I have overwintered palms including robusta, filifera, yucca (tender varieties), chamaerops, trachycarpus, citrus (though NOT limes), and numerous other SUBtropicals in an attached (unheated) garage that must have averaged between 32 and 60 over the course of the winter--staying in the 40's on most of the coldest winter days. But my plants were not in the dark--there were windows that faced directly south. So, in answer to your question, it really depends. How cold is that room and what palms are we talking about? Sustained low temps (above freezing) over weeks can lead to the dead of a palm as readily as one night of temps below freezing. If you do try it with your hardiest plants, I would suggest you also invest in some flourescent lighting (they sell special fixtures designed to operate in colder temperatures). I would not recommend though, that you leave them in the dark for months at a time.

I would definindtly suggest you to warm the basement as most concrete will hold dampness,which will lead to rot palms need some source of light Palms do
not go dormant. I personally think if you do this you
will find a bunch of dead palms come spring probaly before.

get a cheapo "shop light" flourescent light fixture ($9.99 at Home Depot or Lowes) and some "grow light" bulbs, hang it from your basement ceiling & you'll be set. Just do absolute minimal watering and most palms will do fine till spring.

You could over winter palms indoors 2 ways, one is try to keep summer like conditions and keep them in growth mode ( lots of light and water , humidity and so on). Or two is provide minimal care to keep them alive but not growing much. I found the second way is cheaper. I keep most palms cool dry around 60-70 degrees and rarely water them. I keep a fan blowing slowly to keep the air dry and ciculating. most of my palms get just get reflected light from the windows. I do mist them once every 2 weeks with a spray bottle and soapy water to keep mites off and remove dust that may build up on the leaves indoors.I keep them out of direct sun light because that will cause it to dry up. When spring comes around you will have to gradually get them used to sunlight of they will sunburn. I hope that helps some.

Thanks for all of your help. I have a few grow lights that I use, so I will have to decide which palms are more important to me to keep them growing nicely over the winter.

Depressing topic when it's 92 out (here around detroit) having said that one of my labour day projects is to get my spare bedroom turned greenhouse ready. I do everything I can to give my palms all of the sun they need and can easily get temps in this room into the 70s when sunny out (no matter how cold outside it is. the requiremnts will vary depending on the palm but they are not like bananas if you keep them cool, cold, and or dark they will be in extreme distress.

Hi.. see the link of coco bonsai below
the instruction for coconut bonsai available there...

Here is a link that might be useful: coco bonsai

please put me on record as saying the coconut bonsai is a farce. done. I feel better having said that.