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  • Solar System Questions

    Hi All,
    I have a few questions about solar and would like to know the answers to the following:

    1) If one must have distance between the home and the panels, (can't do roof mounted) Which is better longer AC or longer DC run ?
    In other words keep the distance between panels and inverter short and a longer AC, OR
    Have the distance between the panels and the inverter longer and place the inverter on the house wall

    2) For a larger system 10Kw - 20Kw: Which is better micro inverters per panel or a larger Inverter?

    3) When using micro inverters per panel, how does one charge the Battery backup? Convert AC back to DC to charge the battery? Seems a waste (due to energy loss during conversion)
    Does this then imply micro inverters are best when no battery backup, thus using net metering. Pushing to the Grid when making and pulling from grid when demand exceeds generation

    4) Can one have a single 20 kW panel setup with 20 kW battery backup, but then split this into 10 kW + 5 kW + 5 kW inverters and use a single generation for multiple supplies? In other words have a single panel setup and supply 3 houses in a small neighborhood

    5) If wanting to (walk, crawl run,) grow over time mainly to break down the up front costs. Can one start with a 10 kW Inverter and then slowly add panels and batteries until one reaches the 10 kW all around (panels, battery and inverter) ?


    Thanks in advance (sorry if this should have been individual posts)

  • #2
    1) generally higher voltage is going to do better on the longer run. In most cases that is going to be high voltage DC.

    2) for larger systems Micro inverters get expensive

    3) ok you should have lead with it being a battery system. If you use micro-inverters then you will need to AC couple to a bimodal inverter, and yes inefficient.

    4) yes but going to be quite expensive and complicated trying to manage a shared array and shared battery, but multiple inverters.

    5) solar does not grow well, ESPECIALLY off grid solar.

    What exactly is the point of your system here with large multi home backup. This will be quite costly. Is it to take existing grid tied home off grid? or just backup?

    Why not net metering?
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

    Comment


    • #3
      Hello TheBearF8 and welcome to Solar Panel Talk

      I can answer your questions but you first need to answer one of mine.

      Is this system totally off grid or is it a hybrid on grid with batteries?

      So a quick stab at your 5 questions.
      1) AC or DC which ever has the higher voltage on that long run
      2) IMO micros are never a good idea and might not even work with a hybrid battery system
      3) See the second part of #2 answer.
      4) Again if the system is totally off grid you can have a single pv array charging a battery bank with multiple inverters for seperate loads. If the system is hybrid, I think you will have issues.
      5) Increasing a solar / battery system is never a smart option. Adding new batteries to an old set is a NO-NO because the old will hurt the new ones. If you decide your system is too small then more than likely you will need a brand new battery back, pv panels and charging system which may make it expensive and not cost worthy.

      Comment


      • #4
        Thanks ButchDeal

        I'm not opposed to anything right now. purely trying to understand and come to terms with all these aspects that make up a solar system.

        My current setup is I have a single 15 acre property with 3 elec. meters (thus 3 utility accounts). over 300 feet between structures.

        I have only one roof that is south facing and it is partial shaded. All other roofs are East West and most are fully shaded anyhow.
        So there is no way to have all the solar panels on the single small south facing roof.
        So (from my limited understand) I'm probably faced with a ground mounted system. But then I don't want to have 3 (or more) sets of ground mounted solar panels scattered all over
        Plus based on landscaping and ground conditions I would still have to have some distance between ground panels and structures even if I went with multiple solar panel locations.

        So I'm thinking (open to learn) of setting aside one area of the property, that has no shading and full sun access. for solar panels.

        From this one area of solar panels do I :
        (a) have all the batteries and DC to AC at the panel location, and then run AC to each of the 3 structure locations,
        Basically my own "power plant" OR
        (b) have the batteries and DC to AC at each structure location


        I don't mind between grid tied, off grid, net metering etc.. I do need to have power when the grid fails sure. My current thought is start with Solar generation and then gradually add battery backup.
        Cost is the most limiting factor.


        Thanks again

        Comment


        • #5
          Thanks SunEagle

          no current system. Open to any of the options (off grid, hybrid, grid w/ batteries) *based on my limited understanding* grid w/ batteries seems best. There are cases where no power means livestock has no water and suffer. I had a generator (probably a lemon) spent more money repairing this, then that. Probably spent twice the cost of the generator. Not a fan to do that again.

          Honestly going off grid and not paying $900 - $2000 for utility sounds attractive, but nothing for free right.

          Thanks again

          Comment


          • #6
            Originally posted by TheBearF8 View Post
            Thanks ButchDeal

            I'm not opposed to anything right now. purely trying to understand and come to terms with all these aspects that make up a solar system.

            My current setup is I have a single 15 acre property with 3 elec. meters (thus 3 utility accounts). over 300 feet between structures.
            Have you contacted your utility to see if you can get Virtual Net metering for a PV system to credit all three meters???

            Originally posted by TheBearF8 View Post
            So I'm thinking (open to learn) of setting aside one area of the property, that has no shading and full sun access. for solar panels.

            From this one area of solar panels do I :
            (a) have all the batteries and DC to AC at the panel location, and then run AC to each of the 3 structure locations,
            Basically my own "power plant" OR
            (b) have the batteries and DC to AC at each structure location
            Well nothing in your description of wants implies that you need batteries at all.
            You most likely can get virtual net metering since it sounds like all the meters are in your name and on your property, so
            have the array in the field, run high voltage DC to the closest meter, install the inverter or two, lineside tap in and done.


            Originally posted by TheBearF8 View Post
            I don't mind between grid tied, off grid, net metering etc.. I do need to have power when the grid fails sure. My current thought is start with Solar generation and then gradually add battery backup.
            Cost is the most limiting factor.

            Thanks again
            Well gradual growth of battery systems is a very expensive plan. you can add batteries latter to some systems like the SolarEdge StorEdge system, or AC couple almost any grid tie.
            Going to be a lot cheaper to get a generator for infrequent outages.
            If you do go bimodal backup then determine your actual critical loads that need to be backed up. Are they at each location or just one?
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

            Comment


            • #7
              Thanks again ButchDeal

              Never heard of Virtual Net metering. I will find out more on this.

              Generators::
              As I said to SunEagle's post. The larger 200A generator, probably the worst investment ever (but I honestly feel it is just this unit)
              It has failed/quit working every time when we have had power outage, As stated probably have paid for it at least twice, I have replaced everything but the frame, and engine, at least once.
              circuit boards, power controllers, regulators, etc.. have all been replaced, even the generator drum. Also it's only +/- 12 years old, wasn't cheap either. Not happy

              I do have multiple generators. and hook up portable generators to sub panels during a power outage, (all with proper transfer switches, and connections) to at least have limited power at all needed locations (nice to have electrical, simply must wait until outage is restored) not ideal, but a workable solution.

              I've had the utility company replace and often (according to them) up size the transformers. Due to irregular power fluctuations. I have multiple UPSs all over the property protecting sensitive electronics. They will all click 3-5 times in rapid succession between mains and battery supply. Repeat this cycle 3/4 times, then all is well again. Also often around 9am-10am.
              Since their last upgrade (last year) this has been reduced, from 3-5 times a week to maybe 1/2 a month. So major improvement, but still not ideal/perfect


              So experience is, I just don't trust the supply.

              thus, I'm learning and looking for a better alternative.


              Originally posted by ButchDeal View Post
              have the array in the field, run high voltage DC to the closest meter, install the inverter or two, lineside tap in and done.
              Love this, my ideal site for the array is fairly close to one of the meters as it is. (within 50 feet)

              So virtual net metering I must get an answer to this.
              Thanks again

              Comment


              • #8
                It sounds like your utility is doing maintenance at 9-10am that is reducing the voltage enough to trip the UPS units.
                This will have the same effect on grid tie inverters as well as bimodal inverters.

                The problem with having multiple inverters on a single battery bank is that the battery bank is 48V relativly low voltage so you will want the inverters close to the battery. This means that you will be rewiring your entire place for AC from a single location if you want one solar array, one battery bank to cover all buildings.

                Now if you have some buildings that are less critical that could run off a well maintained generator then that will help.
                You may find that there is a minimum charge per meter so eliminating two of them may save you some money each month but not sure how much electric work to rewire those two locations will cost you or if it will have a decent ROI.

                You should find out if you large generator is a problem or if it is maintenance. Bimodal systems are not maintenance free ....

                also virtual net metering is also referred to as meter aggregation in some areas.
                OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                Comment


                • #9
                  Anything you take off-gtrid you need to learn real damn fast is; it will cost you 5 to 10 times more than the mean ole POCO charges you now for the rest of your life. So ask yourself one simple question.

                  Why do you want to pay 5 to 10 times more than you have too, with a very limited supply, spending several days of the year with no electricity, and using generators for cloudy spells?

                  Bet your salesman and green mafia politician will not tell you that. So be careful what you ask for. Not only will it cost you a lot more, it makes you a very heavy polluter.
                  Last edited by solar pete; 03-26-2019, 04:58 PM.
                  MSEE, PE

                  Comment


                  • #10
                    Originally posted by TheBearF8 View Post
                    Thanks ButchDeal

                    I'm not opposed to anything right now. purely trying to understand and come to terms with all these aspects that make up a solar system.

                    My current setup is I have a single 15 acre property with 3 elec. meters (thus 3 utility accounts). over 300 feet between structures.

                    I have only one roof that is south facing and it is partial shaded. All other roofs are East West and most are fully shaded anyhow.
                    So there is no way to have all the solar panels on the single small south facing roof.
                    So (from my limited understand) I'm probably faced with a ground mounted system. But then I don't want to have 3 (or more) sets of ground mounted solar panels scattered all over
                    Plus based on landscaping and ground conditions I would still have to have some distance between ground panels and structures even if I went with multiple solar panel locations.

                    So I'm thinking (open to learn) of setting aside one area of the property, that has no shading and full sun access. for solar panels.

                    From this one area of solar panels do I :
                    (a) have all the batteries and DC to AC at the panel location, and then run AC to each of the 3 structure locations,
                    Basically my own "power plant" OR
                    (b) have the batteries and DC to AC at each structure location


                    I don't mind between grid tied, off grid, net metering etc.. I do need to have power when the grid fails sure. My current thought is start with Solar generation and then gradually add battery backup.
                    Cost is the most limiting factor.


                    Thanks again
                    On grid with net metering will almost surely be less expensive up front and a whole lot more reliable for a whole lot less maint. than an off grid system with batteries. You want reliable off grid power for relatively short periods of power outages or emergencies, figure out how little power you can get by on for short periods and buy an ICE powered generator fueled with propane or dual fuels for those times.

                    Before any of that, get and read a copy of "Solar Power Your Home for Dummies". You'll learn why the generally more experienced and also technically knowledgeable folks here are telling you that maybe off grid PV isn't all sweetness and light you may think or have heard it is. Believe them, or at least try to learn and understand why they feel/write as they do. We disagree on somethings around here some times, but none of us have a dog in the fight that can bite you, or have anything to gain by B.S.'ing you.

                    BTW, w/ 15 acres, why are you worried about south facing roof, or any roof for that matter. Ground mounts are, for many/most applications far superior to roof mounts for a lot of reasons. Most arrays wind up on roofs because most folks don't have as much real estate as you do. Ground mounts are better.

                    Educate yourself and then come back here and fill in any knowledge gaps before you get serious.

                    Welcome to the neighborhood.

                    Comment

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