Micro Inverters

[Earthstore]

The main issue with micro inverters was if they need replacing if one fails, and I did wonder why they were not put in the loft, in a line, but you have answered that one.

 

[Noddy67]

Just looking at the opening request I find it odd that you'd consider changing a solution because PVSol won't allow it but the manufacturer will...

More balance on the Enecsys front. I've fitted five systems - all with Sanyo - and I'd say they were less than a fiddle than traditional inverters.

My concern with pushing enecsys is the warranty - they're warranted for 20 years but i have to retrieve and replace them. But with about 65 in field there hasn't been a problem.

I'd say Enecsys are tried and tested in this country than most other brands - and my experience is they're good solid bits of kit... and they're based in the UK which is a convenience in itself.

 

[mbuckhurst]

there've been some issues reported elsewhere with these inverters and sanyo panels of both types in shaded conditions - ie the conditions the things are designed to work best in supposedly, although I think some of these were at least partly down to the installers not understanding the bypass diode layout on the H series panels (along the long side, not the short)

We looked at these a while back, but couldn't find a situation where after modelling it the improved efficiency of the 4000TL outside of the shaded time didn't over ride the better performance of the micro inverters during shaded conditions, which almost always occur towards the start or end of the day when output is low anyway. Combine this with the 4000TL's dual MPPT and optitrack global peak shading function, and I'd bet on that system to outperform the enecsys micro inverters over the year 9 times out of 10 even in shaded situations.

Then there's the issue of getting on the roof to replace the inverter if one breaks down.... it may have a 25 year guarantee, but if there are 16 of them then the chances of one going earlier than that are pretty high, and they definitely had some quality control issues last year with several failures reported.

Basically it fails the KISS test IMO.

My install is probably up there with the most complicated around, with panels with 4 different orientations, I had no choice to install anything other than micro inverters, which proved extremely difficult with only one installer prepared to consider fitting them, despite that being a demand on my part, several suggesting a single string inverter connecting all panels together, which to my mind did the industry no service whatsoever.

Anyway, if you look at the amount of energy being generated on any individual panel it rarely agrees with any of the others in the same orientation, whether above or to the side (and we're talking quite significant differences), and they definitely never agree with any other panel on a different orientation, this makes me think that the increased inefficiency, something like 2%, can generally be covered by the losses you would get on a string inverter because the panels are not able to operate at the efficiency of the individual panels, but more constrained by the worst performing. An MPPT could not operate effectively under these conditions, unless of course you've got one on each panel, as you have with micro-inverters.

In my particular instance shading is also another problem, with this factored in, I would lose 3 extra hours a day of generating capacity for my most effective grouping of panels and this is likely to be true in the Summer as well as the Winter - this on it's own makes the micro-inverter a bit of a no brainer.

I think a lot of people are making assumptions about the use of micro-inverters without actually knowing the truth, it's only once you have them installed can you see the potential benefits or maybe even failings. It would be interesting to do a side by side comparison but that will never be possible unless we could guarantee identical conditions for each test.

I personally believe my system would not have generated anything if I'd gone the traditional route, and I think the British conditions particularly lend themselves to the use of micro-inverters.

mike

 

[mattiker]

Also, consider an installer who perhaps installs a dodgy connector, or you have a panel fail which results in 1 of your panels being down - how will you know that you are 1 panel down with a regular single inverter? You might never know, and it might be months/years before you twig. Please correct me if you think I'm wrong - I'm no expert.

 

[mbuckhurst]

I would like to echo the statement made by HPSauce:

Provided the installer is properly trained and the customer is not the guinea pig, the installation of the inverters and the commissioning of them is a very quick and painless exercise.

We have 14 micro inverters together with a repeater. The inverters were all installed and the system was up and running in just a few hours. Our website was up within an hour of the system commissioning.

We have had no issues with system communication or with access to the Enecsys website.

Sometimes the customer has no choice, I met an almost complete brick wall over installing micro-inverters, most installers would always quote one of the following answers

1) Unreliable
2) Cost too much
3) Not as good as a string inverter

Sometimes I'd get the 'we're not trained and therefore won't fit them', but I'm sure that's just avoiding saying 1-3. In the end the only installer who was happy from day 1 to install, got the job, despite us knowing this would be his first micro-inverter job, we had to be guinea pigs if we wanted micro-inverters.

In the end we've got an excellent job, we do have communication issues with one panel only ever managing to 'talk' late in the day, when some panels are no longer generating, but this is most likely due to the fact we already have a home security and automation system using Zigbee on the same frequency, personally have 2 wifi networks with a further 8 visible and my loft is insulated with foil backed material, so I've yet to find a spot for the repeater that can receive from all the panels. But since the generation meter in the garage is the only important thing and that's showing all panels generating fine I'm happy.

And if you need proof that micro-inverters can be helpful, my lifetime figures to date suggest between 40 and 50% variation in generation from the worst to the best in my 3 main groups of 5, 4 and 4 panels (i.e. the groups that would each be on a single string), and 5-30% between the best and the second best in each group. I assume that in reality, in a string, I'd only generate roughly the lower amount on each panel, wasting the difference.

mike

 

[SolarCity]

Also, consider an installer who perhaps installs a dodgy connector, or you have a panel fail which results in 1 of your panels being down - how will you know that you are 1 panel down with a regular single inverter? You might never know, and it might be months/years before you twig. Please correct me if you think I'm wrong - I'm no expert.

To be fair, one panel going down will more than likely take down the whole string - you'd soon know.

 

[JohnDee]

My Enecsys + 10 panel Sanyo HIT250 system went live late on Friday and I had the monitoring system installed this afternoon. I am in Cambridgeshire. The roof is tricky, with dormer windows and some of the best (high) roof space already occupied by an old (but working) solar thermal system. We put 5 panels on the rest of the high roof space in a 2, 2 and 1 landscape configuration around a velux window; the other 5 went in a landscape row at the bottom of the roof at first floor level, just above the conservatory roof. The roof is steep at 47 degrees, concrete tiled and faces 10 degrees east of south. I will publish a picture later if anyone is interested, after the scaffolding is down. The house is about 23 years old.

My installer commented that the upper part was really tough work - on the positive side I had suggested he put those 5 micro-inverters in the loft for ease of access and that worked out fine. The other 5 are behind the panels but much easier to get to if there is ever a failure. The whole install took about a day and a half rather than the planned day, mostly because of the difficulty in working on the top part of the roof. All the cables have been laid underneath the tiling which is cool.

To add to the debate about ease of install of micro-inverters, there were no problems with the mechanical part and the inverters all self started. The commissioning of the data logging system took just 45 minutes from start to finish, the only problem was that my wireless router decided to die for some reason though I got it going again soon after. The gateway is in the middle of the ground floor near the router. It took about 5 minutes for the gateway to find all the panels and we don't seem to need the repeater, though I have kept it just in case. Once Terry (my installer) had logged on the Enecsys monitoring site with his password on my PC it took me (not him) about 15 minutes to allocate and register all the panels - I didn't even need to read the instructions as it was pretty intuitive. I am tecchy and computer literate but this was not hard! I had no training at all. Nor am I exactly a youngster either

We had to wait a few minutes to get my log-in back from Enecsys and then that was it. I downloaded the i-phone app too at the same time and got that running - my only (geeky) disappointment is that this is a lot more limited than the PC app so I can't see individual panel data.

I was pleasantly surprised to see that the inverters had logged their performance from the moment thay had received power from the PV panels, albeit all lumped as today's output. It was easy to see the 2 high mounted panels that get a little bit of shading during some parts of the day from a chimney and a dormer window; they were down about 10% from the other 3, which each managed 3.3KWh from Saturday to Tuesday - two sunny days and 2 very overcast ones. The 5 low panels are so far much worse (-50% or so for 4 of them, -60% for one), probably because the scaffolding is still up as well as a little tree shading. We shall see what happens when the scaffolding goes! Overall the Enecsys gateway says the system has generated 23.2 kWh so far - interestingly this agrees almost exactly with the 23.1 kWh recorded by the generation meter. This suggests the post-inverter losses are under 1% - the AC cable from the loft is 6mm (thanks Forum), so that probably helps!

Once the system has settled down I will keep the Forum posted on the effects of shading - obviously there is no direct way of comparing with a 2 MPPT inverter (I would have used a Power One) but I am quietly confident that what I have, though more expensive, is ultimately a better yielding solution.

Finally my installer is local - Solar Merge - and I am glad I chose Terry Mann and his crew over a larger company from the midlands, even if there was a small cost penalty. I introduced him to Enecsys and this was only his second system - he is putting in a third next week as well. Several other companies I contacted refused point blank to consider micro-inverters - that's their loss.

I hope you all find this helpful; I am happy to answer any questions.

John

 

[Vegelen]

SMA is introducing a micro-inverter product later in the year. Hopefully a bit of competition will make micro-inverter pricing keener.

SMA UK have said that their microinverter range wont be available in the UK until 2013.

 

[fiardor]

Power one have also produced a micro inverter I have posted the link somewhere in this vast forum! Lol

 

[finchy]

Great thread found ! Shame SMA have delayed micro inverters to 2013 however it shows their lack of commitment in the very uncertain UK market.

 

[SolarRoofSols]

This is a great post, i am looking at a quote for a customer with big space/ shading issues, at least 1/2 of the panels will be in shade at one point as the sun moves round. Unfortunately they have thermal in the best spots for PV!

I was thinking of SMA 4000TL with opti track turned on or do you think that micro is the way to go? I am looking at 15 x Sanyo 250w.

Also how much more in % terms is it to install a micro system over a string inverter?

 

[finchy]

£240 each plus gateway £160 !

I'm actualy trying to find Enecsys designer tool ... I've got all the other from SMA, Frontius Mastervolt even solar edge ....

 

[finchy]

the guys at Enecsys seem helpful i just called them !

 

[Gavin A]

My install is probably up there with the most complicated around, with panels with 4 different orientations

just seen this, so I'll reply a little late.

When commenting on micro inverters, I'd usually have added a proviso, that there are certain exceptional circumstances in which they could well be the only viable, or the most viable option. It seems I missed this from my comment, but your situation would certainly seem to satisfy that criteria, so I'd think it likely that micro inverters would have been the best option for you.

Personally, we've not yet come across such a situation ourselves that I can recall.

 

[mbuckhurst]

The thermal panel in the best spot was our biggest problem, not that it would have provided a roof with enough space for a complete install.

In terms of cost, I don't think installation should take much longer than normal, probably the majority of the extra time would be lack of familiarity rather than because it takes longer. So basically it's the difference in cost for cabling which may or may not make a difference, plus the difference in cost of the Enecsys kit minus the SMA kit. I reckon ours cost £1000 more to use micro-inverters vs string inverters, plus an additional £500-1000 because of the lack of competition for the installer (partly because practically no one wanted to install them and also because the government gave us a deadline meaning we chose the most likely to complete in time).

It's very difficult to say whether micro-inverters are best or not, since no one I'm aware of has a comparison. It all boils down to just how good MPPT really is, and how much shading of one or more panels occurs at a time and therefore how efficient the string inverter is going to be, if you find a string shuts down for part of the time the shading occurs, I reckon a micro-inverter will always achieve better results, my experience suggests there's little to choose between them once you balance out all the postitives and negatives, but if there's any variation in the cooling, orientation or angle of the panels the lower efficiency of the micro-inverter will be more than compensated by the more efficient generation.

mike