Building a better mousetrap: an interview with SolarBridge CEO Ron Van Dell on designing for longevity, distributed solar and a new strategy for microinverter integration

Ron Van Dell
Ron Van Dell

Ron Van Dell serves as president and CEO of SolarBridge Technologies Inc., which on April 5th, 2011 won a gold medal from the Edison Best New Product Award for its solar photovoltaic (PV) microinverter solution. Since joining SolarBridge in 2008, Van Dell has been leading SolarBridge in executing a capital-efficient business model, as well as launching the company’s microinverter solution on the market.

Before Van Dell joined SolarBridge, he served as president and CEO at Primarion, president and CEO at Legerity, general manager for Dell Computer’s Dimension product line, and vice president-general manager of the Communication Products Business at Harris Semiconductor (now Intersil Corporation). Van Dell also held previous international management positions in the U.S. and in Europe at Groupe Schneider, Square D Company and General Electric.


Solar Server: First off, I wanted to congratulate you on achieving CSA certification for SolarBridge's Pantheon microinverter.

Ron Van Dell: Yes, it’s a CSA organization doing the Underwriter's Laboratory approval, which we're very pleased to have done. That's a very stringent sort of test that we've now been through successfully.


Solar Server: Lux Research recently put out a report which states that while microinverters are gaining popularity in residential PV installations, they are not as popular in the commercial and utility market segments. Can you comment on SolarBridge's target markets, and the suitability of microinverters for larger systems?

Ron Van Dell: Our focus initially is on residential and what we call light commercial. And we think that the border between light commercial and larger scale commercial is in the 100 to 200 kW range. So residential might be 5-10 kW and commercial might be 10 kW up to 100 or even 200 kW for our purposes.

And the issue as you get into the larger scale systems, particularly if you look at very large scale ground-mount utility kinds of systems, is that when you have a central inverter that is 500 kW or even 1 MW apiece, then you can get some economy of scale with that huge a piece of custom electrical machinery, that gives them an advantage for systems that are that large, but there are some disadvantages of course in doing very large PV systems instead of distributed generation systems.

We're very focused on distributed generation, and therefore on rooftop solar because we think it has some fundamental advantages compared to the large single-site systems anyhow. In particular you have no environmental or land use issues with using rooftop space.

Everybody, even environmentalists, are happy to agree that the rooftop space is already wasted space. So why not do something with it? You also don't have any of the big project finance issues with distributed generation. Nor do you have to deal with the cost and timing delays of constructing transmission lines and right-of-ways for transmission lines to wheel the power to where people already live, because you are generating it where it is being used.


Solar Server: So given the strong presence of microinverter industry leader Enphase, can you talk about the strategies that SolarBridge has employed as an emerging company?

Ron Van Dell: Well, our strategy is actually very simple and it has not changed, since we put it in place for SolarBridge Technologies. And that is to fundamentally go after the market from the standpoint of an AC-PV solution, and to do that via a partnering relationship with top tier global solar module leaders.

And essentially to go to market as an OEM partner or as a subsystem supplier that enables a top tier company to put an AC module into their product line, and not, as is the case with really everybody else in the industry right now, to sell a detached microinverter into a diffused channel of installers.

So we do not go to market the same way as other microinverter companies do, and we think there are advantages in that to us, and we think there are advantages to that for the market. Because fundamentally if you want to leverage installation costs for these small or medium-sized jobs, you have to do that by putting the microinverter together with the solar panel, at the solar panel factory.

So that is the first big difference for us. A second and very related difference, and a significant competitive advantage for us, is that we have a solution based on a very unique and very well patent protected microinverter, that enables us really for the first time in the entire PV industry, whether they are small systems or large systems, to have the power conversion functionality last as long as the solar panels in the project, and last as long as the service life that the overall economics of the PV project are depending on.

And we think those are compelling advantages.


Solar Server: Certainly. Now to get into the inside of the inverter, I have read that capacitors with a thin film dielectric typically have lower efficiencies than electrolytic capacitors, but longer life spans. Can you talk about the factors that your company has weighed in the choice to use thin film capacitors?

Ron Van Dell: Well first of all we don't think that there is any inherent difference in efficiency because of the capacitor technology. There are other factors that relate to the overall electrical conversion efficiency of an inverter, but technically we don't see film caps compared to electrolytic caps compared to any other kind of class of capacitors being directly linked at all to efficiency.

What we were able to decide, therefore, is that because the film caps have orders of magnitude longer lifetime, then they were one of several choices that we had to make to achieve a high performance single-phase microinverter with this very long life that would be compatible with the 25-year warranty.

So, we didn't really look at it as a trade-off, we looked at it as mandatory if you want to achieve those advantages of having the microinverter last as long as the rest of the system.


Solar Server: I noted that in a report that SolarBridge's inverters are competitive with other products using electrolytic capacitors.

Ron Van Dell: Our actual peak efficiency is at 95.5%. So if you think about efficiency in terms of when does it matter most, for your power losses, it is when you are trying to harvest a lot of power from the system, and our systems are extremely efficient at high power level. And frankly, when it matters most in the overall calculation of energy harvest.

And we are continuing to move that number up. The other thing that is important to think about in terms of overall economics, is that the difference of say, half a percent of efficiency, when you already have numbers that are like 94, 95, 96%, is that if you have half a percent difference in efficiency between one inverter and another on purely an electrical basis, then that is very easily swamped out by other factors that are much, much larger than the half a percent or even a 1% change.

So for instance, just the derating calculations that everyone does in doing a PV system design now, just the derating calculations for a DC-based system with a central inverter, are typically 80% when you put all the factors together, an AC-based system that is more like 90%, so if you have a 10% gain because of switching from DC to AC.


Solar Server: Very interesting, thank you. So far, microinverters have been most popular in California and other U.S. PV markets. Where is SolarBridge's current market presence, and what markets does SolarBridge seek to expand to in the near future?

Ron Van Dell: We will be launching in the North American market first, like the first half of this year, we are going into production now, our partners will be announcing their AC module products for market the middle of this and this summer, and more like the end of this year, we will be announcing the version of our product for sale for the European market.

So it is North America first and Europe second for AC-PV, which we think is similar to what anybody is doing, frankly.


Solar Server: Right. I noted that Enphase just opened an office in Europe, and that seems to be the direction that everyone is going.

Ron Van Dell: There were some bad experiences with AC-PV in Europe back in the 90's, so it is probably a more natural degree of skepticism in Europe for those reasons. I think as new companies with newer approaches and new technologies really prove themselves in the U.S. first, then that is where you will see the demand generate first, but it will certainly become the

way that residential and small to medium commercial systems get done globally over the next few years.


Solar Server: Microinverter makers are claiming that they will take over the residential markets, but I have heard analysts question that, saying that some installers are going to stay with something that they are familiar with.

Ron Van Dell: The thing about our business approach is that installers large or small will be buying from solar module companies that they already know and that they know well, and that they trust, so the issue about being risk averse, or thinking that this is outside their usage model, really doesn't come up in our case.

And when you think about how an installer would do jobs with AC modules, instead of with either DC modules that require special certifications, and dangerous high voltage DC wiring, etc., or how an installer would work with detached microinverters, that have to be individually installed and wired up one at a time, up on the roof, this is a very very good deal for an installer, because he can turn more jobs with the same size crew requiring less specialized skills.

And the end user gets a solution that is a 30% lower cost of overall energy, a safer system because it is based on just standard AC wiring, not high-voltage DC wiring, and he gets a system that he can add to heterogeneously and progressively over time. So he doesn't have to build out the system all at once and match all the panels together almost exactly the way that you have to now with DC systems.

So the end-customer is going to prefer it. The installer is going to prefer it because he gets the same throughput with a better head-count, and the module companies like it because now they are just a bigger share of the total project, and they like doing that.


Solar Server: So is there anything that we haven't discussed, in terms of SolarBridge's product and the future of microinverters?

Ron Van Dell: I think there is one point that is probably worth throwing in here, and that is the whole question of what are the warranties and what are the expected lifetimes of microinverters. And to me, there is a lot of kind of interesting claims and counter-claims and things being said out there that would merit some clarification.

So I would leave you with two thoughts on that very important subject of warranties and lifetimes, because it impacts on that replacement cost question, which is a big part of that total cost question for PV systems. The first point is that some companies are trying to get people to believe that the early life failures, kind of those infant mortality, kind of "do I have field recalls within the first few years?", which are standard for any kind of new technology, are exactly the same as the wear-out mechanisms that might happen 10, 20 or 30 years from now.

Of course, that's just not reality. The reality is that you could have a product that is very successful in the marketplace and have no field issues say for the first few years, but that still is likely to do a total face plant for wear-out mechanism reasons in ten years.

So the idea that the first year or two is going well and therefore that equates to long-term life is just not the way reliability works in electronic systems.

And the second point, and this is probably very interesting for your readers as well, is that if the service life of your system, which is kind of the denominator for the economic payback on the system is, say, 25 years, which is pretty typical, then if your product goes out of warranty at five years or 15 years or 20 years, the point is that it is still out of warranty before you get to the end of life of the system, so you are still going to carry a cost reserve in how people do the financial calculations for a system like that.

So there really are no shades of gray where it might be ten years, fifteen years, or whatever in terms of the lifetime of the inverter. You are either going to have the same expected lifetime and the same warranty as the rest of the system, or you don't.

So I think the other thing that is worth clarifying is this idea that there is somehow this proportional advantage of slight increases in warranty time. And that is really not the way the math works. You either have to have confidence, which is really based on the design and the architecture, that you are going to have a long enough life that you are not going to have to roll a truck, or you don't.

And I think people should start thinking about it in those black and white terms, and realize that the shades of gray really don't make economic sense.


Conducted by Christian Roselund on March 15th, 2011