Going solar

It looks like it’s going to happen this year – we’re going solar! It has been on my wish-list since 2008, so it’s time to do something about it. The decision to finally cover our roof with solar panels was the easy part – and now I’m overwhelmed with all kinds of questions!

Solar panels

Of course, I want the best there is in terms of quality, the amount of electricity they produce, power degradation caused by aging, guarantee (and all that within our budget of course..).

What brands should I look for, which ones should I avoid? The panel dimensions seem to differ a bit as well (lengths from 160 to 180 cm); which dimensions are optimal for our situation (orientation, available space)? How much room do I actually have to place solar panels? Should I buy mono- or poly-crystalline panels, or should I not even worry about that?

Inverter

Again, which brands have a good reputation, have well documented monitoring capabilities.  And what’s this Optitrack Global Peak, do I need it? Or maybe all recent inverters have it built-in already?

These are all questions related to the hardware; but there are some other issues to resolve as well and not all are that easy to deal with.

Should I go all the way now or save some space (and money) for next year? And should I buy an inverter with more capacity than I really need, so that I can easily add more solar panels next year? Will this have a considerable impact on efficiency this year? What’s the best place to install the inverter? As close as possible to the solar panels sounds like the best thing to do, but that’s not so practical in our case.

Another thing to tackle is that we don’t have a crawlspace under our house, which makes it harder to easily hide cables; how difficult will it be to get cables from the inverter to where the connection to the utility grid will be made? I don’t really like cable ducts on the outer walls of our house; however, I like them even less inside! How much do our roofs suffer from shading caused by surrounding objects? What will this do to the solar panel output?

Oh my… all those questions, decisions to make, things to dive into… so I decided to first take one ‘easy’ decision: I will install our solar system myself (with a little help here and there). Mounting the panels on the roof, the cables from the panels to the inverter and to the mains distribution panel. That should all be not too complex for me, I guess.

I’ve been sketching, surfing, measuring, reading, searching, discussing during the last 3 weeks and I think I know a bit more now. For instance, in our case it looks like it’s better to give the solar panels a SW (South West) instead of a 100% South orientation, since the number of panels that can be placed on the roof in SW orientation is much higher; and those extra panels can easily (over-)compensate the efficiency loss caused by the SW orientation.

Another thing is that it looks like a good idea (efficiency-wise) to give the solar panels an angle of 30° inclination, but this will result in a very large distance between multiple arrays of panels, sometimes as much as 2.40 m! By using an angle of 20° this distance can be reduced drastically, which might give enough room for an additional array..

Portrait or Landscape, another thing I’ve been thinking about. With partly shaded panels the preferred orientation is landscape, cause (assuming that it’s the lower part of the panel being shaded) in portrait orientation the bypass-diodes can/will shutdown a complete panel instead of just a part of it.

Talking about shadow; how much shadow will the solar panels face? I really don’t know! I don’t spend that much time on our roofs… I do know where the sun rises and sets approximately, but never really paid attention to if, where and when we suffer from shadow – especially on the roofs.

To get some more grip on this I made a Google SketchUp Model and created 6 animations, for January 1st, March 1st, May, July, September and November. Just to give me some more insight on the amount of shadow. And now I know that (what a surprise) November till January are really shady months up there! Watch the 6 animations yourself here:

 

Well, it seems I’m still in a stage where trying to find an answer to a question brings up more questions than answers…

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7 Responses to Going solar

  1. Malcolm says:

    Hi. May I suggest

    for your solar questions.

    I use PowerOne Aurora 3.6kW & very satisfied with
    3996kWh last year. Separate Aurora forum in above forum.
    Regards Malcolm

    • Hi Malcolm,
      Thanks. I think I’ve already been on the forum you mention, searching for protocol information for Samil inverters.
      Solar panels and everything that comes with it is a whole new world for me and there’s so much to learn 😉

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  3. Soitjes says:

    Hello Robert,

    I can share some of my experiences with solar panels :

    – I don’t think you should look much at what people have installed on their roof, because the panel efficiency improves at a rapid rate. When I installed my panels they had a higher capacity than a friend of mine only a year before.
    – The inverter I have is from SMA, which is a very well known brand. Connecting it to my application was a journey which you can follow here : http://www.digitalhomeserver.net/148/. Delphi code is available on request if you would go for SMA.
    – Don’t underestimate the efficiency loss, both for the sun position and shadow. I can clearly see in my application that the productivity peak is quite short (around 1PM), before and after it’s a steep curve ! And as panels are partly connected in serie shadow is having a serious impact. To be avoided at all cost.
    – if you have more electricity production than your consumption you should remove your double meter (day/night), because it has no use anymore. Worse, you will still pay for what you consume during the night (where you don’t produce), and the overproduction during the day is lost. If you have less production than consumption you can leave the double meter, but some careful monitoring is needed to optimize the electricity bill.

    Regards,

    Walter.

  4. Ysbrand says:

    Hi Robert,

    SOunds like you have a flatroof (like we do). I also had to make a decision between more panels (with a consequently lower tilt) or go for an optimized panel. I did a lot of research on this and in the end I decided to go for 15% which resulted in an extra row without having having to deal with shadow (especially in the winter). So far it turns out that we have quite good production results when compared with other sites. You might want to read http://www.siderea.nl/artikelen/hellingshoek1/hellingshoek1.html for more info on this very subject.
    Also, I’m using an SMA inverter as well, using bluetooth. smatool, which allows you to query the inverter, works ok but it has some quirks. One thing to keep in mind when selecting the inverter is the potential noise, some of them are producing quite a bit of noise, so either select a different one, or keep it into consideration when looking for a suitable mounting spot.

    Regards,

    Ysbrand

    • Hi Ysbrand,
      You’re right, we have a flat roof. The surface is quite large, but divided over 2 height levels, which adds some additional complexity regarding which areas can be used and which not. 15 degrees elevation is something I didn’t really ‘play’ with yet although I know it can have a big effect on the number of panels – back to the drawing board! Again 😉

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