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Renewable Energy: Solar PV questions + ASHP or GSHP?

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  1.  
    Hi again all.
    I've not been here for a long time for various reasons but since I've finished my first self-build I'm now doing another self-build!!
    I aim to do things slightly differently this time. Last time I went as far as the budget would allow with insulation etc and a GSHP. It's done well but these days electricity isn't cheap as we know.

    I'm in Wales.
    I want to install solar PV with micro-inverters. From what I can gather the panels are fairly similar efficiency wise when cost is taken into account. The weakest link is the inverter. That's my micro-inverter thinking so if one fails it doesn't knock the whole system off. So, roof or ground mount? I have land available for ground mount. I think that without PP I'm limited to 3Mx3M so that's too small. I was aiming for 10kWish as we also have an EV. I'm also thinking of battery storage to cover the evenings following charge during the day.
    I'm on the coast with 3 acres so I'm thinking my COP on an ASHP might be better than a GSHP considering the milder climate on the coast. It's also cheaper but the ASHP unit may corrode in time due to the salty atmosphere. I'm probably 1/2 mile to the beach.
    So many questions. UK climate, triple glazing or double. I'm fitting MVHR. Good window companies that aren't too expensive? UK based?
    Many thanks all.
    It's good to be back :bigsmile:
  2.  
    Welcome back Gusty!

    I was surprised how much has changed in 10 years between our previous project house and our current project. We needed to go back and relearn.

    Main thing for me is that renewably sourced heat is becoming easily available, so our previous project's focus on heat conservation/insulation/fabric etc is no longer the only consideration. The impact of the build itself is becoming more significant, eg minimise high-impact materials cement/steel/glass.

    ASHP tech has improved, is becoming the default rather than GSHP.

    We are buying-in renewable electricity rather than building our own, the economics of scale favour GW solar and wind generators rather than kW.
    • CommentAuthorrevor
    • CommentTimeFeb 23rd 2023
     
    I think microinverters and batteries are not very compatible without expense. Your battery needs DC to charge so you will have another inverter / charge controller to do that then you want to convert that DC in battery to AC for use. Those with microinverters will be able to putt me right. It is easier to have a hybrid inverter that looks after everything. If you can, go for ground mount the panels do get dirty and need cleaning a few times in the year. I am in a rural area and clean my GM about 3/4 a year. Try for pp I got pp for 18 panels producing 6kw, wish now gone for bigger array. I was restricted to 3.6kw export but that got raised last year to 5kw. So check if your location can export more as it will be useful if you have 10Kw panels. Is your 3 acres all garden i.e within the property curtilage or is it classed as agricultural that needs checking for pp. I am in Wales also 1m from sea don't have HP as insulated to the gills and fabric first approach so energy use very low £300 on bottled gas it has turned out as. If you decide you may want a wind turbine in future make sure that what you go for in terms of your pv set up, that is compatible with a WT, my system is not I would have to have a stand alone turbine and another battery set up.
    • CommentAuthorJeff B
    • CommentTimeFeb 23rd 2023
     
    Gustyturbine - if I had the choice I would opt for ground mounted PV array, not just for ease of cleaning the panels but for easy access to the micro-inverters. Any problems with mine and it means ladders and scaffolding to access the roof every time!

    Revor - I was interested to read your statement: "I was restricted to 3.6kw export but that got raised last year to 5kw". Was that just for your installation or is that a Wales-wide allowance? Also is yours an MCS installation with FIT payments?
    •  
      CommentAuthordjh
    • CommentTimeFeb 23rd 2023
     
    I have a PV system with Enphase microinverters and am very happy with it/them. They maintain power when there's shading on a few panels, which happens every afternoon in winter due to nearby trees and has also happened when it snowed and covered a couple of panels. The Enphase system even sent me an automatic email telling me two panels were not generating :bigsmile: The microinverters and the panels I chose both have 25 year warranties, so I can relax. No problems so far and no cleaning needed in nearly 8 years - they still perform well. I know Enphase also sell batteries that will integrate. I believe Tesla batteries will as well. It all depends whether the battery is DC-connected or AC-connected.

    I'm not yet convinced batteries are worthwhile in our situation. I own part of a wind turbine instead.
    • CommentAuthorrevor
    • CommentTimeFeb 23rd 2023
     
    Posted By: Jeff BRevor - I was interested to read your statement: "I was restricted to 3.6kw export but that got raised last year to 5kw". Was that just for your installation or is that a Wales-wide allowance? Also is yours an MCS installation with FIT payments?


    Think it was my area. I was conscious in the summer of my inverter clipping the export when I could have been exporting up to about 5.5 at times so asked my DNO how much it would cost to get it uprated and they said (same day) up to 5kw no charge more than that a fee of £750 plus a witness test whatever that would have cost. I had to make another application which was basically what had been submitted before with a declaration that the inverter would be set to 5Kw max. And by return got the ok.
    My installation is an MCS but do not get fit I am on Octopus Agile and get variable payment which is not good at moment. You need MCS regardless of what export tariff you are on without it you just giving grid free juice. A friend has 17kw roof mounted but the max he is able to export is 8kw the panels are on different orientations but he is also close to a biggish transformer.
    • CommentAuthorJeff B
    • CommentTimeFeb 23rd 2023
     
    Revor - thanks for your response. Very interesting. Where is your area, if I may ask? We are in Pembrokeshire.

    I am a "pioneer" as far as MCS/FITs goes, as we had our PV system installed in 2011, hence am on the highest FIT payment regime. As much as I would love to do it, I think it will be complicated (not permissible even?) to try to extend my system to increase the output. Our PV array faces southeast rather than due south and we have a southwest facing roof which catches the sun for the whole of the afternoon in summer and on which I could attach several more panels. I need to check the latest regs but your post has got me thinking!

    P.S. Sorry Gustyturbine for hijacking your thread but hopefully this may still be of interest to you of course.
    • CommentAuthorphiledge
    • CommentTimeFeb 23rd 2023
     
    @Jeff b. OFGEM changed the FIT rules a few years back allowing FIT accreditted systems to be altered so you can now increase generation, add batteries, change components etc. Down side is youll still only get paid FIT for the original registered capacity so if you go from 4kw to 5kw you only get paid for 4/5 of what you generate and export. If your existing inverter can handle extra DC input its a cheaper way of adding extra capacity compared to a second system, but......

    If youre adding panels on a different facing roof pitch the panels on the differing pitches will effectively be shaded for part of the day compared to the other pitch. To stop the differing pitches affecting each other, they'll need wiring separately each to their own MPPT input or use optimisers/micro inverters.
    • CommentAuthorrevor
    • CommentTimeFeb 24th 2023
     
    Posted By: Jeff BRevor - thanks for your response. Very interesting. Where is your area, if I may ask? We are in Pembrokeshire.


    Anglesey

    Posted By: djhI'm not yet convinced batteries are worthwhile in our situation


    I was not sure originally whether my investment in a battery was justifiable as a lot depends on what you can get for export, where it would go if not used and not in a battery. The economics keeps changing. Practically all I have produced this year has gone to battery or used and very little exported. What I have been paid is about 15p kwh. Yesterday was a good sunny day 22 kwh generated used a bit, filled the battery which lasted from sundown to 9AM this morning and 11kWh was exported. At a bought in cost of 35p and export of 15p the electricity is better in the battery. Also being a sunny day yesterday the solar gain was enough that we did not need heating on other than a wood fire in our lounge stove.
    •  
      CommentAuthordjh
    • CommentTimeFeb 24th 2023
     
    Yes, this early in the year we export very little. Anything not taken up by immediate consumption is used to heat the hot water. But we have less capacity than you. Just a regular 4 kWp. Also interesting that location makes such a difference. Today was better than yesterday, which was better than Wed. But Monday was the standout good day here. Nearly 12 kWh - probably nearly heated our DHW to max, but didn't actually reach the limit.
  11.  
    Thanks all.
    I think then in reality I need to get the 10KWp ground mount, hydrid inverter with battery if permitted in Ceredigion. I'll then go for ASHP as I'm near the coast and it's milder generally and it has lower install costs compared to GSHP. I'll also install MVHR as my last build needed it really and I'm not building a home to be as airtight as possible then whacking extractor fans and trickle vents in again. It's madness. All of the above whilst insulating as best we can. I'm also installing a log burner as I don't believe in relying on the state anymore to provide anything the way the world is these days. Secondary form of heat is essential and the PV should help.
    Thanks.
    • CommentAuthorphiledge
    • CommentTimeFeb 27th 2023
     
    If youve got the roof space I think youd be better roof mounting what you can as youve got longer exposure to the sun and less chance of winter shading, unless the ground mount is on the side of a hill.

    With 10kw of panels youll need planning permission for a ground mount system over 9m2, I beleive. Unless you want to restrict what you export to 3.68kw you probably need to speak to your DNO to see what export restrictions you have, before you comit to any generation/export capacity or configuration.
  13.  
    Posted By: philedgeIf youve got the roof space I think youd be better roof mounting what you can as youve got longer exposure to the sun and less chance of winter shading, unless the ground mount is on the side of a hill.

    With 10kw of panels youll need planning permission for a ground mount system over 9m2, I

    But with ground mount you get to install at the optimum angle and direction which is unlikely on a roof, also ground mount provides a bit more output in the summer due to better cooling (air flow) than roof mounting - but PP may be a pain - so a few things to think about between a ground or roof array.
    • CommentAuthorJeff B
    • CommentTimeFeb 27th 2023 edited
     
    Posted By: philedge@Jeff b. OFGEM changed the FIT rules a few years back allowing FIT accreditted systems to be altered so you can now increase generation, add batteries, change components etc. Down side is youll still only get paid FIT for the original registered capacity so if you go from 4kw to 5kw you only get paid for 4/5 of what you generate and export. If your existing inverter can handle extra DC input its a cheaper way of adding extra capacity compared to a second system, but......

    If youre adding panels on a different facing roof pitch the panels on the differing pitches will effectively be shaded for part of the day compared to the other pitch. To stop the differing pitches affecting each other, they'll need wiring separately each to their own MPPT input or use optimisers/micro inverters.


    My existing system already uses microinverters. Because it is facing south-east, the output drops off dramatically after about 2.00pm. This is when a south-west facing add-on system would take over. I had some data from a small PV panel (the type you would use on a caravan) which I mounted temporarily on the south-west facing roof back in May 2020 and there was a good output from 2.00 pm right through to 7.00 pm. Unfortunately I have lost the data but I remember it was quite impressive.

    The existing 21 panels have a nominal output of 180W each, so theoretical maximum output would be 3.78kW but in reality the highest figure ever achieved was 3.05 kW (approx 150W per panel). On the south-west facing roof I would be able to fit 4 panels (it's much smaller than the main south east facing roof), with modern panels of say 250W output each, then a bit less than 1.0 kW should be possible. As the total output would still be within the original 4 kW "limit" do I need to inform OFGEM or whoever?
    • CommentAuthorphiledge
    • CommentTimeFeb 27th 2023
     
    AFAIK your "limit" is whatever the installed capacity declared on your MCS cert says. Anything over that and you're supposed to notify your FIT payer.

    You'll do well to find new 250 watt panels. Mainstream size of current panels seems to be 350 watt upwards
    •  
      CommentAuthordjh
    • CommentTimeFeb 27th 2023 edited
     
    There's what looks to be a reasonable guide at https://blog.spiritenergy.co.uk/homeowner/adding-more-solar-panels

    AIUI the microinverters talk to one another and/or their monitor gateway thingy so as to limit their output to the 3.68 kW limit. I sometimes see my generation 'flat-topping' in summer, instead of following a smooth curve.
    • CommentAuthorphiledge
    • CommentTimeFeb 27th 2023 edited
     
    Posted By: djhThere's what looks to be a reasonable guide athttps://blog.spiritenergy.co.uk/homeowner/adding-more-solar-panels" rel="nofollow" >https://blog.spiritenergy.co.uk/homeowner/adding-more-solar-panels


    There's a couple of things that stand out as not being quite correct! If youve got a 3.68kw/16A limited inverter your first port of call to see if you can add panels is the inverter manual, not the DNO. Our 16A limited inverter currently has 4 kw of panels attached but it can have up to 5.4kw of panels attached and still retain its 16A output limit, so no DNO involvement. I assume that a 16A limited micro inverter system can be expanded in a similar way??

    The guide says you can't alter a FIT system but that's not been the case for a while.
    • CommentAuthorJeff B
    • CommentTimeFeb 27th 2023
     
    Posted By: philedgeAFAIK your "limit" is whatever the installed capacity declared on your MCS cert says. Anything over that and you're supposed to notify your FIT payer.

    You'll do well to find new 250 watt panels. Mainstream size of current panels seems to be 350 watt upwards


    Even better, I'd only need 3!
    • CommentAuthorGareth J
    • CommentTimeFeb 28th 2023
     
    If no shading, and on roof, I wouldn't bother with micro inverters. For me, it's relatively easy to swap out an inverter indoors, compared with scrambling about on a roof. Inverter prices have also dropped a lot.

    As you have space, I'd consider building a separate shed/carport with the exact pitch(es) you want to maximize winter output, which if you're hoping to power heating will have a pitch/pitches geared towards winter production, rather than total production. Corrugated tin roofs are very easy to fix panels to.

    Regarding the location and ashp, is the humid environment likely to cause more icing up, and therefore defrost cycles, despite the relatively mild temperatures? I don't know either way but could imagine it's a possibility.
    •  
      CommentAuthordjh
    • CommentTimeFeb 28th 2023
     
    Posted By: philedgeThe guide says you can't alter a FIT system but that's not been the case for a while.
    Is there a good explanation of the current rules somewhere?
    • CommentAuthorphiledge
    • CommentTimeFeb 28th 2023
     
    Try this- https://www.ofgem.gov.uk/publications/feed-tariffs-guidance-renewable-installations-version-16
    •  
      CommentAuthordjh
    • CommentTimeFeb 28th 2023
     
    Thanks, I'm not sure that applies to my 4 kW system?

    "This document is intended for owners, or potential owners, of Solar PV and wind installations
    with a Declared Net Capacity (DNC) over 50kW up to a Total Installed Capacity (TIC) of 5MW"
    • CommentAuthorGareth J
    • CommentTimeFeb 28th 2023
     
    I would be inclined to leave anything FIT related well alone. Or any replacements required done like for like if at all possible. Especially considering that it's relatively easy to put a completely separate system in if you want/need to expand. I'm pretty sure expansion of a FIT linked setup is not allowed and, if detected, will stop any payments. Though can't link to a document that says so.
    • CommentAuthorphiledge
    • CommentTimeFeb 28th 2023
     
    Try this- https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ofgem.gov.uk/sites/default/files/2021-12/Feed%2520in%2520Tariffs_Consultation%2520on%2520the%2520treatment%2520of%2520replacement%2520generating%2520equipment_Decision_13122021.pdf&ved=2ahUKEwiV37eQhLn9AhUILsAKHY-yAaMQFnoECDkQAQ&usg=AOvVaw0l46qMEQAdIwmJgw1ZmS1x

    And these FAQs- https://www.ofgem.gov.uk/environmental-and-social-schemes/feed-tariffs-fit/generators
    • CommentAuthorJeff B
    • CommentTimeFeb 28th 2023 edited
     
    This is taken from the FAQ reference supplied by philedge above:

    "Can I extend the capacity of my installation?

    You can modify your accredited installation to either increase or decrease its capacity as long as the total installed capacity (TIC) of the installation and any extensions does not exceed 5MW (or 2kW for micro-CHP). 
    However, you cannot receive FIT payments in respect of electricity generated from any additional capacity unless the extension was commissioned before 15 January 2016".

    This is the closest reference I can find on this topic. It still doesn't really answer the question if by adding extra PV panels, does this affect the need for notification if the total generating capacity does not exceed the original specification?
    • CommentAuthorphiledge
    • CommentTimeMar 1st 2023
     
    Posted By: Jeff B It still doesn't really answer the question if by adding extra PV panels, does this affect the need for notification if the total generating capacity does not exceed the original specification?

    Not quite sure what you mean by original specification? AFAIK the definition of your capacity is whats registered on the MCS database which hopefully is the same as on your MCS cert. Seems that any deviation from that figure should be notified
    •  
      CommentAuthordjh
    • CommentTimeMar 1st 2023
     
    Jeff, as far as I can tell looking at everything so far, for a regular domestic installation (i.e. installed under MCS-FIT regulations) you need to inform your FIT licensee of any changes you make to your installation at all. You don't need to inform OFGEM of anything (presumably the FIT licensees do that in aggregate). It doesn't matter whether you extend or reduce the system or simply replace something that has broken, you need to tell them.
    • CommentAuthorphiledge
    • CommentTimeMar 1st 2023
     
    Posted By: Gareth Jconsidering that it's relatively easy to put a completely separate system in if you want/need to expand. .


    If youve already git a typical 4kw system limited to 3.68/16A then adding a second system is subject to G99 application and DNO approval. The beauty of expanding the DC side of an existing inverter is you are free to do as you wish up to the inverters limit.

    This was one of the drivers for OFGEMs original consultation on expanding FIT systems, as with rapidly rising prices people were wanting to get more out of what they already had
    • CommentAuthorGareth J
    • CommentTimeMar 1st 2023
     
    Posted By: philedge
    Posted By: Gareth Jconsidering that it's relatively easy to put a completely separate system in if you want/need to expand. .


    If youve already git a typical 4kw system limited to 3.68/16A then adding a second system is subject to G99 application and DNO approval. The beauty of expanding the DC side of an existing inverter is you are free to do as you wish up to the inverters limit.

    This was one of the drivers for OFGEMs original consultation on expanding FIT systems, as with rapidly rising prices people were wanting to get more out of what they already had


    Good point!

    However, G99 with export limitation isn't that tough (well, wasn't a few years ago) wouldn't like to say if it would be more or less of a pain than notifying the FiT side.
    •  
      CommentAuthordjh
    • CommentTimeMar 1st 2023 edited
     
    AIUI, you have to do the notification to the FIT licensee whatever you modify, Whether on the DC or AC side. Any time you make any change at all.

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