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  1.  
    Hi All,

    I've not been on for a while so it's good to catch up.

    I have finished by self build now and I am considering PV installation as the price has plummeted.

    I couldn't afford the installation during the build unfortunately.

    what should I expect to pay for a simple roof installation these days?

    Is it worth paying the extra for Monocrystalline panels?

    What fixing system is best for a modern slate roof?

    I hope to use the power to pay for some of the GSHP running costs.

    Would you install a larger system if possible as my roof is around 12mtrs long and is one flat surface with usual pitch.

    Many thanks for any advice all.

    Gusty.
    •  
      CommentAuthordjh
    • CommentTimeApr 28th 2017 edited
     
    Posted By: gustyturbinemy roof is around 12mtrs long and is one flat surface with usual pitch

    When you say usual pitch, what do you mean? And which way does it slope? Roofs come with all kinds of pitches.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 28th 2017 edited
     
    Hello Gusty, good to see you again.

    In my opinion there is little to be gained by gettign monocrystalline modules. Just hunt out the cheapest as you are limited to 4 kWp (actually 16A per phase).

    You may find that by playing about with the module size in Wp, you can get an extra module on, but 16, 250Wp modules will cover a little over 25.6m^2.

    Don't think that the fittings have changed any since I was involved with them. Slate fittings tend to be just bolts that are through the tiles (holes drilled first).

    If you want to contribute to the GSHP you may want to fit a timer onto the heat pump so that it is only activated during the most likely times that the PV is producing.
    • CommentAuthorskyewright
    • CommentTimeApr 28th 2017
     
    Posted By: SteamyTeaas you are limited to 4 kWp (actually 16A per phase).

    N.B. The 16A limit is on the connection to the mains not on the size of the array. It's possible, with the right[1] equipment, to have a larger array, with output to the mains limited to 16A. This sort of thing gets discussed on the Navitron Forum quite often.

    I believe there's no longer a 'step' in the FIT rate at 4kWp, as there used to be, so that's no longer an obstacle either.

    [1] Emphasis on right as it needs to be a DNO approved limiter, & different DNO's have different views on what's right.

    DNO might or might not be the correct term, but you probably know who I mean... :wink:
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 28th 2017
     
    You will have to check on all that as I have no idea of the current rules.

    There was something about the installed array being 4 kWp, rather than the inverter limiting it.
    But I would think that no one would notice an extra couple of modules, 10 extra and they might.

    Ask the installer to leave a couple of extra metres of rail (say it is for solar thermal), then add some modules when they have gone and the scaffolding is still up. :wink:
  2.  
    I don't want to derail the thread with a question I'm selfishly interested in, but are you looking at the cost of FIT / non-FIT eligible installations?

    It seemed to me there was a lot of bureaucracy involved in my FIT eligible installation, which must have driven up the cost. Now the FIT has been dramatically reduced does it make more financial sense to cut out all those overheads and install non-FIT eligible system?
    • CommentAuthorEd Davies
    • CommentTimeApr 28th 2017 edited
     
    As has been said, the limit is 16 A per phase which comes out as 3680 watts at 230 V or 3840 W at 240 V. If you stay within one of those power levels (sorry, I've forgotten which) the DNO will be happy even though technically you'd be exporting more current if the voltage was lower than 230 volts.

    There are two ways to have more PV panels than that but still stay within the limit:

    1) Have an inverter which limits the generation to no more than the required power (or current) level.

    2) Have a device (of the sort Skyewright is thinking of) which limits your export to the required level by diverting any excess to a suitable load. This allows you to generate more so long as you're self-consuming enough not to export too much.

    Obviously 2 allows more generation.

    Still, 1 has the advantages of simplicity and a cheaper inverter. In other countries it has been common to have a bit more PV panel nominal power than the inverter can deal with because this allows the inverter to operate at maximum power more of the day, effectively widening the peak and increasing the off-peak power. The actual amount of energy lost by shaving off the top of the peak for the day is quite small. Traditionally it's not been done so much in the UK because of the step down in the rates for PV at 4 kW which was done on the nominal panel power, not the inverter output.

    It'd be interesting to know how much, in anything, having a non-FIT eligible system would save. I wonder if the installers are set up for that (yet).
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 29th 2017
     
    I am not totally sold on the savings by not registering for FiTs.
    There may be a case for DIYing, as in really doing it your self, but the paperwork side of FiTs registration was pretty simple and streamlined when I was involved in it.
    There is a need to get the roof assessed by a structural engineer these days, and a few other, more minor, changes.
    Generally took me less than an hour to do the official paperwork i.e. design, DNO registration online MCS system registration etc.

    Much of the price of a FiTs system was nothing to do with it, was just a normal business expense i.e. marketing (cost us £40/lead), salesperson fees (about £800 on a 4 kW system), scaffolding (£300-700).

    As ususaly, if you hunt arond you will probably find a decent deal.
    •  
      CommentAuthordjh
    • CommentTimeApr 29th 2017
     
    Posted By: Ed DaviesHave a device (of the sort Skyewright is thinking of) which limits your export to the required level by diverting any excess to a suitable load.

    I don't think that's what skyewright was thinking of. I think he was implying an EMMA, or similar product if there are now some approved.

    I'm not sure what the current rules are, but the problem with trying to use an inverter to limit the power was that it wasn't approved for such, and the system size was based on the panel ratings anyway (though I think that part was for FIT purposes).
    • CommentAuthorEd Davies
    • CommentTimeApr 29th 2017 edited
     
    What's an EMMA if it isn't a “a device … which limits your export to the required level by diverting any excess to a suitable load”?

    http://www.solarwindapplications.com/products/emma/

    Usually these things will try to limit your export to a very small amount (a few watts) but in some cases they can only limit it to a higher power. E.g., if you have 6 kW of PV and an EMMA, or the like, connected to a 3 kW immersion you might finish up exporting 3 kW.

    There are a lot of these devices around but AFAIK the EMMA is the only one accepted by (some?) DNOs for the purposes of staying within the 16 A limit but I'm way out of date on the subject.
    • CommentAuthorskyewright
    • CommentTimeApr 29th 2017
     
    Posted By: SteamyTeaAsk the installer to leave a couple of extra metres of rail (say it is for solar thermal), then add some modules when they have gone and the scaffolding is still up. :wink:

    I hope we all appreciate that ST wasn't being serious about that... :bigsmile:

    It's extremely easy for the FIT system to automatically monitor performance against reasonable expectation, and they do check up on anomalies...
    • CommentAuthorEd Davies
    • CommentTimeApr 29th 2017
     
    Posted By: djhI'm not sure what the current rules are, but the problem with trying to use an inverter to limit the power was that it wasn't approved for such, and the system size was based on the panel ratings anyway (though I think that part was for FIT purposes).
    I'm pretty sure there are some properly done installations with more than 4 kW of PV which limit using the inverter which are quite acceptable to the DNO. As you say, it used to be a problem for FiT purposes but that's a) a separate matter and b) history (I think).

    A typical case is where there's only room on differently facing bits of roof for smaller arrays. E.g., 3 kW facing SE and 3 kW facing SW feeding into a dual-string inverter with a maximum output set to 3800 W or whatever. A dual-string inverter allows separate power-point tracking on two inputs which then share the output side.
    • CommentAuthorskyewright
    • CommentTimeApr 29th 2017
     
    Posted By: djh
    I don't think that's what skyewright was thinking of. I think he was implying an EMMA, or similar product if there are now some approved.

    Actually I was thinking of all 3 (or all 2, depending on how you see it). :bigsmile:

    I believe the EMMA has quite wide, but not yet universal(?), approval now. I gather that at least some other systems have been approved too by some DNO's; SolarEdge is a name that comes to mind, but it would certainly need checking out.

    Some of the other possible arrangements involve some element of battery storage (essentially another variation on the load diversion theme?).
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 29th 2017
     
    I think there is the risk of confusing total generation over a period of time and peak power. These are not the same thing.
    As far as I know, the maximum power of a PV system is set by the modules and governed bu the FiT/MCS rules.

    Larger systems can be fitted with approval from the DNO, but that is done on an individual basis and generally after a survey.

    So you can have a larger system fitted by an MCS installer, or fitted yourself, as long as your DNO approves it.
    What, I think, you cannot do is get a bog standard 4 kWp (via the inverter limitations) system fitted that has say 4.5 kWp of modules fitted i.e. an extra couple of modules, even if it is an MCS approved installed system (it used ot happen but not allowed now).

    I may be wrong as it is a while since I was involved, but that was my interpretation of it about 4 years ago.
    • CommentAuthormike7
    • CommentTimeApr 29th 2017
     
    Hi Gusty - I've been asking myself much the same questions. I could do most of the installation myself, but IIRC I would be paying 20% VAT against 5% charged to a pro installer.
    • CommentAuthorskyewright
    • CommentTimeApr 29th 2017
     
    I Am Not An Expert, but my understanding is...
    Posted By: SteamyTeaAs far as I know, the maximum power of a PV system is set by the modules and governed bu the FiT/MCS rules.

    The FIT rate is based on the kWp of the modules. What's happens with the output from the modules is a separate matter.

    Since nowadays there isn't a step change in the FIT rate at 4kWp this is less of an issue than it used to be. It used to be the case that a 4.1kWp (& above) system would 'earn' substantially less FIT per kWh generated than a 4kWp system. Now, the first step change in the rates is at a considerably higher kWp (more than most folk would be likely to consider?).

    Larger systems can be fitted with approval from the DNO, but that is done on an individual basis and generally after a survey.

    Roughly speaking a bog standard system that can't produce more than 16A output (e.g. <3.68kWp of panels) is the simple case and there is a (sort of) 'right' to a connection; for anything beyond that you need to obtain permission from the DNO before making the connection. The extra permission might be in the form of a relaxation of the 16A limit (to some other agreed fixed limit), or it might be in the form of approval for additional measures that ensure the 16A limit is never exceeded.
    • CommentAuthorEd Davies
    • CommentTimeApr 29th 2017 edited
     
    Posted By: SteamyTea: “As far as I know, the maximum power of a PV system is set by the modules and governed bu the FiT/MCS rules.”

    Yes, historically FIT payments were set by the panels but DNOs (except when they're confused) aren't interested in that, only the output of the inverter (either strictly 16 amps or a nominal power level as an approximation for that).

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=7632

    http://www.yougen.co.uk/blog-entry/1547/Is+there+a+limit+on+solar+PV+generation'3F+Q'26A/ (see comment by Steve Milesworthy).
    • CommentAuthorjamesingram
    • CommentTimeApr 30th 2017 edited
     
    What's your location , rural? In an urban situation it's easy to go over 4kW without the need for additional relay.
    Contact your DNO mircogeneration connection department
    they may be able to give you an idea over the phone. Usually they'll do a survey pre G53 (procedure for installation >4kW) before for installation , some charge ( SSE charge me about £350 and didn't visit site) some don't.
    I've got 6.2kw , went for an additional 2.2kw.
    What you'd be looking for is that sweet spot above 4kW that doesn't incure to much additional cost.
    The reason I'm saying this is the Fits payment for < or > 4kW are much closer so to me I'd fit as much as possible to off set as your really energy eater is the GSHP
    I've not registered my extra 2.2kW with FITS mainly because I've been to busy :bigsmile:
    • CommentAuthorjamesingram
    • CommentTimeApr 30th 2017 edited
     
    Clearly I'm a little out of date, they now appear to just one rate for >10kW 4.14p per kW produced for the higher rate (EPC related)
    https://www.ofgem.gov.uk/environmental-programmes/fit/fit-tariff-rates
  3.  
    As to best fixing system , you'll hate me , but for a slate roof I'm gonna say this one
    http://www.windandsun.co.uk/products/PV-Mounting-Structures/GSE-Integration-Roof-Integrated#.WQWfExnTXqA
    • CommentAuthorEd Davies
    • CommentTimeApr 30th 2017
     
    Interesting that the rate per kWh for more than 10 kW is actually higher than for less than 10 kW on the higher and medium rates (4.36p/kWh for > 10kW vs 4.14 for less on the higher rate (EPC D or better)). Also, having an EPC of D or better before commissioning the PV is pretty critical.
    • CommentAuthorskyewright
    • CommentTimeApr 30th 2017
     
    Posted By: jamesingram
    I've not registered my extra 2.2kW with FITS mainly because I've been to busy :bigsmile:

    In case you weren't aware...
    One of the other changes in the last big shake up in FIT arrangements was that now you only get one bite at the cherry, i.e. it is no longer possible to get FIT payments for a second system, or an extension to the original system.
  4.  
    Thanks Skyewright , I check it out , looks like I missed out there , not to worried did well on the main system
  5.  
    Thanks all.

    My roof is slate so the integrated system is way too late for me now.

    I need to wrap my head around the possibility of installing more than the standard 4kW system.
    Does this involve more inverters?

    Would fitting PV impact on my GSHP RHI payments in some way?

    Cheers.
    :confused:
  6.  
    you can just get the inverter to suit array size.
    depending on layout. I'm a fan of the optimiser system with dumb inverter making each panel an individual.
    certainly safer installation for DIY .
  7.  
    Many thanks all.
    • CommentAuthorTimSmall
    • CommentTimeJun 6th 2017
     
    Waterproofing the slates with roof hooks is tricky, these seem good - http://www.geniusroofsolutions.com/products/solarflash/ - I've used them on clay plain tile roofs. Make sure you get suitable roof hooks for your slate size.

    I used the GSE roof-integrated system on my low pitch extension roof (600x300 synthetic slate - although it ended up 70% PV, 20% roof window, 5% flashing, 5% slate), and it was reasonably smooth to install.
  8.  
    Hi Tim, how low was the pitch? I've got a very low pitch roof (felt and plywood) that I'd like to add solar panels to and I was looking at the GSE system.
    • CommentAuthorTimSmall
    • CommentTimeJun 7th 2017
     
    15°, which is the limit for the BBA cert for the GSE panels I think.
  9.  
    Thanks, I'll measure my pitch and see what it is. Is the GSE system as easy to install as it looks? I'm installing onto plywood sarking rather than onto battens, but I don't think that'll be a problem.
   
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