There's a handy midi-sized dehumidifier on sale at ALDI on 23rd Dec. for €39.99
As it is Peltier effect (like those 12v cool-boxes it will be silent (I think - though there might be a small fan.....) - AFAIK these are not as efficient as normal dehumidifiers on the other hand they may be less likely to go wrong, are quieter (you could use them while asleep perhaps, if on-site) and a side benefit of dehumidifiers is the provide a little bit of heat (more efficiently than heaters - dehumidifiers are heat-pumps!).
I wouldn't be at all surprised if these units are 12V with a mains adaptor - it doesn't say this though.
I used a dehumidifier in my van a lot as I was sleeping in it 4 days a week last Winter while in College. It is stunning to realise how much perspiration we give off each night! (and that's just me on my own !)
Definitely worth having a dehumidifier for the van. Nice find.
It will not provide heat however as the peltier is heating and cooling the same body of air the nett heat product is effectively zero. In order to provide heat it would need to have the condensing side outside the van and the heatsink inside the van thus dehumidifying mother nature.
Hmmm.... yes you are quite right about the "heatpump" aspect - since it is not taking heat from the air outside the van, and is, as you point out, heating and cooling the same volume of air - my bad!
If I want to be picky, though, if you consider the unit as a black box, it is going to consume whatever electrical energy is delivered to it over the power cable (maybe 20 Watts or so?) and thus will produce a nett heat gain exactly the same as any other 20 W electrical item so dehumidifiers do 2 jobs - remove moisture and add a little heat, though probably not enough to ward off freezing!
Seems these are only usable above 15 deg C and only usful for very small areas - see here http://www.meaco.com/guide.html
Hmm.. that's worrying:
I was hoping they were more like the dessicant ones they use in keeping boats dry - those work down to near zero.
At 15 degrees - that's really not much use for say overnight use - outside in Ireland will always be less than 15 degrees....
Think I'll give this a miss - have to watch for some good deals on a 'normal' one from B&Q or Argos in the New Year.
If I had the dosh I'd probably go for the Meaco one for €199 at CH marine (and other places I guess):
The 15 celcius limitation is common to compressor dehumidifiers too due to icing, you'd need to spend a lot for a defrosting one. Theoretically I suppose you could reverse polarity the peltier for a short period to defrost it.
so what happens if you use it under 15c?
below about 15' its just completely ineffective, as in it goes through the motions but doesnt dehumidify.
I'm resurrecting a year-old thread just to point out that this ALDI dehumidifier is on sale again on Dec 29th 2011.
However as people have pointed out earlier in this thread it seems that it would NOT be suitable for use in a camper parked outdoors at an ambient temperature of 15 deg or less (i.e anywhere in Ireland in winter).
It is 3 years on now. aldi are at it again.
I got one of the MIDI dehumidifiers today.
60/ 65 watrs. not cheap to run for 400 theoretical mls per day.
It is not suitable for outdoor winter temperatures as I found out..... It freezes over, continues to freeze, and I think then draws substantially more power. It may have been co-incidence that my almost new leisure battery died completely in 2 days of the de-humidifier freezing over, but I wouldn't like to put it to the test again. A tray of crystals for me in future!