1904 experiments with solar energy
Here's one for all of us who, in our childhood, set dry leaves on fire with a magnifying glass. I'm putting this here more as a curiosity than anything else, since I can't say I have personal experience or intentions with this device (!) and I doubt anyone here does either. But I just cannot resist.
The picture is from a collection of photos from 1904 in my city. A Portuguese man brought his sun ray concentrating device for demonstration. The huge device was being called a pyrheliophor. It took six months to set it up, including 6,117 5 X 10 inch mirrors. It tracked the sun, using a clock. It produced over 7,000 degrees F, said a NY Times article.
I think in this photo, it is not yet complete. But in the pdf link below I think think completed construction is depicted in the middle picture. The article in the pdf gives credit to previous experimenters with solar energy concentration-- if you are curious.
Sat, 12/10/2022 - 09:40
Some folks took that kind of idea and ran with it
Here's a project built in the 60s in Southern France -- the image is from https://en.wikipedia.org/wiki/Odeillo_solar_furnace
For reference, the parabolic mirror there is a bit taller than the Statue of Liberty (as in the statue itself, not including the base it's on).
Mon, 01/02/2023 - 10:38
Concentrating solar collectors are just the thing you need...
... when you want high temperatures without fuel, and don't really care whether it's going to work on any particular day or hour (weather dependent). Other concentrating collectors that I've seen have usually been round (or trough-shaped), but all that's really required is a surface that can be cut out of a paraboloid, not necessarily with symmetry. This one reminds me of the Ku-band satellite TV dishes, that have the feedhorn at the edge (so they don't block any of the aperture).
As far as total heat collection goes, a flat plate can be just as good as a reflective dish, though it can't reach the high temperatures of a dish. If we're going to run a heat-engine, high temperature is important for efficiency (see Carnot Cycle), but if we just want human-scale temperatures, it's not important to start with high temperatures.
Thanks for posting!