Enter Zipcode

Page 1 of 5 1 2 3 ... LastLast
Results 1 to 10 of 41

Thread: 20kWp domestic installation with a twist

  1. #1
    Junior Member
    Join Date
    Feb 2015
    Posts
    14

    Default 20kWp domestic installation with a twist

    Dear all

    I'm currently looking into to do a complete rooftop PV installation where the PV panels also will act as roofing material. It is a one-side roof so the installation will be rather simple.

    A complete roofing system would in my case entail a total power output of nearly 20 kWp. However, I do not wish to export this much to the grid. The system is simply oversized in order to ensure better self sufficiency during winter here in the northern climate.

    Actually I would like to make a really simple installation using maximum 16 micro inverters and therefore never exceed 3,6 kWp delivered to the grid/house. One might argue that it is a waste of PV capacity but I don't see it this way. PV panels are decreasing in price and when also utilised as roofing material the price/m2 becomes realistic. A more traditional 5-6 kW system would be plenty during summer, but not nearly enough during winter. My main goal is to achieve near self sufficiency without relying on the ever changing feed-in tarifs and subsidies.

    My question is therefore if someone is familiar with a setup of this sort? The main problem is to limit the production of the PV panels during summer in order to not overload the micro inverters.
    One idea would be to use a form of PWM based controller right before the micro inverter in order to limit the current delivered to the micro inverter? Naturally it should last 25+ years like the panels and micro inverters.

    The goal is to build a complete solution including the roofing solution, inverters and grid connected battery storage.


    Best regards

    Kristian

  2. #2

    Default

    How do you intend to use the panels as a roofing material? How will they be mounted, sealed, ventilated and wired?? What happens when they expand and contract due to temp changes?

  3. #3
    Junior Member
    Join Date
    Feb 2015
    Posts
    14

    Default

    The roofing solution is being developed as a separate project by a local company.

    I would appreciate if we could keep focus on the electrical aspect

  4. #4

    Default

    So on that note, it would be easy to only tie in part of the array to the grid, but what will you tie the rest of it into? Around here, they send you a check for any excess power generated in a year.

  5. #5
    Member
    Join Date
    Sep 2014
    Location
    Staten Island, NY
    Posts
    83

    Default

    using maximum 16 micro inverters and therefore never exceed 3,6 kWp delivered to the grid/house
    As far as I know a microinverter would only work with a panel. So 16 microinverters would only work with 16 panels.
    How many panels you would have on the roof?
    If you have more than 16 panels then some panels would just work as "roof" and not producing any electricity?

    3.6kW /16 = 225W panel?
    20kW / 225W = 89 panels?
    8.2KW 32x(PVmodule+inverter)+online monitoring

  6. #6
    Junior Member
    Join Date
    Feb 2015
    Posts
    14

    Default

    That is what I'm trying to avoid

    Here in Denmark there is a very big difference between summer and winter with regards to production from the system. With my roof slope the production will be more than 11 times higher in the summer than in winter. It is therefore crucial that all the panels will be connected to the grid during winter to maximise production.

    It is the aim to become self-sufficient as many months of the year as possible. There will be integrated a 5 kWh battery pack in order keep the supply from the grid to a minimum. The task of the system will be to match the consumption of the house during the day + filling the batteries. Feeding electricity back to the grid is not really in my interest.

  7. #7
    Member
    Join Date
    Sep 2014
    Location
    Staten Island, NY
    Posts
    83

    Default

    Quote Originally Posted by Krisharley View Post
    That is what I'm trying to avoid

    Here in Denmark there is a very big difference between summer and winter with regards to production from the system. With my roof slope the production will be more than 11 times higher in the summer than in winter. It is therefore crucial that all the panels will be connected to the grid during winter to maximise production.

    It is the aim to become self-sufficient as many months of the year as possible. There will be integrated a 5 kWh battery pack in order keep the supply from the grid to a minimum. The task of the system will be to match the consumption of the house during the day + filling the batteries. Feeding electricity back to the grid is not really in my interest.
    Is it a NET metering system there?
    If it's a NET metering system then you produce more in summer and save for winter.
    There is no need for self-sufficient in winter unless the grid is down.
    8.2KW 32x(PVmodule+inverter)+online monitoring

  8. #8
    Junior Member
    Join Date
    Feb 2015
    Posts
    14

    Default

    @myfriendSUN

    The panels used are custom made 80W panels. The micro inverters are normally made for use with one 240-250W.

    As long as you don't exceed the limits of the micro inverter (typical 60V/250W) it doesn't matter how many panels you connect.

    One way might to connect 12 x 80 W (960Wp) panels to one micro inverter but with a "limiter" in between. The limiting function could be done by doing rapid connect/disconnect ala PWM + DC/DC conversion to the panel array and then deliver maximum 250 W to the micro inverter. In winter when the 12 panels will in insufficient to even produce 250 W combined the limiting circuit will be inactive.

  9. #9
    Junior Member
    Join Date
    Feb 2015
    Posts
    14

    Default

    No NET metering.

    This system is made for actual self-sufficiency. Otherwise a 6 kWp system would be sufficient for me.

    The grand idea behind this is to become as independent as possible and not rely on the ever changing tarifs and legislation. This will require an oversized system here up north.

  10. #10
    Member
    Join Date
    Sep 2014
    Location
    Staten Island, NY
    Posts
    83

    Default

    Quote Originally Posted by Krisharley View Post
    @myfriendSUN

    The panels used are custom made 80W panels. The micro inverters are normally made for use with one 240-250W.

    As long as you don't exceed the limits of the micro inverter (typical 60V/250W) it doesn't matter how many panels you connect.

    One way might to connect 12 x 80 W (960Wp) panels to one micro inverter but with a "limiter" in between. The limiting function could be done by doing rapid connect/disconnect ala PWM + DC/DC conversion to the panel array and then deliver maximum 250 W to the micro inverter. In winter when the 12 panels will in insufficient to even produce 250 W combined the limiting circuit will be inactive.
    Now I got what you meant.
    A microinverter works with a string of panels!!! Not "micro" anymore.
    Do they have the "limiter" out there in the market?
    8.2KW 32x(PVmodule+inverter)+online monitoring

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •