crazedguy - 11-6-2014 at 07:52
I have been doing some reading and had a thought that possible would make an easy efficient solar converter.
You take something like Acetone in a container and get a parabola or a few mirrors. The mirrors point at a container of some sort, probably black or
clear and have micro flakes in it to ensure faster heating.
Now the big difference between this system is instead of using water, you use a Acetone or some other low boiling point fluid. Acetone boils at 133
which is fairly easily attainable from solar energy.
133 is low enough outside temp will allow it to liquify after turning to gas.
Is there a reason that all large systems use water other than its easy and cheap to get?
Is this an idea that makes sense to attempt?
IrC - 11-6-2014 at 09:03
I would prefer a system which was inherently safe in the event of failures even if it was not as efficient. Picture 1940's or 50's tenements and the
terrible suffering survivors endured when a refrigerator filled with liquid Ammonia sprung a leak while all were sleeping. An event which occurred so
often the system was done away with by law forcing the manufacturers to start using the far more expensive (at the time) Freons. Somehow I doubt
waking up on fire during an earthquake (or maybe it was just a seal failure from poor quality mass production) would feel much less painful than those
tenement people waking up with lungs full of Ammonia did. Even if your idea was valid I sure would not want to sleep in a house with many gallons of
hot Acetone on the roof.
Or am I just being paranoid?
crazedguy - 11-6-2014 at 09:11
Acetone was just a suggestion, unless there are no chemicals with a low boiling point. Alcohol has a lower BP but not quite that low.
Possibly Methanol with a BP of 151
[Edited on 11-6-2014 by crazedguy]
IrC - 11-6-2014 at 16:08
You have a good point, hopefully you did not perceive my reply as 'shooting you down', for this was not my intent. Finding substances with properties
which work for your idea is actually quite hard when safety considerations are included. One must always think of possible worst case scenarios, say
an earthquake wrecking your system up on the roof. Or a forest fire if you live in the woods. I mentioned the Ammonia concept as decades ago I had
experience with it. They were replacing old refrigerators with modern freon units and I had access to the surplus units. Needing a vacuum pump and not
knowing the danger (I was a stupid preteen at the time) I decided to cut the tubing. After narrowly escaping injury and waiting many hours before I
could return I did finally get my compressor. I think the outcome was overall positive since I started taking more time to understand the dangers in
my madsci quest before I did experiments in the future.
Anyway my point is one should consider a subject from all angles. Water has a fairly high specific heat, is inherently safe, and boils quite easily
from solar energy. You can melt asphalt with a low tech solar concentrator so I don't think going for low boiling points is all that critical if one
must risk fire or explosion just to find a better fluid. Have you considered adding regular car antifreeze since this would further increase the
specific heat and not add much in the way of danger to the design. Just a thought anyway.