a PWM heat pump!

Discussion in 'General Electronics Chat' started by retched, Jan 12, 2010.

  1. retched

    Thread Starter AAC Fanatic!

    Dec 5, 2009
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    this is interesting. Fujitsu uses PWM to fake AC to achieve super efficiency on heat pumps and A/Cs. 20,000btu for under 20amps. Way less. you only need a 20amp breaker.

    Even if your not interested in air conditioning, read it for the AC to DC conversion technique and you can use it in you own projects. VERY good info.

    If you want a residential A/C and you are using batteries for solar, wind, water, power, this will help alot.

    http://www.fujitsugeneral.com/PDF_06/halcyon06_brochure.pdf
     
  2. 3ldon

    Active Member

    Jan 9, 2010
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    While this is new for residential systems, industry has been using VFD's for years to save money on HVAC.

    Thermal dynamic systems often have non intuitive efficiency curves, and that curve is 3 dimensional, you have evap, condenser temps and the load to worry about,
    You might be surprised what running your heat pump at 110 volts and 55 hz will do to your heating/cooling bill.
     
    Last edited: Jan 13, 2010
  3. retched

    Thread Starter AAC Fanatic!

    Dec 5, 2009
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    I agree. Commercial has used it for years. The exciting part, for me, was the fact that now it is available to home users.

    I think it is great that alternative power users can now have a part of there pie that doesn't lose more power to AC inversion. Also. the slow start compressor cuts the spike of start up that would normally result in big loss and expense of having to have an inverter that can handle it.
    [ed]
    I seem to believe that when using air-conditioning, for instance, you need to spend more on an inverter JUST to handle the start-spike.
    ^^^ Notice my confidence in the above statement

    I also think the basics of the design could help alot of us to use DC and PWM to help control our power losses in smaller cases. Even using the slow start principle for many other high spike situations.

    I'm interested in a little more behind this. Are you saying a positive or negative effect on the heat/cool bill?
     
  4. Duane P Wetick

    Active Member

    Apr 23, 2009
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    I've read with interest, all these schemes for improving cooling efficiencies of HVAC and other appliances and I will add some input on the subject. Back when NASA started looking at improving the operating efficiencies of the motors used in space flight is when the circuits started showing up with all kind of claims of efficiency improvements for a myriad array of houshold appliances. We built one of these circuits specifically to run a 2 HP refrigeration compressor in a commercial ice machine. There was a definite improvement in the amount of power used over a 24 hour period when the ice-maker was running; about 5-7% less...but at a cost. The result of the power savings was the ice-maker produced less ice over the period, about 5-7% less ice by weight because the cycle times were slightly longer to produce a batch of ice.

    We concluded that the circuit we used worked to only supply current when the compressor demanded current, but the tiny intervals between supply and demand all added up to prolong the ice making cycle.

    Regards, DPW [ Always remember that you are not going to live forever.]

    As long as these Heat Pump guys are willing to accept 5/60 less heating or cooling in their lives, there is definitely a power savings.
     
    Last edited: Jan 13, 2010
  5. 3ldon

    Active Member

    Jan 9, 2010
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    There is no current spike when you start the motor at 5hz and 10% voltage, the inverter need only be sized for 110% full load current.

    If you want to be able to keep the TV running while you start up the AC, then of course you need 500% surge capacity.

    Transformers and motors scale to the 4/3rds power, running a 10 ton unit at 33% duty cycle will consume less power than a 3 ton unit 24/7. (there are exceptions to this)

    Duane,
    There are 6 variables here, it isn't easy. Throw in a turbo expander instead of a capillary and now you have 8 variables. I have no doubt that you can save money by running a stock heat pump 10% faster or slower, but the fact that heat flow remains the same means that you could save more money by changing the volume of refrigerant to an optimal value, or finding a heat pump that is 10% larger or 10% smaller.

    Centrifugal water pumps are similar, their efficiency drops exponentially with RPM increase or decrease, as do jet turbines, taxing to a runway throttle is at ~30%

    You can gain a lot more by measuring exactly how much heat you have to move and correctly sizing the system to handle it rather than relying on electronics.
     
  6. retched

    Thread Starter AAC Fanatic!

    Dec 5, 2009
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    For consumer grade technology, PRE-bulit, buy and install, air conditioning systems, the technology helps a great bit. The sheets speak of avoiding high amp drains by variably running the compressor. All of the systems I have worked on had a all on or all off approach to compression. The only variable part was the blower motor.

    I agree with your point of efficiency by putting the refrigerant where it is need when. Thats why I thought of this as such a good premise for a home product. It allows compressor power savings at the begining and end thirds of the cycle. It would act as if you had a variable tonnage system. (power wise) It allows the compressor to vary the pressure on the liquid side. That allows the compressor (if 10% overcharged) to run 10% slower to get the proper temp refrigerant to the coil.

    I see that as a good savings. Also, this would be a VERY tough thing to do with a piston compressor, needing much more power to overcome the initial cycle, where a screw-type can curve out the pressure line.
     
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