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Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
I get across this link : obviously it's not a nuclear reactor and it have a limited use but I like the concept ,a power cell base on this idea could reload batteries in very improbable location:like the catacomb of Paris, or be use to power a small beacon for very long time... I try to match the color from the phosphor to an absorption pick from different type of solar cell.does any one have some idea about it?
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Most solar cells are very inefficient at low power levels so you need to hunt out one that is good for this application. Some low efficiency polycrystalline cells used in garden lamps keep their efficiency at low light and are more efficient than common high efficiency cells for this sort of thing.
You should probably concentrate on getting as much light as possible on to the cell at the highest concentration you can before considering the wavelength.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
do you mean that the input vs output of solar cell is not linear? I know that amorphous silicon cell work great in low light situation but there efficiency is very small (10/100?) I south the difference came from the fact that outside ,when the light goes down ,the spectrum shift to the red,making low wavelength cell more efficient.
I found some tritium exit sign for 300 euro a piece on Internet ,they contain 5 vial of 25 cm long in it,my idea was to space them of 0.5 cm and to have two solar cell ,one on each side,with the tube in the middle...the efficiency will be small anyway but having a perfect match in between the light wavelength and the semiconductor gap should help...
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Did you try using a ceramic capacitor in parallel with the cell?
this ought to charge up slowly with even nanoamps of current.
Also, IIRC your average cheap silicon solar cell is appallingly inefficient at green wavelengths. You might be better off with a large area red LED such a Luxeon emitter, the efficiency of these can be pretty high as I have tested this with smaller diodes..
see
I did wonder if an interesting hack would be to find a large area emitter such as one from a surplus 1980's era calculator, parallel connect the diodes and install the tritium tube over it being careful not to damage the diode interconnects.
A bubble concentrator lens would increase the efficiency though, perhaps use the existing one from the calculator?
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
no I didn't try ceramic cap ,but that's a good idea,for the rest ,some semiconductor must work better than some other (depending on the gap)using led as receiver can help to determine it . I don't like the idea to use some light concentrator with tritium light source ,because this type of light is already very diffuse ,having a direct light path should work better.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I think a betavoltiac could be a better option...
3H emits beta paticles at an enegy of about 5keV, so if I am correct you'd need 6241000000000000000 decays in one second to make 1 ampere of current provided you capture all those beta particles. My 6" tritium lamp has an activity of only about 67gigabecquerels, so only 67,000,000,000 electons ae emitted a second: that's 10 nanoamps. Since tritium costs $50K an ounce it would cost quite a lot to make a 5kV 1A betavoltiac... so a tritium powered item isn't exactly economical.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
Grenadier wrote ...
I think a betavoltiac could be a better option...
3H emits beta paticles at an enegy of about 5keV, so if I am correct you'd need 6241000000000000000 decays in one second to make 1 ampere of current provided you capture all those beta particles. My 6" tritium lamp has an activity of only about 67gigabecquerels, so only 67,000,000,000 electons ae emitted a second: that's 10 nanoamps. Since tritium costs $50K an ounce it would cost quite a lot to make a 5kV 1A betavoltiac... so a tritium powered item isn't exactly economical.
Just my $0.02
I suppose a 5kw generator witch would be noise less ,caring 10 year of carburant and requiring no maintenance at all could have some interesting application but I am only interested by much smaller amount of power ,10's of a what would be very nice already,I like the idea of power-source witch would defied man time scale ,like a camera taking picture of a valley every days for 10 or 20 year(very poetics interest)also the perspective of having daily life object witch would not need battery replacement and who would stay operational no matter what .
however ,you are right ,beta-voltaic cell would be much more efficient ,I suppose it could be possible to use 2 mono-crystalline solar cell very close to each other and to let a bit of tritium in between,but I doubt the efficiency would be high ,as the cell itself would generate very low voltage.is there a set up hitch make it possible to use the 5kev as to get a 5kv output from the cell ? is it possible that in cell with low band gap like silicone cell ,the beta particle trigger the relize of more than one electron?
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