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Cool things to do with old satellite dish
Anyone have any ideas for a cool project involving an old school satellite dish? It's maybe 6-8 feet in diameter. I've seen some stuff like make an art project or an umbrella but I was hoping to use it for picking up signals again. I don't imagine I can use it to get TV but is there any satellites from universities or maybe hobby cube sats that I might be able to use?
Apologies if this is in the wrong topic it was this or ~space.
Probably fits better under ~hobbies or ~space. You can convert your satellite dish into a radio telescope
https://www.technologyreview.com/2014/07/23/171978/how-to-convert-a-satellite-dish-into-a-radio-telescope/
Above article has technical details here: https://arxiv.org/abs/1407.3346
http://www.aoc.nrao.edu/epo/teachers/ittybitty/procedure.html
Related to above link: http://www.setileague.org/articles/lbt.pdf
https://hackaday.com/2019/10/22/a-miniature-radio-telescope-in-every-backyard/
http://www.arrl.org/files/file/ETP/Radio%20Astronomy/Build%20a%20Homebrew%20Radio%20Telescope-QST-0609.pdf
and do observations of things like the Sun, passing satellites (with visible relativistic doppler shifts), and even radio galaxies or black holes like Cygnus A.
Edit: I found the website I was looking for: https://radio-astronomy.org/node/248 This link has tons of good resources on the topic.
Oh damn that's cool and way more interesting than I expected!
If you're really dedicated, you can also use multiple to make a DIY interferometer. You hook up two or more and combine their signals to get the resolution of a telescope the size of the distance between them.
I recently discovered a YouTube channel called saveitforparts that has several videos doing just that.
I had one once that had a solid dish, not mesh. I spray painted it with chrome paint to make it reflective and point it at the sun. I used a thermometer to measure the temperature at the focal point. It got up to about 325 degrees farenheight. My plan was to put a water block there and use a steam turbine to generate electricity. I never got the chance to finish it, but it was a fun experiment. I think there are similar projects on YouTube.
size of the dish (lets assume he as a very old model of dish, which got up to 3 m in diameter, or 28.3m^2) (CORRECTED BELOW)
multiplied by the energy density of sunlight (lets assume about 300w/m^2, the value for the middle of the sahara, for most of the US it will be more like 150-200) (note that in most maps, including the figure Im using, this is averaged out across both day and night. Im using this map for these figures, and multiplying the kwh/m^2/day by 41.666 to get watts/m^2)
multiplied by the thermal efficiency of your steam stage. (heat engines, which all steam turbines are, have efficiencies dictated by the difference in temp between the hot side and the cold side. If we assume you are going from 325f down to the point where the water starts to condense, your thermal efficiency will be 14.5%, at absolute maximum, assuming no heat loss to environment, etc.)
multiplied by the mechanical efficiency of your turbine (also known as the isentropic efficiency) (lets assume 90%, seems to be the upper end, found on large power generation turbines)
multiplied by the efficiency of your electrical generator (lets assume 95%, which seems to be the upper end, found on multi-megawatt power station generators, so very much giving the benefit of the doubt)
this comes out to 1132w, or a bit more than a kilowatt, averaged out across both day and night. (CORRECTED BELOW)
this is of course, the absolute best case given the information given, not using any energy for pumps, using the generators electricity directly without having to convert it to local grid frequency and voltage, etc, and that the small turbine and generator they are using are just as efficient as the ones used in large power plants.
EDIT: to be clear, the above uses absolutely outlandish assumtions. Lets try something slightly more realistic:
dish size: 20 in dia (.5 m) (the larger of the directTV dishes)
solar irradiance: unchanged, assuming he lives in el paso, texas
carnot efficiency: unchanged, assuming hes still using 325F steam.
isentropic efficiency: 20%, wikipedia lists this as the low end of steam turbine efficiency, I guarantee you a little hobbyist piston steam engine will be lower than this
electrical efficiency: 80%, using a car alternator
total: 1.3 watts...
Yah, just go with a solar panel.
EDIT2: I just realized for the first calc I mis-interpreted a 3m diamater dish (7m^2) with a 3m radius dish (28.3m^2), meaning that even my optimistic estimate only produced 280 watts of power...
This is great! A kilowatt seems actually quite a lot. In real life situations you’d of course get way less, but it could still power a home alliance or two, no?
Yah. Keep in mind that that in the sahara desert, and with a dish so large I dont think it was ever made in anything but a mesh. Also, the last 2 efficiencies are very handwavey, and for non megawatt scales, should be more in the range of 20-50%, which due to how multiplication works, means youd actually be seeing somewhere between 350 to 50 watts, out of a 10ft dish, in the middle of the sahara desert. A solar panel will easily give 10x power per area, as cool as solar-thermal concepts are
Edit: edit to original calc incoming, with more realistic assumptions
Wouldnt be more efficient than just covering the pool in a black tarp, as the pool has more area exposed to the sun than the dish.
If you don’t do any of the wonderful suggestions that others have provided in this thread, you could turn it into a bird bath!
This might be a complete waste, but you could live out my childhood dream - turn that bad boy into the most kickass realistic Beyblade battle arena there is.