The Kingtec K25Z-4 Solar Air Conditioner

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RSSfeed Registered Users Posts: 3,810 ✭✭
in Solar Product Reviews & Opinions #1
Driven by a passion to create a window air-conditioner that runs off solar power, Kingtec Solar’s Jamie Edens took inspiration from the DC-powered air-conditioners that cool long-haul trucks across the USA and created a window air conditioner that runs on solar air conditioning. If truckers are using such energy-efficient devices, why can’t homeowners and businesses benefit from a similar concept. While there are other “energy...

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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    RSSfeed wrote: »
    Driven by a passion to create a window air-conditioner that runs off solar power, Kingtec Solar’s Jamie Edens took inspiration from the DC-powered air-conditioners that cool long-haul trucks across the USA and created a window air conditioner that runs on solar air conditioning. If truckers are using such energy-efficient devices, why can’t homeowners and businesses benefit from a similar concept. While there are other “energy...

    Interesting.
    Combines a 48 volt 20 AH AGM battery with 48 volt DC motor(s) and a 45 Amp Charge Controller all in the package. Just add 1000 Watts of the solar panels of your choice and it is ready to go. The battery will keep the 17 Amp unit going for up to one hour of shade or darkness.
    Then, as they say, you can either get a bigger external battery pack or just grid connect it. :-) Something very wrong with that last part!
    It would be more suitable for on-grid if it did not have all of the batteries and other stuff inside. And more suitable for well planned off-grid if it just took the 48 volt DC input and did not bother to integrate all of the components which would be better shared with other loads.
    SMA SB 3000, old BP panels.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #3
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    There are so many wrong assumptions in the original post, it is hard to know where to begin.

    First and formost, why does this guy assume that because a truck A/C is running from DC it is more efficient?

    This is another one of those cases where just because something can be done does not mean it should be.
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  • novalucy
    novalucy Registered Users Posts: 3
    #4
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Hey Northern Arizona-
    It would probably be smarter not to post anything as critics can be cruel- But I am that “guy”
    Jamie from Kingtec Solar. I owe a lot to the online community for shaping my product. “Thank Y’all”
    So it seems there are some questions and I will love to answer them here!- If you have just installed a 30k grid tie system and want to bash my concept- go ahead- but I'm not you kind- I'm the kind that really wants to call the utility and tell them to get the darn* meter off my property- realisticly though - harmonious solar-grid living is OK too. You can have sustainability and still be connected to the grid- That is what the K25Z-4 is all about. A simple go green- go solar now product... Expand it latter with a battery bank, more panels, Add a .. frig, freezer lights, fan.. Add a solar hot water.. This is just an option for those that like to jump in slowly and not with a big mortgage, lease it now , or a money no object approach.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    I am glad to have you here.

    I cannot spend the time right now, but others will, I am sure, will help with some constructive questions and suggestions.

    We are a very practical (and cheap :roll:) group here. And happy to see new products that push the limits of conservation (vs just throwing more panels+batteries+inverters at a problem).

    Take care,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    I find the criticisms of the product to be entirely reasonable and valid.

    Converting from 120 VAC to DC to run an A/C unit is not more efficient. DC A/C's in trucks are more efficient because the source power is DC to begin with; having to convert that to AC to run the unit would be less efficient.

    Likewise, equipping the A/C with a small 48 VDC battery bank is not as functional as simply attaching it to the main DC bank of an off-grid house. Although usually any off-grid place that has a 48 Volt bank would also already have sufficient inverter power to run a standard A/C.

    novalucy; your comment that your product is "A simple go green- go solar now product" indicates it is a marketing ploy, rather than an actual solution to an existing problem. I suggest you spend a lot of time reading through this forum and get a good understanding of just how familiar with and practical about the members are with solar energy. You will be amazed.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #7
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Running from 48 volts DC might make it usefull for some off-grid systems, but I looked over the specs again, and am not sure what makes it "greener" than an off-the-shelf 120 volt unit.

    The EER rating is quite a bit higher than many other window A/C's, but the cost is nearly $3,000 compared to a similar GE 18,000 BTU unit of around $500.

    Nowhere in your writeup did I see any explanation of how a 20 amp-hour battery will run the A/C for 8 hours per day (for free). To supply that, you would need to have a 48 volt solar panel setup that would supply at least 18 amps for 8 hours per day, or roughly a 1200 to 1600 watt solar array. If you already have a 48 volt battery system, probably a great unit - but I don't see a huge market for it otherwise.

    And personally, if I were wanting to buy a DC powered A/C, I would prefer that the battery and controller NOT be part of the unit.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #8
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Windsun wrote: »
    Nowhere in your writeup did I see any explanation of how a 20 amp-hour battery will run the A/C for 8 hours per day (for free). To supply that, you would need to have a 48 volt solar panel setup that would supply at least 18 amps for 8 hours per day, or roughly a 1200 to 1600 watt solar array. If you already have a 48 volt battery system, probably a great unit - but I don't see a huge market for it otherwise.

    From my earlier post, my interpretation of what they say about the 20 AH internal battery:
    Combines a 48 volt 20 AH AGM battery with 48 volt DC motor(s) and a 45 Amp Charge Controller all in the package. Just add 1000 Watts of the solar panels of your choice and it is ready to go. The battery will keep the 17 Amp unit going for up to one hour of shade or darkness.
    Then, as they say, you can either get a bigger external battery pack or just grid connect it.     Something very wrong with that last part!
    SMA SB 3000, old BP panels.
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  • novalucy
    novalucy Registered Users Posts: 3
    #9
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Hello again Northern Arizona- from Jamie- owner of the Kingtec Solar Air Conditioner
    The Kingtec K25Z-4 is a DC powered air conditioner-- The air conditioner is all DC- There is no conversion from DC to AC-
    This eliminates start-up loads associated with AC compressors . This eliminates large inverters to start that load. This eliminates the the inefficiencies associated with converting DC to AC. And driving the cost higher than it has to be.

    The DC powered air conditioners for trucks were designed to run typically 8 hours on battery power. Anti-idle law stuff) - (usually 4 group 31's). The truck market is driven by the need for efficiency as opposed the the US residential air conditioner being driven by price.

    #1 This air conditioner was designed to be simple- Plug the solar panels into the air conditioner and turn it on. That's why the 20 ah battery bank is in the unit-
    #2 Expandable- The unit can be connected to the grid to run at night. The unit can also have an external battery bank if you want to run off grid.
    Also the air conditioner can serve as the hub for adding other DC appliances (frig/freezer, lights, fan etc..) All the solar engineering is in the air conditioner.
    #3 Sleek- you can put lip stick on on this Air conditioner- but....(I'm still working on this)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Jamie, I sincerely hope you haven't wagered your life's savings on the sales potential of this thing.
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #11
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    While I agree that all-DC units can be more efficient, my biggest issue is with the built in battery and charge controller. I suspect that the market for this will be rather small, and you are further restricting it by including items that would already exist in any off-grid 48 volt system.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #12
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Windsun wrote: »
    While I agree that all-DC units can be more efficient, my biggest issue is with the built in battery and charge controller. I suspect that the market for this will be rather small, and you are further restricting it by including items that would already exist in any off-grid 48 volt system.


    On the other hand, given what we have all seen about the problems new solar PV users have getting to a practical working design in which all of the elements play together properly, there may be a market for such a turnkey system for those who are off-grid with generator only or with a 12 volt battery system. And I do like that the CC is oversized to allow it work with an external battery bank.

    My biggest concern is with the marketing of this to an on-grid audience, where IMHO the economics are questionable.
    SMA SB 3000, old BP panels.
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  • novalucy
    novalucy Registered Users Posts: 3
    #13
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Hello again. I'm glad to finally get some positive feedback. The only offense I take from this is that its all about my return on my investment of my time and money. I'm free to do with both as I please. If I can only get just the few people that only run their off grid system with a 12 volt battery and a generator - a cool comfort solar air conditioner- then my investment is worth my while. I'm here for all. Thank you
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #14
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    At 6 times the cost of an equivalent AC unit, it's hard not to think of price gouging.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #15
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Windsun wrote: »
    While I agree that all-DC units can be more efficient, my biggest issue is with the built in battery and charge controller. I suspect that the market for this will be rather small, and you are further restricting it by including items that would already exist in any off-grid 48 volt system.

    Totally agree. Plus I don't care for the promoters attitude. It won't help his sales.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    waynefromnscanada wrote: »
    Totally agree. Plus I don't care for the promoters attitude. It won't help his sales.

    When you do a Google search on this most of the returns are carbon copies of the press release.

    We have seen integrated charge controller/inverters before (outside the US) and it is a good idea basically. However, wrapping the concept up in an A/C as its main function limits its saleability from my POV. Having it cost 6 times a conventional A/C unit of the same size? If true, that would nail the coffin lid down firmly.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #17
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Cariboocoot wrote: »
    When you do a Google search on this most of the returns are carbon copies of the press release.

    We have seen integrated charge controller/inverters before (outside the US) and it is a good idea basically. However, wrapping the concept up in an A/C as its main function limits its saleability from my POV. Having it cost 6 times a conventional A/C unit of the same size? If true, that would nail the coffin lid down firmly.

    In our world of easy solutions (or the belief in them anyway) the appeal of a totally (except for the panels) integrated product may be enough to bring in people who are afraid of the work involved in designing and assembling a system on their own. They get an assurance that if they just add the right array of panels, they will have a working (and optimized?) system.

    As a marketing point, it could work, price notwithstanding.

    "Try this can of instant water! All you have to do is add water!"
    SMA SB 3000, old BP panels.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #18
    Solar Powered Air Conditioner

    Interesting new product I found....http://kingtecsolar.com/

    Looks like $2900 for a window-unit type A/C 16,000 BTU complete with battery/inverter/MPPT. Apparently you can run it on direct solar, plug it in to the grid, or run it off a battery.

    First one I've seen or heard of.

    YouTube Vids Below:
    https://www.youtube.com/watch?v=NqAEyEt5DAQ

    For those interested looks like it takes about 3 ~200 watt cells to run.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #19
    Re: Solar Powered Air Conditioner
    Texas Wellman wrote: »
    Whoops...Looks like it was posted before. Sorry.
    http://forum.solar-electric.com/showthread.php?17347-The-Kingtec-K25Z-4-Solar-Air-Conditioner&highlight=kingtec+solar

    No problem, and thanks for providing the link back to the existing thread for others who come along!
    SMA SB 3000, old BP panels.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #20
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Wow, I think you guys were really harsh on the inventor. When I stumbled on this product I immeidately recognized that this is a first one I had seen. A commercially available, plug-n-play, solar-powered A/C.

    I think the ideas behind the unit are sound-a small battery to keep the unit running when a cloud or otherwise short-duration shade covers the panels, and way to run it off the grid (or generator, or whatever). I may be wrong but since the unit already has a battery and inverter from A/C to D/C it pretty much needs a charge controller and MPPT also.

    As far as price goes....I'm just not seeing how you can justify comparing this one-of-a-kind unit to an off-shelf A/C from a big box. Yes, $3K IS pricey, but I could see the price coming down if the demand was there and the technology grows...just like everything else solar.

    I think this A/C is a perfect example of how someone like myself, who lives in SE Texas, could go solar for a fraction of the cost of installing a grid-tie unit. Most of my electrictiy costs during the summer go toward A/C, and I'm not going to spend the money or the time to install a GT system at this time. Not that I couldn't do it, but the red-tape and gov't paperwork add so much cost and complexity to a system that it just isn't worth it right now. Something like this could be installed in a half-day and 16K BTU of cooling could probably take care of my entire upstairs, and I'm already considering adding a 2nd AC up there right now to help out the main unit.

    Of course I realize that this little unit is not going to eliminate my monthly electricity/AC bill from the utility but I could see where you could save hundreds of dollars over the course of a year or two. I would have to look at the numbers to figure out a pay-back (if any) but I think that a lot of people here put payback at a distant 2nd or 3rd place sometimes when looking at solar.

    To the inventor: have you considered an option for homeowners like myself who would be interested in this unit as a strictly on-grid system so that minus the battery and charge controller the cost could be brought down?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #21
    Re: Solar Powered Air Conditioner

    Thanks guys... I have combined this with the original thread.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #22
    Re: Solar Powered Air Conditioner

    My gosh you guys are fast!! LOL I was editing my OP when I noticed that it had already been moved etc.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #23
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Texas Wellman wrote: »
    To the inventor: have you considered an option for homeowners like myself who would be interested in this unit as a strictly on-grid system so that minus the battery and charge controller the cost could be brought down?

    Take away that portion and it wouldn't work: the A/C unit itself is DC powered and needs that DC power source.
    Otherwise you're talking about a standard A/C unit plus GT solar off-set, which would not be legal without the usual GT install permits/inspection. As has been explained in other threads, there is no (practical) way to isolate a standard GTI system so that it only supplies the household needs and does not back-feed the grid. Et cetera, ad infinitum.

    As it is this fills a very small niche, which is going to keep the price high. If they would sell a unit sans solar that could be integrated with an existing 48 VDC system there might be more sales. Making it similar in function to the Grundfos water pumps that can be run off either/or AC/DC.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #24
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    I guess my understanding gets a little fuzzy on this front. I understand that the unit is DC powered. I see it has a battery, charge controller, inverter (A/C to D/C), and MPPT. What you're saying is that once you have an inverter that goes from A/C to D/C you pretty much run into the same legal problems that any GTI would have?

    What I am saying is that if the unit ONLY accepted A/C power and NEVER backfed back to the plug. The A/C would only be used when the solar power runs low, like if a cloud passes or at nite (and at nite you need much, much less cooling). If you ditch the battery and charge controller then put me in the "Seriously Interested" category.

    Oh, and for those complaining about the price....Grundfos SQF pumps sell at about $1800. I do not get a discount on that either, the GP can probably buy one for the same cost I can. All they have is a motor and pump, with the motor having the inverter technology built right in. So at ~$2K you're ONLY getting a motor+pump+inverter+MPPT. This price does not include the wire, pipe, panels, or interface controller (which can be real simple or really fancy). And they've been making and selling them for 20 years. Now figure having a compressor, condensor, fan, coils, refrigerant, battery, inverter, MPPT, charge controller. I can easily see where the inventor may not even break even at $3k for such a small run.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #25
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    I have read and re-read your post. You and I are on completely different planes here. I can very easily see how this could be a viable product from day one, not everybody lives in a small cabin or has an existing 48V system. For those of us who don't, this is a fast and relatively easy way to get into the game.
    Cariboocoot wrote: »
    Take away that portion and it wouldn't work: the A/C unit itself is DC powered and needs that DC power source.
    Otherwise you're talking about a standard A/C unit plus GT solar off-set, which would not be legal without the usual GT install permits/inspection. As has been explained in other threads, there is no (practical) way to isolate a standard GTI system so that it only supplies the household needs and does not back-feed the grid. Et cetera, ad infinitum.

    As it is this fills a very small niche, which is going to keep the price high. If they would sell a unit sans solar that could be integrated with an existing 48 VDC system there might be more sales. Making it similar in function to the Grundfos water pumps that can be run off either/or AC/DC.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #26
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Texas Wellman wrote: »
    I guess my understanding gets a little fuzzy on this front. I understand that the unit is DC powered. I see it has a battery, charge controller, inverter (A/C to D/C), and MPPT. What you're saying is that once you have an inverter that goes from A/C to D/C you pretty much run into the same legal problems that any GTI would have?

    What I am saying is that if the unit ONLY accepted AC power and NEVER backfed back to the plug. The A/C would only be used when the solar power runs low, like if a cloud passes or at nite (and at nite you need much, much less cooling). If you ditch the battery and charge controller then put me in the "Seriously Interested" category.

    If it only accepted AC power it would be the same as any other, cheaper, air conditioning unit: AC only. Solar only comes in DC (from the panels) so to use it to power an AC device you need to "invert" it. Without batteries, this becomes a standard GTI. Since such can not power a load directly but can only feed to the common AC wiring, you're right back to an ordinary non-battery GTI system - complete with legal requirements.

    As a DC (motor) unit it could be run directly from solar panels with a linear current booster. Downside being it would only run when the sun shines. Fine for a water pump that can store water under pressure, but there's no practical way to "store" air conditioning. So you need some form of power available whenever the unit needs it. Now you're back to needing batteries.

    Running the DC unit from AC requires a power supply with its inherent losses. Again; no advantage over using a unit with an AC motor to begin with.
    Oh, and for those complaining about the price....Grundfos SQF pumps sell at about $1800. I do not get a discount on that either, the GP can probably buy one for the same cost I can. All they have is a motor and pump, with the motor having the inverter technology built right in. So at ~$2K you're ONLY getting a motor+pump+inverter+MPPT. This price does not include the wire, pipe, panels, or interface controller (which can be real simple or really fancy). And they've been making and selling them for 20 years. Now figure having a compressor, condensor, fan, coils, refrigerant, battery, inverter, MPPT, charge controller. I can easily see where the inventor may not even break even at $3k for such a small run.

    Well the A/C unit itself is probably around $800 worth, so for $2,000 you get panels controller and batteries. Not bad, if it's sufficient to run the unit where you live. Naturally when the system design is dedicated to one use there is some cost advantage over one designed to meet varying uses. The irony of the panels losing power due to the heat the A/C is trying to overcome is obvious.

    I think he's got about 3/4 of a good idea. :D
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #27
    Re: The Kingtec K25Z-4 Solar Air Conditioner
    Texas Wellman wrote: »
    I guess my understanding gets a little fuzzy on this front. I understand that the unit is DC powered. I see it has a battery, charge controller, inverter (A/C to D/C), and MPPT. What you're saying is that once you have an inverter that goes from A/C to D/C you pretty much run into the same legal problems that any GTI would have?

    What I am saying is that if the unit ONLY accepted A/C power and NEVER backfed back to the plug. The A/C would only be used when the solar power runs low, like if a cloud passes or at nite (and at nite you need much, much less cooling). If you ditch the battery and charge controller then put me in the "Seriously Interested" category.

    You have hit on a point of great importance and frustration, so let me try to go into more detail than Coot did.

    You have a compresor motor which runs indirectly off DC, in that there is a DC to AC inverter which delivers the right voltage and frequency to the motor for whatever partial load it may have. But internally the motor is running off variable frequency AC, just as it would in an AC powered inverter driven mini-split unit.

    So the only thing connected to the motor is the inverter output.

    Now to get the input DC to the inverter (from the battery connection at all times), you have two separate systems: DC coming to the battery from the built-in solar PV CC and DC coming to the battery from what is in effect an AC-powered battery charger. The only interconnection between the two charging systems is the DC connection to the battery.
    And it is easy to make sure that DC flows only in one direction by using diodes, so there will be no way that one could possibly backfeed into the other. Not to mention that backfeeding the battery charger's output would not produce AC at its input. (There are a very few CC/Inverters, Xantrex in particular, which can work this way, but they are not relevant here)

    Unfortunately, there is no similar simple way to limit the direction in which power flows when you connect two systems together on the AC side. That is why a GTI's anti-islanding circuitry is both complex and all-or-nothing. And why what we call AC-coupled systems are so tricky to design and manage.
    SMA SB 3000, old BP panels.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #28
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Let me re-phrase-It only accepts A/C power if the D/C power is insufficient, i.e. a cloud or outage or nightfall. And I know this can be done because that is what the grundfos sytem does. It uses D/C power from the panels and when that's not available it automatically swaps over to the A/C source, whether that is a generator or grid-tie.

    No, you cannot "store" Air-conditioning, but on the other hand, when the sun is shining the most is when you need the A/C the most. I am aware that there are inherient losses going from A/C to D/C, but you're going to have that even with a regular grid-tie system, and you're going to have the same heat losses regardless of the output (GTI, Off-Grid, etc).

    And as for the "$800" dollar worth of A/C, go look up a 16,000 BTU window-style A/C and tell me what the SEER factor is. My bet is that you cannot find one higher than 10, maybe you might see one at 11. 1970's efficiency in the 21st century. If I'm not mistaken, these units have a SEER of up to 16, which can easily compensate for the inverter efficiency losses.
    Cariboocoot wrote: »
    If it only accepted AC power it would be the same as any other, cheaper, air conditioning unit: AC only. Solar only comes in DC (from the panels) so to use it to power an AC device you need to "invert" it. Without batteries, this becomes a standard GTI. Since such can not power a load directly but can only feed to the common AC wiring, you're right back to an ordinary non-battery GTI system - complete with legal requirements.

    As a DC (motor) unit it could be run directly from solar panels with a linear current booster. Downside being it would only run when the sun shines. Fine for a water pump that can store water under pressure, but there's no practical way to "store" air conditioning. So you need some form of power available whenever the unit needs it. Now you're back to needing batteries.

    Running the DC unit from AC requires a power supply with its inherent losses. Again; no advantage over using a unit with an AC motor to begin with.



    Well the A/C unit itself is probably around $800 worth, so for $2,000 you get panels controller and batteries. Not bad, if it's sufficient to run the unit where you live. Naturally when the system design is dedicated to one use there is some cost advantage over one designed to meet varying uses. The irony of the panels losing power due to the heat the A/C is trying to overcome is obvious.

    I think he's got about 3/4 of a good idea. :D
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #29
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Grundfos does it with their SQF. No need for red-tape, bureaucrats with their inspections and codes, paying an electrician whether you need one or not, or any other non-sense. Just plug and play right out of the box, and you're doing it legally.

    Oh, and BTW, the avg. homeonwer uses about $10 of electricity per month on a regular well pump, yet there are lots and lots of folks on here looking at putting in a solar-powered well pump with grid-tie capabilities.


    inetdog wrote: »
    You have hit on a point of great importance and frustration, so let me try to go into more detail than Coot did.

    You have a compresor motor which runs indirectly off DC, in that there is a DC to AC inverter which delivers the right voltage and frequency to the motor for whatever partial load it may have. But internally the motor is running off variable frequency AC, just as it would in an AC powered inverter driven mini-split unit.

    So the only thing connected to the motor is the inverter output.

    Now to get the input DC to the inverter (from the battery connection at all times), you have two separate systems: DC coming to the battery from the built-in solar PV CC and DC coming to the battery from what is in effect an AC-powered battery charger. The only interconnection between the two charging systems is the DC connection to the battery.
    And it is easy to make sure that DC flows only in one direction by using diodes, so there will be no way that one could possibly backfeed into the other. Not to mention that backfeeding the battery charger's output would not produce AC at its input. (There are a very few CC/Inverters, Xantrex in particular, which can work this way, but they are not relevant here)

    Unfortunately, there is no similar simple way to limit the direction in which power flows when you connect two systems together on the AC side. That is why a GTI's anti-islanding circuitry is both complex and all-or-nothing. And why what we call AC-coupled systems are so tricky to design and manage.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #30
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Yes, you can definitely have a DC unit draw from an AC source if the DC is insufficient. I plan such systems frequently.

    The point is you are then converting from AC to DC to variable frequency AC and every time you change power types you lose some efficiency.

    As it is, having that solar equipment dedicated to running the A/C works. Switching over to AC when needed adds complexity and inefficiency. How much better to have the DC as the constant power source by storing the power in batteries (which is what the original plan does).

    And yes, lots of people come on here looking for off-grid sources to power all sorts of things. It can be done, no doubt about it. Whether or not it makes sense to do so is quite a different situation. Not just from an economic POV either.
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  • Texas Wellman
    Texas Wellman Solar Expert Posts: 153 ✭✭
    #31
    Re: The Kingtec K25Z-4 Solar Air Conditioner

    Absolutely you are losing some efficiency going from A/C to D/C, just like when you are going from D/C to GTI A/C. It works both ways, does it not? So then I guess all the millions of people running GTI should just quit the game then? I just re-looked at the literature, the SEER is up to 18. That's better than 99% of central A/C's in this area. Certainly better than anything other than geo, and there are very, very few geo units here.

    I think you are just looking at this from the wrong angle. Of course it's more efficient to draw the power from the batteries or directly from the sun or whatever. And then you've got to maintain the batteries, and pay for them, and store them, and mount them. Pull off your scientific glasses for just a minute and look at it from a practical stand-point.

    I see from your location that you are in BC, Canada. I'm betting that Air Conditioning is not that big of a deal up there. I once had several friends from Canada who had no AC in either their homes or cars. I assure you that is hardly an option here in the South.

    We recently had a major hurricane run through this area, would you care to guess how many people were running air-conditioners for their homes (window-unit types) via generators for weeks on end with gas at ~$4+ per gallon? One person I know was spending $60/day to run his generator and running his window AC was a major factor in that. Sad as it seems, people in these parts simply will not live without AC.

    The first time a hurricane knocks the power out for a few weeks this unit would pay-back the cost almost immediately, even without figuring in the normal savings throughout the year. Maybe not in a dollars/cents way, but in the "glad I've got it" way.

    Cariboocoot wrote: »
    Yes, you can definitely have a DC unit draw from an AC source if the DC is insufficient. I plan such systems frequently.

    The point is you are then converting from AC to DC to variable frequency AC and every time you change power types you lose some efficiency.

    As it is, having that solar equipment dedicated to running the A/C works. Switching over to AC when needed adds complexity and inefficiency. How much better to have the DC as the constant power source by storing the power in batteries (which is what the original plan does).

    And yes, lots of people come on here looking for off-grid sources to power all sorts of things. It can be done, no doubt about it. Whether or not it makes sense to do so is quite a different situation. Not just from an economic POV either.
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