Microinverters: A major advancement in solar energy technology

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Published on August 23, 2008 by Dan Hahn.
Categories: Solar Technology.

082308 1854 microinvert1 Microinverters: A major advancement in solar energy technology

While it may appear as though Dave has fallen asleep recharging himself, he’s actually got a sexy new piece of solar equipment in his arms. The slim metal box is called an Enphase “micro-inverter”. No, a micro-inverter is not akin to a kickflip, ollie, or other skateboard trick.

If you’re just getting familiar with solar electric technology, you probably know at this point that there are two major components necessary to produce usable electricity from the sun. Simply slapping panels up on your roof and running wire down to your home won’t do a whole lot of good unless you plan on vaporizing your spouse. To convert that direct current from the panels into usable electricity, what is required is a pretty bulky box called an inverter. So, you might imagine that a “micro-inverter” would simply be a smaller version of this box, right? Kinda like a “micro-chip” or a “micro-machine” or “micro-economics” (ugh)? The short answer is, “uh-huh”. In sum, this micro-technology is a hell of a lot better for many reasons. To understand why though, let’s get a little more familiar with “regular” inverters and how they work with solar panels.

Pretend for a minute or two that you are newly named foreman of a very unique Peruvian diamond mine. Diamonds from this mine sparkle with a luminescence unlike any other diamonds. However, to create these special gems, the raw diamond material must be polished minutes after it is extracted from the earth to attain this luster. The previous foreman (let’s call him Hector), only trusted one person (let’s call him Jose) to polish the rough unfinished diamonds into highly desirable, glittery diamonds. Of note, Jose has recently called off work with illness more than usual, is nearing retirement age, and you sense he’s becoming a little disgruntled. The rest of Hector’s miners (Juan, Domingo, and Maria) extract raw diamond material from the mine but are highly interdependent on one another to get their rough diamonds to Jose before they lose their ability to be special and glittery. Meaning, if Domingo decides to take a break, Juan and Maria have to stop what they are doing to wait for him to get back to work before they can pass more diamond material along the line for Jose to polish. Consequently, a lot of valuable diamond material gets wasted. Hector was fired because the daily yields from his mines were, well… lackluster. To alleviate this problem and get more special sparkly diamonds out of the mine, what do you do? Hold that thought.

In a conventional solar power system, interdependent strings of panels are placed on roofs and operate in much the same fashion as Hector’s miners. Panel A, Panel B, and Panel C are a lot like Juan, Domingo, and Maria. If one panel gets obstructed even by just a little bit by a big leaf, bird poop, or lovely tree shade, the entire string of solar panels suffers, sending significantly less or even no raw power down the line. Each panel needs to work with other panels in the string to get raw power to the inverter. The regular inverter is a lot like Jose, taking the direct, rough, unfinished current from the combined panels and converting it into sparkly, glittery alternating current you can use in your home. So, when shading or obstructions impact one of the panels (a lot like Juan, Domingo, or Maria taking a breather), the inverter (Jose) has a lot less raw material or current to work with. Let’s go back to the mine.

What if you placed small robots alongside Juan, Domingo, and Maria to monitor their performance and carefully polish raw diamond material into finished diamonds? Then, even if Domingo is unable to find any raw diamond material to extract, Maria can still be extracting, polishing, and producing. In addition to teaching your employees new skills (which by the way has been related to lower turnover), you are now a lot less reliant on a disgruntled employee (Jose), you can increase your diamond harvest, and you are able to eliminate a point of failure along your production line. Your only concern is that your workers get along well with their new micromanaging robot companions.

This is precisely the reasoning which led Enphase Energy engineers to create micro-inverters. Micro-inverters are attached to every single solar panel in the system and each one is capable of converting direct current from its solar panel into usable electricity – independent of other panels on the string. This means that even if one panel gets shaded a little bit by dust, bird poop, or a tree, the other panels are still capable of feeding usable electricity into your home or business. Moreover, you are no longer reliant on the regular inverter, a bulky eyesore of a box that has a lifespan of 10-20 years. Currently, if you have a massive solar installation on your commercial plant, when your inverter fails, you need to purchase all of your electricity from the grid until it gets replaced. That can represent a sizable chunk of unplanned cash out of pocket.

In addition to more uptime, micro-inverters allow system owners to monitor the energy output of each individual panel, alerting them if one is underperforming (Each micro-inverter can send a signal through your internet connection so that you can see how well each one is doing). What’s more, you can now combine different types of panels together and place them at different orientations to the sun and still expect good production out of them – unheard of before.  Finally, micro-inverters allow your solar system to be scalable – meaning you can purchase a few panels to start out with, then add onto your system without additional engineering outlays. Lab tests indicate these micro-inverters will have a lifespan of about 120 years.

Read the 15 brilliant comments below or add yours!

Nathaniel Identicon Icon Nathaniel
Comment on August 25th, 2008.

So… Any idea on how long it will be before these are commonly available? Will they be integrated into the panels we buy from a particular manufacturer or added to each one by you the installer?

Comment on August 25th, 2008.

Nathaniel,

Micro-inverters are available currently through Enphase energy. The trick is getting installers up to speed on how to mount them and city permitting. In a recent conference we attended, the VP of Sales mentioned they’d have a newer model out in the next 2 to 3 months. While Enphase is the most well capitalized and has been the fastest to market, other manufacturers are in the fray and are watching closely.

As far as panel integration goes, it’s funny you ask as I was just talking to Dave about this 10 minutes ago. I thought it would be a good idea for Enphase to form a sort of joint venture with several panel manufacturers to make installation simpler and create a more compelling value proposition. However, they are proceeding with selling the modules separately.

Comment on August 26th, 2008.

Not to harp or be disgruntled because fundamentally it doesn’t bother personally me (as a mexican), but as someone who edits a lot of content for public release… You might want to refrain from using stereo typical “Mexican” names in the diamond mine… a little racist that all the help is Mexican and only one is skilled and even he is disgruntled and takes a lot of breaks… Try a John and a Bill maybe… Other than that I really like your blog and after I got sick of all the “Green hype” blogs I continue to read yours due to the facts and the genuine experience you portray… Keep up the good work. Cheers

Leesa Lee Identicon Icon Leesa Lee
Comment on August 26th, 2008.

Hi Dan,
Thanks for the posting and glad to hear that we didn’t put you and Dave to sleep at the conference. In terms of integration with panels, we are indeed in discussions with panel manufacturers, but the reality is that the main driver for these discussions is really to streamline sales and marketing, not for ease of installation. The installation of our micro-inverters is actually super easy. The units install on the existing racking used for the panels, and take only minutes (or seconds, once you’ve done a few) to install. We encourage everyone to view our installation video to see what we mean: http://www.youtube.com/watch?v=hJPXsN_gFz8. As for the plans for additional products, we are working on broadening our compatibility with a wider range of solar modules. I can’t give any specifics or dates just yet, but our website has a list of modules we’re compatible with and we’ll add to it as we expand our compatibility. Again, thanks for the interest and kind words.
Leesa Lee
Director of Marketing, Enphase Energy

Pingback on August 28th, 2008.

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Comment on August 31st, 2008.

Cool idea. It could also eliminate the need for circuit interrupters (fuses) on the roof.
I tried the video link and got this error: “The URL contained a malformed video ID.” Poking around, I found this one:
http://www.youtube.com/watch?v=hJPXsN_gFz8 Which is the same, except it does not have the dot at the end messing up the URL.

Comment on September 14th, 2008.

HI, I WANT TO KNOW IF YOU DO ORGANISE TRAINING ON HOW TO MANUFACTURE MICRO SOLAR ENERGY FOR HOME AND OFFICE ELECTRICITY SUPPLY AND MACRO SOLAR ENERGY FOR ESTATES, FACTORIES ELECTRICITY SUPPLY.THANKS.

Comment on September 29th, 2008.

How does the cost compare to traditional inverters? Obviously on an individual basis they would be cheaper. Is there a point where an installation gets large enough that the traditional inverter is the cheaper way to go? Not debating value at the moment, just upfront cost.

Comment on September 29th, 2008.

Hi Patrick,

Good question. For large installations, it could be sensible to include a mix of conventional string inverters as well as microinverters to bring the cost down. If you own a business and are considering this, give me a buzz.

Keith Identicon Icon Keith
Comment on May 11th, 2009.

I’m building my own solar panels, will your micro inverters work with any panels or do I have to make a specific watt panel, can they be used with a battery storage bank for when there is no sunlight?

Mark Identicon Icon Mark
Comment on August 12th, 2009.

Inverters have always been the weakest link in the system. In terms of reliability, operating temperatures and temperature cycling play major roles to life. With these micro inverters, they are installed in the worst possible area being on the roof behind the modules. I do like the idea of the micro inverters as the scalability is ideal but can’t support them until they have a chance to prove the reliability.

More Points:
1: They have only been on the market for a little more than a year- no track record in the field.
2: The potential for 1 problem ( 1 inverter) vs as many problems as there are panels on a roof.
3: If a microinverter panel is installed in a non-optimal location because it can tolerate shading, why install it at all if it doesn’t have a chance at working efficiently to begin with.
4: Degredation from heat and cold exposure.
5: Here’s a big one: I an inverter goes bad, you have to take a panel off the roof. What if multiple inverters go bad in intervals. The installer would have to come back all the time to replace them as they go. Who pays for this service? If it’s after the 15 year warranty period, the customer will have to pay the installer to get up on the roof every time an inverter goes bad. You can replace a single inverter in less than an hour.

Pingback on August 20th, 2009.

[...] 9, 2008 by David Llorens. Categories: Solar Trends.A few weeks ago, Dan wrote a post about micro-inverters for beginners, comparing them to the inner-workings of a Peruvian diamond mine.   This article is [...]

Pingback on February 10th, 2010.

[...] September 9, 2008 by Dave Llorens. Categories: Solar Trends.A few weeks ago, Dan wrote a post about micro-inverters for beginners, comparing them to the inner-workings of a Peruvian diamond mine.   This article is [...]

Ken Identicon Icon Ken
Comment on March 12th, 2010.

I am looking for microinverter, other than Enphase, which model or brand name you would recommend me to find out more about it?

Comment on March 12th, 2010.

Hi Ken,

I’m really only familiar with Enphase, and just from knowing about their initial reliability studies and engineering team brought over from the cell tower industry, I don’t believe you should be looking anywhere else.

- Dan

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