Satellite based wireless charging

[lancethibault]

I know anything is possible, but I'm looking for more of a science based answer to the question of whether or not satellite based wireless charging could be a reality for EVs? My guess is that the limitation isn't as much the distance, but rather the power source (satellite itself), since they would require "refueling" or "recharging" routinely just as gas stations do. It would be awesome if this could be done, especially if it could be done while driving...ie in-flight refueling. I know I've seen articles that talk about having charging built into the roads, which would of course be grid connected, but the infrastructure changes to make that happen would be huge even if it only applied to interstate hwys. Might as well spend the money on global coverage satellite coverage if something like this is within the realm of feasibility taking logistics and economics into account.

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[ajdelange]

The idea of transferring power from space to the earth has been discussed from time to time. There is certainly plenty of it out there in the form of sunlight which has not been filtered through the atmosphere and the sun never sets in space (except for an occasional ecliplse). The concept is for vast orbiting (possibly synchronous) solar arrays to collect the sunlight. It would then be converted to microwaves and the microwaves beamed to earth. This aspect is what kills the idea practically for a vehicle. The beam spreads as it propagates towards earth. The collector on earth must be big enough to encompass the entire beam as spread at the surface in order to capture all the power in it. No downlink power is collected from parts of the beam that are not within the collecting area.

Forming and accurately aiming a small beam from space (or anywhere) is difficult to do. When you say "wireless" I assume you envision an antenna on top of the car directly receiving power from the charging satellite in the same way an antenna on top of the car receives the SiriusXM signal. The general principle would be the same - the SiriusXM satellite is transferring power to the receiver in the car. The difference is that the aperture of the SiriusXM antenna subtends a tiny fraction of the satellite's beam width so that only a tiny fraction of the satellite's power is received. This is adequate for signaling. For charging the receiving antenna would have to capture the entire beam and the beam would, thus, have to be tiny. Such a system would in no way come anywhere close to being practical.

 

[ricinro]

If the microwaves could charge your CT it will also cook everything around. Good weapon concept though.

 

[ajdelange]

Good point! The interior of the beam would certainly exceed the mw/cm^2 safety limits for RF exposure.

 

[lancethibault]

I was thinking something more along the lines of trickle charging. So the beam width does not have to be so focused that individual vehicles are receiving all the focused power. Think of it as just another avenue to add range incrementally. In the same the way Tesla updates software that extends the range of the vehicle. Maybe this could also extend the range so long as the vehicle is in the footprint of the beam(s). Even if it's not much...say 2% to the total range if you spend a full day in the footprint (day or night). After all, people are talking about having solar panels on the CT that might add 15 miles a day to their range. It could be subscription based or built into an upfront cost as an option...or both I guess. As the tech to do this advances, the battery sizes could be decreased, further reducing environmental stress caused by mining the required resources for the all the batteries.

 

[ajdelange]

Well just think of the problem in terms of the sun. It delivers, with efficiency considered, about 230 W/cm^2 in order to give us a few mile per day. The safety limit for microwaves is about 1/20th this (note, of course, that continuous exposure to the sun isn't so good for you either but clothing blocks solar while it does not block microwaves).

Also the sun can deliver 4 GW to each acre because it has plenty of GW to spare but a satellite, even with unlimited solar panels attached, would have to be huge in order to deliver that kind of flux to the surface of the earth.

 

[Newton]

Is there not a way to capture laser rather than microwave based transmission?
I would assume you would lose tons of energy, but I'm also guessing u lose alot with any wireless energy type thing.

 

[lancethibault]

Newton....The big obstacle with something as focused as a laser would be the beam steering that would be required to maintain contact with individual vehicles. Whether the vehicle is moving or not, the satellite is (even at geo) and the limited number of vehicles could be "fueled" at a time.

 

[ajdelange]

Light and radio waves are the same thing so the same principles apply. It is easier to get a tight beam with a laser but the steering and safety problems still pertain. Also conversion of DC to radio waves is done much more efficiently at microwave frequencies than at optical.

 

[ldjessee]

Acres of land with antennas above to capture the microwave energy (and let the visible light through, so could be over farmland) dumping into the grid and using a induction charger to recharge an EV seems like a much more efficient solution... but that is because induction charging has gotten much better and more efficient.

 

[CyberCop]

I’m waiting for the development of transparent solar panels to be used as windshields, windows and roofs.
It wouldn’t be a lot of charging power but it would help.
I know I know it’s not practical but it sure would be cool.