Powering circuits with light - Page 1
Forum section: electronics / projects

author: blueskull
author_rank: Unknown
timestamp: July 01, 2016, 07:15:40 pm
content: Is there a way to get ~2W of power from a laser carrying fiber?In other words, is there an effective way to convert 915nm or 808nm laser to electricity in a fairly compact device?I'm open to all sorts of suggestions, whether is is an optical-thermal-electrical solution or a direct electrical solution. If you think it is possible to miniaturize, mechanical solutions are also welcomed.I'm not constraint by budget, but excessively expensive and non prectical things are out of consideration such as UV lasers or turbo encabulators.Thanks,Bo, aka blueskll

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 08:06:09 pm
content: Yes it is possible.The fibre carrying the laser light needs to terminate in a beam splitter and spreader that illuminates an array of PV cells shaped in a ball around the beam splitter. A prism can be used for the splitter. It is important to fully illuminate each PV cell. The PV 'ball' is around 50mm in diameter.Fraser

author: m98
author_rank: Frequent Contributor
timestamp: July 01, 2016, 08:21:42 pm
content: Just wanted to suggest the same thing as Fraser. Just add a beam diffusor and a high efficiency solar cell. IXYS has some nice low cost and high efficiency cells, alternatively you could try to get Ga/As cells from a solar concentrator panel manufacturer.If cost and know-how are unlimited, design an MEMS stirling engine with an piezoelectric generator. Nobel prize granted.

author: Marco
author_rank: Super Contributor
timestamp: July 03, 2016, 11:10:08 am
content: Quote from: blueskull on July 01, 2016, 07:15:40 pmWhat does the energy have to bridge exactly that you want to do it optically?Is it just about achieving very low capacitance and very high insulation?

author: Kilrah
author_rank: Unknown
timestamp: July 03, 2016, 12:31:06 pm
content: Beam spreader and Peltier element coated with the proper matrial to best absorb the working wavelength? Compact and it seems you've got the cooling sorted.Gotta live with the low efficiency though.

author: Fraser
author_rank: Super Contributor
timestamp: July 03, 2016, 12:41:41 pm
content: Without knowing the exact scenario it is hard to come up with more ideas. Does the unit have to use fibre optics and light ? How about miniature hydraulics. If insulation is important, use transformer oil in the lines and drive a small impeller/motor combination. Hydraulics can be quite efficient and a motor generator can easily meet your power needs. Simple high reliability pump can push the oil around the circuit and flow may be controlled easily. You could also use a pneumatic system.Fraser

author: Artlav
author_rank: Frequent Contributor
timestamp: July 03, 2016, 03:36:59 pm
content: Why must it be light? What are the constraints?Would a plastic air hose work?If yes, try looking at an air turbine + generator.A turbine can be tiny - think dental drill head.And at these kinds of RPM the efficiency would be quite high.

author: Fraser
author_rank: Super Contributor
timestamp: July 03, 2016, 05:28:49 pm
content: If you have cooling fluid circulating through hoses to the device, you have a flow that can produce power via an in-line impeller that can drive a small motor or alternator. The triggering of the device is then done via fibre optic without the need to provide the actual device drive current. You would only need a few additional components and no additional pump. You can even build in redundancy with two impeller generators running in parallel.What is the duty cycle of the equipment ? If the device is not being continuously used, you could even use a reservoir capacitor of battery that collects energy from either a fibre/PV or impeller generator at a lower rate than the max energy needed when the device is being driven. I personally dislike relying on capacitors or batteries though due to aging issues.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: July 03, 2016, 06:06:23 pm
content: Thanks. I see your challenge now.What is the MTBF hours rating on the 8W laser running in continuous mode ? Reliability is presumably important too ?Fraser

author: Marco
author_rank: Super Contributor
timestamp: July 04, 2016, 03:02:09 am
content: Quote from: blueskull on July 03, 2016, 05:17:09 pmWhat is very high though? Up to a couple 100 kV insulation requirements aren't that onerous.A 100 kV cable has 2 cm diameter, so as far as I can see you should be able to do a loosely coupled transformer in less than 5 cm cubed for those kinds of voltages (2 pot cores gapped, vacuum impregnated with some sealant rated for high voltages).

author: Marco
author_rank: Super Contributor
timestamp: July 04, 2016, 04:53:01 am
content: Power transfer is a separate problem from signaling, what I described was for power transfer. You couldn't really use a loosely coupled transformer as a GDT.You could do the signaling with transformers too, even at ~100 MHz bandwidth, but that would not be worth the effort compared to optical signaling.

author: Marco
author_rank: Super Contributor
timestamp: July 04, 2016, 06:05:18 am
content: I wonder why I never hear much about output side powering of isolated gate drivers (so trickle charge during turn on, once all the modules signal they have sufficient power you start switching, recover power from the switching transient after that). To me it would seem to be ideal for high voltage stacks such as HVDC inverters.

author: nfmax
author_rank: Super Contributor
timestamp: July 04, 2016, 08:29:04 am
content: Products like this have been around for ages, and (locally-made) fibre lasers can deliver multiplekilowatts, should you so require. A spot of Googling showed me Lumentumhttps://www.lumentum.com/en/3d-sensing-and-industrial-diode-lasers/products/power-over-fiber, and it appears Photonic Power Solutions were bought by JDSU, who are now selling thire products, e.g.http://www.laser-technology.com/en/component/k2/item/download/34_5c9f8f5b930d181a2234cbeca3404202through the usual distrubution channels. You should be able to find a COTS solution easily enough, hopefully one that is suitable for your requirement.Max

author: Marco
author_rank: Super Contributor
timestamp: July 04, 2016, 02:06:17 pm
content: Quote from: blueskull on July 04, 2016, 06:13:22 amI understand that, but generally there are kWs of potential energy available at the drain.For instance lets say you use the trace from drain connection as a single winding in a PCB transformer with some high frequency clamped core (-17 iron powder for instance). Rectify the secondary to get power during switching transients and short the secondary when no more power is necessary.In some applications this might be able to guarantee you retrieving sufficient energy to run the isolated driver.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: July 04, 2016, 02:48:26 pm
content: the spheres you speak of are called optical integrators, often used for laser power measurement