How micro inverters are solving problems

13 May, 2014

In our previous post on micro inverters, we looked at how they have the potential to change business models. In this second installment we look at how they are solving real world problems for installers and consumers.

A crucial starting point is some Australian context. For a wide variety of reasons, Australia has a market that is almost exclusively driven by small scale residential sales. By the end of 2014, we predict that the National average rooftop penetration rate will be almost 30%; an astounding and unique scenario in the world.

Obviously this varies by region, but one thing is unequivocally clear; those huge North facing roofs are less common than they used to be in the PV buying market place. We have been banging on about the probability of this for some time but recent events provided some evidence that this is now occurring with increasing frequency.

The first example I recently found was by scouring some of the online forums that talk about solar. A year ago, the talk was all about which installers and which products were best. The main thrust was about how to get a system installed as quickly as possible at the best price from a reputable supplier.  But when I did a search recently, I found thread after thread talking about “difficult roofs”, “multiple orientations”, “the need to put PV on an upper and lower roof” and low and behold, a number of installers saying “the price difference between micro inverters and string inverters is not that much”.

Again and again the issue of tricky roofs came up and suddenly the light bulb went on for me; I’ll be damned if we aren’t now seeing a whole lot more difficult roofs starting to emerge. Anecdotally, perhaps the most interesting thing about roof top penetration levels in Australia may be that once you pass around 25%, you can pretty much count on that being the trigger for a different type of roof scenario and that makes for some really powerful business planning information.

The second example I can point to is even easier; open your eyes when you are driving through heavily solar populated suburbs. I’ve done this a lot lately and typically around 20% of the systems I’m seeing are on split roofs or subject to partial shading. A random sample of eight systems I recently looked at (selected from 200 potential sites) had partial shading on 35% of the roofs and multiple orientations on around 20%.

The third example is a story published in Ecogeneration magazine recently. Their article “Smart solar is good news for retail outlet” highlighted how a shaded commercial site could only 18kW using string inverters but using micro inverters, the capacity was lifted to 29kW. That seems like a win for the shopping centre and a win for the installer if you are asking me.

So, the proportion of difficult roofs is increasing rapidly, I would suggest. It’s logical and backed by multiple sources of anecdotal and varied data sources. Micro inverters just make a world of good sense here of course, for all the reasons you know.

But there is way more to micro’s than just dealing with difficult roofs or shading.

Many installers were quick to point to publicly available data logging sites showing back to back data comparisons of micro’s and string inverters. Several sites showed similar performance benefits of around 5% in unshaded, back to back tests. One installer has a great data set on the same roof, with the same orientation and pitch and was completely smitten with the results. Over a sample of 60 days of data, there was an average 7.7% more energy delivered by the micro inverter based systems.

So micro inverters deliver more energy, even in unshaded sites? The data certainly seems to show that this is the case. The diagram below from the Enphase website shows why.

enphase array crpd

 

Solar arrays are not uniform and a whole lot of things can affect performance as we talked about in our last post. What I also learned from analysing the installer data and from their comments is that not only do these typically add up to more energy, but micro inverters also tend to start up earlier than string inverters, fattening up the daily production curve. They also generate more energy on low light days which is really helpful in the winter months when energy production is lowest, a point discussed at length on some of the forums and backed up by some of the data.

So, as Enphase highlight so well in their graphic, there is a whole lot more to micro inverters than just shaded sites.

The other interesting thing I observed in the forums was a little bit of history repeating itself. Just like the slow but inevitable realisation that all inverters aren’t created equally, the same discussion is now happening with micro inverters. There is a lot of debate and some good benefit of hindsight when it comes to choosing reliable, well supported products. (Option to link to a good thread here?)

Like the flood of crappy inverters we saw in the rush, the number of micro inverters available has increased dramatically too. However, it seems that everything happens faster in the micro inverter world; industry is already very tuned in to the fact that cheap imitations are simply not going to last mounted on the roof, under a solar module. You really need to focus on companies who have big market share and are intensely focused on quality and service to get this right.

One major micro inverter supplier I spoke to was stunned at the recent growth in their sales of the top selling micro inverter brand in the world “Last year we didn’t really offer the product and this year, I reckon the majority of our sales will all be that one brand. Installers have wised up very quickly”.

In our next installment, we’ll look at how micro inverters are opening up entirely new markets.

 

 

Post expires at 11:21am on Tuesday May 13th, 2014

About the author

Nigel Morris
Nigel Morris

Nigel is the Director of SolarBusinessServices. After almost 20 years working for other companies SbS Director Nigel Morris, established the company in 2009 with a view to providing other organisations with the benefits of his wide experience in the renewable energy industry.

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5 Comments

  1. May 14, 2014

    Hi Nigel,

    Yes, I’m seeing a surge in interest in micros too.

    Will be interesting to see how the bottom end of the market, e.g. APS fare with their reliability problems though. The dealers are admitting 2%-5% failure rates in the field, and installers I talk to are claiming up to 10% failure rates. When a typical install has 20 micros on the roof, those are unsustainable rates of failure.

    Higher end micros like Enphase and Solarbridge are getting rave reviews from many installers though.

    I still like micros. So much I got an infographic done:

    http://www.solarquotes.com.au/blog/microinverters-vs-central-inverters-infographic/

    Finn

    • Nigel Morris
      May 14, 2014

      Hi Finn

      Awesome Infographic mate! tells the story nicely OK if I re-publish that?

      You are right; quality really matters with Micro inverters

  2. May 14, 2014

    Hi Nigel,
    Would you be able to ask these questions of any micro manufacturer and get a straight answer? Because I certainly haven’t been able to ;o)
    1) Please provide a thermal photograph of an array at 45degC ambient on a sunny day. Object being to see what temperature differences/gradients is/are shown across the faces of panels with micros underneath.
    2) Does this indicate an ambient under the panel in excess of 65degC? – which is the datasheet limit for most brands.
    3) If the ambient temp datasheet limit is exceeded, what guarantee does the customer have that the manufacturer will honour the warranty? Because legally they do not have to!
    4) Do any manufacturer warranties for micros provide any part or full funding for the labour to climb on the roof and exchange any failing micro? Otherwise of course it is an additional risk-cost of ownership for micro customers.
    5) Please provide comparative annual data for a micro array in Australia. This last point should be a no-brainer, and yet I often hear gains of “25%” over string inverters arbitrarily quoted in the market place, but with no apparent data reference, and certainly not one applicable to Australia
    Thanks in advance!

    • Nigel Morris
      May 14, 2014

      Hi Chris

      Great set of questions – any Micro inverter manufacturers want to take up Chris’ challenge and give him a response?

    • May 14, 2014

      Hi Chris,

      Great questions you have put forward. I am Duncan Macgregor, a Product Trainer with Enphase Energy in Australia. Here are some answers to your questions:

      1) Enphase has completed a study on this topic, using thermal imaging. Here is a link to the document: http://bit.ly/1oNqtfo

      2) I do not know the data sheet limits for all brands, however, Enphase M215 the microinverter internal operating temperature range is -40 to +85.

      3) So long as the microinverter system is installed as per the installation recommendations, the Enphase M215 warranty will apply.

      To understand the impact of temperature on micro inverters here in Australia, we run tests and monitor Enphase installations across Australia (every Enphase microinverter has an internal temperature sensor). Have a look at this Technical Brief where over 2000 Enphase microinverters were analysed across Australia in January 2014: http://bit.ly/1oqmVSN

      4) To minimise cost to an installer, Enphase provides an installer payment associated with a replacement in the event of a microinverter failure under warranty.

      5) As I write this, Enphase is setting up monitoring on real-world side-by-side installations here in Australia. A number of installers have put Enphase systems in with string inverter systems for comparison, and I have seen positive results for Enphase on these sites. I was recently impressed by a site I stumbled across, a side by side installation in Bendigo, Vic that showed an 85kWh production benefit using Enphase over a string system.

      All Enphase systems can be viewed online. You can view system energy production at hundreds of live sites across Australia. Link to the public view is found here:

      https://enlighten.enphaseenergy.com/public_systems

      Happy to answer any other questions you have!

      Cheers
      Duncan.

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