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Why microinverters are a safer design for solar

Solar power is gaining a coalition of fans, their numbers growing as PV spreads around the globe. But many emergency responders aren’t yet sold, and understandably so. They, and others, are concerned with the electrical safety of these new and often unfamiliar systems. The idea of high-voltage DC sizzling across a rooftop is a stark prospect for anyone who might come in contact with a PV array while battling a building fire, or even performing routine maintenance.

APsystems-supportSeeing the need for safety standards, regulators enacted “Rapid Shutdown” requirements (found in NEC 2014 690.12) to protect first responders from any high-voltage DC hazards that might remain after AC service has been disrupted or shut off. While manufacturers have responded to NEC 2014 with varying strategies–including add-on “DC combiner boxes” for string inverter arrays–one popular PV product already has Rapid Shutdown built into every unit: the microinverter.

When the AC circuit goes down for any reason, each unit in a microinverter array performs its own shutdown function in just 100 milliseconds–100 times faster than the code-specified standard of 10 seconds for shutdown.System voltage at shutdown is about 30V DC, meeting the stringent NEC 2014 requirement and well below the 80-V threshold generally considered safe for contact.

chrisSafety doesn’t end there. Microinverters also offer safety advantages when it comes to the DC conductor requirement in the standard. For example, a system designed using APsystems microinverters will have no DC conductors energized more than 5 ft in length within a building or more than 10 ft from the array, which meets the NEC 2014 standard (and is already looking ahead to NEC 2017).

Also, any present low-voltage lines will be located beneath solar modules, eliminating the chance of contact during rooftop activity.
Powerful, reliable, economical, microinverters have had plenty to recommend them since they entered the MLPE product field. As electrical codes evolve to protect responders and homeowners alike, the humble microinverter is not only meeting these tough new standards, but anticipating them.

By: Christopher Barrett, engineering and technical services manager for APsystems USA. Contact him at christopher.barrett@apsystems.com.

To learn more, watch his webinar presentation here. 

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ECU + EMA = a powerful duo for your microinverter array

Module-level monitoring is an essential feature of a microinverter solar array. APsystems offers advanced and user-friendly system monitoring for installers and end users alike.

The APsystems Energy Communication Unit is the gateway to our microinverters. An array can be easily configured BEFORE reaching the jobsite, so commissioning is a breeze. And the ECU requires no additional wiring; the simple plug-and-power design simplifies setup at the customer’s home or business.

The Energy Monitoring & Analysis software offers comprehensive, round-the-clock assurance of system performance. The homeowner’s EMA account provides module-level data, production and savings over time, while the installer account offers a more robust feature set for system configuration, mapping and control.

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Find out all about the ECU and EMA and our advanced microinverter solutions here.
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5 Reasons a String Inverter Won’t Cut It.

Microinverters or string? PV system designers fall into two camps, some favoring big inverters and others moving toward the powerful little boxes that meet each module where the real action is: on the roof.

Knowing the limitations of string inverters may tell you just why the Module Level Power Electronics segment – microinverters – is on the rise.

 

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Not made in the shade:
A PV array only works as well as the lowest-performing module. That means intermittent shading from trees, flagpoles – even fallen leaves – can cripple a string of modules as even minor shadows pass across the array throughout the day.

By offering independent, module-level inversion, a microinverter installation can outperform a conventional string array by up 20 percent. You’ll get the most out of every module, every hour of the day.

 

Want to add modules? Too bad:
A string inverter that’s right-sized for an array today may be too small if you want to add more modules tomorrow. That means buying a bigger inverter, too. Ouch.

Microinverters are the forward-thinking choice, letting you add on to your array at any time, easily and cost effectively.

 

Better value in the long run:
Startup costs of a string system might be lower on a per-watt basis, but what you save up front, you’ll lose over time in lower performance.

The key metric of Levelized Cost of Energy – that is, system cost measured over its lifetime – favors microinverters. The microinverters start generating power at lower light levels than string inverters, so the power curve raises and peaks earlier in the day and extends further into the afternoon and evening.

Thanks to module-level inversion at these lower light levels, microinverters enjoy a superior output and higher rate of energy production.

 

Don’t forget safety:
Every module in a string adds more to the DC current flowing across the rooftop – quite a volt load by the time it reaches a inverter, up to 1,000 volts DC. Not very safe for installers or emergency responders who may have to cross the roof.

Microinverters take the jolts out of the volts. Module-level inversion means only low-voltage DC in each circuit, keeping you safe over the life of the system.

 

Module-level power is the future:
String inverters still have their niche, but module-level power inversion is tomorrow’s technology today. A leading analytics firm recently noted that sales of microinverters and related products should top 2 gigwatts by year’s end, and predicts the microinverters’ share of the larger MLPE market could triple by 2018.

That’s a product with a bright future.

Still not convinced? Hear what solar professionals have to say at our APsystems video channel on YouTube. Find out why installers choose APsystems microninverter technology over conventional string systems, and then put module-level power to work in your next PV project.

 

Module-inverter mismatch:
For best performance, the power rating of modules must be matched to that of the string inverter that serves them. Yet these inverters offer a narrow range of power ratings that may not correspond to the cumulative output of the array. You may be buying more inverter than you really need.

Module-level inversion lets you to match inverters to modules throughout the array. Pay for the inversion power you need to get the job done – and no more.

 

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University of Kansas architecture students take solar construction into the future

Powering old homes with solar is only half the renewable-energy equation.

Designing and building new homes that make the most of that renewable power – achieving ultra-efficient “Net Zero” construction, and beyond – is the next frontier for sustainable living.

Graduate students in the University of Kansas Department of Architecture, Design and Planning are pushing construction into the future through Studio 804, a nonprofit organization that tests their drafting-board skills against real-world challenges.

Where conventional construction ends, the Studio 804 program begins.

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“If a group full of students who have never worked construction or designed and built a project can accomplish these highly sustainable buildings, it shows what the industry as a whole should be capable of,” said Taylor Pickman, now in his fifth and final year in the colloquially known “M-Arch” program. “We like to think we’re setting an example in that sense.”

Their most recent success: the East Lawrence Passive House, an innovative solar home set among the tree-lined streets of a quintessential college town, a mix of modest historic homes, and even the mansions of nineteenth century industrial tycoons.

Outside, the home was designed to fit in with the scale and aesthetics of the neighborhood, while maximizing square footage on a prominent but narrow corner lot. Cut-cedar siding offers a look familiar to the neighborhood while carrying a low carbon footprint. Generous windows maximize passive solar potential.

Inside, the home boasts a laundry list of energy-saving features. A triple-thick blanket of insulation achieves dramatic “R” values, while an advanced air barrier wrap further reduces heat loss. A low-energy HVAC system and energy-recovery ventilator supplies fresh air without energy waste, while the plumbing includes an insulated hot-water recirculation system for more efficiency still.

The home meets the rigorous standards of the LEED Platinum, Net Zero and Passive House certification programs – a trifecta for sustainable construction.

Net Zero, for instance, requires that all heating, cooling and electrical needs must be met through energy-conserving design features and onsite renewable sources.

That’s where solar comes in. The East Lawrence home features a 6kW rooftop system powered by 20 Trina modules and 10 APsystems YC500 dual-module microinverters.

Studio 804 students approached APsystems for help with the project, and the Seattle-based solar technology company offered the microinverter units as a donation.

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“These students are really leading the way forward for energy-efficient design and construction,” said Thomas Nelson, APsystems vice president for sales, USA. “As a leader in innovative solar technology, we were glad to sign on to the project and be included in this showcase home.”

Pickman said microinverters represent “a huge innovation” in the solar field, helping students meet their project goals even without real experience as solar installers.

“I have to say that those microinverters were very simple to install, very simple to work with and very simple to use,” Pickman said. “We had more trouble getting the panels up onto the roof than we ever did working with the micro inverters.”

Bigger, more ambitious projects

KU’s Studio 804 program is committed to the research and development of sustainable, affordable, and inventive building solutions, from the standards of human comfort to the nature of urban spaces.

Two education tracks are offered: a three-year Master of Architecture program for students who already hold undergraduate degrees, or a five-year program that melds both undergraduate and graduate studies and also culminates in the master’s degree.

The final year is a rigorous practicum in which students tackle all aspects of design and construction: from site selection to negotiating building and zoning codes, to working with neighborhood associations and project engineers, to pouring concrete and pounding nails.

“A lot of our projects are speculative, so we are also in charge of making sure the project gets sold,” Pickman said.

To date the studio has completed seven LEED Platinum buildings and two with Passive House certification, meeting the most rigorous environmental standards for materials and construction.

Solar has become a regular feature of Studio 804 work, Pickman said, because it is one of the most effective means of achieving onsite energy production in the Midwest.

“Solar is relatively simple and it functions relatively well with different housing configurations,” he said. “And every year the technology gets better, so every year, we can demonstrate that technology as well.”

Studio 804 produces one building per year, and they keep getting more ambitious.

Twenty years ago, the first Studio 804 project put a simple metal roof over a historic farmhouse. Two years ago, students designed and built a lecture hall and auditorium addition to Marvin Hall, a treasured, 1908-vintage engineering building on the University of Kansas campus.

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Pickman said their next challenge may be achieving the WELL Building standard, which considers interior design and the ergonomics of the living spaces and fixtures – anything that will “reduce wear and tear on the human body.”

“Every year we set slightly different goals,” Pickman said, from building scale to advanced materials and construction and renewable energy techniques.

“And great architecture, or at least very good architecture,” he added. “There’s not a lot of it in Kansas.”

East Lawrence Passive House
East Lawrence, Kansas
Designer/installer: Studio 804, graduate students in the University of Kansas Department of Architecture, Design and Planning
System output: 6kW
No. of modules: 20
Module type: Trina TSM-290
Microinverters: APsystems YC500 dual-module
No. of microinverters: 10
croinverters: 10

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Seattle project produces solar-savvy graduates

A new PV array on the roof of a Seattle-area college is a clean-energy investment with a different sort of payback: solar-savvy graduates.

The Education Building at North Seattle College now sports a 7.4-kW PV system, its primary array perched atop a rotating armature that tracks the sun across the sky each day.

While the array will only yield a small fraction of the building’s energy needs, “power” per se wasn’t the point.
“This isn’t really about generating electricity,” said Mark Weber, faculty and program coordinator for the college’s HVAC and Sustainable Energy Program. “This is an educational tool for our students. It’s a dynamic learning environment rather than a static one, where we can do all sorts of experimentation with module orientation, the effects of weather, all kinds of things.”

About half of the $75,000 system cost was funded by a grant from the Portland, Ore.-based Bonneville Environmental Foundation, which promotes renewable energy and resource conservation. The college made up the balance.

Artisan Electric of Seattle was selected from among three local installers submitting proposals. The combination of a solar tracker, 3-phase output and a mentoring component for students set Artisan’s design apart in the bidding process.

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An APS YC1000 is installed on the underside of the array.

The primary array includes thirty 240-watt modules by Talesun. A secondary, fixed-position array of three modules is planned to serve as a system “control,” allowing students to compare the output of the two designs – one that continually aligns itself with the sun to optimize solar harvest, the other pointing eternally south.

Anthony Sarno, system designer for Artisan Electric, selected APS YC1000 microinverters for their true 3-phase output. The APS units tied into the building’s 480-V circuit without the need for step-up transformers, in an electrical room that would have been too small to accommodate a central “string” inverter.

“When I saw the 480 panel, the light bulb went on,” Sarno said. “I saw potential savings by using the YC1000 microinverter, and there was an element of allure to having a cutting edge product in the mix.”

APS and its Washington state distributor, Blue Frog Solar, provided the YC1000 microinverters below cost as a donation to the college.

“The chance to help students learn about PV system design and train for the renewable energy trades was compelling,” said Paul Barlock, APS Senior Vice President. “This project is a showcase for true 3-phase microinverters in a commercial setting, but the fact that it’s in a college environment provides much greater benefit still.”

Tracking the sun
Marketed under the name SolarTrackr, the “smart tracking” system was designed and fabricated by Wovn Energy of Seattle.

Putting the 2-ton apparatus atop a three-story building added a layer of design complexity, the first question being whether the roof could support it.

The structural engineer responsible for the building’s original plans was still in practice, Sarno said, and provided new calculations proving that the roof could bear the load.

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The team from Artisan Electric begin attaching modules to the tracking system’s steel armature. The array will rotate and incline to track the sun through the sky. Photo Credit: Wovn Energy

Next came the question of ballasting. Fortuitously, the rooftop featured several low concrete parapets that extended down through the building to the ground. These walls became the foundation for the massive steel armature that was assembled over five days in March.

The completed array rotates around a circular steel rail, inched along by a small electric motor, while a second motor and a piston provide inclination. Together the two motors draw about the same power as a 100-watt light bulb, said Alan Tilley, Wovn Energy vice president and tracking system designer.

Wovn’s solar tracking software uses algorithms provided by the National Renewable Energy Laboratories, and also accounts for local weather and atmospheric conditions to optimize the array’s positioning. Solar harvest is projected to be about 45% higher than a static array. Computer control can be manually overridden so students can set the array to other positions for research and data collection.

“Compared to a static system, this thing has so many more opportunities for learning,” Weber said, “not just for solar, but also for engineering. The control system is going to be way cool to play with. We can bring in people from other disciplines, not just our program.”

The founders of Wovn Energy set out on a mission five years ago to provide distributed-energy management systems, out of which the SolarTrackr system evolved, Tilley said.

The product was designed to offset the then-high cost of modules, allowing buyers to achieve greater yield from a smaller array, Tilley said. As module prices have come down, the SolarTrackr is now marketed as a way to make full-sized arrays more powerful still.

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Workers assemble the circular steel track on which the 30-module PV array will rotate at North Seattle College. The tracking system was designed and fabricated by Wovn Energy of Seattle. Photo credit: APS USA

The North Seattle College project was the company’s fifth installation, and the first on a rooftop. The biggest challenge previously was a ground mount perched on the side of a mountain.

“That one was a real bear,” Tilley said. “This one is tame by comparison.”

Wovn expects to have about 15 installations in its portfolio by midyear, he said, with two more already underway in the Seattle area.

For students, by students

Befitting an educational venture, the North Seattle College project engaged students from the start.
Students from nearby Shoreline Community College, which offers a two-year degree in Clean Energy Technology, were brought in to do a solar site assessment. Their report became the baseline against which formal proposals were evaluated.

North Seattle information technology student Christoph Strouse was a key member of the solar project team, and system designer Sarno is a graduate of Shoreline program.

“Artisan kind of plucked me out of the program, and things have fallen into place very well,” Sarno said.
Because the array shoots up 25 feet above the roof of an already tall building, it has become a billboard of sorts for North Seattle College. The array is visible from adjacent neighborhoods, from a popular commercial center a mile to the east, and to passing motorists on the busy I-5 freeway.

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Alan Tilley, engineering vice present and tracking system designer for Wovn Energy. The North Seattle College project is the Seattle company’s fifth installation. Photo Credit: APS USA

It is also becoming both a valuable asset and a recruiting tool. Weber said the college is in talks with other area schools and a major research university to share solar performance data collected by students. The colleges are also beginning to collaborate on programs to meet the evolving demands of the clean-energy and construction industries.

Weber and Strouse envision a hybrid program in “High Performance Building Technology.” Students might someday take electronics and IT classes at one school, HVAC or facilities management at another, and PV system design at a third toward an integrated degree.

Having an advanced solar installation could make North Seattle College the program’s logical hub, and the investment is already paying off for students.

“I’m very lucky to have been here at the right time to be a part of this team and experience this project from paper to completion,” Strouse said. “As a learning experience, it doesn’t get much better than this.”

Project Details
North Seattle College 3-phase 7.4-kw PV system
Designer/installer: Artisan Electric, Seattle
Tracking system and racking: SolarTrackr by Wovn Energy, Seattle
Microinverters: 8 APS YC1000 true 3-phase
Monitoring: APS Energy Communication Unit/Energy Monitoring and Analysis software
Modules: 30 Talesun 240W

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APS YC1000 offers unprecedented features

YC1000-closeup-webThe challenge: How to bring the advantages of microinverters to a commercial solar environment and be cost competitive in that market.

The solution took more than three years of research and development, but now it’s here: the YC1000 microinverter from APS.

The native 3-phase, 277/480 unit brings microinverters finally into the realm of large-scale commercial installations, with a groundbreaking approach to the technical challenges of these most demanding environments.

Simplicity of design: The YC1000 requires no extra equipment like transformers or optimizers, and no extra wiring. All needs are resolved within the unit’s native design.

Unprecedented cable management: The YC1000 revolutionizes trunk cabling with a new and innovative approach. There’s no need to branch cables or deal with the “landscape vs. portrait” complexity of a standard trunk cable system. These issues are solved by shifting the solution to the trunk cable itself.

Increased flexibility to add modules: The YC100 supports 4:1 and a 3:1 module-to-inverter ratios, so modules can be easily added for customized or space-limited projects.

Optimized monitoring and control: The YC1000 allows monitoring of individual modules, reducing shading issues and allowing more precise control of the whole PV array.

 Dr. Yuhao Luo, co-founder, vice president and chief technology officer for APS, began working toward these solutions in Silicon Valley based on his experience with PV systems in one of the world’s fastest-growing solar markets.

“Four years ago, there was no residential PV market in China,” he says. “All projects were 3-phase. We used a single-phase microinverter for those projects, but clearly a 3-phase microinverter would make those projects much easier in both design and installation.”

The YC1000 spent three years in design and development before rollout, and has been successfully deployed in installations in Australia, China and Africa.

It is now shipping to distributors across the US market.

Add up the technical breakthroughs – simplicity of design, revolutionized trunk cabling, outstanding flexibility, and optimized monitoring and control – and the YC1000 microinverter from APS represents distinct advantages and cost savings over every other microinverter solution on the market.

“This really is a gamechanger for commercial solar,” says Michael Ludgate, vice president for sales for APS USA. “We’ve shifted the paradigm again.”

See the groundbreaking YC1000 at SPI Las Vegas, Oct. 20-23. Visit the APS booth #3124, or email us sales@apsamerica.com to discuss specific installation and distribution opportunities.