Hello:

My son (age 10) is getting started on a solar power science project. Most of the kids are doing solar ovens, solar showers and the like but not my kid. Nope nothing that common for him. After doing some internet searches for solar power he ran across this site:

http://www.homepower.com/files/solarice.pdf

It’s a description of a solar powered ice maker. The construction of the device actually looks fairly straightforward. A good bit of detail work but overall I think he can do it with a bit of help. As far as I can see there is only one real issue. The refrigerant used is pure (anhydrous) ammonia. It’s kept under pressure in a sealed configuration. I’m looking for some advice from someone familiar with pure ammonia on whether or not using a small amount of this is a good plan for a school science project. Anyone ever use pure ammonia for anything? How hard is it to find this stuff? Am I going to get myself on some terrorist watch list for even asking about it?

Thanks for any help...

Originally posted by Steve0
Anyone ever use pure ammonia for anything? How hard is it to find this stuff? Am I going to get myself on some terrorist watch list for even asking about it?

I'm not a chemist but I'm married to one (http://www.mouseplanet.com/kkrock/) (his bio's on that page,) and he's sitting right next to me as I read this out loud to him.

He's used real ammonia before in an academic setting and the short answer to your question is: Not a good idea. First of all, it's very caustic, (inhaling it will cause really bad burns and other problems, for example.) It's really, really nasty stuff, much, much worse than household strength ammonia.

Second, you're probably not going to be able to find a source for it anywhere- it's a gas and therefore requires the ability to handle compressed gasses which is a non-trivial complication.

Doc suggests you find a new project.

Hope that helps, sorry to be the bearer of bad news,
Adrienne

Hello:

Actually I have found a laboratory supply house that carries it in small quantities for experiments. Typically it's used in farming applications but I don't really need a tanker truck full of it. I've also read a number of hazardous materials warnings on this and generally they say the same thing. Use some common sense, work in a well ventilated area, keep some water nearby for the gas to react with in the event of a leak, wear protective gloves and goggles rated for use with ammonia. We talked to the chemistry teacher up at the school and she’s O.K. with us brining in this project as long as the ammonia is a small quantity and carefully sealed.

I've also read that propane can be used as a replacement refrigerant for ammonia, but that's in a more standard compressor type setup. I have no idea if it would work in this case with the salt and I'm not careless enough to take a try it and see approach. Any thoughts on other refrigerants I could use that might be a bit less toxic? Efficiency is not a big deal here; we just need to be able to show a significant temperature drop.




Of course it's possible the school might have an issue with us bringing this project in.. :eek: