DISQUS

Peter · 2 years ago

So, we know that laptops consume so much power that the resultant dissipated heat makes the "laptop" too hot to actually put on one's lap.

We also know that solar panels are perhaps 12% efficient, meaning that there would need to be at least 8.33 (1/0.12) times the optical power radiated onto the solar panel to power the laptop.

So, not only would this be remarkably energy INEFFICIENT (12% or less of the original laser's power actually being used), but one would have an intensified scalding hot death ray projecting around the room, hopefully hitting just the laptop and not the humans. Remind me not to walk into that room.

I don't get your "potential" bit. The greens might be choked up, but certainly not because they would be pleased. It is offensively wasteful to beam energy in such a way. Just plug the darn thing in.

Matt Marshall · 2 years ago

Well, who cares if it is inefficient, if it is renewable?

I agree, though, there are huge obstacles overall.

RC · 2 years ago

What Peter said x10. Dean's story speaks of a toy powered by the laser? Why not prove it to do something useful like power a laptop? Oh probably for all the reasons peter stated and a few more.

Lasers have line of sight transmission. Solar cells are affect by the incident angle of the incoming light. How will they locate and track the power cell?

This idea is about 30 years old but the last time I heard it they wanted to use microwaves from orbiting satellites to beam energy from space to earth.

Peter · 2 years ago

Matt,

what makes it "renewable"? The power for the laser has to come from somewhere. Unlike green technology that harvests existing energy from the sun; this is squandering energy that could be more efficiently transmitted via wires.

Even if the laser itself is itself powered by solar panels (sun to rooftop-solar-panel to electricity-to-power-the-laser to laptop-solar-panel to electricity-to-power-the-laptop), that means no more than 1.44% (0.12 x 0.12) of the sun's power actually winds up powering the laptop. That's shameful.

We should very much care about it being inefficient. If only 12% of the laser's power reaches the laptop, that means 88% is lost. By simply plugging in the laptop, that 88% of energy could be saved and used elsewhere to reduce our energy dependence.

david · 2 years ago

Peter x10. What is the *beneficial* use case for this cool science project?

DV Henkel-Wallace · 2 years ago

Matt asks, "Well, who cares if it is inefficient, if it is renewable?"

If that's the beginning and end of your analysis, well, oil and coal are renewable too, on a multi-megayear timescale. Yes, of course that's ridiculous! But so is your "who cares". Consider the most trivial thermodynamics:

(sorry to harsh on you Matt, I read your blog every day. But please take off the rose-coloured glasses).

If the solar cell is 12% efficient (according to another poster) that means that 88% of the energy is going somewhere else, i.e. radiating into the air (if you're lucky -- some is reflecting elsewhere, hopefully not into your eye). My PB has a 65-watt adaptor, thus to use this scheme, the solar sell would be reflecting/radiating/otherwise losing 477 watts. And to get the 540 watts (the amount lost and the amount actually used) delivered to the cell, the laser would have to deliver even more power since some would be lost in transmission (hitting dust, water vapour and the like into the air). And all your cameras, computing power for same etc would take power too.

So that's a hell of a lot less efficient than just delivering electricity via a wall socket even though the dc-dc converters used in most PC power supplies suck.

Now you could improve things by using a solar cell on the roof, it's true (though let's not go into how big the array would have to be -- that 12% applies to both ends after all so you'd really get only 1.5% efficiency) since the net amount of energy is approximately the same (the sun was radiating that energy onto the earth anyway). But you'd be concentrating it into your room, which around here means you'd probably switch on the air conditioner...oops!

If you have to be wireless, use one of those magnetically-coupled pads and throw your blackberry onto _it_. But frankly, I haven't found it a barrier to the old-fashioned approach to charging, which is just to stick a bunch of cradles in the corner and plug everything in at night. The big problem is: why do most people still use proprietary charging connectors????

nemrut · 2 years ago

..what if the solar panel was bypassed altogether and instead, just use a big manifying lense that would focus sun's rays into an energy storage device..?

Matt Marshall · 2 years ago

Shows you how much I know.

Azeem · 2 years ago

Also don't forget Splashpower which has had wireless charging pads for an age.

RC · 2 years ago

Matt,

Some critical review of the technologies that you present would be nice. Merely relaying press releases is not all that useful or interesting. I could just go to PRwire if that was what interested me.

Inductive energy transfer is old news and as Azeem points out has already been done.

Lasers are a pretty dumb idea for energy transfer at the consumer level and probably at the industry level.

The MIT effort is seemingly new and warrants more interest than either of the others mentioned.

In the end it all comes down to efficiency which nobody seems to be concerned with. In a report that I read about 70% of all energy generated(all sources) is wasted. Energy hungry devices and the ever present power supplies/wallwarts would be great places to start.

A watt saved is better than a watt generated by solar/wind etc.