My First Grid-Tied System

vidhanvidhan Registered Users Posts: 14

I'm planning to install my first system(with the help of my electrician)here on the Big Island of Hawaii. We pay the nation's highest electric rates and PV has become, to my way of thinking, an absolute no-brainer.

I got a good deal on 16 Evergreen Solar ESVL-195 panels which I am planning to mount on my roof. I expect that this installation will offset about 75% of my electric bill, but I want to wait and see actual vs. expected power production and then expand my system as needed to offset the entire bill. I am guessing that I may expand to 22 panels.

I am thinking about using a Fronius IG4000 inverter. I would have preferred an SMA SB4000, but the string sizing seems to be better with the Fronius. I would like to hear from someone with some experience, whether this seems like a good inverter for the system.

Aloha All


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: My First Grid-Tied System

    Greetings from the opposite end of the spectrum: frozen Canada with really cheap electric rates!

    First thing you need to do is determine your usage. Getting a good deal on panels/inverter is fine, so long as it fits your needs. Otherwise it's not such a good deal.

    So get yourself a Kill-O-Watt meter (or similar) and start measuring the watt/hrs of everything in the place. Then look to see if there is something that can be improved upon - like installing cfl's or more insulation to off-set air conditioning costs.

    A shortcut for you is to look at your energy bills and see how many kW/hrs you use per day (warning: math involved!) You want to replace 75%? You may find a 4kW inverter isn't enough. Do you have electric stove/hot water/heat? Heating anything with electric is the big user and should be your first consideration for improvement.

    When it comes down to designing the actual system, this will be grid-tie, no? That would probably be better in your case (if allowed) because any excess power produced from all those panels will get sold back to the grid. 16 panels is a lot: @195 W = 3.1 kW - whatever efficiency loss your particular installation will have. A rough estimate would be nearly 12 kW/hrs per day, given your sunny location (assuming 60% ER & 6 hrs sun/day - there are a lot of variables). So how does that compare with your current usage? How bad is the electric rate in Hawaii?

    If you have problems with frequent blackouts you may want a battery back-up grid tie setup. This would cost a bit more.

    As Icarus so famously says: "Avoid the ready, fire, aim"
  • BB.BB. Super Moderators, Administrators Posts: 31,688 admin
    Re: My First Grid-Tied System

    For those that are not in the "progressive" states of America--Many times just replacing XX% of the electric bill is actually a cost saver--whereas replacing 100% may not be.

    In California (and many other states) we have a "tiered" rate system... For example:

    First 300 kWhrs is $0.12 per kWhr (flat rate)
    First 300 kWhrs is $0.09 per kWhr (time of use, off peak)
    ...several more tiers
    >~1,000 kWhrs per month is $0.41 per kWhr (flat rate residential)
    >~1,000 kWhrs per month is $0.59 per kWhr (time of use, summer afternoons)

    So, if you have heavy loads (summer A/C, other electric devices), then you can really save money with Grid Tied Solar that does not address 100% of your utility bill.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vidhanvidhan Registered Users Posts: 14
    Re: My First Grid-Tied System

    Our daily usage is about 16KWH. Net metering is available which means that, although we cannot sell "excess" electricity to the utility company, we can "zero out" our bill, so optimal will be producing electricity equal to but not greater than our total usage. Our rates are dependent on fuel pricing (the electric company burns diesel). The rates have fluctuated this year around .40 per kwh with a high around .44/kwh.
    I don't want to get involved with batteries, as I have a generator for the rare times that we lose power. The only extended foreseeable blackout would be if a major hurricane hit us, and in that case, who knows how the panels would fare. I am going to insure them for hurricane damage.

    Any comments on the Fronius inverter? Do you think it's a good choice?
  • Solar GuppySolar Guppy Solar Expert Posts: 1,970 ✭✭✭
    Re: My First Grid-Tied System

    I would suggest Xantrex or SMA for an inverter, they are the top two. Fronius is fan cooled, limited operational range and if you read the other thread in this forum will see the have issues with dual arrays not facing the same direction. It also been reported the Fronius units report higher kWh production than is actually being produced

    Xantrex has everything built in, IE disconnects, and free communication software, all extra on the SMA units
  • vidhanvidhan Registered Users Posts: 14
    Re: My First Grid-Tied System

    Hi SG,

    I read the thread about MPP hunting with interest and concern. I was leaning towards an SMA SB4000 and putting all 16 panels on a single string, but the values in the SMA string calculator looked marginal and the guy who is selling me the equipment steered me toward the Fronius. Do you think the Xantrex GT4.0 would be a good match for my system with all 16 panels in a single string?
  • BB.BB. Super Moderators, Administrators Posts: 31,688 admin
    Re: My First Grid-Tied System

    Have you tried the Xantrex string sizing tool?

    I am not sure what the "ESVL" model is... I did not find anything about them.

    There are several Evergreen 195 Watt panels with wildly differing Vmp numbers...

    From what I have seen, the Xantrex sizing tool is very accurate (and conservative. Play with it and see what your options are.

    Personally, the Xantrex GT 3.0 (BP-4175 175watt panels as 3.5kW in two strings of 10 each) unit under 3.5kW of solar panels has been ticking along just fine on my home for the last 3+ years.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,970 ✭✭✭
    Re: My First Grid-Tied System

    I run a GT5.0 with 30 of the blemished 170 watt Evergreen's in two 15 panel strings no problem ( vmp is ~26 volts STC per panel ), in a temperate climate I would think 16 should be fine but use the Xantrex Calculator and set you min/max temperatures to what is correct for your location. Highest Voltage I've ever seen is in the mid 400's in the morning.

    I ran the Xantrex tool, with both 12V & 18V modules , green all the way with 12V, and with 18V modules, even at 32F for your low, its below the 600V maximum. I would think your probably more like 50F minimum, so it should do fine

    For 16 panels, you can use a GT3.3, they have a street price under 2K, very solid and proven inverter, many here on this board have them.
  • RoderickRoderick Solar Expert Posts: 253 ✭✭
    Re: My First Grid-Tied System

    Howzit!! Molokai stay more worse than you. 50 cents one kWh...

    <pidgin off>

    Seriously, though, this sounds like a good plan. Try to make contact with the VolcanoSolar person that logs in here, occasionally. He's also on the big island.

    There are a couple concerns for a Big Island installation that don't apply to the majority of systems on this board. First, if you're near the beach, then salt corrosion. And second, account for vog, especially if you're in the wind shadow of the volcano. And if you have a flat root, it's still a good idea to tilt the panels, so that the rain cleans them. Otherwise, the water will puddle up, and dirt will accumulate, possibly that reddish stain if you live in a red dirt area. And I hear that iron is good at blocking infrared.
  • autoxsteveautoxsteve Solar Expert Posts: 114 ✭✭✭✭
    Re: My First Grid-Tied System

    I've got a Fronius 4000 inverter and 22 Evergreen 190's.

    I've presently exceeded 7.4MWhrs of production in my micro climate in 11 months. REC Solar (my installer) had forecast 5.8 MWHrs....

    I'm very pleased with the Fronius but I also had someone install it and they warrant it.

    Since you're doing a home brew system you might consider a Xantrex inverter. they seem to be comperable and have that nice open built in rs-232 interface....
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