Space-based solar power

Space-based solar power (SBSP) is the technique of collecting solar power in outer space and distributing it to Earth. It is sustainable, green, renewable energy.

It is comprised of:

 * collecting solar energy in space onto photovoltaic (PV) panels mounted to satellites, or light sails
 * wireless power transmission to Earth via microwave or laser
 * receiving power on Earth via a collector or rectenna (a microwave antenna)

The collecting satellite would convert solar energy into electrical energy on board, powering a microwave transmitter or laser emitter, and transmit this energy to a collector (or microwave rectenna) on Earth's surface.

The problem with this method is that you have to convert the electricity produced by the solar panels into microwaves, have those microwaves pass through the Earth's atmosphere, and finally those microwaves must be converted back into electricity using pretty expansive rectennas. A lot of power would be lost during all three steps. The solution could be attaching the PV panels to an orbital ring and send the electricity down its tethers, or use cables attached to a space elevator.

Advantages over the Earth's surface

 * It is always solar noon in space and full sun.
 * 55–60% of incoming solar energy is lost on its way through the Earth's atmosphere.
 * The intensity in orbit is at least 150% of the maximum attainable intensity on Earth's surface.
 * Reduced plant and wildlife interference.

Disadvantages (solved by Type I)

 * Cost of launching satellites and receiving station vs. return on investment (ROI)
 * Inaccessibility and high radiation dangers for maintenance led to telerobotic solutions
 * Space is hostile. Fixed by self-repair nanobots and defence mechanisms like auto-targeting lasers.
 * Space debris. Was cleaned up via a major global initiative.
 * GEO (Geostationary Orbit) had too much atmospheric absorption. Fixed by LEO (Low Earth Orbit) space power stations, either sun-sync LEO via Polar Orbit or Equatorial LEO.

Current projects
Caltech has $100 million in funding for their Space-based Solar Power Project (SSPP), which is described as “collecting solar power in space and transmitting the energy wirelessly to Earth through microwaves enables terrestrial power availability unaffected by weather or time of day. Solar power could be continuously available anywhere on Earth.”

The Japanese construction firm Shimizu Corp. plans on building a Luna Ring of solar panels around the equator of the moon. The panels will beam energy back in the form of microwaves.

There are tests that collect sunlight and convert it to electrical energy, transfer energy wirelessly in free-space using radio frequency (RF) electrical power, and deploy ultralight structures that will be used to integrate them. In 2023, prototypes with solar power generators and RF wireless power transfer should have a deployable structure measuring roughly 6 feet by 6 feet. SSPP aims to ultimately produce a global supply of affordable, renewable, clean energy.

Reference: Caltech’s Space-based Solar Power Project

Later designs

 * Moving beyond PV panels, a solar wind loop, or Dyson–Harrop satellite was used. Here the satellite makes use of the charged particles in the solar wind which via electro-magnetic couplings generate a current in a large loop.
 * Dyson Dots: where a multi-terawatt primary collector would beam energy back to a series of LEO sun-synchronous receiver satellites.
 * Any of the spacecraft launch-assist platforms, such the skyhook, space elevator, or mass driver.

Future
It’s expected that these types of satellites could appear in orbit around the Moon and Mars to provide energy to human bases. Enough of these satellites could eventually orbit the Earth so that virtually all of the sunlight is captured and harvested in some way. This could be a precursor for the Dyson Swarm and be an important step for humanity to become a Type I civilization.

News

 * June 2023 - The California Institute of Technology has beamed solar power from space to Earth without a single wire, a world's first.