bill von novak ✭✭✭✭


bill von novak
Last Active
Solar Expert
  • Re: Supplementing off grid system with extra AC

    Ravemind said:

    I have some extra panels lying around and I connected them to the little GTI I purchased on Ebay. It recognized my home power as a grid and started feeding power into it. Shaving about 200 watts off of my 1000 watt AC load according to the Conext SCP. Can I safely feed 800 watts with a better GTI? Is it really reducing my AC load and allowing my main PV to do it's job and fill the batteries? Looks like it.
    The time you will have an issue is when batteries are full and loads are low.  The question then is what will trip due to overvoltage sooner - the main inverter or the grid tie inverter?  If grid tie, all is well - but if it's the main inverter you'll lose power. 

    When my batteries are full, the charge controllers stop. They aren't feeding PV to anything. They are sitting there being wasted until I hit the rebulk voltage. I want to avoid that.

    You can do that without a grid tie inverter.  When your batteries are fully charged, your power is going from the panels to the inverter.  You are still using that power.  Whether or not it goes through your main inverter or a grid tie inverter doesn't matter.

    I have a generator, but I hate using it. It's a Honda eu3000. Somehow I got a lemon and it requires tons of maintenance to keep it running. I even have an eu2000 but it's now to small for what we are drawing.

    I believe the SW4024 has a generator support mode; that allows you to use any size of generator.

  • Re: Dominica post Hurricane Maria

    I am trying to learn this subject but feel I could use some advice.
    Currently I am in London shopping for rebuilding materials to ship to Dominica. At the time I write only 3.6% of the island is connected to the grid. We expect to be without power for up to two years.
    Could anyone suggest a shopping list for a solar panel system capable up providing sufficient power for a fridge, microwave, lighting and power tools.
    We are on a latitude of 15 degrees.
    Let's make a wild guess of 10kwhr/day (less than half US average, assumes very efficient fridge.)  That's a 30-40kwhr battery with a ~4kW inverter.  You'd need about 3kw worth of solar panels to charge that.  Go for 48V; it will be easier overall.

    Choose battery types.  Do you want cheap and short-lived (a few years) or more expensive but lasting 10-20 years?  Maybe cheap is the way to go since you don't anticipate this lasting forever.  There are lots of options out there now.

    Make sure you get a hybrid inverter capable of doing grid tie, so when the power comes back you can still get benefit out of the system.
  • Re: Connecting solar PV system to main-grid

    fazilcv said:
    We are going to install on-grid zero injection roof top pv system and design is already done by using Helioscope. So my questions is,
    If the solar system is not producing the needed power maybe because of rain or cclooudy days etc.. can we take that additional power from main grid?,if yes how then connection should be made or additonal equipment is required for this?
    You can get a hybrid inverter with a small battery.  (The Outback line, for example.)  They support operating modes like Grid Zero that will use your own solar power preferentially over grid power.  If you draw more than the solar system can supply, it draws from the grid.  At night it draws from the battery for a short time then reverts to just the grid.

    You can do this without a battery as well.  SolarEdge has a non-battery grid tie inverter that will support zero export.  You use your own solar power.  If you don't use it all the extra solar is wasted.  If you need more than that it's pulled from the grid.
  • First day at Solar Power International

    I'll post some updates as I come across interesting seminars/exhibits.
  • Re: Sharing PV input with two different MPPT inverters

    BB. said:
    MPPT charge controllers--No, each should have its own array so it can mange Pmp=Vmp*Imp.

    . . .

    There are a couple Positive Ground PWM controllers out there--I am not sure how to share a single array with them (don't know how they are designed internally). So I cannot say for those types.

    The switched-positive vs switched-negative is also big issue.  A system that uses two dissimilar charge controllers on the same array - one that switches on the positive side, one that switches on the negative side - will apply full array voltage to the battery, with no way to stop it other than the breakers  (disabling the charge controllers will not stop the current.)  This, of course, will rapidly destroy the battery.

    If you are using the same charge controllers for both that MIGHT work; the big problem then will be the MPPT algorithms fighting as you mention above.