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  • Question for offgrid system

    Hi, this is the first time i work on a design for offgrid system (and first time to post on solarpaneltalk as well ). So the system i m working on has loads of 50bulbs of 9watts each to be working night only (around 10 hours) as well as 3 motors of .5HP each (how can i have a smart guess of the operating time of the motors?).

    i m thinking to set it as an offgrid system, but not sure can i set it up to be a DC system (with no inverter) only panels, charge controller and batteries. we are still to buy the motors and bulbs so can ensure them to be DC.

    Thanks

  • #2
    A DC system is easy. but no point if you have Grid power avail. OFF GRID requires lifestyle changes. 50 light bulbs @ 9watts each for 10hrs at night would require 450 watts and that's before you add the demand of the motors. you are looking at a $11,000 battery bank. When you are off grid "Less is More"
    4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrf

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    • #3
      Once you find out what it cost, the required maintenance,, and battery replacement cost every 5 years, you will forget all about solar.

      Just to do the 50 Light Bulbs x 9 watts x 10 hour is 4500 watt hours.

      Panel Wattage = 2500 watts or around $4000
      50 Amp MPPT Charge Controller around $400
      48 volt 500 AH battery around 1350 pounds, $5000 every 5 years.

      Now you want to run 3 x 440 watt motors for how many hours on top of that?
      MSEE, PE

      Comment


      • #4
        Originally posted by Engy View Post
        Hi, this is the first time i work on a design for offgrid system (and first time to post on solarpaneltalk as well ). So the system i m working on has loads of 50bulbs of 9watts each to be working night only (around 10 hours) as well as 3 motors of .5HP each (how can i have a smart guess of the operating time of the motors?).

        i m thinking to set it as an offgrid system, but not sure can i set it up to be a DC system (with no inverter) only panels, charge controller and batteries. we are still to buy the motors and bulbs so can ensure them to be DC.

        Thanks
        That's about 1500 watts of motors and 450 watts of lights; total about 2000 watts. Best approach is to get a 48 volt battery system, get 48 volt lights and motors (could go to 12 volts on the lights if you want) and get a 48 volt 50 amp AC charger, then wire it into your panel. Voila! You have a system. (And since it will really be powered via AC, and you'll just float the battery, the battery will last a fairly long time and will be cycled only during power outages.) Or if you don't need the battery, go straight from a DC supply to the lights etc.

        If you want to add solar later, just add a charge controller and panels. As long as you have those motor loads throughout the day, the solar will offset some of their draw.

        Or (easiest way) get 120 volt AC lights and motors. Later add a grid-tied solar system. Same outcome but a lot cheaper.

        Comment


        • #5
          The motors are deal breakers, no way will an affordable solar power system be able to run several half hp motors.
          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

          solar: http://tinyurl.com/LMR-Solar
          gen: http://tinyurl.com/LMR-Lister

          Comment


          • #6
            Thank you all, so now my customer is convinced to get the motors out of the deal, and to get connected to the grid, and have small solar system with battery backup for the lighting. So here is what i have in mind

            - 4 260Wp aleo panels
            - Bluesol charge controller - 150/70
            - Multiplus C24/1200/25
            - 2 victron Deep Cycle AGM Battery - 12V 220Ah each


            does that sound reasonable? anything i can do to get it optimized even further?

            Thank

            Comment


            • #7
              Why take anything off the grid or use solar? Anything you take off grid is going to cost more. Your customer can have what he wants but no solar is needed. All that is required is a Battery Rectifier sized to supply the load and recharge the batteries. As long as the grid is up, the rectifier is supplying the power to the loads. If power fails then the batteries supply power until commercial power comes back on.It wil cost less than solar and more reliable.

              MSEE, PE

              Comment


              • #8
                Originally posted by Engy View Post
                Thank you all, so now my customer is convinced to get the motors out of the deal, and to get connected to the grid, and have small solar system with battery backup for the lighting. So here is what i have in mind

                - 4 260Wp aleo panels
                - Bluesol charge controller - 150/70
                - Multiplus C24/1200/25
                - 2 victron Deep Cycle AGM Battery - 12V 220Ah each
                You have 450 watts of load and a 1200 watt inverter; probably overkill. Exceltech makes good 600 watt inverters - might look at them. Also look at 12V DC lighting. At 450 watts of light, it's fairly practical to run 12V.

                At 600 watts you don't really need 24 volts. 12 volt systems will cut down on costs and improve availability for low power DC equipment.

                You will need a charger. Iota makes reasonably good chargers. Drop the solar panels and get an AC charger like the Iota DLS-45. Then if he wants to add solar later, he can.

                Comment


                • #9
                  Originally posted by jflorey2 View Post
                  You have 450 watts of load and a 1200 watt inverter; probably overkill. Exceltech makes good 600 watt inverters - might look at them. Also look at 12V DC lighting. At 450 watts of light, it's fairly practical to run 12V.

                  At 600 watts you don't really need 24 volts. 12 volt systems will cut down on costs and improve availability for low power DC equipment.

                  You will need a charger. Iota makes reasonably good chargers. Drop the solar panels and get an AC charger like the Iota DLS-45. Then if he wants to add solar later, he can.
                  Ditto on the Exceltech Inverters. Not so sure I would use anything less than 48 volts using them though. Whateever charger is used make dang sure it is rated for continuous duty and has EQ.

                  MSEE, PE

                  Comment


                  • #10
                    Originally posted by jflorey2 View Post
                    You have 450 watts of load and a 1200 watt inverter; probably overkill. Exceltech makes good 600 watt inverters - might look at them. Also look at 12V DC lighting. At 450 watts of light, it's fairly practical to run 12V.

                    At 600 watts you don't really need 24 volts. 12 volt systems will cut down on costs and improve availability for low power DC equipment.

                    You will need a charger. Iota makes reasonably good chargers. Drop the solar panels and get an AC charger like the Iota DLS-45. Then if he wants to add solar later, he can.

                    Sorry for late response, was out of country. So i m not sure i understand that. If i use the LOTA charger or something similar, i will be charging batteries from AC source and get my loads working from batteries all the time? or would the charger power my loads and charge the batteries?

                    Then if we need solar panels later i will just add them with the charge controller as another input to the batteries? is that it?

                    Comment


                    • #11
                      Originally posted by Sunking View Post
                      Why take anything off the grid or use solar? Anything you take off grid is going to cost more. Your customer can have what he wants but no solar is needed. All that is required is a Battery Rectifier sized to supply the load and recharge the batteries. As long as the grid is up, the rectifier is supplying the power to the loads. If power fails then the batteries supply power until commercial power comes back on.It wil cost less than solar and more reliable.
                      Yup i agree to that, but because grid goes off pretty often over here, and for safety purposes my customer wants to avoid the risk of getting the fence lights off by all means.

                      Comment


                      • #12
                        Originally posted by Engy View Post
                        Yup i agree to that, but because grid goes off pretty often over here, and for safety purposes my customer wants to avoid the risk of getting the fence lights off by all means.
                        Bimodal would be the most reliable possible, not off grid.
                        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                        Comment


                        • #13
                          Originally posted by Engy View Post
                          Sorry for late response, was out of country. So i m not sure i understand that. If i use the LOTA charger or something similar, i will be charging batteries from AC source and get my loads working from batteries all the time? or would the charger power my loads and charge the batteries?
                          Well, all your energy comes from the charger, but depending on sizing some power might occasionally come from the batteries. If your charger is greater than your loads, then all the power comes from the charger. If your charger is smaller, then the batteries supply some of the load, and are recharged when you turn off the loads.
                          Then if we need solar panels later i will just add them with the charge controller as another input to the batteries? is that it?
                          Yep.

                          Comment


                          • #14
                            Originally posted by Sunking View Post
                            Why take anything off the grid or use solar? Anything you take off grid is going to cost more. Your customer can have what he wants but no solar is needed. All that is required is a Battery Rectifier sized to supply the load and recharge the batteries. As long as the grid is up, the rectifier is supplying the power to the loads. If power fails then the batteries supply power until commercial power comes back on.It wil cost less than solar and more reliable.

                            Though I am fairly new to solar, and have a grid-interactive, battery backup system, I routinely tell people - "if you're interested in doing any of this to save money, look somewhere else". I think an absolute first step everyone should take before ever considering otherwise is a generator. It is not financially beneficial to setup a system like this as far as I can see - not with access to grid power.

                            So why do it? For me, there are a few reasons - but in a nutshell these systems are just a very expensive and intricate diesel fuel extender. My power goes out ~5-10 times a year. I'm self-employed so that causes me financial loss - sure. There are some benefits there -sure, but it might not be enough for some to justify a system like that.

                            I could run on generator power for that time, and did that before going the route I have gone (which I do not regret doing). However, batteries and an inverter allow me a few advantages...
                            1. ​Battery and inverters immediately begin inverting in a grid failure providing darn-close to whole-house battery backup. I am not aware of a generator that can power on and take a load in < 1 second. For my work needs - this is essential.
                            2. PV Can assist with charging said batteries, and also allow for some reduction of the power bill - though nowhere near enough to make financial sense. I see that as more of a consolation prize vs a benefit
                            3. Combined with a generator, in a long-term power outage (fill in your own crazy conspiracy or natural disaster reasons), they allow the generator to run for a shorter period of time to recharge the batteries. 4 hours of diesel to recharge batteries is less than 24h of diesel to run critical structure. Further, diesel generators aren't really keen on running at very light loads which would be the case much of the time. When charging batteries at 60 amps (or the generator's max), the generator is loaded quite nicely and powers off when finished. So... this can allow someone to store less fuel, or get more out of their stored fuel.
                            4. Though I have a grid-powered home, in this way and in others, my home is "Off-Grid Capable". I enjoy the peace of mind that comes with that. In fairness, I am fully aware that a generator can do likewise. I just happen to be a "belt and suspenders" type of guy.
                            These aren't my reasons for using solar, but some of the reasons for having batteries. Is all of this foolish? Yeah - maybe it is to some it is. Financially, batteries may not be a good bargain with battery costs as they are (1575 AH of storage). For me all the reasons combine to make it worthwhile for me.

                            Personally, I enjoy the tinkering, the engineering, and the hobby aspects of such things - and quite honestly - the redundancy of having a grid, pv, battery, generator system.

                            In summary - unless there is no grid-power available, and some reason to not want to use a generator, you'd have to have "other" reasons for going such a route. They may be legitimate reasons - but save money over traditional grid power one will not.
                            Last edited by gmanInPA; 03-14-2016, 11:56 AM. Reason: clarity

                            Comment


                            • #15
                              As long as you understand the disadvantages of batteries (they are not the magic cure for everything) and are willing to pay the price, we're happy for you.
                              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister

                              Comment

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