The European Sail Tower SPSThe European Sail-Tower SPS (short for Solar Power Satellite) is a large tower-like orbital system that is similar to the Sun tower. The satellite deployes rectangular solar panels from sail-like structures that line the sides of the tower. The satellite stays in orbit and generates electricity that is transmitted back to Earth via microwaves. This design was developed in the late 90s, although there hasn't been much activity in the last couple of years.
This margarita glass-shaped space setup is nicknamed, SPS-ALPHA – which is short for Solar Power Satellite via Arbitrarily Large PHased Array. It consists of a large array of thin-film mirrors attached to the curved surface of a massive satellite. These mirrors are moveable and will be used to redirect incoming Sunlight towards the solar cells that are fixed on the backside of the device. A collection of microwave power transmission panels is placed on the Earth-side of the array, which enables the transportation of the electricity generated by the solar cells to earth in the form of radio waves.
John Mankins, the leader of the concept says: “The needed next steps are to develop a working prototype of one or more of the modules and demonstrate the assembled system in the field. Over the next several years, the goal is to realize a low-Earth orbit flight test of the system.”
Image credit: JAXA
Japan Aerospace Exploration Agency (JAXA) is aiming to launch their space-based solar power prototype by 2020, with plans to set up a full system in space by 2030. JAXA`s SBSP system is a satellite designed to run in stationary orbit 22,400 miles above the equator, where it will absorb sunlight with chromium-enhanced solar cells. Neodymium plates fixed on the satellite’s surface will zap the energy down to Earth by using laser beams with 42% solar-to-laser energy efficiency. Current estimations predict that a single solar SBSP satellite in space would be able to generate enough energy to power 500,000 homes.
Even though The Dyson–Harrop Satellite is technically not a space-based photovoltaic power design, it does harness the sun’s energy for the good of the planet. This satellite is in really a giant “sail” – 8,400 kilometers (5,220 miles) wide – designed to harness solar winds. The sail generates a magnetic field by pointing copper wires at the sun. This field is capable of capturing the electrons found in solar winds, which in turn are funneled into a spherical receiver that produces a current (a fundamentally different approach than photovoltaic solar panels). The plan is to send this energy back to Earth with powerful infrared laser beams. The total potential for harnessing solar winds is 1 billion gigawatts of electricity, so figuring out how to tap into this energy source could be a revolutionary step for mankind.
Image credit: NASA artwork by Pat Rawlings/SAIC.
The SunTower is a supertall gravity stabilized structure that uses inflatable circular solar concentrators, multi-junction solar cells and magnetron segments to transmit the sun’s energy down to earth. In laymen terms, it is similar in design to a sunflower, with the flower facing the Earth and sending the energy down the stem using microwaves. The predicted cost – before any energy has been produced – of one SunTower is estimated at $12 billion. Though the SunTower is an interesting concept, it soon became clear that the approach could only deliver power to a given ground station for a few minutes a day.
Image credit: Space Future
This SBSP concept involves an axisymmetric, modular space segment that extends in geostationary Earth orbit. It is covered with high-efficiency thin-film solar cells. One SolarDisc along with its ground component could be scaled to produce as much as 10 GW of energy.
The European Sail Tower SPS
The European Sail-Tower SPS (short for Solar Power Satellite) is a large tower-like orbital system that is similar to the Sun tower. The satellite deploys rectangular solar panels from sail-like structures that line the sides of the tower. The satellite stays in orbit and generates electricity that is transmitted back to Earth via microwaves. This design was developed in the late 90s, although there hasn’t been much activity in the last couple of years.
Peter Sage of Space Energy Inc., said the following in his space energy presentation at TED: “The challenge has never been technology, but economics […] We have the technology to convert electricity into a transferable radio frequency, send it back down to Earth with pinpoint accuracy safely and reliably to create constant energy generated by the Sun 24 hours a day”
SBSP is the holy grail of renewable energy. These systems have the potential to supply the entire Earth with clean, base-load electricity. A coordinated effort from China, India, Japan, EU and United States, both in terms of funding and research collaboration, could bring us closer to making science fiction become reality.