1 mm^2 PV Cell

Solar calculators are cheap, as are those LED garden lights. A small polysilicon PV probably costs pennies in production.

What's really surprising -- no one has even commented on this either

-- is the size of the smallest micro electronic item is still as large or larger than DARPA's insect drones.

It's as though everything sold to consumers _must_ have a key pad, buttons or switches that require cm^2 of surface area.

How this mentality got grandfathered in is a mystery. Garden lights have no buttons or size requirements so there is no reason not to miniturize garden lights for Dollar Store "Glowing Sand" or confetti.

In that case the LED, PV and battery would be printed up on paper and cost almost nothing.

Bret Cahill

Different colors could be used to "paint" on the sides of buildings.

Bret Cahill

There's already glow-in-the-dark-paint.

When I type "glow" into Google's search field, the first suggestion to pop up is "glow in the dark paint".

It won't glow all night w/o UV or other illumination.

Rail roads won't light up their rolling stock with garden lights because it would get stolen. Something the size of sand would be too time consuming to vandalize. Graffitti artists would have to paint the entire box car to blot it out.

Box car artists might even turn to using the PV_LED-battery sand themselves. This stuff could be printed up on huge sheets and then cut into little bits so all they'd need is some spray adhesive and a leaf blower.

Bret Cahill

Well, it looks like you have a business plan then. Time to stop posting and start building your company.

--
My liberal friends think I'm a conservative kook. 
My conservative friends think I'm a liberal kook. 
Why am I not happy that they have found common ground? 

Tim Wescott, Communications, Control, Circuits & Software 
http://www.wescottdesign.com

This is nothing less than the next phase of the microelectronics revolution.

Bret Cahill

"A long habit of not thinking a thing _wrong_ gives it a superficial appearance of being _right_ . . .."

-- The infamous incendiary Thomas Paine

The strontium aluminate stuff is impressive, 10:1 or so better than zinc sulfide.

People in remote villages could leave sheets of that outdoors and take them in at night as usable illumination. No batteries to degrade.

I wish there was a really good glow-in-the-dark stuff, but it's probably physically impossible.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

Scaling down garden lights might go as far as originally hoped for the simple reason PV energy/day ~ surface area, while battery energy /day ~ volume.

Battery box energy density would have to be 25X higher than a garden light at the 1mm characteristic length.

Bret Cahill

Just make it into an impedance matching exercise. Like your imaginary wind-powered car that tapped power off one wheel to travel downwind faster than the wind that pushed it.

The car wasn't mine and it wasn't imaginary. It was silly.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

Fun in the father of invention.

Bret Cahill

I would ge even further and make it a quasi Law of Thermo

It's the same energy storage problem as micro garden lights. The only material / battery / super cap that could store enough energy would be a high explosive much higher than anything except nukes. Li-ion is probably the limit and has been misleading as to future breakthroughs.

The only thing that would put out enough light all night or keep drive trains turning would have to be air breathing.

Either you burn something in air or you sit in darkness at night.

Bret Cahill

in

A single D-cell would get you through the night, powering enough LEDs to read a book or study for school or cook your dinner. And a D cell isn't explosive.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation

ors and take them in >> at night as usable illumination. No batteries to de grade. >> >> I wish there was a really good glow-in-the-dark stuff, but it' s probably >> physically impossible. > >I would ge even further and make it a quasi Law of Thermo > >It's the same energy storage problem as micro gar den lights. The only >material / battery / super cap that could store enoug h energy would be >a high explosive much higher than anything except nukes. Li-ion is >probably the limit and has been misleading as to future breakth roughs.

read a book or study for school or cook your dinner. And a D cell isn't exp losive.

A book light maybe but cooking 200 gms of rice? No way.

Back to the OP issue of scaling down garden lights to coarse sand size ~ 1 mm^3:

The rechargeable AAA cell has a volume of 4300 mm^3 and the PV is 30 mm X 3

0 mm or 900 mm^2 of photo voltaic.

Reducing the PV area and battery volume by 900 results in a 5 mm^3 battery.

If the battery was printed 1 mm thick on a sheet the battery area would be

2.2 mm X 2.2 mm so if it existed cheap 3% efficiency PV would be just as go od at keeping the light on all night. 2.2 mm X 2.2 mm X 2.2 mm cubes would be more like small pebbles than coarse sand and only put out 100 microwatts of light maximum.

Bret Cahill