Hacker News Reader

Comment by bracketfocus | Hacker News Reader

They mentioned that it was 20% efficient at a closer distance.

So likely much lower than that.

20% efficiency in terms of light -> electricity. A 50% laser efficiency (electricity -> light) is really good, possible for some diode lasers, if you pump a fiber laser with diodes to get a high quality beam for cutting materials or weapons purposes maybe you get 25%.

That demo would require about 45 kW of laser power with good beam quality which would be totally possible with a fiber laser

https://www.rp-photonics.com/wall_plug_efficiency.html

Wow that's a long way from the proposals for sending GW of microwave power from satellites.

Those sat to ground power sources use gallium arsenide switched FETs = synchronous rectification, avoiding the voltage drop of diodes has been tested on a small scale, the 10GW orbital 35% efficient solar arrays, maybe next week... Solar boilers, end to end, are more efficient than solar cells, but mechanical complexity(leaks, corrosion, worker avarice) made one US plan in the South West non viable. As we sit silicon-perovskite tandem solar cells will top out around 42-45% - unless Schockley is end runned? Ternary -??. A good lecture = https://www.youtube.com/watch?v=Ft0VJX0_Td0&t=2s&ab_channel=...

Solar thermal as well as solar-chemical systems have the problem of start-up.

PVs do not have any problem starting up, they produce less than full power with less than full illumination but they produce something and once the illumination is full they produce full power immediately.

Many solar thermal power plants are fired with natural gas in the morning to get them spun up to the point where they can take advantage of the solar energy. Without that they'd probably lose a few hours of production.

Laser power beaming from space could be useful at lower power levels than that, for example for powering aircraft.

But pretty close to powering drones from ground stations

Reply on news.ycombinator.com