A Siimple PV system just to run a Dehumidifer?

[PastTense]

Looking at my household energy use, behind space heating and at about a fourth of my total household energy use is running a dehumidifier for my basement. It basically runs all the time except for a while in the winter when I shut it off. It uses 522 watts, at 120 volts.

Suppose I wanted a PV system which would run just when the sun shines (no batteries). The humidity would thus build up over night or I might manually switch to the grid system on cloudy days.

What would it take to do this?

What about a more complicated system with automatic switching to the grid system?

Thanks.

[ghurd]

Yes, simple.
But it does need a battery.
And a huge pile of money.
Maybe 2 or 3 huge piles of money.

120V means it is AC.  It needs an inverter.  Compressors are notoriously hard to start on an inverter, so it needs a huge inverter.  The Chinese 1000W $99 special ain't gonna do it.

Solar, and an inverter, means it needs a battery.

522W means it needs a whole lot more solar panel than that.  Maybe 4~5KW of PV? ('Runs all the time')

522W of AC powered from solar panels also means it needs a big (BIG) battery bank.

'Runs all the time' means it needs an LVD to protect the batteries, because the one in the inverter is set to go LVD way to low to be good for the batteries.

Could put some kind of an inverter to grid switch on it, but it would be kind of complex (or expensive).
Could put some kind of grid assit on the battery, but that is inefficient.

"Summer"?
Is it hot where you are?  Do you use any A/C at all?
I expect it would be more efficient to run a very small window A/C unit.  Maybe not.  Just a thought.
G-

[DanG]

Your 522 watts at 120 volts is running current - the surge current to start the fan motor will be 3-5 times its running current, probably around 100 watts - and the surge to start the compressor, even with a soft start, will be 3-5 times running current which may be around 400 watts. The timing on those two rarely happen simultaneously so you'll need 1500 or even 2000 watts minimum inverter sizing to cope there. The raw DC current surge is most easily handled by batteries, you're not going to have 1750 watts of solar panels just waiting for the dehumidifier to start.

Money would be better spent trying to reduce - eliminate the paths ground water is taking to reach your basement - channeling roof runoff twenty, fourty feet away from the house, changing the grade of the soil to a similar radius, digging out the top soils and putting in plastic membrane to channel water to dry-sumps X number of feet from your house foundations, coating the foundation walls with water proof barrier and adding insulation, digging sump channels around the perimeter of the basement floor and adding half-pipe channels and gravel to route liquid water to a sump-pump....

[Beaufort]

I can confirm that my dehumifier doesn't work on a 700W rated MSW inverter (1800W peak).  It just runs at a lower speed and doesn't even try to kick up the compressor.  Not sure if it's due to MSW or the startup current.  I suspect that it's because of the sine wave and typical compressor motors don't play nice with funny waveforms. 

I think someone should direct-drive a compressor using wind.  Just guessing, but a large drag VAWT might be able to overcome the stating torque...maybe switch it over to a higher ratio when it gets going.  I don't like AC and dehumidifiers running all the time either, and the poor VAWT might just be a good fit.  Naah, won't work.

[Clifford]

Do you have Grid Power?
Do you need to run it when the grid goes down?

If you have grid power...
Just plug it into the grid.

Set your panel as a grid-attached system.
100% (well...  about 95%) of the solar power gets pushed up onto the grid.
You probably should get inspections and notify the utility company.

The problem with grid attached systems is that many of them have nothing when the power goes out...  so it is only half effective.

If you are off-grid...
You can buy 8000W/16000W inverters on E-Bay for relatively cheaply, or anything up to that size.  I was welding with mine.  
I don't think the Damn Chinese thing ever had its base voltage set properly.  And, the biggest problem is that the instantaneous voltage drop with some devices would kick it below the low voltage cutoff and it would shut off.  It would work reasonably well when I configured my batteries for 14.8V, but it also had a high voltage shutoff so I couldn't go too high.

You can't run your batteries flat though.  So, you'll need adequate solar capacity to keep them up.  Are you running this in the winter?  Do you have sunlight in the winter?

It would be interesting to take a dehumidifier apart someday.  It sounds like it is running a compressor like a refrigerator or heatpump.  Perhaps one could install a 12V motor.  Or, replace with an adsorption heat exchanger.

I was thinking of a sealed ammonia/water or lithium bromide/water system.

But, if the goal is to dehumidify...  then no sense using a salt to pick up water to refrigerate...

So...  here is an idea.

Take a tube and pack it with your favorite desiccant.
Design an air recirculation system so when it is cold... you blow air through your desiccant & back into the area being dehumidified.  
When it is hot...  blow air through the desiccant and outside (source of the air?)

I can almost imagine a system that would work on a parabolic trough collector.

Now...  if you kept the desiccant pipe inside the house, all you would need is solar (or wood) heated air for the regen cycle.

At least in theory it should work.  

Or...  hmmm...  there are possibilities.
Assuming you have warm air inside and cold air (or ground) outside...  perhaps you could use that as part of your condensation (or regeneration) cycle.  I'm kind of thinking of a very low volume vacuum pump for the regen with a condenser in the cold outside.

[Opera House]

I basically do this now, except I run a chest fridge.  You do need a battery but it could be just an old car battery just for starting power which will be about 90 amps.  I monitor the battery voltage and when it reaches a value of 14.5V it turns on a 10-15 minute timer that turns on the inverter.  No other controller is needed.  Basically a dump load controller.  Running current is about 9A and as long as the panels are under that there will be no problem.  Don't  try this with less than a 1500W inverter,

[wooferhound]

Are you trying to save money or save the planet. It normally costs more money and time to make your own power than buy it from the inexpensive grid power. If you are trying to save the planet, then carry on . . .