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Power Technology

Sharp Announces Sales of DC Powered Air Conditioner, Other Products To Follow 239

AmiMoJo writes: Sharp has announced that sales of DC powered air conditioners will begin by the end of the year. Most appliances use the standard AC electricity supply in homes, but as solar panels become more common switching to DC can save on conversion losses. Solar panels produce DC, which is then typically converted to AC before being fed into the house's wiring, and then converted back to DC again by appliances. Sharp has announced that it intends to produce a range of DC powered appliances for home use.
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Sharp Announces Sales of DC Powered Air Conditioner, Other Products To Follow

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  • DC power? (Score:5, Funny)

    by Joce640k ( 829181 ) on Thursday July 30, 2015 @05:36AM (#50212717) Homepage

    Nikola Tesla is turning in his grave.

    • by K. S. Kyosuke ( 729550 ) on Thursday July 30, 2015 @05:37AM (#50212725)
      Let's attach him to a DC generator, then. He can make himself useful once again. ;)
    • by MichaelSmith ( 789609 ) on Thursday July 30, 2015 @05:38AM (#50212727) Homepage Journal

      At 60Hz?

      Single phase obviously.

    • Re:DC power? (Score:5, Insightful)

      by fuzzyfuzzyfungus ( 1223518 ) on Thursday July 30, 2015 @06:13AM (#50212841) Journal
      Did he have anything against DC period, or just take the position that it wasn't so hot for transmission systems, especially since high efficiency DC-DC converters weren't exactly off the shelf items at the time?
      • Re:DC power? (Score:5, Interesting)

        by AmiMoJo ( 196126 ) <mojoNO@SPAMworld3.net> on Thursday July 30, 2015 @06:59AM (#50212963) Homepage

        That's it exactly. Back then things like frequency conversion and DC level switching had to be done mechanically. To change frequency you ran a motor that drove a gear that drove a generator at the new frequency, and did something similar for switching DC voltage levels.

        Nowadays high voltage DC is used widely for transmission. Everything is solid state and highly efficient.

        • Re:DC power? (Score:5, Informative)

          by Mr D from 63 ( 3395377 ) on Thursday July 30, 2015 @07:45AM (#50213167)
          High Voltage DC transmission makes sense in some applications. Its best as a single point to point solution over a fairly long distance, as line losses are minimized. High voltage DC switching and DC to AC conversion equipment is very expensive compared to AC, and typically has a shorter lifecycle, so you don't really want to have a lot of DC switchyards.
          • High Voltage DC transmission makes sense in some applications. Its best as a single point to point solution over a fairly long distance, as line losses are minimized. High voltage DC switching and DC to AC conversion equipment is very expensive compared to AC, and typically has a shorter lifecycle, so you don't really want to have a lot of DC switchyards.

            How are line losses minimized for DC over AC, given the same "RMS" voltage (yes, I know the term means nothing in DC) and Current?

            It seems to me that the only application of HV DC would be to stack up a bunch of PV panels in Series, and then buss the result together before sending it to a HV-input Inverter.

            But, unless the EPA revised the laws of physics, it seems like AC transmission will pretty much always "win" over DC, especially over distance.

            Or is it because maybe HV DC has less coronal discharge

            • How are line losses minimized for DC over AC, given the same "RMS" voltage (yes, I know the term means nothing in DC) and Current?

              In the simplest terms, DC current losses are only result from the line resistance. AC losses are due to the line resistance plus reactive losses. Reactive losses are basically the capacitive and inductive losses that result from the constantly changing current and voltage. Various factors are at play, but you wind up with the voltage and current sine wave getting out of sync with each other. If that doesn't seem intuitive, imagine something at work trying to bring those two back into synchronization... that

      • Both.

    • Re:DC power? (Score:5, Informative)

      by Spazmania ( 174582 ) on Thursday July 30, 2015 @07:42AM (#50213145) Homepage

      Basically, Sharp is eliminating the rectifier circuit from one of their existing products. Sharp currently sells it as an 'Inverter Air Conditioner".

      Unlike most air conditioners, inverter air conditioners are always-on. The inverter varies the -frequency- of alternating current sine wave in order to change the cooling output of the air conditioner. It continuously outputs just enough cooling to maintain a steady temperature in the room.

      To do this, the A/C converts the incoming wall power to DC and then back to variable frequency AC. Eliminating the initial AC to DC conversion here makes good sense.

      • Re:DC power? (Score:4, Informative)

        by rmdingler ( 1955220 ) on Thursday July 30, 2015 @08:38AM (#50213421) Journal
        Not only Sharp, but nearly every major ductless split air conditioner [enviromaster.com] runs the inside air handler with DC voltage from an inverter in the outdoor condenser.

        This is a clever, but predictable evolution in design production.

      • Unlike most air conditioners, inverter air conditioners are always-on.

        Hmm...apparently you're not familiar with "AC" Air Conditioners in the New Orleans area.

        My Air Conditioner comes on basically late April and does not shut off till about early November.

        :)

        Frankly, I don't know how people lived down here in the old days without A/C....not to mention looking at the old pictures from the 1800's and so where men have full suits on and women with 14 layers of clothing on, and deodorant not really being pre

        • Re:DC power? (Score:5, Informative)

          by Gryle ( 933382 ) on Thursday July 30, 2015 @10:20AM (#50214023)
          Early Southern architecture had passive cooling systems, like double-hung windows, high ceilings, and constructing doorways and windows in such a way as to generate breezes as the air heated up during the day. The Spanish were particularly good at things like this.

          Folks also had a different daily routine. They were up before the sun, worked until about lunch, had a big meal and a nap during the hottest part of the day, and then worked until late in the evening. The Spanish siesta is a good example of this, but the Italians have a similar concept. In modern days I see a lot of construction workers doing this too, particularly on road construction. The job site will be empty during the afternoon and work begins in the evening and lasts all night. (Some of this is to keep from interfering with day-to-day traffic patterns too.)
    • Nikola Tesla is turning in his grave.

      ...at 1800 RPM

  • Why not both? (Score:4, Insightful)

    by aaaaaaargh! ( 1150173 ) on Thursday July 30, 2015 @05:38AM (#50212733)

    Wouldn't it be possible to have both in the same appliance?

    • Re:Why not both? (Score:4, Insightful)

      by K. S. Kyosuke ( 729550 ) on Thursday July 30, 2015 @05:46AM (#50212761)
      Possibly, but maybe it's simply cheaper for the manufacturer to simply sell 95% of the same product plus different power interfaces. I've long thought that whole local power grids would switch to DC eventually anyway. With broader deployment of PV technology (and potentially power-to-gas) and improvements of power electronics, it only makes sense.
      • It makes sense, except where industrial users use a ton of 3-phase AC induction motors, which are a simple design. And AC transformers are still a more simple method of switching voltages for distribution.

        • Maybe you could always have a mid-level AC grid or something similar (below long-range HVDC and above municipal DC). I assume that fewer large inverters would be better for the overall economy than every small PV installation having their own stuff.
        • More and more commercial AC equipment is moving to variable frequency drive compressors for efficiency, so if you can provide sufficient DC current at the necessary voltage to can shave a few percent off of the conversion losses.

          =Smidge=

      • AC has far lower transmission losses over long distances, however with the advent of rooftop solar now people can generate DC closer to where they're using it.
        Converting AC to DC and DC to AC will always incur losses, and as AC is far more efficient for transmission, we've historically used AC everywhere (well, except inside just about everything you plug into an electrical outlet, where DC is generally used)

        • AC has far lower transmission losses over long distances

          Actually, it doesn't.

          • The advantage of AC for transmission is that it can be transformed up into the 100kV range, at relatively low current, thus minimizing losses in the resistance of the transmission cables. To do the same with DC would require up/down converters which would require chop->transform->rectify anyway (the transformers might be smaller and more efficient, though)
            • And yet, in practice, HVDC is still more efficient than current AC lines in the end, even if still somewhat more expensive at the moment.
              • HVDC equipment will always be much more expensive due to the high cost of switching and conversion equipment, which must have a much greater interruption/arc reduction capacity.
              • Re:Why not both? (Score:4, Informative)

                by Smidge204 ( 605297 ) on Thursday July 30, 2015 @10:01AM (#50213895) Journal

                And yet, in practice, HVDC is still more efficient than current AC lines in the end, even if still somewhat more expensive at the moment.

                Yes and no.

                AC power is far more efficient at higher voltage and short to medium distances, and you save a lot of material (and thus money) on conductor sizes. The voltage can be changed easily and it is safer and easier to switch on and off since there's 50 or 60 times per second where the voltage/current is zero - allowing for the circuit to be opened without arcing or inductive voltage spikes. AC arcs also tend to be self-extinguishing for this reason.

                But AC systems also have inductance and capacitance to deal with. For very high power, very long distance runs, the capacitive losses start to add up. More current is required to charge/discharge this inherent capacitance, which means more power losses. This is where HVDC really shines.
                =Smidge=

                • Re: (Score:3, Informative)

                  by Anonymous Coward

                  AC power is far more efficient at higher voltage and short to medium distances, and you save a lot of material (and thus money) on conductor sizes.

                  Line voltage is limited by peak voltage (both from spacing and things like corona discharge), while carrying capacity comes from the RMS values. At higher voltages, DC wins because you can drive a higher RMS voltage, allowing a lower current. AC wins at the short to medium distances precisely because those are not the higher voltage links, and it comes down to switching equipment cost instead of transmission line costs. In other words, shrinking the conductor doesn't save much on short runs compared to o

            • High voltage only saves you on resistance losses. There are still inductive and capacitance losses with AC that you can't avoid.
        • Re:Why not both? (Score:5, Insightful)

          by heypete ( 60671 ) <pete@heypete.com> on Thursday July 30, 2015 @06:49AM (#50212935) Homepage

          AC has far lower transmission losses over long distances

          Does it? I was always under the impression that AC was used for long-distance transmission because it could be easily stepped up to very high voltages with transformers while efficient DC-to-DC conversion was not possible until relatively recently. For the same power transmitted, resistive losses are lower at higher voltages as power lost to heat goes as I^2*R and lower currents could be used.

          However, modern solid-state DC-to-DC converters are extremely efficient, can step DC voltages up to very high voltages and thus benefit from lower resistive losses in transmission. HVDC also benefits from not having to deal with inductive or capacitive losses in the cable.

          In short, as far I know the key to minimizing losses in transmission lines is to use high voltages, not because of any inherent advantage of AC.

      • Sure instead of using synchronous AC motors which are simple and efficient you can switch to much more complex DC digital motors.

        Sounds brilliant.

        • Re:Why not both? (Score:5, Informative)

          by Spazmania ( 174582 ) on Thursday July 30, 2015 @07:57AM (#50213219) Homepage

          It's called an "inverter" air conditioner. It produces a variable-frequency AC sine wave from the DC voltage. The variable-frequency to the compressor changes the cooling output, so instead of turning the air conditioner on and off as the temperature wanders back and forth across the set point, it varies the frequency to keep the temperature steady.

          http://www.acson-international... [acson-international.com]
          https://en.wikipedia.org/wiki/... [wikipedia.org]

          It is brilliant.

          Sharp already sells these air conditioners. They're just removing the DC rectifier circuit and running directly on DC instead of starting with 50hz or 60hz AC.

        • There are good reasons to be skeptical of complexity(such as basically all software); but at least for motors small enough that solid state switching isn't heroically expensive and/or practically disposable, 'complex' and 'digital' also mean 'has convenient ways to monitor and control the motor's activity in some detail'. Simple is good; but when the complexity is in solid-state parts you get a serious discount and sometimes some cool features.
          • Your points are valid, I'll just add that we are not really even talking about a high level of complexity either way. These power/control approaches are nothing new, they are used and proven and quite simple and reliable, they are just being adapted to this application. In some ways having DC input really makes motor control easier and you don't have to deal with current/voltage frequency to begin with, and digital controllers are so easy to implement.
      • I've long thought that whole local power grids would switch to DC eventually anyway.

        Unlikely to happen any time soon. Too much installed base of AC power. Not like people are going to rip open their walls to switch from AC to DC and virtually everything you plug into the walls is designed with AC in mind. The only wide spread DC cabling standard is USB and that's mostly low power stuff.

        I have no principled objection to DC power but I think any switch will take many decades if it happens at all.

        • by Holi ( 250190 )
          >The only wide spread DC cabling standard is USB and that's mostly low power stuff. more like RV and yachting equipment, it all runs off DC.
    • Certainly possible; but probably only efficient or sufficiently cheap for some items.

      My (admittedly limited) understanding is that motors are one of the parts where you can get a relatively refined and mature design for almost any remotely normal flavor of electrical input; but the design of the motor is going to reflect your choice, and work either inefficiently or not at all from some other input. Since AC units are basically all motor(some fans, a compressor, maybe a pump), that is a problem.

      Some d
    • by AmiMoJo ( 196126 )

      It would, and some specialist devices do support that. It's not clear if that is what Sharp intends to offer, or if they are going to be DC only. It might make more sense to do the latter use an inverter that can run in "reverse", i.e. using the mains AC to provide central DC when solar energy is not available.

      AC made a lot of sense when solid state switching regulators didn't exist, but nowadays having a central DC supply in a home that also generates its own DC isn't a bad idea.

    • Re:Why not both? (Score:4, Informative)

      by monkeyxpress ( 4016725 ) on Thursday July 30, 2015 @07:32AM (#50213101)

      The growing trend for appliances is to move towards using brushless DC motors instead of traditional induction motors. These are more compact, more efficient, and variable speed in nature - which opens up new opportunities in some applications. The main problem is they cost more as they require a controller, unlike induction motors which will run directly off the AC supply.

      The neat thing about this product is that it recognises that the DC to AC inverter in a solar power system is basically just a motor controller (a box of power electronics). So by moving that box of electronics into an area where it has an additional benefit, they have offset the inverter cost of a solar installation. This has potentially huge implications for the solar industry as inverter cost is becoming one of the dominate components of a solar power system as panel costs continue to reduce.

      It would be interesting to see how the added efficiency of the brushless motors and extra abilities - such as being able to vary compressor output to match solar input - impact the overall economics. There are also new technologies such as linear motor compressors that could continue to tip the economics in favour of solar systems. Either way an interesting development.

      • by trawg ( 308495 )

        Thanks for the explanation. When we talk about "more efficient", how much are we talking about here? The article link mentions "5% or more of the power loss occurs" but as it's a Google Translate, not sure if it's talking about the same thing.

        Does it basically mean these DC A/C units are 5% more efficient?

      • by SIGBUS ( 8236 )

        One potential problem with the typical brushless DC motor is that it has permanent magnets using rare earth elements. The rotor in an induction motor, on the other hand, is just copper and iron. Induction motors can operate on variable frequency as well (the Tesla cars are a very good example of this, as are locomotives with AC traction motors).

        Induction vs. brushless is a tradeoff of compactness vs. expensive rare earth elements.

    • DC and AC motors are fundamentally driven in different ways. You either need a really esoteric motor design which will come with it's own set of drawbacks, or you will need to provide conversion in the gear itself at which point why would you bother going to DC at all.

      • Especially if you are dealing with solar-derived DC, which is going to be (reasonably) steady. For some purposes, it doesn't matter that much whether or not the voltage actually crosses zero; but the ripple is essential if you want the magnetics to work correctly. If you have to go to the trouble of switching the DC to get that working, odds are that it's time for a pure DC design.
    • by OzPeter ( 195038 ) on Thursday July 30, 2015 @08:05AM (#50213257)

      Wouldn't it be possible to have both in the same appliance?

      Yeah, that AC/DC appliance would be really rocking, and a company that succeeds in doing it really would be a rising power. But I'd be worried about the low end manufactures doing dirty environmental deeds, dirt cheap as well as the build quality of the system overall. After all you don't want to be shaken all night long by your air conditioner - that would really lead you down a highway to hell.

    • It is. Fridges desiigned for RVs and such are (often) dual input.

  • by storkus ( 179708 ) on Thursday July 30, 2015 @05:50AM (#50212773)

    Noticeably missing from both linked TFAs. As discussed here and elsewhere previously, 48V would probably have too much ohmic loss unless this A/C is right next to the supply. Higher voltage would work better, but call into question safety issues you don't have with AC due to it passing through zero volts 100-120 times a second.

    • > Higher voltage would work better, but call into question safety issues you don't have with AC due to it passing through zero volts 100-120 times a second.

      AC running from hand to hand will likely kill you, causing your heart to try beating to it.

      • > Higher voltage would work better, but call into question safety issues you don't have with AC due to it passing through zero volts 100-120 times a second.

        AC running from hand to hand will likely kill you, causing your heart to try beating to it.

        So will DC. And at a given voltage, DC is worse as the current is constant and doesn't like to be interrupted.

    • Noticeably missing from both linked TFAs. As discussed here and elsewhere previously, 48V would probably have too much ohmic loss unless this A/C is right next to the supply. Higher voltage would work better, but call into question safety issues you don't have with AC due to it passing through zero volts 100-120 times a second.

      I'm not sure the resistance losses would be that significant as to be an issue. The safety question is a good one. 48V home DC systems are common enough and I believe they are well covered by code, so installations done right should be safe. DC can be problematic in that you can't always detect certain faults as there is not ground fault current, so there is inherently some greater chance of something like a bad connection overheating and causing damage, but that should not really be a concern if stuff is q

      • Re:What Voltage? (Score:5, Informative)

        by jenningsthecat ( 1525947 ) on Thursday July 30, 2015 @08:42AM (#50213443)

        DC can be problematic in that you can't always detect certain faults as there is not ground fault current, so there is inherently some greater chance of something like a bad connection overheating and causing damage, but that should not really be a concern if stuff is quality and installed correctly.

        There's no connection between ground faults and bad connections that might cause overheating. But to the extent that DC systems might have lower voltage and therefore higher current, bad connections ARE more likely to overheat and cause fires. Also, there's no reason a properly installed DC system can't have Ground Fault Interrupters, although the ones currently used for AC won't work on DC. The ones designed for DC would be somewhat more complex, and probably bigger as well.

        Another note: interrupting Direct Current without arcing can be difficult. AC has a zero crossing that extinguishes an arc across switch contacts, whereas the equivalent DC circuit may continue to arc across switch or relay contacts. Such switches and relays typically have heavier contacts and the contacts, when open, tend to have more space between them. The may also have permanent magnets nearby to act as 'blowouts' to extinguish any arc that develops.

        • There's no connection between ground faults and bad connections that might cause overheating.

          I understand that and did not mean to imply there were. I suppose my wording could have been better. Just meant to point out some specific inherent differences that relate to safety.

    • Yes I am curious too. My panels will generate somewhere between 250 and 330VDC if I remember right. The inverter refers to this as MPP maximum power something to extract the most power from the panels. I am wondering if the sharp unit allows for a range of voltages. If it does not, then it still may be more efficient to convert to AC then back to DC so the panel efficiency is maximized. If not that, then a DC to DC converter may be needed in front of the sharp unit if it does not like variable DC voltages.

      • Maximum Power Point Tracker. The more current you draw, the lower the voltage. Since P(V,I) = ~V x I(V), you want to operate at the voltage that maximizes the power (at the first stage off of the solar panel). Once you have the energy stored (in a capacitor or inductor), you can convert it to whatever level you need [wikipedia.org].
  • by sglow ( 465483 )

    I love it, a DC AC

  • by RobinH ( 124750 ) on Thursday July 30, 2015 @07:30AM (#50213089) Homepage

    I've been saying for a few years that if you just had a few solar panels in your back yard, and didn't want to go through the expense of all the inverter stuff, you could just use it to charge a small battery and power a DC air conditioner. That's because you generally want air conditioning at the same time that you have the most solar power. At the time, the only DC air conditioners available were for marine use, and so they were expensive. However, in the last year and a half I noticed a lot of DC air conditioners on the marker on AliExpress [aliexpress.com] (in China). Some of them even come as a kit including solar panels. The difference here is that presumably the Sharp ones are UL and/or CSA certified, so you could use them in North America.

    Honestly, some of the stuff on AliExpress is impressive for how cheap it is. You can buy 500W grid-tie inverters [aliexpress.com] for a solar array for the $200 range. Unfortunately they only have a CE rating, so they're not OK for North America yet. In comparison you can spend 3 to 4 times that much here.

    • by dj245 ( 732906 )

      I've been saying for a few years that if you just had a few solar panels in your back yard, and didn't want to go through the expense of all the inverter stuff, you could just use it to charge a small battery and power a DC air conditioner. That's because you generally want air conditioning at the same time that you have the most solar power. At the time, the only DC air conditioners available were for marine use, and so they were expensive. However, in the last year and a half I noticed a lot of DC air conditioners on the marker on AliExpress [aliexpress.com] (in China). Some of them even come as a kit including solar panels. The difference here is that presumably the Sharp ones are UL and/or CSA certified, so you could use them in North America.

      Honestly, some of the stuff on AliExpress is impressive for how cheap it is. You can buy 500W grid-tie inverters [aliexpress.com] for a solar array for the $200 range. Unfortunately they only have a CE rating, so they're not OK for North America yet. In comparison you can spend 3 to 4 times that much here.

      It's really eye opening how much middlemen mark up chinese goods. My wife has ordered high-end clothing and a fabric baby carrier from Aliexpress. Sometimes the quality is typical of cheaply made goods, but in many cases we can't tell if it is an excellent knockoff or a case of "Prada ordered 10,000 units, let's make 12,000 and sell the extras ourselves". The markup on mainstream high-end goods is extreme. Independent entrepreneurs have taken advantages of this in some sectors, but not others. Only th

    • Yeah, but do you trust a random product purchased from AliExpress to actually meet the certifications it claims to? AliExpress has the problems of online merchants and contemporary Chinese business ethics all put together.

    • That is not a DC air conditioner. Note that it comes with a 2kw inverter. It's just a regular 220V AC air conditioner. Also, that whole package is sketchy. The stated BTUs don't match throughout the page (title and description says one thing, specs say another). It comes with 4 solar panels, but there are absolutely no specs on them - not even the wattage. Anyway, that package is solar panels, batteries, huge inverter and a regular air conditioner. The efficiency would have to be very low.

    • I've been saying for a few years that if you just had a few solar panels in your back yard, and didn't want to go through the expense of all the inverter stuff, you could just use it to charge a small battery and power a DC air conditioner.

      The big advantage of the DC air conditioner is that you can run it in parallel to a traditional air conditioner and don't have to worry about the grid connection. This will take load off of the main air conditioner and save money. No special controllers needed, just set the target temperature on the DC unit below the target of the traditional system. That way the traditional system should only run when it's both hot and dark/cloudy.

  • Is this not just a change in power input but a substantially more energy efficient air conditioner, too?

    I've seen small A/C systems for cars and marine applications that can run off DC power, but they're usually pretty small which helps cut the overall power consumption. In marine applications they also have the advantage of being able to use sea water to move the heat versus a fan and coils in open air.

    One of Sharp's smallest split system units has 8500 BTU of cooling with an EER of 13 which is roughly 65

    • by ledow ( 319597 )

      An A/C capable of cooling a car or boat isn't really comparable. First, they move through outside air when in use or are submerged, so cooling is aided quite a lot. Second, they barely have to cool the equivalent of one room in a house. Maybe more rapidly, but that's just a case of brute power.

      However, the volume covered means they aren't actually cooling at max power for more than a few minutes anyway, and the sealed interior of a car means they can dial-down quite quickly. They also don't have to worr

    • The good news is that, potentially, this would be tied to a large PV battery bank. He who shall not be named's battery packs are Li-ion at 400V which, if run directly, would be just over an amp and a half (about 25% of the basic battery pack's continuous delivery capacity). I agree it's not going to make a whole house system work, though. I don't do the hardcore side of ME, so I don't know what separates the typical residential 2.5-3.0 CoP of a whole house unit from the mini-splits that seem to get closer t

      • by swb ( 14022 )

        It'd be interesting to know what Sharp plans for the power input. I would suspect the market starts to shrink dramatically for input voltages over 48V because pretty much all battery arrays are 48V or lower and AFAIK (which isn't very far) only the newest solar installs run at high DC voltages.

        I'd guess that this would be a 24-48V system (highest common DC voltage in battery arrays) and lets say you have 6 hours runtime after dark (pure battery load), you're burning 4000 watt hours of power or 80+ amps @ 4

    • 8500 BTU might cool a room reasonably well, but its not going to provide whole-house cooling, either, and would require a pretty large battery array to run off battery. It might make sense for some kind of supplemental cooling setup where it ran direct off solar panels.

      Translation: Turn your detached garage attic into a whole new room. Place solar panels on the roof and cool it with a Sharp Air Conditioner. With renting, you can now pay back your investment and then some. Winning!

  • by 140Mandak262Jamuna ( 970587 ) on Thursday July 30, 2015 @08:04AM (#50213251) Journal
    People in USA and Europe with excellent grid connections are not aware of it. But in places like India with unreliable grid, people have been using backup electricity storage for quite some time. Typically truck lead-acid batteries are used to store enough energy to power a couple of ceiling fans, a few lamps and the TV, never forget the TV, for a few hours. They put up with power outages using these contraptions.

    They use inverters to convert the DC to some square wave and approximate it to A/C using electronic gimmicks. Not a pure sine wave A/C, but close enough to run fans and the lamps. Energy conversion efficiency is not bad, the inverters do hot heat up too much. But they play havoc with the motors. So the Japanese A/C makers have been selling ruggadized air conditioners that can run on the inverter electricity.

    The logical next step is to create A/C to run purely on DC. Probably it would use AC to DC converters to use grid electricity. Again this DC would be poor in quality compared to battery DC. So this Aircon also would need to be ruggadized.

    All these calculations about when residential solar will become viable compared to coal or natural gas are completely different between G8 and rest of the world. Places like India will pay well over the current grid price for steady electricity supply. Not all of them. But the affluent population of India is about the size of Japan, some 120 million people. They have been making do with truck-battery-inverter contraptions, small gasoline generator sets etc. They would probably form the wave of early adopters who pay for the early fixed costs of solar panel factories.

    • by dj245 ( 732906 )

      People in USA and Europe with excellent grid connections are not aware of it. But in places like India with unreliable grid, people have been using backup electricity storage for quite some time. Typically truck lead-acid batteries are used to store enough energy to power a couple of ceiling fans, a few lamps and the TV, never forget the TV, for a few hours. They put up with power outages using these contraptions.

      They use inverters to convert the DC to some square wave and approximate it to A/C using electronic gimmicks. Not a pure sine wave A/C, but close enough to run fans and the lamps. Energy conversion efficiency is not bad, the inverters do hot heat up too much. But they play havoc with the motors. So the Japanese A/C makers have been selling ruggadized air conditioners that can run on the inverter electricity.

      The logical next step is to create A/C to run purely on DC. Probably it would use AC to DC converters to use grid electricity. Again this DC would be poor in quality compared to battery DC. So this Aircon also would need to be ruggadized.

      All these calculations about when residential solar will become viable compared to coal or natural gas are completely different between G8 and rest of the world. Places like India will pay well over the current grid price for steady electricity supply. Not all of them. But the affluent population of India is about the size of Japan, some 120 million people. They have been making do with truck-battery-inverter contraptions, small gasoline generator sets etc. They would probably form the wave of early adopters who pay for the early fixed costs of solar panel factories.

      When I visited North Korea, individual solar panels were everywhere, in cities and in the countryside, charging lead-acid batteries for lighting at night. Being on China's doorstep, it may be cheaper to do this than to build out the grid. Widespread availability of food refrigeration would help poor countries tremendously.

  • what voltage do they expect? 12 volts? 48 volts? 100 volts? can i use my 2 AA cells?
  • So what happens when their home system craps out? Can the unit run when they pull AC power from the grid?

  • The trend in solar is to put mini inverters on the panel itself giving them an AC output. This makes the setup and wiring of an array much easier and cheaper.
  • I was literally thinking about this problem the other day.

    I was day dreaming about the idyllic rustic life living in a cabin in the woods away from civilization etc... Then I got thinking, you know what? I would hate that, this week the temperature has been hovering around 32-38 degrees, which is hot. Sitting in a hot cabin all day doesn't sound so romantic, nor does hiding in a lake all day. AC is pretty much out of the question, as I'm pretty sure it would be too inefficient and drain whatever power you h

  • There is no way to supply a high-power appliance (such as an AirCon) directly out of a PV array. None.

    The panel is always operated at a point (MPPT) where it produces the most power, but that power is highly fluctuating whenever there's a slight obstruction in the incident sunlight (clouds, stray leafs, even passing birds).

    You need a DC/DC power converter feeding a battery array. Then the DC appliance can be powered from that battery pack. Overall, an expensive solution mostly due to the need of local energ

I have a theory that it's impossible to prove anything, but I can't prove it.

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