A new take on power conversion: ArrayPower CEO Wendy Arienzo and the Sequenced Inverter

Wendy Arienzo
Wendy Arienzo

Wendy Arienzo is the CEO of Array Power, which has developed a new inverter technology and product, the Sequenced Inverter.

Arienzo has extensive experience in the technology development sector, bringing 30 years of technical and management experience in the semiconductor industry to her current position. Previous to her work at Array Power, Arienzo worked at some of the leading companies in the technology industry, including IBM, Phillips and NXP Semiconductors.

Arienzo began her career in the solar technology development field developing polycrystalline silicon cells in Florence, Italy.

Arienzo has received numerous accolades for her accomplishments and is a sought-after public speaker in the technology sector. She has been recognized by the New York State Department of Environmental Conservation and the Center for Economic Growth, a non-profit based in New York state promoting economic growth throughout the state’s capital region.

Arienzo holds a doctorate in materials science and engineering from Stanford University. She received her combined bachelor’s/master’s degree in materials science engineering from Brown University.

 

Solar Server: Can you explain your Sequenced Inverter for our readers -- how it works, and what it offers?

Wendy Arienzo: I would be happy to. Our flagship product, the Sequenced Inverter, converts direct current (DC) to alternating current (AC). The Sequenced Inverter is located on the back of a solar module -- in fact, it’s integrated with the solar module. The Sequenced Inverter is a unique offering in the marketplace, and through integration we actually reduce the cost of the solar module. And we all know just how important cost is in the solar business these days.

By being integrated with the solar module, we also reduce the cost and complexity of installation because the module arrives at the job site as an AC module -- in other words, ready to connect.

The other important feature of the Sequenced Inverter is the fact that it offers distributed AC. The DC-to-AC conversion process distributes the energy across an array of Sequenced Inverter-equipped modules instead of relying on one inverter.  The work of each Sequenced Inverter is simplified, translating into a less costly and more reliable system architecture.

 

Solar Server: What scales of PV projects do you see as the prime target markets for the Sequenced Inverter?

Wendy Arienzo: With our first Sequenced Inverter model, we are targeting small and medium commercial with our sweet spot being up to about 250 kW. We are looking forward in 2013 to addressing larger-scale commercial projects with an even more attractive module-integrated inverter.

 

Solar Server: Other power electronics solutions, including microinverters, have been criticized as being too expensive, particularly for large installations. How do the benefits of your Sequenced Inverter outweigh the additional costs, if any?

Wendy Arienzo: We’ve positioned our Sequenced Inverter to compete directly with string inverters in terms of cost. So we offer the functional benefits of a microinverter -- the energy harvesting, the power point tracking, the monitoring -- at each and every module, but at a cost that’s directly competitive with a string inverter. Because we offer all of these benefits without any additional cost, we are well positioned for the commercial marketplace.

 

Solar Server: How did you manage that?

Wendy Arienzo: Our Sequenced Inverter has a very novel architecture. We draw on well-known technologies from telecom, from radio and from commercial electronics to create a very cost-effective and simple design to convert direct current to three-phase alternating current.

That novel and simple design -- well-grounded, if you wish, in standard semiconductor components -- allows us to not only be very cost-effective and cost-efficient, but also very reliable. We have designed the Sequenced Inverter to last the full 25 years of a solar module, and we have done so by avoiding any notably unreliable or less reliable components -- like electrolytic capacitors, like optos, like MOVs.

We are using robust and standard semiconductor components that are industrial grade or automotive grade, and we are using a contract manufacturer for low-cost, high-quality and high-volume production, enabling us to offer a product that will last those full 25 years.

 

Solar Server: Can you talk about the progress of market roll out and market strategy for your Sequenced Inverter? Specifically, what markets have you entered in terms of geography?

Wendy Arienzo: Our business model is to partner with the solar module manufacturer: we supply our Sequenced Inverters to the solar module manufacturer, who then offers the integrated product to the marketplace.

We have a go-to-market partner who announced their AC module at Solar Power International last October, and we are seeing terrific feedback from the market in terms of the Sequenced Inverter’s ease of installation, its cost point and the advantages it will bring through its simplicity to the commercial market.

We will be rolling out the Sequenced Inverter to the North American market in 2012 and shortly thereafter to the European market. In anticipation of that roll out we are in field trials at multiple locations in the United States, as well as in Germany.

These field trials will provide us with the data to convince and reassure our customers of the performance and value proposition of our Sequenced Inverter. We have engaged third-party monitoring services from big names like Fraunhofer, TÜV, and PV Evolution Labs here in Berkeley to provide that independent data to our end customers to demonstrate the robustness and performance of our Sequenced Inverter.

 

Solar Server: Can you talk more about the specific benefits of the Sequenced Inverter to system owners?

Wendy Arienzo: Yes, of course. First, we begin with a product that is cost-competitive from the moment of purchase. Secondly, our product is guaranteed to last the full 25 years. And that warranty is provided through the solar module supplier so the end-customer doesn't receive a warranty from a small company in Silicon Valley, rather from a well-known tier-one solar module manufacturer.

Thirdly, we provide the benefits of what is called energy harvesting. We generate more power than a string inverter. By setting the power point for each and every solar module, we get the best out of each one. We aren’t sensitive to mismatch losses as in the case of a string inverter where power output is governed by the lowest-performing module. With a Sequenced Inverter, you are getting the most out of each and every module on an individual basis.

So those are some of the key advantages. From the installer's perspective, the advantage is the ease of install because the module arrives at the job site AC-ready: there are no additional boxes. When you are working on a crowded rooftop, the simplicity of arriving AC-ready is very significant. You also have ease of permitting because this is a safe product. Like a microinverter, it is fully compliant with the latest NEC 2011 codes.

Finally, it allows flexibility of design, which is also an advantage on a crowded rooftop where an installer sometimes has to work around unexpected obstacles such as HVAC ducts or chimneys. You can add one, subtract one -- you don't have to go through any complex string re-balancing. You can have one to thirty-nine modules on a branch, and it is very, very easy to customize the installation to fit any rooftop.

 

Solar Server: Can you go more into the kind of power that you deliver, and specifically the pulse amplitude modulation?

Wendy Arienzo: The kind of power we deliver is commercial grade. We deliver three-phase power at 208 volts, so it’s a commercial application.

A little bit more about how the Sequenced Inverter works: the Sequenced Inverter has a fixed five-circuit design and a fixed pulse at 15 KHz. By sensing the grid, the Sequenced Inverter uses the grid to modulate the amplitude, or shape the pulse. In the United States, the amplitude is modulated by a 60-Hz grid. The inverters are connected in parallel, with each inverter being slightly phase-set with respect to its nearest neighbors in order to achieve positive waveform reconstruction, which is how you get back your 60-Hz grid signal.

 

Solar Server: Thank you for the clarification. Anything we haven't talked about that you think our readers should know about the Sequenced Inverter?

Wendy Arienzo: We’ve touched on most of the salient points. But again, the Sequenced Inverter offers the function of a microinverter, but is designed for the commercial market not only in terms of price, but in terms of function, ease of use and robustness.

It’s very important to understand that the Sequenced Inverter’s 25-year life is a designed-in result through the selection of industrial-grade components and in terms of the robustness of the circuit and redundancies in the circuitry. We’ve also used aerospace design rules and de-rated the function of each and every device so that we are not stressing our devices to the maximum. We have designed this product to last the full 25-years in the very, very aggressive environment called the outside world.

 

Interview by Solar Server International Correspondent Christian Roselund