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  • #31
    Originally posted by BritishPete View Post
    I can't give you advice for the present sales but below is a link to information new to the market today and pretty amazing I think;


    http://cleantechnica.com/2012/03/14/ultra-thin-solar-cell-company-unstealths-aims-to-cut-cost-of-solar-cells-in-half-images/?utm_source=feedburner&utm_medium=feed&utm_campaig n=Feed%3A+IM-cleantechnica+(CleanTechnica)

    Hope the link works it's long !
    It is another Vaporware just like NanoSolar.
    MSEE, PE

    Comment


    • #32
      Zachary Shahan is one of the ultra green bloggers that would make doggy stuff sensational if he thought it would get hits. If he is right once in a while it is purely by accident.

      Cleantechnica has a number of that type - Susan Kraemer writes about wind and knows nothing about it at all. Others are just as bad!

      I believe they write blogs for pay or favors as well - at least I have seen posts that I am positive the writer knew better from previous discussions.

      I used to read that site until I realized they were just pimping for profit and to make themselves feel good.

      That bunch was pushing One Block Off The Grid - again for profit - Seems like OBOG bought the site a couple of years back.

      [SIGPIC][/SIGPIC]

      Comment


      • #33
        Originally posted by russ View Post
        I believe they write blogs for pay
        That is highly probable. I have had several offers from manufactures and vendors offer me to write articles on their their blogs for pay. The incentive is X dollars for X amount of words. Offers range from $4/$7.50/1K words.
        MSEE, PE

        Comment


        • #34
          When is power deemed direct from Solar Panel ??

          I've a question regarding power coming directly from Solar Panel to run the house ..

          If I've connection such as : PV to CC to Battery to Inverter and use a Changeover switch.

          And, I've a full output from the panel at the peak and a full load being pulled from within the house,
          will this be deemed as direct from PV or will some charge be spent in charging the battery?

          I ask this especially because the connection is made through the battery bank and I really don't
          know how the internals work .. will the charges always settle in the battery bank no matter
          whether is an online pull or not? Or, if the charges will just use the battery terminals
          as a conduit to the inverter.

          I hope my question made sense, I am not sure how to rephrase it.

          If there is a grid, for the changeover automation purpose I am considering buying a switch and I need to set
          one source as primary and other as secondary. If I choose the Solar as primary, this option will
          imply anything to the upstream of inverter (inclusive of battery bank) right?? Or would there
          be three 1) PV 2) Battery 3) Grid

          Comment


          • #35
            Originally posted by solarponders View Post
            If I've connection such as : PV to CC to Battery to Inverter and use a Changeover switch. And, I've a full output from the panel at the peak and a full load being pulled from within the house, will this be deemed as direct from PV or will some charge be spent in charging the battery?
            It will not be "direct from PV." It will still be going through the charge controller and inverter.

            If the inverter draws more current than the PV panel is supplying, then the extra current will come out of the battery. If the inverter draws less current than the PV panel is supplying, the extra current will go into the battery. If they are exactly the same, the battery will "float" at whatever voltage it happens to be at* and neither take nor add current.

            (* - "float" in this context is not the same as float phase of the charge controller; that's a specific part of a charging profile. Also, all batteries self-discharge slightly so you'd actually have to add a tiny amount of current to keep the battery at the same state of charge.)

            If there is a grid, for the changeover automation purpose I am considering buying a switch and I need to set
            one source as primary and other as secondary. If I choose the Solar as primary, this option will
            imply anything to the upstream of inverter (inclusive of battery bank) right?? Or would there
            be three 1) PV 2) Battery 3) Grid
            You likely do not want to do this. If you have a grid connection then by far the cheapest/most efficient/most powerful option is solar to grid tie inverter. No switching or primary or secondary. It just feeds back as much power as it can when the sun is out.

            Comment


            • #36
              Originally posted by billvon View Post
              It will not be "direct from PV." It will still be going through the charge controller and inverter.

              If the inverter draws more current than the PV panel is supplying, then the extra current will come out of the battery. If the inverter draws less current than the PV panel is supplying, the extra current will go into the battery. If they are exactly the same, the battery will "float" at whatever voltage it happens to be at* and neither take nor add current.

              (* - "float" in this context is not the same as float phase of the charge controller; that's a specific part of a charging profile. Also, all batteries self-discharge slightly so you'd actually have to add a tiny amount of current to keep the battery at the same state of charge.)
              Thanks for the clarification.

              Originally posted by billvon View Post

              You likely do not want to do this. If you have a grid connection then by far the cheapest/most efficient/most powerful option is solar to grid tie inverter. No switching or primary or secondary. It just feeds back as much power as it can when the sun is out.
              Note that, in my part of the globe (India) the power cuts are rampant .. And, also the feed from inverter to the grid (and hence get the payback/deduction in the power bill) is not an option, such meters are not sold. Not sure why it is not, but just may be the technology is not here..if it is a big one to get a meter that reverses. So I do not have the luxury of not providing a switch when trying to make a seamless integration of PV solar, battery and grid. I do not want to manually trigger the switch when power outage happens because the power cut is so random that you'd make many such trips to the power/solar room/enclosure.

              Comment


              • #37
                I have a xantrex XW-6048 inverter/charger, that runs off 48V. You can use use it (or several of them) as an automatic backup, they have an internal transfer relay, when the grid fails, you don't even see a blink as it switches to INVERT. It's internal 100A charger can recharge the batteries when the grid returns. I'd only put critical loads on the inverter, till you learn how long it will last on battery, till power comes back. Minimum battery bank would be 600AH @ 48V, and should likely be twice that size, I think 1,000ah would be a reasonable place to start. 4 car batteries will not work well.

                You can add solar PV and charge controller to keep things running longer in the daytime.
                spreadsheet based voltage drop calculator:
                http://www.solar-guppy.com/download/...calculator.zip
                http://www.solarpaneltalk.com/showth...oss-calculator

                http://www.mike-burgess.org/PVinfo_2.html

                solar: http://tinyurl.com/LMR-Solar
                gen: http://tinyurl.com/LMR-Lister ,
                battery lugs http://tinyurl.com/LMR-BigLug
                Setting up batteries http://tinyurl.com/LMR-NiFe

                gear :
                Powerfab top of pole PV mount | 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

                Comment


                • #38
                  configuration

                  http://www.morningstarcorp.com/en/st...38&TmaxUnits=0



                  hi all, here is my pv model of choice and tristar 60a mppt ... the morning star calculator shows
                  that there is "marginal performance" if I connect 2 in series and 2 in parallel, the Min Vmp < Battery Vmax .. Unfortunately,
                  I do need 48 volt battery system because my inverter size demands that. And, I do not want
                  to buy any additional panels now because this is an experimentation phase that I am going through ..

                  Now, how bad does this "marginal performance" sound ... I know this happens only if 2 conditions are met :

                  1) when its very hot outside (close to the average max)
                  2) batteries are fully charged

                  does marginal performance mean, ithat its not peak or its far worse? Because, I will soon upgrade (in 8-9) months to have more panels to mitigate the condition, specifically my question is :

                  avg battery voltage ~ 48 v
                  max battery voltage ~ 62 v

                  if my array Vmp @ hottest temperature = 50v

                  which means there is a drop in the power,

                  instead of : 62v (battery voltage) x 16 Imp = 992 w
                  it wuld be : 50v (array voltage) x 16 Imp = 800 w

                  am I right on the ballpark ignoring all efficiency loss etc?

                  Comment


                  • #39
                    Solarponders the problem you are going to have is PWM and even MPPT controllers cannot up convert voltages. It takes a minimum of about a 55 to 58 volt source to charge a 48 volt battery. So if you have a 50 volt source, it is not going to work. Minimum required panel voltage on a 48 volt system is 64 volts.
                    MSEE, PE

                    Comment


                    • #40
                      Originally posted by Sunking View Post
                      Solarponders the problem you are going to have is PWM and even MPPT controllers cannot up convert voltages. It takes a minimum of about a 55 to 58 volt source to charge a 48 volt battery. So if you have a 50 volt source, it is not going to work. Minimum required panel voltage on a 48 volt system is 64 volts.

                      Ok, I understand.

                      But on the flip side : if I connect 4 PVs in series - the Voc @ Min. recorded low temperature exceeds 150v thats the maximum pemissible for the Tristar 60 amp.

                      Is there any solution without expanding or shrinking my panel output?

                      Comment


                      • #41
                        The only work around on that I can think of would be to put a thermostat in the DC line that would remove one module when the temperature nears the minimum recorded low temperature or a switch disconnect to take the pv off line on the odd occasion that happens.
                        Rich
                        WWW.solarsaves.net

                        NABCEP certified Technical Sales Professional

                        http://www.solarpaneltalk.com/showth...Battery-Design

                        http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

                        www.gaisma.com

                        Comment


                        • #42
                          Originally posted by solarponders View Post
                          Is there any solution without expanding or shrinking my panel output?
                          Change charge controllers. The Apollo Solar T80HV and Midnight Classic 200 will both go to 200 volts.

                          Another option is to leave them in parallel and live with 50V. This will NOT charge your batteries but will keep them from discharging and will supply most of the load. You will still have to charge the pack periodically from the grid (lead acid batteries need periodic full charges.) And of course on hot days you'll lose much of your solar power.

                          Comment


                          • #43
                            ok, thanks all for the inputs ...

                            also, when worrying about the record low temperaturs when the Max Voc is exceeded ... should I also take into account that it is
                            usually cold only in the wee hours of the morning when sun is not up?

                            because I live in tropical climate - it gets very hot but not cold at all. min. recorded is 13deg Celsius and that too not when its
                            bright sunlight.

                            can almost vouch that the lowest temperature at anytime sun is bright is > 22deg c

                            so am I worrying about a worst case that would never happen? and therefore connect them all in series without worrying about
                            the Voc exceeding as the likelihood is very very less.

                            Comment


                            • #44
                              Originally posted by solarponders View Post
                              so am I worrying about a worst case that would never happen? and therefore connect them all in series without worrying about
                              the Voc exceeding as the likelihood is very very less.
                              It likely never will - but it might. Decide what level of risk you want to live with. If that level is "low" then I wouldn't try to make assumptions about temperature without very good data (like actual recorded temperatures during daylight hours taken over years.)

                              If you are OK with higher risks you might just go with the series panel arrangement. If you are comfortable with electronic design you could add a clamp, which is a simple circuit that limits voltage by shunting current through a resistance. The simplest sort of clamp is a zener diode; for your power levels you would need a much larger clamp. Example: http://sound.westhost.com/appnotes/an007.htm

                              Comment


                              • #45
                                What you have to beware of, is a cold morning, when the panels will be at their coldest, and the sun comes up. The panels, without a load, quickly jump to their max voltage, and a few minutes, later when the charge controller wakes up, the load of the charge controller brings the voltage down. But if is cold enough, and you don't have enough safety margin, you fry your controller as it begins to wake up.

                                You can go to the charge controller's mfg page, and check the panel voltage there.

                                What is the mfg/ model of your panels ?

                                If your 2 panels in series are insufficient for charging, I'm not sure why 4 would be too much. The tristar MPPT has a max of 150V input
                                http://www.morningstarcorp.com/en/tristar%20mppt

                                string calculator:
                                http://www.morningstarcorp.com/en/strings/calc.php
                                Last edited by Mike90250; 04-01-2012, 05:54 PM.
                                spreadsheet based voltage drop calculator:
                                http://www.solar-guppy.com/download/...calculator.zip
                                http://www.solarpaneltalk.com/showth...oss-calculator

                                http://www.mike-burgess.org/PVinfo_2.html

                                solar: http://tinyurl.com/LMR-Solar
                                gen: http://tinyurl.com/LMR-Lister ,
                                battery lugs http://tinyurl.com/LMR-BigLug
                                Setting up batteries http://tinyurl.com/LMR-NiFe

                                gear :
                                Powerfab top of pole PV mount | 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

                                Comment

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