2Like many of its peers, the management team at the National Aquarium in Baltimore struggled to find an adequate solution to meet its renewable energy goals. Given the unique architecture of the building, the National Aquarium’s limited and aging rooftop could not support meaningful electricity generation.

Determined to make a substantial environmental impact, and equally resolved to support local development in Maryland, the National Aquarium entered into an offsite power purchase agreement (PPA) for a 4.3-MW PV project. Located in nearby Cambridge, Md., and online as of May, the system will generate nearly 6,000 MWh of energy in its first year of operation, enough power to meet nearly 40 percent of the National Aquarium’s electricity needs for the next 25 years. The Cambridge project embodies the Aquarium’s core conservation values and does so in a fiscally sustainable way.

Over the past decade, the evolution of renewable energy financing models has spurred a massive market expansion around the world. While this is wonderful news for the industry as a whole, to date, these mechanisms have best served only the largest and smallest energy users. What about those entities that fall somewhere in between?

More than ever, mid-size corporate and institutional organizations are searching for ways to reduce their carbon footprint without sacrificing their bottom line. Until recently, the options to support projects of this size have come with some pretty significant economic limitations. The National Aquarium is just one example of a new model that’s arrived to answer that question.

Before examining the new trend, let’s take a step back to get a better sense of just how far the market has come.

Is standardized solar permitting the next industry breakthrough?

The Evolution of Project Financing

● Renewable Energy Certificates (RECs). Fifteen years ago, the Portland-based Bonneville Environmental Foundation and the U.S. EPA’s Region 10 office completed the first retail renewable energy certificate (REC) transaction. A REC, sometimes known as a “green tag,” is a tradable energy commodity that serves as proof that 1 MWh of electricity was generated from a renewable energy resource. Before RECs, commercial customers were at the mercy of their utilities. If the local utility didn’t offer a renewable energy option — and most didn’t — customers were out of luck.

With the advent of RECs, organizations could de-couple the environmental benefits of renewable electricity generation from the electrons themselves. The REC transaction is appealing to many electricity end-users, due to its simple and cost-effective nature. However, because the REC product does not supply the consumer with the electricity generated, customers still miss out on the fixed-price benefits of renewable energy.

Rooftop Solar Leases. Inspired by residential solar leasing products, organizations adopted commercial rooftop leasing as a cost-effective way to leverage solar energy. Rather than investing in the upfront equipment and installation costs of solar power systems, property owners would grant project developers access to rooftop space in exchange for a share of the economic benefits of the installation.

The solar lease model became a staple for commercial rooftop solar projects in the United States because of the value and flexibility, but the traditional leasing model is not feasible for all electricity customers as many firms don’t own the buildings they occupy. Moreover, for those who do own their facilities, rooftop size and condition can limit or eliminate the possibility of installing a PV system.

Offsite Wind PPAs. For large electricity users without adequate rooftop space for solar, offsite wind PPAs offer a solid alternative. PPA customers pay a fixed price for each kWh produced over a contract term — ranging from 10-25 years — allowing organizations to hedge against rate increases and to reap both the economic and environmental benefits of renewable energy. In 2010, Google announced a series of deals with Florida-based NextEra Energy, including a 20-year offsite wind PPA that captured national attention. Because of wind PPA’s compelling economic and environmental story, major organizations like Amazon, Yahoo, Microsoft and Wal-Mart recently joined the bandwagon of institutional wind buyers.

Enter: The Offsite Solar PPA

While those three models all helped to expand renewable energy adoption, the industry was unable, until recently, to serve a key demographic: organizations that don’t have rooftops suitable for solar, and that don’t have electricity loads large enough to support large offsite wind PPA purchases.

The renewable energy needs of the underserved mid-range market were finally met in 2014 with the introduction of the offsite solar PPA. Today, this model enables customers to tap both the economic and environmental benefits of solar power, while freeing them from the practical and logistical challenges presented by rooftop systems.

The beauty of this model lies in the flexibility afforded by offsite projects. No longer constrained to the dimensions of the rooftop, systems can be sited to minimize costs and sized appropriately to meet the unique energy profile of each customer. What’s more, offsite solar projects offer benefits to other stakeholders, supporting utilities and communities, at large.

For the power customers: Offsite projects help customers meet environmental goals, while also offering these organizations budget stability and insurance against future electricity rate increases.

For the utilities: Offsite projects pay to support transmission and distribution networks and serve as distributed generation resources on the grid. As a result, these projects support grid resiliency, a key concern for utilities charged with managing an aging electricity grid and integrating a growing number of rooftop systems.

For surrounding communities: For landowners, these projects generate sustainable, long-term revenue streams from what are often unusable plots of land, including brownfield sites. Solar projects support the local tax base, while causing no environmental damage. Incredibly, the solar industry now employs twice as many workers than the coal industry does.

Catalyzed by technology cost reductions, electricity market deregulation and financial creativity, the booming solar market is finally allowing a wide range of customers to purchase energy in an economically and environmentally responsible way. The offsite solar model represents a key component of our evolving energy system — one that delivers real benefits to an underserved market that demands clean, affordable power.

Bryce Smith is the co-founder and CEO of OneEnergy Renewables.

— Solar Builder magazine

How to select conduit for your next commercial solar installation

 Flexicon’s FPAS nylon corrugated conduit, connected using an FPA T-piece to tap off to each solar array.

Flexicon’s FPAS nylon corrugated conduit, connected using an FPA T-piece to tap off to each solar array.

Today, designers and contractors face many options for protecting the electrical cables and wiring systems in commercial PV installations. One such option is conduit, which is a type of raceway or closed channel that guards wiring systems running through them against hazards over a system’s lifetime.

There are many factors to take into account to correctly size and select a conduit material, from code-, job- and customer-specific requirements, and making the right selection has a big impact on PV system performance.

Conduit options

Conduit used in solar installations is generally divided into two categories: rigid and flexible. Each category can be further divided into metallic and non-metallic types. Some are UL listed, and those that are not may be considered recognized components.

Non-metallic conduit is made from plastics that have to meet the performance requirements of steel while being much lighter, using materials like Nylon, polypropylene or PVC. Metallic conduit can be made from galvanized steel, stainless steel, brass, aluminum or nickel-plated brass. Some contain both metallic and non-metallic materials to offer low fire hazard and anti-static capabilities, external braiding and other features.

Rigid conduit, sometimes called pipe or tubing, is used on long conduit runs and where extra strength or mechanical protection is needed. Rigid pipe can still be turned, but flexible conduit is normally used in installations that require bending or in areas where vibration will occur.

Each conduit category contains many products. For example, AFC Cable Systems offers three new types of flexible metallic conduit products with extreme temperature resistance called Liquid-Tuff. Gene Brown, liquid-tight and flexible conduit product manager, says 80 to 90 percent of the raceways need to use listed products. The listing tests things like bend radius and UV light performance. For these applications, the hi-low temperature flexible steel conduit could be used in hot and cold climates, and it has a flame-retardant PVC jacket that is sunlight resistant.
But, he says, depending on the installation, some customers don’t require UL listed products and protective tubes, and non-listed liquid-tight conduits can be used. In this case, the Non-UL Extreme Temperature Liquid Tight Flexible Metal Conduit 6800 Series has UV and ozone protection and is one of the better options when exposed to direct sunlight.

For those who need improved flexibility for tight bend radii, and where weight is a consideration, another option (that’s not labeled as conduit) exists: Non-metallic protective tubes (NMPTs). AFC’s Ultraflex Liquid-Tight is an extra-flexible mechanical NMPT non-UL liquid-tight raceway with a corrugated shape, is made from flexible PVC and has a rigid inner core for support.

Factors for sizing conduit

During system design, engineers consider many factors to calculate wiring and conduit sizes such as the type of wire used, voltage drops, type of circuit, conductor designation for indoor/outdoor (or both) and the ambient temperature during sunlight exposure. The temperature rating, conduit fill adjustment factors and National Electrical Code (NEC) tables are important for calculating the ampacity and sizing.

“To size conduit correctly, designers look at the constraints of the specific installation,” Brown says. “They consider the raceway route, how tight the footprint is for connections and the field conditions.” Plus, he says the NEC’s 40 percent fill rate rule is important.

Based on the number of conductors inside, the NEC Code specifies that the outer diameter (OD) has to be filled to a maximum amount of 40 percent. Leaving most of the raceway empty is enough to account for the heat generated in the wires and to allow room to safely pull the conductors through. Knowing the length of the raceway, the OD of each wire and the type of coatings (that may slide differently against one another) allows designers to size everything properly to avoid jamming.

Selecting conduit type and materials

Not paying attention to cable protection can be unsafe, costly and lead to downtime and inefficiency. Selecting the right kind of conduit needed for a job will depend on the application, jobsite and expected risks.

More on selection, common practices and options for the long haul (click next page)

— Solar Builder magazine