Large grid tie system in caribbean - many orientations

Hello everyone,

I am writing this post for some input on a system I am working on in the Virgin Islands.
The system will be grid tied with generator backup, roughly 20kW of panels on two structures with radial roof construction.

The buildings are known as "Deltec's", which are pre-fab wooden houses made in NC and shipped in containers around the country.

They range in size from 300 sq ft to 1600 sq ft, each having more sides than the previous.

The two I am working with are 10 and 17 sided, hence the roofs have surfaces facing many different orientations. Of course I would only be utilizing the south east/west and southern faces of the roofs.

The roofing will be a standing seam metal roof.

The owners would love to use thin film even though I have told them that it will not be as efficient as other alternatives. The main reason they are interested is because of its resistance to high winds, which are common during hurricane season. The risk of hurricanes would prevent me from using any traditional panel on the roof. A ground mount system is possible, but would only supplement the roof mounted system because of shading for most of the morning.

I have been looking at solyndra's cylindrical series and have thought about using them. I am not sure if this panel design would perform better on multi-oriented roofs than traditional panels.

In order to account for the multiple orientations I have thought about using either micro-inverters, or using many smaller inverters for each differently oriented roof panel.

If anyone has any input or has dealt with this before, please comment.

Thanks,

Island Mon

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Large grid tie system in caribbean - many orientations

    that lower efficiency will translate to nearly twice the area needed compared to standard pvs. are they going to have that much room on their roofs given the 20kw requirement? i doubt it.
  • Island Mon
    Island Mon Solar Expert Posts: 29
    Re: Large grid tie system in caribbean - many orientations
    niel wrote: »
    that lower efficiency will translate to nearly twice the area needed compared to standard pvs. are they going to have that much room on their roofs given the 20kw requirement? i doubt it.

    No they will not have enough roof area for 20 kW of thin film, I would simply put as much as possible.

    What I am most concerned with is the different orientations.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Large grid tie system in caribbean - many orientations
    Island Mon wrote: »
    What I am most concerned with is the different orientations.

    Micro inverters, and well mounted panels.

    Regarding damage, flying debris will take out twice as many thin film as "regular" panels, because of the larger area. Unless you are looking at the unisolar plastic panels ? Get the version with Stainless Steel backing, not the aluminum, which is unfinished and will corrode to swiss cheese in salt air. Or maybe now the aluminum is passivated, but before, it was not.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Island Mon
    Island Mon Solar Expert Posts: 29
    Re: Large grid tie system in caribbean - many orientations

    I have been thinking that Micro Inverters would be the best solution.

    Does anyone have any idea what the longest wiring run can be from panel Jbox to microinverter. I would like to keep all the inverters in a cupola in order to avoid making many roof penetrations, since the inverters would not be able to be situated on the backside of panels (since thin film is #1 choice.)

    Thanks for info on stainless backed thin film.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Large grid tie system in caribbean - many orientations

    Micro inverters are mounted below the panel...

    I don't think it matters if you choose DC or AC roof penetrations.

    I would not plan on adding cabling to each micro inverter. It is not cost effective and you add losses with longer cables. Also, you would end up with a lot more wire to manage (2-3 wires per panel to micro inverter or 10-15 sets of wires running to all the inverters in the cupola) vs the daisy chain AC connections (micro inverter to micro inverter under each panel to something like 10-15 inverter per 3 wire cable).

    A central inverter is pretty much the same--You put ~10-15 panels daisy chained (+ to - to + to - etc..). Then run that pair of wires to the central inverter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Large grid tie system in caribbean - many orientations

    there isn't a simple answer for your question on the longest wiring run. the voltage drop % would also need to be from the pvs to the main breaker box before going out to the utility. now you would probably need to check with your local rules and regulations as i've no idea what a caribbean country would state for this.

    i would think at a minimum that they would go by the amount of current to be passed with a given distance at the specified voltage for your area with a specified gauge or size of wire. most here would not recommend more than 5% for the voltage drop.

    the voltage drop calculator in my sig line can be used for ac by specifying the ac voltage used instead.
  • Island Mon
    Island Mon Solar Expert Posts: 29
    Re: Large grid tie system in caribbean - many orientations

    Thank you for the replies.

    I am still trying to determine the best configuration of panels and inverters for the radial roof design. I know that to deal with the many orientations I will need multiple inverters or many micro-inverters.

    Has anyone here designed a system for a radial roof? or any comments/ideas?
  • nvyseal
    nvyseal Solar Expert Posts: 108 ✭✭✭✭
    Re: Large grid tie system in caribbean - many orientations

    you might have to do something like this:
  • Island Mon
    Island Mon Solar Expert Posts: 29
    Re: Large grid tie system in caribbean - many orientations

    nvyseal,

    That is exactly the type of home I am building, however the one I am building also has another 10 sided 500 sq ft pod.

    I have spoken with Enphase about extending the leads to the micro inverters. They sell 6', 12' and 20' extensions. I want to minimize voltage drop so I will have to determine how close I can get the thin film panels to the peak of the roof near the cupola.

    The owners have decided on a standing seam metal roof, so I will be choosing a thin film module that Enphase recognizes as compatible with their inverters.

    I have thought about this system a lot and it seems that for the roof mounted arrays, this setup makes the most sense, taking into account the 10+ different orientations from E to W.

    Let me know what you think.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Large grid tie system in caribbean - many orientations
    Island Mon wrote: »
    The owners have decided on a standing seam metal roof, so I will be choosing a thin film module that Enphase recognizes as compatible with their inverters.

    Please reconsider the thin film module decision. They do not have as long of proven life, and are nearly twice the size for the same harvest.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Large grid tie system in caribbean - many orientations

    And I would recommend that you never extend the DC leads from the panels to the inverters. Run it as 240 vac instead.

    I cannot think of a good reason to extend the DC wires and a lot of reasons not to extend the DC.

    Sending power at 240 vac is better than at something like 30 to 40 vdc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset