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    Hello all,

    I just registered to your informative forum today. I've been lurking for a few days, trying to learn as much as I can before making an investment this large. Now looks like the best time to purchase. Prices are low. Who knows what will happen with the incentives after 2016.

    I'm in Montana. We're looking to install a 6khw ground/pole mounted grid tied system. We've had the local solar company out for a site analysis. The owner/contractor/installer has been super to work with thus far. He's very patient and explains things thoroughly. His initial estimate using 24 REC panels and a Fronius inverter is $18,300 ($3.10/watt). Final out of pocket should be $11,810 ($1.97/watt). From what I'm reading here, that's very reasonable price.

    I've also asked for two more quotes just to see how much the SunPower (most likely wont go with but am curious on the price) and Sun World panels will increase the cost.

    Here's my site. South is on a line from the center of the photo to the left hand side of the garage. I'm not attached to any of the trees in this area. Anything that casts a shadow will be leveled.




    Right now I'm wondering if there is any benefit to going with a transformerless inverter?

    Cheers!

  • #2
    Hi sunnybean and welcome to Solar Panel Talk!

    The transformerless (TL) design is more common in newer model products and can provide equivalent output and efficiency with a lot less weight and space, but perhaps with more noise (hum.) Will you be putting the GTI itself close to your living space?

    A newer design TL inverter is more likely to include the ground detection and arc fault protection features that the latest [2014] NEC requires.
    But if you are on an older NEC version, that additional complexity may not be worth the cost.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

    Comment


    • #3
      Unless something has changed in the last 5 minutes Montana is on code cycle 2005, and many counties do not have permits and inspections. Code is pretty much limited to the cities and Montana does not have many cities. Rural is still pretty much the Wild West which is a good thing IMHO
      MSEE, PE

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      • #4
        Originally posted by Sunking View Post
        Rural is still pretty much the Wild West which is a good thing IMHO
        Like Panama?
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

        Comment


        • #5
          Pricing sounds good but you also need fairly high electric rates for it to pay off in a reasonable timeframe.

          Comment


          • #6
            Originally posted by inetdog View Post
            The transformerless (TL) design is more common in newer model products and can provide equivalent output and efficiency with a lot less weight and space, but perhaps with more noise (hum.)
            Are you sure about that hum thing? I thought it's the opposite and the hum mostly comes from the transformer itself.

            I have an SMA 7K inverter with transformer and an SMA 4K TL inverter. I just went out and check and my 7K with the transformer is humming loudly, while I can't hear a peep from my 4KTL despite pressing my ear against it. They're running at peak time right now, too.

            Comment


            • #7
              Originally posted by Volusiano View Post
              Are you sure about that hum thing? I thought it's the opposite and the hum mostly comes from the transformer itself.

              I have an SMA 7K inverter with transformer and an SMA 4K TL inverter. I just went out and check and my 7K with the transformer is humming loudly, while I can't hear a peep from my 4KTL despite pressing my ear against it. They're running at peak time right now, too.
              I should not generalize too much.

              A well designed transformer system will have some minimum amount of hum just from the magnetizing current in the windings and the magnetic forces in the core. A less than well designed (or economic trade-off) system will have more hum.

              A TL design will also have some noise from switching elements and the filtering elements. Maybe not as much acoustic noise but more electronic noise in the output voltage?

              I would appreciate other folks' experiences in this area.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                Thanks for the welcome.

                Yes, the transformer will be near my living room and spare bedroom. So, noise will need to be factored. I didn't realize there was much noise with either system. Hopefully someone can tell me which inverters are relatively quite.

                On the electric rates, we pay a bit over $.11 per watt.

                As for the NEC, he's not going off the 2014 codes.

                If you guys had a choice, and the SolarWorld panels weren't more than $35-40/panel more than the REC panels, which would you go with?

                Thanks

                Comment


                • #9
                  Originally posted by Ian S View Post
                  Pricing sounds good but you also need fairly high electric rates for it to pay off in a reasonable timeframe.
                  Montana has some of the lowest electric rates in the country at 6 to 7 -cents per Kwh. As of April 1 with all transport, fuel charges and delivery is 7.3011 cents per Kwh. With the poor insolation and low rates pushes ROI to almost non existent.
                  MSEE, PE

                  Comment


                  • #10
                    Originally posted by inetdog View Post
                    Like Panama?
                    Like the USA it depends on where you are at. However electricity in Panama is almost free at 3 to 4 cents per Kwh USD. Electricity in Panama is limitless and the USA paid for it all and will continue to do so all for free. What is really ironic 3 to 4 cents is a huge profit margin and a money maker for the government ran utility. Absolutely no fuel cost.
                    MSEE, PE

                    Comment


                    • #11
                      Originally posted by Sunking View Post
                      Montana has some of the lowest electric rates in the country at 6 to 7 -cents per Kwh. As of April 1 with all transport, fuel charges and delivery is 7.3011 cents per Kwh. With the poor insolation and low rates pushes ROI to almost non existent.
                      You're right on with the kwh cost. But, when you factor in the delivery charges it is more like $.11/kwh. Well, at least that's what I'm seeing on my NorthWestern Energy bill. I was hoping to see my ROI in 13 years.

                      Comment


                      • #12
                        Originally posted by inetdog View Post
                        I should not generalize too much.

                        A well designed transformer system will have some minimum amount of hum just from the magnetizing current in the windings and the magnetic forces in the core. A less than well designed (or economic trade-off) system will have more hum.

                        A TL design will also have some noise from switching elements and the filtering elements. Maybe not as much acoustic noise but more electronic noise in the output voltage?

                        I would appreciate other folks' experiences in this area.


                        I have two Powerone 5K Aurora's, one is defenitely humming loudly more than the other but no issues with production. It started the first day it was turned on but installer said it was normal. No big deal really since it is away from the living area.

                        Comment


                        • #13
                          Based purely on what your location looks like, you might find power reliability impacting the usefulness of a grid tie system (which will not produce when the grid is down.) You might want to consider a generator (cheapest) or a battery based UPS system (cleaner/quieter/more expandable) or if you still want solar, an SMA SunnyBoy inverter with the secure power supply feature. The latter will give you some power even when the grid is out.

                          Comment


                          • #14
                            Originally posted by billvon View Post
                            Based purely on what your location looks like, you might find power reliability impacting the usefulness of a grid tie system (which will not produce when the grid is down.) You might want to consider a generator (cheapest) or a battery based UPS system (cleaner/quieter/more expandable) or if you still want solar, an SMA SunnyBoy inverter with the secure power supply feature. The latter will give you some power even when the grid is out.
                            Good point. I thought about it for a little bit but don't think the extra cost to the solar system is worth it. In the 20 years of living here I cannot remember a time when the power was out for more than an hour. The snow storms usually don't effect our power. We don't see tornados or hurricanes. Most of the time it's a strong gust of wind or lightning strike that will flip a transformer. The power company responds pretty quickly.

                            I realize in a SHTF scenario I might regret it. But, for 99% of my needs I think my money would be better spent on a generator.

                            Comment


                            • #15
                              Originally posted by sunnybean View Post

                              You're right on with the kwh cost. But, when you factor in the delivery charges it is more like $.11/kwh. Well, at least that's what I'm seeing on my NorthWestern Energy bill. I was hoping to see my ROI in 13 years.
                              I factored in delivery and transmission charges.
                              MSEE, PE

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