Monday, August 4, 2008

Paralyzed by Obstacles (i.e. whining)

(throughout this entry substitute "can't find at a reasonable price" for "can't find" and "free or under $40" for "reasonable price")

The next stage in the parabolic solar collector thing is to have the fluid circulating. I want to have it run through the collector, then down a hose into a tub of water and then back. Measuring the heating rate of the water will give me a better value for the power.

For this, I clearly need a pump. And can I find a pump? Clearly not. For simplicity, I think I want one that has garden hose fittings on both ends. Sump pumps usually have that on one end, but the other end doesn't have any fitting at all. (Maybe I could disassemble one to find out, but I can't find any to do that with either.) I bought a drill pump for like $6 but it was too wimpy to be useful.

Not that it has to be that powerful. According to the back of my envelope, I only need about 60 gph in the worst case. Typical sump pump numbers are 10x that. I could probably do it myself by putting a squeezable diaphragm inline and stomping on it. What a lot of work, though.

But I have feelers out on craigslist and freecycle, so in the meantime how about something else? I know, I can try to make a much larger stirling. What'll I use for the piston? Oooh, brill idea: a cut off bike pump!

Take 2: And can I find a pump? Clearly not.

Maybe I'm just too cheap. Or maybe I haven't figured out the right workaround. Or maybe I'm asking for too much. All of these questions (plus a couple other things I'm stopped on but aren't worth describing) has my brain in vapor lock. I am unable to move on anything.


  1. fish tank supplies? temperature may be an issue, but the good junk shed should have fish tank stuff.

  2. But do aquarium pumps have fittings on both ends? Forget the size--I can't figure out some conversion. I just need a fitting! Sump and aquarium pumps generally just sit in the water and suck it up through an open tube or a filter or something.

  3. My aquarium pumping is not a closed system. I don't know something specifically that will work for you, I just wanted to mention the idea.

    Another idea -- the systems they use for water cooling PCs.

    A third idea -- while it won't transfer heat as well, you could have a passive system. output of your heater connects to a hose that rises up to your water bucket. Input to your system is from the water bucket to a point below your heater and then back up to the input. Hot oil rising, cool oil falling will cause some small flow in this manner.

  4. I looked into the water coolers but they are pretty expensive. Or at least I thought so back when I thought I had tons of options. Maybe they'll look better now. Thanks for the reminder.

    Do you know how well water or oil circulates passively? I don't have a clue. I think my calculations showed I'd need a flow of something like 50 gallons per hour at around 200°F. Not a huge amount, but maybe more than convection alone can provide.