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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, 12:05 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.

            Steve

            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

                  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.
                  If it is for backup why do you want to cycle them a lot?

                  Your system will will not be certified and will be costly.
                  Your best bet is to look into switching one of your inverters to a StorEdge and going from there.
                  OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                  Comment


                  • #10
                    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


                    • #11
                      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


                      • #12
                        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


                        • #13
                          Originally posted by aceinc View Post
                          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.
                          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.

                          OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                          Comment


                          • #14
                            Originally posted by ButchDeal View Post

                            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


                            • #15
                              Originally posted by aceinc View Post

                              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.
                              With StorEdge you do not need a voltage controller or charge controller, as it is solaredge and uses the optimizers for that.

                              yu also do NOT need an automatic transfer switch as bimodal systems have that integrated. Solaredge and outback have the transfer capabilities integrated into the inverter.

                              As a a side note I find it strange that people would ask questions here then lecture as if they are already informed....
                              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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