Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.




    • CommentAuthorneelpeel
    • CommentTimeJun 1st 2022 edited
     
    After the recent electric cost hike (my 5p/kWh overnight rate has gone up to 20p/kWh!) I have plans for a 4.5kW (ish) PV system. Plan is to build a South facing shed (unshaded) with single 22deg slope and mount the panels on top using Unistrut.

    PVGIS tells me I should get 500-550kWh per month in the summer months and down to 80-90kWh in the winter months for a 4.5kW setup (3970kWh/yr total).

    For my EV I average between 5 - 10kWh use each day. Sometimes none, sometimes 25kWh. So I reckon I should be able to cover most of my miles.
    I don't have a water tank so I can't easily dump excess solar, but I am planning for a A2A ASHP install.

    I'm planning to DIY for the most part and looking for Used panels to keep the up-front cost down. I'll get an electrician to do the electrical commissioning.

    This means that I will probably NOT be able to get MCS signoff.

    - Does that mean that I can't tie to the grid at all? Or just that I can't claim for export?

    - I know there is a 3.68kW limit, but my thoughts were to slightly oversize (4.5kW) and use an inverter limited to 3.68kW. I assume there could therefore be some 'clipping' in the summer, but I would get better output in the winter. I could also try and mount some panels for winter generation. Does this make sense?

    - Is it possible to supply the EV (via Zappi charger) and house without grid tie-in? Which, if not grid-tied, I assume I could then bypass the 3.68kW limit?

    - Am I daft to ignore 'export' and just go for MCS install and grid-tie?

    - Any ideas for 'dumping' my excess solar in the summer given lack of water tank?
    • CommentAuthortychwarel
    • CommentTimeJun 1st 2022
     
    My system is self installed partially using second hand kit and is legally connected to the grid, basically as it stands you can't claim for export
    MCS accreditation will probably triple your installation price as you can't use second hand or non mcs approved kit and have to use an MCS approved contractor.

    Put a battery in the system.
    • CommentAuthorphiledge
    • CommentTimeJun 1st 2022
     
    You dont need MCS to grid tie but you do need a 16A limited G98 compliant inverter.

    If you are starting from scratch with your shed roof you may get more useable year round generation with a steeper pitch than 22 degrees, but run things through PVGIS with various pitches. With a 4.5kw array dont expect to be powering a HP much in the winter, if at all
    • CommentAuthortony
    • CommentTimeJun 1st 2022
     
    Might need planning permission if on a shed
    • CommentAuthorjamesingram
    • CommentTimeJun 2nd 2022 edited
     
    As your using a <16A inverter all you have to do to grid tie is fill in the post installation DNO paperwork G98
    which is straight forward (unless there's numerous other installs in your area)
    Array size (DC side) depends on your inverter, oversizing is common, advisable and some can go up to 50% oversize.
    Inverter manufaturers have easy tools for figuring out string sizes etc.
    There are some companies that will MCS for a fee remotely.
    search G59projects or pluginsolar (though these only do it if you buy there kit)

    Im not convinced batteries are viable economically and environmentally just yet
    • CommentAuthorneelpeel
    • CommentTimeJun 2nd 2022
     
    tychwarel, thanks, I think that confirms my system will NOT be MCS cert.

    Thanks Philedge. I'll double check the inverter. For sure a steeper pitch is better, but it's a compromise with blocking the view!

    I do need to check planning, but as I'm in middle of nowhere I'm not overly concerned 😁.

    Batteries... I'm also not convinced on the payback based on the fact I can use most of the generation. If I ever expand the system then a battery may become sensible.

    I was looking at buying Bimble Solar 2nd hand panels but all seem to be now gone. Any other good resellers?
    • CommentAuthortychwarel
    • CommentTimeJun 3rd 2022
     
    I bought my panels and inverter on ebay and facebook marketplace, I have abunch of clamps for 38mm thick panels left over.
    • CommentAuthorphiledge
    • CommentTimeJun 3rd 2022
     
    Theres a few regular sellers of second hand panels on ebay but almost always sub 250watt. I bought a few NOS job lots at the beginning of the year but that sort of thing has vanished and most multi panel sales are near new prices!! Cheapest place Im seeing new panels is solarsparky so good for a benchmark price.
  1.  
    I am also going down the solar route and have acquired probably 30 x 550w bifacial panels. Was looking to put in a 3 phase system with batteries. Getting totally confused with all the options but a V2H system using a Nissan Leaf seems possible but I dont understand how that could integrate with 3 phase. Thinking 48v system as that is close to the panel output. Any suggestions as will be ground mount away from farmhouse as its listed.
  2.  
    Would it be possible to ground mount the solar panels? Perhaps instead of the shed if the solar generation is more important than a workshop/tool store.

    You could then either angle the panels permanently for winter generation or have a way to adjust the angle a few times a year for maximum efficiency in each of the seasons.
  3.  
    Renewable John. I presume A 3 phase hybrid inverter will do the job. <16A per phase will allow you a 10kW 3ph inverter without doing a g99 preregistration.
  4.  
    Posted By: jamesingramRenewable John. I presume A 3 phase hybrid inverter will do the job. <16A per phase will allow you a 10kW 3ph inverter without doing a g99 preregistration.

    I presume it requires a battery bank per phase.
    •  
      CommentAuthordjh
    • CommentTimeJun 6th 2022
     
    Posted By: renewablejohn
    Posted By: jamesingramRenewable John. I presume A 3 phase hybrid inverter will do the job. <16A per phase will allow you a 10kW 3ph inverter without doing a g99 preregistration.

    I presume it requires a battery bank per phase.
    Don't think so. e.g. http://www.windandsun.co.uk/information/solutions/on-grid-solar-pv-battery-storage-solutions/solaredge-3-phase-storedge%E2%84%A2-battery-storage-system.aspx or search for 3 phase hybrid inverter
  5.  
    Depends how much PV you want to store, IE what are you planning to do with it?

    The proposed 16.5 kW array with 3x3.6 kW inverter will only generate that much during daytime in the summer, when you likely won't have sustained uses for so much power? How many kWh are you likely to consume overnight, to empty the battery ready to receive more charge the next day, and are you ok to import that power when it's not sunny, maybe at cheaper off-peak prices?


    A 40kWh EV with a domestic charger would prefer to charge at about 4-7kW, so you would be exporting most of the 16.5kW PV? That battery would last for several days of average home consumption or driving.

    The problem with all energy storage projects is that, to get your money's worth, you need to fill and empty it many times, such as several times per week. If you store up 100s of kWh of summer PV for winter heating then the battery will only be cycled once per year, which is not good value. You need to trade off to find the best size of storage to match your needs.

    AIUI if you have several inverters (such as a PV inverter and a V2H charger) the G99 notification is based on the combined power of all the inverters. There aren't many V2H chargers on the market yet afaict.

    Is the 16.5kW PV all going to be oriented the same direction, or can you have different strings pointing east/west/up/down, so you get less power but spread more evenly over the day and year?
    •  
      CommentAuthordjh
    • CommentTimeJun 6th 2022
     
    Posted By: WillInAberdeenThe problem with all energy storage projects is that, to get your money's worth, you need to fill and empty it many times, such as several times per week. If you store up 100s of kWh of summer PV for winter heating then the battery will only be cycled once per year, which is not good value. You need to trade off to find the best size of storage to match your needs.
    Exactly. That's why I ended up with a 250 L thermal store for DHW heated by solar PV rather than a 20,000 L ex-milk tank heated by solar thermal for space heating.
  6.  
    Posted By: WillInAberdeenDepends how much PV you want to store, IE what are you planning to do with it?

    The proposed 16.5 kW array with 3x3.6 kW inverter will only generate that much during daytime in the summer, when you likely won't have sustained uses for so much power? How many kWh are you likely to consume overnight, to empty the battery ready to receive more charge the next day, and are you ok to import that power when it's not sunny, maybe at cheaper off-peak prices?


    A 40kWh EV with a domestic charger would prefer to charge at about 4-7kW, so you would be exporting most of the 16.5kW PV? That battery would last for several days of average home consumption or driving.

    The problem with all energy storage projects is that, to get your money's worth, you need to fill and empty it many times, such as several times per week. If you store up 100s of kWh of summer PV for winter heating then the battery will only be cycled once per year, which is not good value. You need to trade off to find the best size of storage to match your needs.

    AIUI if you have several inverters (such as a PV inverter and a V2H charger) the G99 notification is based on the combined power of all the inverters. There aren't many V2H chargers on the market yet afaict.

    Is the 16.5kW PV all going to be oriented the same direction, or can you have different strings pointing east/west/up/down, so you get less power but spread more evenly over the day and year?


    Summer production is not a problem as I want to run both a 3 phase briquette plant and wood pellet plant on any excess production. My daily household usage is very low at the moment (8kwh) but that will change if I get a Nissan leaf as a cheap storage battery (24kwh) and V2H connection. In winter I also have 700w hydro 24/7 which could go into batteries or direct into the UFH. As for strings being bifacial panels was looking to put 10 panels each E S W
    • CommentAuthorphiledge
    • CommentTimeJun 6th 2022
     
    If youre charging batteries surely you want to maximise overall production and have the whole array facing south??

    AIUI you only have a spread of orientation if theres no storage and you accept lower overall production in return for a longer period of useable generation???
    • CommentAuthorneelpeel
    • CommentTimeJun 6th 2022
     
    Posted By: Pile-o-StoneWould it be possible to ground mount the solar panels? Perhaps instead of the shed if the solar generation is more important than a workshop/tool store.

    You could then either angle the panels permanently for winter generation or have a way to adjust the angle a few times a year for maximum efficiency in each of the seasons.


    The shed is my attempt at 'ground mount'. I just thought if I was going to all the bother of building a large load bearing frame then I may as well board it up and stick a door on it. The perfect spot in my garden just happens to be South facing and unshaded - but I may be able to work a way of ground mounting some extra panels for winter generation. I may try and tweak the angle slightly higher too.
    • CommentAuthorneelpeel
    • CommentTimeJun 6th 2022 edited
     
    Posted By: renewablejohn
    ... but that will change if I get a Nissan leaf as a cheap storage battery (24kwh) and V2H connection. In winter I also have 700w hydro 24/7 which could go into batteries or direct into the UFH.


    Interesting. I thought it was just the newer (40kW+) Leafs that you could use for V2H. Or is that just V2G?
  7.  
    Posted By: neelpeel
    Posted By: renewablejohn
    ... but that will change if I get a Nissan leaf as a cheap storage battery (24kwh) and V2H connection. In winter I also have 700w hydro 24/7 which could go into batteries or direct into the UFH.


    Interesting. I thought it was just the newer (40kW+) Leafs that you could use for V2H. Or is that just V2G?


    Was told all Leafs were capable of V2H but will now have to double check. Certainly has always been part of Nissans policy that batteries would have a second life as home usage so dont see why it would only apply to 40kw+.
  8.  
    Posted By: philedgeIf youre charging batteries surely you want to maximise overall production and have the whole array facing south??

    AIUI you only have a spread of orientation if theres no storage and you accept lower overall production in return for a longer period of useable generation???


    But you loose a lot of power charging batteries so was only looking to put the excess into the batteries. With bifacial panels I expect E,W, orientation to probably produce more than S with silver foil covering on ground under panels.
    • CommentAuthorneelpeel
    • CommentTimeJun 7th 2022
     
    Posted By: philedgeTheres a few regular sellers of second hand panels on ebay but almost always sub 250watt. I bought a few NOS job lots at the beginning of the year but that sort of thing has vanished and most multi panel sales are near new prices!! Cheapest place Im seeing new panels is solarsparky so good for a benchmark price.

    Thanks for the solarsparky link. These do seem great value. For my needs...Circa £1700 delivered for new vs £1100 for reclaimed. So it's making me think that brand new with a warranty is maybe the way to go after all.

    So what technologies should I be looking for in a panel? Do I need to spend the next 3 weeks Googling!?
    Any brands / tech to avoid? Or good impartial websites?
    • CommentAuthorphiledge
    • CommentTimeJun 7th 2022
     
    Posted By: renewablejohn
    But you loose a lot of power charging batteries so was only looking to put the excess into the batteries. With bifacial panels I expect E,W, orientation to probably produce more than S with silver foil covering on ground under panels.

    Id assumed battery charging was the priority as previous post said excess generation was going to briquette and pellet production??????
  9.  
    Posted By: philedge
    Posted By: renewablejohn
    But you loose a lot of power charging batteries so was only looking to put the excess into the batteries. With bifacial panels I expect E,W, orientation to probably produce more than S with silver foil covering on ground under panels.

    Id assumed battery charging was the priority as previous post said excess generation was going to briquette and pellet production??????

    I see the peak production only being summer time which fits in well with the pellet and briquette production. Rest of the year I think it will be a struggle to both generate enough from solar for a home and car. The idea being EW solar to cover the home and S for charging the car which can then top up the home when the solar ceases. All panels hung vertically with white or silver reflectors to aid the bifacial panels.
    • CommentAuthorphiledge
    • CommentTimeJun 7th 2022
     
    Posted By: neelpeel
    So what technologies should I be looking for in a panel? Do I need to spend the next 3 weeks Googling!?
    Any brands / tech to avoid? Or good impartial websites?


    Weve got a mix of JA, Trina, Longi, Canadian Solar and Viridian. All reputedly tier 1 suppliers, all working well for us, all seem well built, all mono and a mix of half cut and full cell. Mono are supposed to maintain their output for longer over their life and perform better at high temp, compared to poly panels. The high temp performance probably isnt an issue in the uk unless youve got roof integrated panels where they may not be as well ventilated??
    • CommentAuthorphiledge
    • CommentTimeJun 8th 2022
     
    Posted By: renewablejohn
    I see the peak production only being summer time which fits in well with the pellet and briquette production. Rest of the year I think it will be a struggle to both generate enough from solar for a home and car.


    You might be surprised. On a sunnny february day this year I had 3kw of panels temporarily propped up on the ground facing south generating 2kw late morning. With a much larger array pitched and orientated well youd likely be able cram a fair bit into batteries. If you are ground mounting it makes it easier(less difficult) to change angle for winter generation.
  10.  
    If I were you and did decide on a ground mounted system (re: my earlier question regarding the shed), I'd be very tempted to install bi-facial panels. I'd cover the ground beneath the panels with a deep layer of white gravel on top of a textile sheet to prevent weed growth but more importantly to reflect light back up through the panels to maximise generation. If the panels are mounted at the boundary of the garden (which I'd imagine you will be doing as people tend not to have shed's or ground mounted solar in the middle of the garden), then I'd also look at painting the boundary wall/fence behind the panels white to reflect even more light.

    Bi facial panels are a little more expensive, but they generate more power and are supposed to be better for generation in the UK's low-light/overcast climate. Not many of us have acres of land (or roof space) to site panels so maximising the area we do have to mount panels with high efficient bi-facial panels seems to be the best approach.

    If money is an issue (as it it to a lot of us right now), then the benefit of a ground mounted system is that you could install the frame relatively cheaply and just add panels to it as and when you can afford them.

    If you're wedded to having a building to mount the panels to, then the roof could be constructed from white metal roof panels and the bi-facial panels added to that, with light bouncing up from the white roof. Again, as a shed roof is relatively easy to access (i.e. no scaffolding required) then you could add additional panels, as and when funds allow.
    • CommentAuthorneelpeel
    • CommentTimeJun 8th 2022
     
    Back to shed mounting...is there an efficient (cheap) way of waterproofing between panels such that I could use my panels as the shed roof and do away with my planned OSB sheeting and roofing felt?

    I like the idea of having easy access to the backs of the panels from inside the shed.

    I see that Viridian do all sorts of guttering for their panels, but looks like they will cost £££s and be a bit overkill.


    Also, my plan was to mount the inverter and any other gubbins on a panel inside the 'shed'. This is 30m from the house consumer unit. Any issues foreseen with this?
    • CommentAuthorrevor
    • CommentTimeJun 8th 2022
     
    Posted By: neelpeelAlso, my plan was to mount the inverter and any other gubbins on a panel inside the 'shed'. This is 30m from the house consumer unit. Any issues foreseen with this?

    Yes voltage drop could be an issue. From what I can make out inverters do not like a voltage drop of more than 1% between it and the consumer unit. I built a small shed next to my array to house the inverter and battery but when got into the detail the size of the cable between the shed and the CU in the house would have meant a much heftier SWA so had to in the end house the gear in an outside WC. This brought me to within a 1%VD. With you being just 30M away then you may be able to upgrade the SWA without too much expense my array was 70 M away from the CU
    • CommentAuthorphiledge
    • CommentTimeJun 8th 2022 edited
     
    The concern you have is voltage rise, the reverse of volt drop. UK Solaredge inverters trip at 262volts and I beleive this is a G98/DNO requirement so could well apply to all inverters?? If you try and feed 16amp over a long distance down a small wire the voltage at the inverter will rise. If it gets above 253volts its outside UK limits but practically not a problem at the inverter end. If it rises to 262volts youll have the inverter tripping, restarting, tripping continuously.

    You can probably get on line volt drop calculators so you can work out what the volt drop will be at max 16amp through a 6mm/10mm/16mm cable. The voltage rise will be the same as the drop for the same current/distance/cable size. Once you know the likely rise, measure the house voltage and add the voltage rise to give you the likely voltage at the inverter with the 16amp max generation. You can then decide how big a cable youll need to keep the voltage where you want
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press