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  • Non roof mounted solar option?

    I am investigating installing solar panels at the house on the family farm in Louisiana, unfortunately this would likely not be the run of the mill roof top installation due to roof shading, and unusual electrical hookup.

    The existing setup has a single CT style pole mounted meter that distributes power from one transformer to 2 structures each with their own service entrance heads, one building with 2 service entrance heads. The main house, the building with the water well, and swimming pool. The house and building with the water well are also connected to a backup generator (33KW) through 2 manual transfer switches (one with solid neutral one with switched neutral for ground loop concerns, one service entrance is not backed up and only powers non essential loads).

    Also there is little roof top space that would be appropriate for solar panel mounting on the house due to shade trees, existing solar pool heater, etc. So instead the panels would need to mounted on some type of rack located probably 125-200 feet away from the main house disconnect / transfer switch (which is also pole mounted, house is fed by underground 500 MCM in conduit from the disconnect / transfer switch to the indoor main breaker box about 85 feet away, this would be an L shaped wiring layout or maybe more like a Y with on short leg if you include the pump building)

    It is an all electric house so power consumption is highly variable, ranging from an idle load of 3-4 KW on a nice spring day, to typical summer daytime average runs 14-23KW in the daytime with air conditioners ( 2 of 3 central air units) running, in some fringe cases draw can exceed the capacity of the 33KW generator (which has a KW meter on it) more so during winter conditions than summer, the 33 KW generator will allow for life as normal in summer, but in winter will only power 2 out of 3 electric furnaces plus usual hot water, cooking, laundry, etc.

    The area also suffers from relatively frequent power outages, although most are brief, lasting less than an hour, many just lasting a few minutes so hybrid system with limited battery capacity would be preferred. Ideally this would allow for a continuity of power and provide carry over power for many of these short outages without the requirement to start and run the generator, say ability to handle around a 35KW load for 15 -20 minutes.

    Ideally I would like to build this as a DIY install, I just need some help on the design given the complexity both geographically and electrically). I do have some experience with solar electric, but it is all small off grid DC stuff (50-150 watt, boats, remote equipment battery charging, remotely mounted wifi relays, remote security cameras, etc)

    Any suggestions on rough layout and equipment type needed would be most welcome, I am sure there are many ways to do this, I just don't know the trade offs, particularly with voltage loss concerns with the panels needed to be mounted so far away.

    Thanks Ike

  • #2
    Originally posted by Isaac-1 View Post
    Ideally I would like to build this as a DIY install, I just need some help on the design given the complexity both geographically and electrically). I do have some experience with solar electric, but it is all small off grid DC stuff (50-150 watt, boats, remote equipment battery charging, remotely mounted wifi relays, remote security cameras, etc)
    While you can do some of the prep work yourself you are unlikely to be able to do much of the electrical work, nor will you be able to "start small and expand later."

    With your loads you are looking at a large inverter e.g. 4 Radian GS8048's so that's about $16,000 worth of inverters. (That will give you 36kw for 30 minutes, and 32kw continuously.) Outback says 400ah minimum battery per inverter, so that's 1600ah of 48 volt battery as a MINIMUM (and you probably want to go higher with those loads.) The Rolls S2-1895 is 1750ah; you will need 24 of them so that's $30,000. To maintain that much battery you'll need at least 10kw of solar for another $12,000 or so. Charge controllers for that will run you another $2000.

    So far you are at $60,000 for just the hardware, not including racking, wire, protection, switchgear, battery boxes, labor etc. Is that in your ballpark?
    Last edited by jflorey2; 09-23-2016, 06:20 PM.

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    • #3
      That is a bit more than I think can be justified on this project. My initial thought was 48V Forklift batteries for the limited storage capacity, say in the 600 amp hour ballpark range, lets say 3 595 AH 48V forklift batteries, I have not priced these in 3 or 4 years, but last time I bought some for work they were running about $2,500 or so each for good condition 85+% capacity off lease (typically 3 year old) batteries. Call that 1500 AH with the 85% derated lost capacity for about $7,500 For solar I was estimating closer to 15KW worth of panels at an estimated price of around 75 cents per watt. This is all ballpark pricing, but the Radian GS8048's give me something to look at, the estimated installation date would be no sooner than next spring, and may even be a couple of years off.

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      • #4
        Originally posted by Isaac-1 View Post
        That is a bit more than I think can be justified on this project. My initial thought was 48V Forklift batteries for the limited storage capacity, say in the 600 amp hour ballpark range, lets say 3 595 AH 48V forklift batteries, I have not priced these in 3 or 4 years, but last time I bought some for work they were running about $2,500 or so each for good condition 85+% capacity off lease (typically 3 year old) batteries. Call that 1500 AH with the 85% derated lost capacity for about $7,500 For solar I was estimating closer to 15KW worth of panels at an estimated price of around 75 cents per watt. This is all ballpark pricing, but the Radian GS8048's give me something to look at, the estimated installation date would be no sooner than next spring, and may even be a couple of years off.
        If you are serious about this the very first thing to do is reduce your load. If you have any other options for heat (i.e. natural gas, propane, fuel oil) go that route first; it will save you tens of thousands of dollars on your backup system. Replace all lights with LED's. Get rid of resistance heat. Upgrade pumps, large appliances and A/C systems to more energy efficient versions. For every $1 you spend on energy efficiency you'll save $5-$10 on your eventual PV+battery system.

        What you want to get to is a list of essential loads you can't live without. Those get backed up on an essentials panel. They might include the furnace blower motors, outlets and lights, computers and media systems but not remaining resistance heat or A/C. If you can get those loads down to, say, a max of 8kW, then you can live with a system that is 1/4 the size (and cost.)

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        • #5
          In an ideal world that would be nice, and there are some improvements that can be made here, however cost to replace the resistive heat with heat pumps is high due to location of central air units, existing underground refrigerant lines and deck that was built over those lines after the house was built. It is a fairly large house which is well insulated , and has 2 fireplaces, and the use level for the resistive heat is low, however it is needed at or near capacity on rare occasions when we have extremely cold weather by local standards for multiple days. Add to this that even with heat pumps emergency resistive heat would still be needed for those nights when temperatures get down below heat pump operating ranges (temperatures in the upper teens are not uncommon here in the winter some years) There are also limited options of getting power into the house due to that underground fed main panel, 500 MCM is not cheap, plus it also runs under concrete, wood deck, etc. Complicating that is the Central air conditioner outdoor units are fed from a sub-panel at the disconnect /transfer switch location for the main house, and not through the main panel in the house. So regardless of how you cut it heating and cooling will be the major loads. In the summer that major load would be through the subpanel out at the main disconnect point and in the winter it would be the resistive heat through the main house panel indoors.

          I am not sure exactly how these hybrid inverter chargers work yet, reading the manual for the one you mentioned now, if they have an overload connect direct to grid option, then downsizing inverter bank to typical max load might work while having them mounted near the main disconnect (a new small shed would need to be built to house batteries and inverters) mounting at / in the house is not an option as there is no easy way to run additional power lines from the PV module to the house itself, and no good place to place batteries.

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          • #6
            You have received good advice above. Understand that ANY backup system will involve a generator. Starting the generator and
            operating transfer switches can be inconvenient and time consuming. My approach would be to install an AUTOMATIC backup
            generator system, powered by natural gas, diesel, or propane. The time delay of the automatic transfer, and inconvenience,
            would be at a minimum. The cost would be at a minimum too. Battery systems still need a generator, but have extremely limited
            extended operation at extremely high cost, then in minutes you are starting the generator anyway.

            I don't see that solar has much to do with backup. The line or the generator can quickly recharge a battery system for short outages.
            A grid tie solar system could reduce your electric bill, to be based on your KWH annual usage. Bruce Roe

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            • #7
              Originally posted by Isaac-1 View Post
              In an ideal world that would be nice, and there are some improvements that can be made here, however cost to replace the resistive heat with heat pumps is high due to location of central air units, existing underground refrigerant lines and deck that was built over those lines after the house was built.
              We have a calibration issue here, I think. If you completely tore the deck out and replaced it, that would still be a fraction of the costs we are talking about here. Heat pumps will still use refrigeration lines - in fact they will use them more than an equivalent resistive heating system will.

              It would be foolish to spend an extra $45,000 on a renewable power system to avoid spending $10,000 rebuilding a deck, IMO.

              It is a fairly large house which is well insulated , and has 2 fireplaces, and the use level for the resistive heat is low, however it is needed at or near capacity on rare occasions when we have extremely cold weather by local standards for multiple days. Add to this that even with heat pumps emergency resistive heat would still be needed for those nights when temperatures get down below heat pump operating ranges (temperatures in the upper teens are not uncommon here in the winter some years)
              Then use oil, propane or gas (or even pellets) for the very cold days. Those do not require resistive backup heat.

              There are also limited options of getting power into the house due to that underground fed main panel, 500 MCM is not cheap, plus it also runs under concrete, wood deck, etc.
              If you cannot get access to run new lines to your service entrance/main panel, then abandon any hope of adding a renewable energy system.

              Complicating that is the Central air conditioner outdoor units are fed from a sub-panel at the disconnect /transfer switch location for the main house, and not through the main panel in the house. So regardless of how you cut it heating and cooling will be the major loads. In the summer that major load would be through the subpanel out at the main disconnect point and in the winter it would be the resistive heat through the main house panel indoors.

              I am not sure exactly how these hybrid inverter chargers work yet, reading the manual for the one you mentioned now, if they have an overload connect direct to grid option, then downsizing inverter bank to typical max load might work while having them mounted near the main disconnect (a new small shed would need to be built to house batteries and inverters) mounting at / in the house is not an option as there is no easy way to run additional power lines from the PV module to the house itself, and no good place to place batteries.
              OK. Sounds like renewable energy/hybrid inverter systems are not an option for you, then.

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