Something from nothing

**nsaspook** · April 2nd, 2012, 13:21 PDT

Originally Posted by ggunn

Programmable gate arrays (PGAs) have been around for decades. They are useful for short product runs but they are very inefficient in terms of silicon real estate. They also run slow compared to optimized custom circuitry.

Correct, this proposed device would be very similar to a FPGA but would be photonic instead of electronic in nature with a speed and memory capacity far in excess of anything possible today. http://en.wikipedia.org/wiki/Quantum_optics

**SolaRevolution** · April 17th, 2012, 12:24 PDT

It isn't "something from nothing" but it is certianly getting something from what is now being wasted:

"Researchers are developing a technique that uses nanotechnology to harvest energy from hot pipes or engine components to potentially recover energy wasted in factories, power plants and cars."
http://phys.org/news/2012-04-nanocry...rs-energy.html

From the article:
"The ugly truth is that 58 percent of the energy generated in the United States is wasted as heat," said Yue Wu, a Purdue University assistant professor of chemical engineering. "If we could get just 10 percent back that would allow us to reduce energy consumption and power plant emissions considerably."

I've got a thermoelectric fan for my wood stove. It powers the fan with electricity converted from the heat differential between the base (in direct contact with the stove) and the top which constantly receives cooler air via the turning fan. Some heat is turned into work to move the air but it ends up making better use of the stove's heat by actively spreading it out into the room instead of just relying on convection.

It isn't something from nothing, but it makes better use of my cord wood without me having to provide any additional input. Using new technologies to harvest waste heat would be similar. I wonder how much more efficient a generator would be if the waste heat was harvested using nanocrystal coated fibers.
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Alex Aragon

**SolaRevolution** · June 14th, 2012, 23:25 PDT

Here is another new electricity source which comes from what was previously considered "thin air".
http://phys.org/news/2012-06-power-g...batteries.html

Could be used to power a light?
Cell phone charger?

-Alex

**ggunn** · June 15th, 2012, 6:27 PDT

Originally Posted by SolaRevolution

Here is another new electricity source which comes from what was previously considered "thin air".
http://phys.org/news/2012-06-power-g...batteries.html

Could be used to power a light?
Cell phone charger?

-Alex

Again, there's no free lunch. Whatever power the unit produces is ultimately made from resistance to movement in the knee joint. Whether it's noticeable or not to the wearer I don't know.

When I was a kid I had a little generator on my bike that powered a light. It mounted on the frame next to a wheel and had a little rubber roller that rode on the rim and spun its armature. I could definitely feel the drag from it. Of course, part of that drag was due to the low efficiency of the incandescent light; with LEDs it probably would have been a lot less.

**Cariboocoot** · June 15th, 2012, 7:36 PDT

Originally Posted by ggunn

When I was a kid I had a little generator on my bike that powered a light. It mounted on the frame next to a wheel and had a little rubber roller that rode on the rim and spun its armature. I could definitely feel the drag from it. Of course, part of that drag was due to the low efficiency of the incandescent light; with LEDs it probably would have been a lot less.

I put a diode and capacitor on mine. Couldn't resist tinkering even then.

**waynefromnscanada** · June 15th, 2012, 11:10 PDT

Originally Posted by Cariboocoot

I put a diode and capacitor on mine. Couldn't resist tinkering even then.

Hahaha Mine was before the days of solid state diodes, but it sure got a lot of use! We used to see if we could go fast enough to burn out the bulb. Never did, but did it ever get bright! lol

**niel** · June 15th, 2012, 21:10 PDT

why the diode? a cap is semi understandable. did they not rectify the output on the bike generator?

**waynefromnscanada** · June 15th, 2012, 23:34 PDT

Originally Posted by niel

why the diode? a cap is semi understandable. did they not rectify the output on the bike generator?

Nope, pure AC right from the single coil. The faster you went, the higher the Hz. If you hooked it to a loudspeaker, you could really make it scream :)
It would also work as a synchronous motor if you hooked it to a door bell transformer, but ya had to give it spin to get it started. Hahaha The things I did as a kid, and then failed to grow up

**john p** · June 16th, 2012, 0:20 PDT

before solid state diodes we only had selenium rectifiers. they were about 3in sq and about 1in thick. And from memory not very effecient. on a bicycle dynamo its doubtful if you would have got enough out to light a bulb. for audio/amplifiers/radios etc a "rectifier valve' tube was used. Not so good on a bicycle.

**waynefromnscanada** · June 16th, 2012, 0:37 PDT

The losses of trying to force current through a selenium rectifer would have drastically cut the overall efficiency of the system, and for what? Even a silicon bridge rectifier would cut the voltage to the bulb. A capacitor would likely bring the voltage back up, but you'd still have the losses of the rectifer, and when you only have about 3 watts to work with, and you had to produce it yourself while trying to peddle the bike, any loss would be unwanted. The "generator" did add a very noticeable load, but nothing young legs couldn't handle