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  • #16
    Originally posted by SolarEU View Post
    I found this US Patent: US8536495B2
    From just the abstract on the first page, I do not see anything particularly innovative or patentable, but I guess that may be in the details.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #17
      Patent

      Originally posted by inetdog View Post
      From just the abstract on the first page, I do not see anything
      particularly innovative or patentable, but I guess that may be in the details.
      Lots of things get patented. If they are obvious to someone familiar with the state of the art,
      they can be ignored or overthrown in court. Happens a lot.

      I know how to deal with the power issues. Buck reg, control, no big deal. The issue is
      doing all this safely in a real environment, not covered in the theory. Another issue could
      be ground current leakage if this gets strung out too much. Bruce Roe

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      • #18
        DC heating patents

        Originally posted by inetdog View Post
        From just the abstract on the first page, I do not see anything particularly innovative or patentable, but I guess that may be in the details.
        I just learned that many patents are on-line at Google. This one is here http://www.google.com/patents/US8536495

        I for myself do not see any special innovation.

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        • #19
          Originally posted by SolarEU View Post
          I just learned that many patents are on-line at Google. This one is here http://www.google.com/patents/US8536495

          I for myself do not see any special innovation.
          Many fools are impressed by the number of patents a firm has so firms patent anything they can think of and all possible variations - maybe 1 in 1000 patents are really relevant in the world.
          [SIGPIC][/SIGPIC]

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          • #20
            DC solar heaters to work with 2kWp panels directly

            My question is still left open: Is somebody making the DC solar heaters to work with 2kWp panels directly? I mean just 8 panels of 250Wp directly to the water heater. I cannot find anything like this.

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            • #21
              Originally posted by SolarEU View Post
              My question is still left open: Is somebody making the DC solar heaters to work with 2kWp panels directly? I mean just 8 panels of 250Wp directly to the water heater. I cannot find anything like this.
              Nobody that I know of is making this. Two reasons:

              1. DC to heater versus AC to heater does not make a bit of difference except to the contact rating of the thermostat (which is not a minor problem).
              2. A constant resistance heating element (which is pretty much all you will be able to find except for self-regulating heating tape which will do you no good) cannot be driven efficiently from a solar panel which is a near constant current source whose current varies with the incident light. To get efficiency requires an MPPT controller in the picture.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #22
                Not to mention that on a practical basis (meaning no government involved) solar thermal is far more efficient than PV.
                [SIGPIC][/SIGPIC]

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                • #23
                  DC to heater versus AC to heater

                  Originally posted by inetdog View Post
                  Nobody that I know of is making this...... DC to heater versus AC to heater
                  I was able to Google this: https://www.google.com/search?q=evboiler It seems to have two heating spirals one for AC and one for DC.

                  Any comments?

                  tumblr_mxibbvVTjH1qa2swjo1_500.jpg

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                  • #24
                    Originally posted by SolarEU View Post
                    Any comments?

                    Sure, two comments:

                    1. Using two different heating elements allows both to be used at the same time and removes any safety issue that might arise from trying to switch one element from an AC connection to a DC connection. (The transfer switch provides a point in the wiring where two very different voltage systems come together.
                    2. If the panels are used in parallel mode, you need a much lower resistance heating element for the DC connection than for the AC connection. But it is the voltage rather than the AC versus DC that makes the element different.
                    SunnyBoy 3000 US, 18 BP Solar 175B panels.

                    Comment


                    • #25
                      Originally posted by russ View Post
                      Not to mention that on a practical basis (meaning no government involved) solar thermal is far more efficient than PV.
                      Solar thermal is indeed more efficient in terms of the energy it collects per unit area but there are maintenance problems with solar thermal that discourage me from using it.

                      I think electric water heating by solar PV has much promise - especially for off grid.
                      All it requires is an off-grid inverter with MPPT control which does not need to be connected to batteries.

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                      • #26
                        Originally posted by Bintang View Post
                        Solar thermal is indeed more efficient in terms of the energy it collects per unit area but there are maintenance problems with solar thermal that discourage me from using it.

                        I think electric water heating by solar PV has much promise - especially for off grid.
                        All it requires is an off-grid inverter with MPPT control which does not need to be connected to batteries.
                        A silly and expensive waste of PV panels and roof space. There are few problems with solar water heaters if you buy quality systems and they are properly installed.

                        One has 50% plus efficiency while PV has less than 20%.
                        [SIGPIC][/SIGPIC]

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                        • #27
                          Originally posted by russ View Post
                          A silly and expensive waste of PV panels and roof space. There are few problems with solar water heaters if you buy quality systems and they are properly installed.

                          One has 50% plus efficiency while PV has less than 20%.
                          If available space is not an issue it doesn’t necessarily matter if the energy consumed is collected at 50% efficiency or 20% efficiency. What does matter, imho, is the relative cost for the different systems and their levelized cost of the energy consumed over , say, a 20 year period.

                          What are typical all-in installation costs for properly installed quality solar thermal systems and what are the usual ongoing maintenance costs? I realize these are capacity dependent, so for an example how about something like the following:

                          Tank storage volume: 150 to 200 liters (40 to 50 gal)
                          Average daily hot water consumption: 204 liters (54 gal)
                          Average daily energy consumption required: 8.8 kWh per day (30,000 Btu/day)

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                          • #28
                            Originally posted by Bintang View Post
                            If available space is not an issue it doesn’t necessarily matter if the energy consumed is collected at 50% efficiency or 20% efficiency. What does matter, imho, is the relative cost for the different systems and their levelized cost of the energy consumed over , say, a 20 year period.
                            You can figure that out for yourself.

                            The only time electric water heating has worked out so far is in the event of off grid with a system sized for winter meaning it is oversized most of the year.

                            The difference between 20% efficiency and 50 plus % efficiency is the square meters of panel that you have to buy.
                            [SIGPIC][/SIGPIC]

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                            • #29
                              Originally posted by russ View Post
                              You can figure that out for yourself.

                              The only time electric water heating has worked out so far is in the event of off grid with a system sized for winter meaning it is oversized most of the year.

                              The difference between 20% efficiency and 50 plus % efficiency is the square meters of panel that you have to buy.
                              I live in a tropical location where the seasonal variation of solar irradiation is fairly benign meaning less oversizing.
                              Also it is a location where grid-tie makes no sense because it is not yet allowed by Government or the utilities. But PV-grid hybrid systems have potential in some circumstances and that might include solar electric hot water with some grid boosting.

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                              • #30
                                Originally posted by russ View Post
                                You can figure that out for yourself.
                                Ok … thought you might be willing to offer some help to a newbie but never mind ….so I have tried to figure it out myself. I found a comparison at the following link though how reliable it is I have no idea:
                                http://sagebrushsolar.com/solar-ther...lectricity-pv/

                                I cannot see a date anywhere in the article so the costs maybe out-of-date. The article concludes that solar thermal gives bigger bang for the buck but the conclusion is heavily dependent on the assumption of incentives – both federal and state incentives:

                                “The installed cost of a typical solar thermal system with one evacuated tube collector and an 80-gallon tank is typically around $8,000. After federal and state incentives, the net investment comes in around $4,300. By comparison, the installed cost of a typical 3.6 kW PV system (eighteen 200W collectors) is around $10,000 ($4.5 per watt installed). After incentives, this system costs about $5,400.”

                                In my country there are no such incentives and likely never will be. So the cost to me for the solar thermal system would be the full $8,000 and probably more due to import taxes.
                                However, I do have a reliable knowledge of local costs for PV systems and I could install the PV system described for around $5,500 (without any government subsidies). So in my world it looks like PV would give a bigger bang for the buck.

                                And all of this analysis conveniently excludes any mention of maintenance costs. I'm sure solar thermal has them but as I have no experience with such systems I have no idea what they might be.

                                Each to their own, I suppose.

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