Off-world Power Generation

Concept

Premise:

• <Earth> <-clearsky-burst-laser-- <Earth-orbit satellite>

Less likely:

• <Earth> <-clearsky-burst-laser-- <L1 solar array>
• <Earth> <-microwave-- <Earth-orbit satellite> <-laser-- <Earth's moon> <-laser-- <L1 solar array>
• <Earth> <-clearsky-burst-laser-- <Earth's moon> <-laser-- <L1 solar array>
• <Earth-orbit satellite> <- <Earth's moon>
• <Earth's moon> <- <Earth-Sol Lagrange-point solar array>

Given:

• earth to moon: 238,900 miles
• there are four lagrange points that provide constant sun exposure at predictable locations
• l1 to earth/moon: 1 million miles
• A geosynchronous orbit takes one sidereal day, and is 35,786 km (22,236 mi) above the Earth's surface. Those closer to Earth orbit faster than Earth rotates, so from Earth, they appear to move eastward while those that orbit beyond geosynchronous distances appear to move westward.
• other interesting earth orbits: low goes across poles, medium used by GPS, high is slow and crawls west, Molniya spends more time away from equator; relative distances diagram
• the sun primarily produces visible light (not microwaves or gamma...)
• laser transmission is more efficient than microwave, except where earth's atmosphere interferes
• current status: A Gigawatt-range microwave system would weigh ~80,000 tons (prohibitively expensive) more lots more
• Solar cell efficiency

Laser transmit antenna in space: 1 meter diameter per GW Receive: Several hundred meters across

Targeting the energy requirement of NYC:

• Power is measured in Newton-meters per second or Joules per second or Watts.
• ~3000 trillion BTU in 2016 = 3000 trillion btu / 365 days = 3.4E+11 btu/hr = 1.0036680479e+11 watts = 100 GW

PV energy collection

• PV power stations collect more power than solar thermal power stations. They seem to average ~3 MW/km^2 (throwing out 2 ridiculous outliers).
• Traditional single-junction cells have a maximum theoretical efficiency of 33.16% more. In reality it is around 18.7%.
• A 65"x39" (1.64 m^2) solar panel made in 2018 produces ~320W.
• About 48% of solar energy hitting the Earth reaches the surface. Perhaps optimistic, but we will divide by .48 to get energy-in-space vs on-earth.
• Approximate energy absorbable by a solar panel in space: 320W / 1.64m^2 / .48% = 400W/m^2 in space
• Approximate required size of a solar array "near Earth" (including l1) to power NYC: 100GW / 400W/m^s = 250 sq km
• Dan: 1 out of every 811 humans on earth live in NYC, so 250 sq km dish * 811 (assuming every human uses as much energy as a New Yorker) requires a solar array of only around 200,000 sq km - the size of Nebraska - to power the globe.

Conclusion

Keep it as simple as possible, but no less.

• We need to optimize free space power transmission in lab conditions using currently-available consumer electronics.
• We need to create a solar panel array with robotics that can self-assemble.
• We need robotics that can precisely and safely aim laser energy to a distant target using a real-time handshaking protocol.
• We need to determine the cheapest possible way to launch a payload from Earth and navigate it to a final stable destination (lagrange or Earth orbit).
• We need to determine the requirements to receive laser power at an Earth-based power plant.
• We need to crowdfund the project.