By Umay Salma
How often have the movies featured the humans abandoning the planet Earth on account of depletion of resources. What remained the subject of sci-fi for decades is now becoming a reality. Lo and behold, Japan has taken this quest for new resources to a whole new level and plans to build a solar farm about 36,000 kilometers above the Earth. With this, Japan definitely kicks off a next space race.
The idea for space-based solar power generation first emerged in 1968 by Dr. Peter Glaser. His idea was to deploy large solar panels in space for power generation, and convert the energy into microwaves to transmit to the ground. NASA and United States Department of Energy tried discovering the scope of implementation of the project, but it was soon shut down because of the high cost. Meanwhile in Japan, the scientists continued to pursue this idea particularly under the umbrella of Japan Aerospace Exploration Agency (JAXA). This says a lot about the Japan’s keen interest in finding a practical clean energy source. Thanks to the technological advances in wireless power transmissions, lightweight materials, space transportation and assembly robots, that the idea of solar farm is finally being materialized after four years.
According to the proposal, for producing 1GW of power, an SPS weighing 10,000 metric tons will be required. JAXA researchers are still working to optimize the design. In one idea, the upper side of one huge square will be covered with photovoltaic elements and will act as a receiver, while the lower side will have transmission antennas, sending microwaves to the fixed spot on the Earth. By using a technique called gravity gradient stabilization, the panel will face more centripetal and less centrifugal force, and hence it will remain stable in its orbit cutting on millions of dollars required for fuel otherwise.
The problem with this idea is varying rate of generation. With the photovoltaic side fixed, when the whole assembly moves in its geostationary orbit, the amount of light hitting it varies. This will cause problem at later stage of the circuit. To cater this, two freely floating mirrors are planned to be launched which will reflect the light on photovoltaic panel 24/7. This will keep the upper side receiving energy even when the earth spin has caused the geo-synchronous panel to be on the side of Earth opposite to the sun.
That’s just the beginning of this multibillion-dollar challenge. According to Professor Susumu Sasaki, a professor at JAXA, they need several breakthroughs before the successful launch some of which would be in areas of microwave power transmission, light materials for mirrors and high-voltage power transmission cables that could channel the power from the solar panels to the transmission unit with minimal resistive losses. These are the areas that humans have been studying for decades but have yet to perfect.
The intense microwave beam will then be focused on a magnificent man-made island covered with 5 billion tiny rectifying antennas. This is definitely going to be big! The scientists have let their imagination go wild to fancy microwaves, generated by panels floating in geosynchronous orbits with an assembly of reflecting mirrors, beaming over a glorious island that is made by them. We, however, need to be patient till 2030s to see this at work.
Once the station is installed, the imbursement will be enormous because in space there is 10 times as much available solar energy as on Earth. There will be no efficiency reductions due to the day-night cycle, seasonal variation, or weather conditions. The space-based solar collectors in geosynchronous orbit will be able to generate power nearly 24 hours a day. Why? Because, it’s always sunny in space!
The name of this article is inspired from an American television sitcom “It’s always sunny in Philadelphia” which was aired in 2005.
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