Converting a laser beam to electricity with photovoltaic cells

Ant1Vanden

Hi, I'm new to this forum so plz don't get mad if this post is in the wrong place.

I have a laser beam pointed at a solar panel (regular PV cells) and the current comes out as expected on my oscilloscope (small waves varying like pulses between 0.45 and 0.50 V regularly). I tried rectifying the current with a full wave bridge and then simply a diode but I can't seem to get a DC output. Any insight? Does anyone know where I can find some PV cells more suited to a red or green laser?

Any help is strongly appreciated
Ant1

davenn

Hi, Welcome to the forum

well you are going to loose ~ 1.5V through the diodes of the bridge. So therefore your tiny voltage being produce is going to be lost (dropped across the diodes)

the cells are going to be much more efficient under sunlight and you dont need a bridge rectifier, the cells produce a DC voltage anyway :)

cheers
Dave

Ant1Vanden

I think in that case I'll scale up the model I'm designing in order to make the 1.5V less significant. Still are there cells that would be more suited for lasers?

Thx
Antoine

davenn

I think the real problem is that the cells are manufactured to respond best to strong bright white light. The Red (assuming (green--- it doesnt really matter)) light from you laser is so pinpoint and fainter than the sun.

cheers
Dave

Ant1Vanden

That's my question, are there cells made for lasers?

davenn

I wont say no, just I have never heard of them. They are too busy designing better and better cells to work in sunlight :)

Ant1Vanden

Thx for the help:).
I think I'll just use 10V cells and stronger laser

cjameshuff

Solar cells give DC output. There's no possible benefit to putting a rectifier after them. If the output is pulsing it's because the laser is pulsing, and you need to smooth it, not rectify it. Add some capacitors across the solar cells to filter the output.

Ant1Vanden

@cjameshuff, thank you very much!! Works perfectly, although the solar cells aren't very efficient (I put in 10V and get 1 out).

cjameshuff

It's true that solar cells aren't very efficient, especially when not designed specifically for the light source, but output voltage versus the voltage used to run the laser isn't enough to measure efficiency. 100 cells of 1/100th the area in series would give you 100 V output but 1/100th the current with the same (resistive) load, the efficiency at converting power would be no higher.

Also, your laser really takes a 10V power supply?

pallidin

Uh... I don't understand any possible benefit from this.

It takes electricity to power a laser, and the power generated from the solar cell is MUCH less than required to run the laser. So, what's the point of even doing this?

Enlighten me(no pun intended) if I'm missing something here...

cjameshuff

Simple: the photovoltaic collector doesn't have to be located where the laser is. Wireless power transmission, at fairly decent (~50%) efficiency when high efficiency cells designed for the laser wavelength are used and scalable to higher powers than other techniques. There's several situations where not having to use cables would be worth the efficiency loss.

Dr Lots-o'watts

Here's something:

http://gentec-eo.com/Content/uploads/downloads/4-Optical_Detectors/4_PH/1-Documentation/1-Specifications_Sheet/PH_2011_V1.01.pdf

Ant1Vanden

I'm using this set up to power a small remote controlled helicopter (requires about 5V) at a distance, to allow it to stay in the air indefinitely (i'm not quite there yet, but the cells is lighter than the battery that it's replacing). There are obviously several applications for this technology such as to create a telecommunication network easily in a remote area, or have a drone surveil a military base without ever needing to land and refuel...

@cjameshuff yeah it's a 'home-made' laser (well I assembled parts according to instructions), the laser isn't really a problem - I live in Hong Kong and they sell lasers of different size and shapes almost at every street shop...
@Dr Lots-o'watts thx for the link, I'll look into it.

cjameshuff

That's a detector, not something for handling any amount of power.

Large area photovoltaics suitable for converting light to electrical power, but designed for a specific wavelength band other than sunlight, are certainly technically feasible, but the demand is almost nonexistent right now, cells generally being designed to convert as much sunlight as possible at the desired price point...such a thing would probably be a custom part, and thus quite expensive.

I've poked around a bit, but they generally don't even give any sensitivity curves in the data sheet, just the output power under various lighting conditions. This information might be available if you ask the manufacturer...you may also get some free samples this way. You're probably best off trying various solar cells to find one that works well. There's some information out there on general performance of different types, for example: http://www.greenrhinoenergy.com/sola...s/pv_cells.php

Look at the "Spectral Sensitivity" graph. Going by their graph, amorphous silicon would be best in the green range, crystalline silicon deep in the red-infrared. The text somewhat contradicts the graph, though, I suspect the GaAs and a-Si may have gotten swapped.

Ant1Vanden

I've looked around quite a bit and found this:
http://jxcrystals.com/4sale5.pdf
The cells are suited for what I'm doing but I need to place a minimum order of 2000 US $ :S

pallidin

I see. Well, I would first start with determining the POWER(watts) required by your helo.
That's voltage times current. Just saying 5 volts is not enough. The important aspect is how much current is required.
Multiply each and you get a figure in WATTS.

Do you by chance happen to know how many watts are required to run your helo(with the battery)?