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  • #61
    Originally posted by littleharbor View Post
    "Why run an ac/dc appliance with an inverter while you can run these with dc power only with less amps on 12v?"

    How many times and how many ways does it have to get explained to you till you get it?
    My one and only comment here. Stop wasting our time.
    This was entertaining reading, for a while. Now, it's just gotten frustrating.
    For tv's i think its sure dc= more efficient. Also for small offgrid houses i think using an inverter is inefficient when you can run appliances on dc power.

    Quote:We find that LED-LCD TV energy consumption can be reduced by about 50% by deploying commercially available, cost-effective efficiency technologies, including DC-only systems. This efficiency improvement reduces total SHS cost by about 25% because it allows use of 50% smaller PV and battery capacities compared to a base case.

    https://www.sciencedirect.com/scienc...52728516300057

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    • #62
      Originally posted by fivewin View Post
      Is the above just marketing bs or facts? Or do some posters here have to learn more?
      Just YOU.
      OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

      Comment


      • #63
        Originally posted by fivewin View Post

        For tv's i think its sure dc= more efficient. Also for small offgrid houses i think using an inverter is inefficient when you can run appliances on dc power.
        The operative phrase is that you think this. No one else does.

        Yes a TV can be made more efficient by using DC by removing the slightly inefficient AC-to-DC conversion inside of the TV, the TV gets more efficient.
        You have However moved that responsibility to provide decent DC power outside of the TV. LED TVs and computers use 5V and 12V DC, So you need to provide decent 12V DC to this TV.

        DC distributions systems are more costly, switches rated for DC distribution cost more, wires are heavier (yes I know you have read some fantasy BS about wireless transmission of power but what you seem to fail to grasp is that wireless transmission of power is not NOT NOT! DC power). And even with the larger wires you are going to have some voltage drop and thus lose in on the way there. Now look on the market for low voltage, DC powered efficient LED TVs, yep thats right there are very few of them, they cost more. There are more LED TVs that are AC powered and more efficient versions.

        Also adding quotes to something without reference to the person (and thus their credibility ) is not helping your point.
        OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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        • #64
          Ofcourse its unfortunately the case that residential appliances that can run on dc low voltage is still not in mass production. I did remark though in one of my previous post that most likely companies will develop and produce more and more efficient appliances that can run on dc low voltage power. So, im wondering -awaiting further development of wireless transmission- if its efficient to have different powersources (batteries) in one house to minimise cable loss without using inverter and how i can efficiently charge different batteries.

          If i walk in my area where i live now i see many houses of only 32m2 with grid connection and they even not have a fridge, only tv & some lamps + 1 fan. So, i thought is it not more efficient if they go offgrid dc only. Pls do not compare with the living standard in your country.

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          • #65
            Originally posted by fivewin View Post
            Quote:
            Brushless DC motors, on the other hand, will outperform AC motors in almost every regard.

            * 1 horsepower AC = 750W. A 500W multi-pole 3 phase DC motor will do a similar job (around one third less power is required)
            * 2-3 times the motor life
            * 70% quieter

            Is the above just marketing bs or facts? Or do some posters here have to learn more?
            A lot more to learn starting with you and you are not capable of learning. For example most people know 750 watts is not equal to 500 watts. A 1 Hp motor is not equal to a 2/3 Hp motor. Allow me to show you how Ignorant and Gullible you are. Go look up 3-Phase Power genius.

            Perhaps a picture of 3-phase power. Wake up, a BLDC motor is an AC motor. You have been told that 9 times, and you still do not get it.
            Last edited by Sunking; 05-15-2018, 09:57 AM.
            MSEE, PE

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            • #66
              Originally posted by Sunking View Post
              Here we are two years later and have not made any progress. I can only conclude the student is a lost cause.
              Then why continue ? Doing the same things over and over with no result while expecting a different or improved response is one form of madness.

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              • #67
                Originally posted by fivewin View Post
                Quote:
                Brushless DC motors, on the other hand, will outperform AC motors in almost every regard.

                * 1 horsepower AC = 750W. A 500W multi-pole 3 phase DC motor will do a similar job (around one third less power is required)
                You don't even comprehend what you are parroting.
                Most brushless DC motors are more efficient than a plain AC motor, because the inverter electronics has been optimized for the load. Most AC motors are off the shelf, and used for 40,000 different applications.
                As to the amount of work performed vs watts AC/DC I don't have data. Let a mech engineer sort that out.

                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

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                • #68
                  Originally posted by fivewin View Post
                  Ofcourse its unfortunately the case that residential appliances that can run on dc low voltage is still not in mass production. I did remark though in one of my previous post that most likely companies will develop and produce more and more efficient appliances that can run on dc low voltage power. So, im wondering -awaiting further development of wireless transmission- if its efficient to have different powersources (batteries) in one house to minimise cable loss without using inverter and how i can efficiently charge different batteries.

                  If i walk in my area where i live now i see many houses of only 32m2 with grid connection and they even not have a fridge, only tv & some lamps + 1 fan. So, i thought is it not more efficient if they go offgrid dc only. Pls do not compare with the living standard in your country.
                  Depending on what your electric utility charges for each kWh it is usually hard to justify going off grid even if your total load is small. The cost of a battery system still calculates out to close to $1 (US) /kWh it can safely generate each day regardless if you have DC or AC loads.

                  Comment


                  • #69
                    Originally posted by Mike90250 View Post
                    As to the amount of work performed vs watts AC/DC I don't have data. Let a mech engineer sort that out.
                    I'll not speak for others, but as a retired M.E., or even as someone with hopefully more than one eye and one balloon knot, trying to explain anything to the OP seems a waste of time. I believe the OP needs more help than (s)he can get here.

                    Comment


                    • #70
                      Originally posted by J.P.M. View Post

                      I'll not speak for others, but as a retired M.E., or even as someone with hopefully more than one eye and one balloon knot, trying to explain anything to the OP seems a waste of time. I believe the OP needs more help than (s)he can get here.
                      Your entitled to an opinion, but let me make you clear that poweroutages here are more frequent than perhaps ...... of each poweroutage is im sure longer than the time ........ Average 3-4 liters of fuel for generators they daily need which is in 1 year more expensive than a small solar system.
                      Talking about efficiency arent we?

                      MOD NOTE: I deleted the personal attack references. Please refrain from future posts or you will get a nice vacation.
                      Last edited by SunEagle; 05-15-2018, 11:53 AM.

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                      • #71


                        We talked about tv & dc. Lets talk about dc lighting vs ac in an offgrid situation.

                        Using standard ac wire for lamps 1.5mm2, 11 mOhm/m, a 12V 10watt led for example draws 0.83A DC which amounts to 76 mW per 10m of cable.
                        With 12V current you have more cable losses comparing to ac (2mW) but still TORABLE, especially in small houses. Slightly thicker wire is much more cheaper than a psw inverter or even msw.

                        So, i think no need inverter with the solar system for lighting (and tv) especially if you are able to design with short wires which is not difficult in small houses.

                        Comment


                        • #72
                          Originally posted by fivewin View Post

                          Your entitled to an opinion, but let me make you clear that poweroutages here are more frequent than perhaps .....
                          What does power outages have to do with any of the discussion?

                          If you want backup fine, do a grid tie bimodal, very efficient and only cycles batteries when needed.

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

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                          • #73
                            Originally posted by fivewin View Post
                            An AC induction motor greater than 95% efficient
                            Can you show me a link to an AC induction motor under 50HP (37kW) that exceeds 95% efficiency?

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                            • #74
                              Originally posted by fivewin View Post

                              We talked about tv & dc. Lets talk about dc lighting vs ac in an offgrid situation.

                              Using standard ac wire for lamps 1.5mm2, 11 mOhm/m, a 12V 10watt led for example draws 0.83A DC which amounts to 76 mW per 10m of cable.
                              With 12V current you have more cable losses comparing to ac (2mW) but still TORABLE, especially in small houses. Slightly thicker wire is much more cheaper than a psw inverter or even msw.

                              So, i think no need inverter with the solar system for lighting (and tv) especially if you are able to design with short wires which is not difficult in small houses.
                              we are not talking about SLIGHTLY thicker wire.
                              inverters are still pretty cheap and for doing lighting you would only need a small one, so lets be clear here. 200W inverters go for $20 US. (since you want to look at every little piece in isolation)
                              That is probably cheaper than a set of DC rated light switches.

                              and stop trying to do calculations based on amps..

                              your 10watt light that draws .83A at 12V DC
                              Guess what a 10watt light at 120V draws only 0.083a
                              but they both use 10W
                              The real difference is in COST and LUMENS


                              LEts just take a look at what you can get

                              So here is your DC bulb nice, 10W 800Lumen 12V 3 pack for $19.99 or $6.66 for one bulb

                              https://www.amazon.com/Xtricity-Equi...GME7DQ3XZRBWQQ

                              And here is an AC 120V bulb, 9W 820 Lumen 6 pack for $17.50 or $2.92 per bulb

                              https://www.amazon.com/dp/B01HJ4XRI6...=8121571950601

                              so AC 120V gets you 20 extra Lumen and 1 less watt for less than half the cost.
                              Last edited by ButchDeal; 05-15-2018, 01:03 PM.
                              OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                              • #75
                                If you compare the lumen/watt efficiency of 12V and 230V bulbs, also the price and availability, i would choose for 12v cr195 for example is more than acceptable in spite of line losses.

                                about gridtie netmetering, ununfortunately not yet available in this area.

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