Grid tie systems questions

booboo
booboo Solar Expert Posts: 39 ✭
in Grid Tie and Grid Interactive Systems #1
I am getting ready to purchase a grid tie system and would like some advice.

My thoughts are to get a PVP 4800 inverter and 13 200W solar panels. My reasoning for this is I can put the 13 panels in one string for now. Down the road when I save up enough money I can add another 13 panels to a second string.

When I add the second string does it have to be the same as the first string? Can I use different panels for the second string?

Would it be better to get a smaller inverter now and add a second one when I want to expand?

I will get a $4 per watt rebate from my electric company and 30% from the feds and $1000 from the State on the first installation. If I wait one year to expand the system I will get another rebate of $4 per watt from the electric company but will I get another tax credit from the feds and state?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #2
    Re: Grid tie systems questions

    From what I quickly read--the PVP family has a single input DC Solar
    Array Input. The Vmp of both strings should be pretty close to the same. The farther apart the Vmp is between the two arrays, the more lost energy you will have (non-optimum collection of solar energy).

    If both arrays are on the same roof (i.e., same mounting orientation to the sun)--then one large GT inverter is a good solution (check the final price and do one or two inverters, based on the final price).

    If the panels are not facing the sun in the same way (say one array facing east, the other facing west)--it would be better if each had it own GT inverter. The panels will operate at different temperatures, and Vmp (being temperature sensitive) will be different--and you will lose some power with installing one inverter (there is a debate if this is 1-2% difference--or 5+% loss of power).

    The tax code and rebate programs are always changing. Get the current code/regulation to make sure you do it correctly.

    Also, confirm that if you install the 2nd solar array later--that they will accept this for credits/rebates (should be OK--you may have to attach a copy of your first paper work to show that you are connecting the 2nd array to an existing GT inverter).

    Talk with your city/county building department (and electric utility) to see how you can keep the permit costs low (approve the whole system, with just a second inspection when the 2nd array is installed--instead of a whole new round of fees).

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