Rob Cockerham happened upon a crew setting up an outdoor ice skating rink and took the opportunity to find out how it's done. It turns out the whole thing rests on a series of tubes.
The ice was to be kept frozen with very cold liquid flowing inside the tubes. There was 40,000 ft of tubing in the rink, filled with 1,620 gallons of water mixed with propylene glycol to a 35% solution. These were the numbers off of the top of his head, but 5 ounces per foot of tube sounds about right to me.
Propylene glycol is antifreeze, so in essence the water can circulate at a temperature much lower than the freezing point of water, which sucks the heat from the water outside the tubes, turning it to ice. Read the rest, with plenty of pictures, at Cockeyed Science Club. Link
Comments (1)
I've still never seen one of those $100 computers that were supposed to take over the world a few years ago.
The last time I checked it's about 350 for the two.
This on the other hand will blow up in price if, and that's a big if, it comes to the states.
Sad.
It may go the way of the Indian Tata as far as the price going out of reach of those who really need it after the safety commission and good old american import/export taxation.
Just like the OLPC fiasco - first it was $50/ea then when the prototype was released it was $99/each and then reality set in and it's a $250 piece-o-crap that nobody wants and can easily be replaced by numerous Netbooks off the shelf at Walmart for less money.
Besides - there are more studies showing that technology interferes with learning then there are that shows it helps.