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  • Hybrid system components, a step wise approach

    I currently have a 10 KW system. There are 2 Solar Edge HD Wave 5KW inverters and 44 285 watt panels in the system. I would like to take a stepwise approach to converting it to a hybrid system.

    Steps

    1) Design the final goal ~30-50 KWH batteries usable, 10 KW constant power consumption, 20 KW peak consumption, Automatic switch over and switch back.

    2) Assemble electronics and minimal batteries, a few KWH.

    3) Install minimal configuration.

    4) Add batteries as I can afford them, when I see good deals, etc. (a mix of batteries may be possible).

    Since batteries seem to be the biggest cost I would stretch the acquisition of those over time as prices seem to be coming down.

    I need help with step 1. I am unclear where I can get help on designing the core switching and solar array throttling components needed.
    Last edited by aceinc; 06-08-2018, 01:05 PM.

  • #2
    Hi aceinc,

    This is similar to some of the issues I have been researching. What I am guessing you want to lookup is an AC coupled system. This link, if allowed, explains some of the background with micro inverters (https://www.solarquotes.com.au/blog/...up-compatible/)

    To manage the switch to a hybrid you will need a new battery based inverter which you will tie your various AC sources into and join to the battery bank.

    I was also planning on building a battery bank up over time. The issue here though is that depending on the type of battery you choose and how they age over time makes it physically impossible. My basic understanding is that the worst battery in the bank will then limit your system (way over simplified I am sure others can explain better) but it makes more sense to save your money until you can buy a bank big enough to support your defined load/requirements. If you don't want to wait go ahead and undersize it as you will probably be replacing the whole bank in a few years anyway and can buy more the next time.

    Comment


    • #3
      Sure hope you like loosing a lot of money. Something like loosing $5000 every few years.
      MSEE, PE

      Comment


      • #4
        Originally posted by Sunking View Post
        Sure hope you like loosing a lot of money. Something like loosing $5000 every few years.
        I like loosing my inner demons, but do not like losing money.

        BTW, What value does this comment add to the conversation? If you provide constructive comments, I will ignore the misuse of words, but if the comment adds no value and it misuses words, I cannot help my self. I know what batteries cost, I know the difference between Lead Acid,Gel, AGM, Lithium Ion, LiFePo4, Lithium Titanate batteries and which to use, their relative costs and energy densities, do you?

        Comment


        • #5
          Originally posted by BillSunGen View Post
          Hi aceinc,

          This is similar to some of the issues I have been researching. What I am guessing you want to lookup is an AC coupled system. This link, if allowed, explains some of the background with micro inverters (https://www.solarquotes.com.au/blog/...up-compatible/)

          To manage the switch to a hybrid you will need a new battery based inverter which you will tie your various AC sources into and join to the battery bank.

          I was also planning on building a battery bank up over time. The issue here though is that depending on the type of battery you choose and how they age over time makes it physically impossible. My basic understanding is that the worst battery in the bank will then limit your system (way over simplified I am sure others can explain better) but it makes more sense to save your money until you can buy a bank big enough to support your defined load/requirements. If you don't want to wait go ahead and undersize it as you will probably be replacing the whole bank in a few years anyway and can buy more the next time.
          My reason for buying batteries over time is to be able to afford better batteries. By better batteries, I am referring to LiFePo4 or Lithium Titanate, which both can be cycled very deep thousands of times. Since this is primarily a "backup" system so they will not be cycled deep that often, and should out live the solar panels.

          Comment


          • #6
            Originally posted by aceinc View Post

            I like loosing my inner demons, but do not like losing money.

            BTW, What value does this comment add to the conversation?
            It's a warning that you're about to begin spending a lot more for power than you might have expected, and if you've OK with that, to others who might be thinking of doing the same thing.

            Comment


            • #7
              Originally posted by aceinc View Post
              I currently have a 10 KW system. There are 2 Solar Edge HD Wave 5KW inverters and 44 285 watt panels in the system. I would like to take a stepwise approach to converting it to a hybrid system.
              You will likely be unhappy going that direction, for several reasons:

              1) Batteries are expensive, whether you use them regularly or not. About the only time they make financial sense is if you have something absolutely critical that can't lose power, ever, like a server farm, some scientific/industrial process or runway lights. If you are just looking for some backup power, get a $99 UPS and a generator.

              2) You can't do it incrementally because of the inverters. Most inverters have a (fairly large) minimum battery size, below which they will have problems. For example, with a Radian inverter, you cannot go below 400 amp hours.

              3) You can't do it incrementally because you can't mix old and new lead acid batteries. So you'd have to throw out the old pack and buy all new every time you upgrade.

              Comment


              • #8
                As far as I am aware there is no battery technology that is mix and match for a single bank. You can get away with it if they are close (and close for LiFePo4 seems to be a few years) but just starting to read about the charging requirements of LiFePo4 batteries was enough for me. (There are already some good discussions on here that I wasn't aware of so thanks for the idea.) Are you thinking something like a Tesla powerwall where the inverter is built into each bank individually?

                Comment


                • #9
                  Originally posted by aceinc View Post
                  BTW, What value does this comment add to the conversation? If you provide constructive comments, I will ignore the misuse of words, but if the comment adds no value and it misuses words, I cannot help my self. I know what batteries cost, I know the difference between Lead Acid,Gel, AGM, Lithium Ion, LiFePo4, Lithium Titanate batteries and which to use, their relative costs and energy densities, do you?
                  Sorry but I am not going to help you loose you a$$. Fools and their money will soon be parted.
                  MSEE, PE

                  Comment


                  • #10
                    OK, so far the consensus seems to be that I am a fool, and want loose my a$$.

                    Now that we've gotten that out of the way, is there anyone on this forum, that is interested in providing technical help?

                    Comment


                    • #11
                      Originally posted by jflorey2 View Post

                      You will likely be unhappy going that direction, for several reasons:

                      1) Batteries are expensive, whether you use them regularly or not. About the only time they make financial sense is if you have something absolutely critical that can't lose power, ever, like a server farm, some scientific/industrial process or runway lights. If you are just looking for some backup power, get a $99 UPS and a generator.

                      2) You can't do it incrementally because of the inverters. Most inverters have a (fairly large) minimum battery size, below which they will have problems. For example, with a Radian inverter, you cannot go below 400 amp hours.

                      3) You can't do it incrementally because you can't mix old and new lead acid batteries. So you'd have to throw out the old pack and buy all new every time you upgrade.
                      1) I am in IT. I know the traditional use for batteries vis-a-vis computers & servers.

                      2) Radian Inverters seem to be focused on Lead Acid battery technology. I would imagine LiFePo4 or LTO with appropriate BMS modules coupled with an appropriate inverter/charger wouldn't have these problems.

                      3) I have no desire to use Lead batteries.

                      Comment


                      • #12
                        Originally posted by ButchDeal

                        Radian or any outback will work with just about any battery in the voltage range which includes the LG RESU10 ( 48 v version), lifepo etc. etc. etc.
                        you would be AC coupled or tossing your existing grid tie though.

                        StorEdge would be a more direct route with RESU10h ( high voltage version)

                        whats your issue with lead acid? If it is just for backup that is the best bet.
                        My issue with lead acid batteries is the number of cycles before maintenance/replacement. AGM require little maintenance, but they still have a short life/cycle expectancy. I am bad at doing maintenance, or periodic service, I know this about myself, and have come to accept it. I would rather spend a few more $ and not have to replace batteries every 3-5 years. LiFePo4/LTO have the promise of 10-30 years of use without replacement.

                        Irrespective of whether I use StorEdge, or something else I will need a voltage controller, and some sort of automatic switching. I will not be giving up the grid connect portion of the system, so automatic disconnect from the grid needs to be part of the design.

                        Comment


                        • #13
                          According to SolarEdge, whom I spoke with about this, they indicated that when integrating a Storedge with my existing HD Wave inverters, I would need a device which I may have mis identified as a voltage controller (I believe the device is called WattNode Modbus).

                          While I am looking for assistance in accomplishing my goals, I have already educated myself to some degree regarding battery technology.

                          I can't say that I was lecturing anyone, I certainly did not intend that, but the limitations of lead acid batteries are well known, and over my career, I have seen how short their life expectancy is, in the real world (I have been in IT for decades). Were they practical, I would be looking at large capacitor banks, but the technology is not there yet. If everything were equal I would use LTO batteries.

                          I also get quite frustrated when I am looking for help in a specific DIY project, and most of the posts are nay-sayers telling me that what I want to do is too expensive. I am aware of the costs (or will be). I do know that a generator may be a more practical $olution, I know that lead acid batteries have a lower initial capital cost per kilowatt hour (even per usable KWH) and have been around since Eve bit the apple. But based on my research the Total Cost of Ownership (TCO) of Lead Acid Batteries is higher than some other technologies.

                          If there is a technical reason I can't put together a system similar to what I want then that would be important to hear. If however you are concerned about my sending money down the crapper, let me worry about that. It's my money after all. If I want someone to tell me how not spend money, I can talk to my wife.

                          Comment


                          • #14
                            Back to what I think I need;

                            1) A device to charge the batteries, probably from AC.
                            2) A device to recognize when the power from the grid is down.
                            3) A device to disconnect my mains, making my home a micro-grid or an island.
                            4) A pure sine wave inverter with constant power of about 10 KW, burst power to 20 KW.
                            5) A device to tell the existing HD-Wave inverters how much power I need at that moment (effectively throttling the inverters). Or something between the inverters and the rest of the microgrid to throttle the power, so the solar panels don't try to dump more power than what is needed to charge the batteries and run everything else.

                            This is what I think I need, however I am somewhat sketchy on this, and am looking for help in both the design as well as the bits & pieces necessary.

                            Comment


                            • #15
                              Originally posted by aceinc View Post
                              OK, so far the consensus seems to be that I am a fool, and want loose my a$$.
                              Now that we've gotten that out of the way, is there anyone on this forum, that is interested in providing technical help?
                              Not me, because you are wanting to do something that is environmentally and economically unwise.
                              LiFePo4/LTO have the promise of 10-30 years of use. without replacement.
                              and there is the rub. 10-30 years. is it 10 ? or is it 30 ? Big discrepancy between the 2 numbers. The accelerated age testing might indicate that, but none have made it that far in real life,
                              and I don't expect them to attain that goal for some time. But do your research and place your bet. Cold Fusion was also supposed to be a done deal by now...

                              But - listen to you sales droids, I'm sure they are sincere. Or listen to folks living and breathing this stuff for years. your choice.



                              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

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