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In the wake of a horrible realization that Earth is nearing destruction and we as humans are “woefully off track” to saving it; any possibility in generating clean energy is much welcomed even if we have to go to space to achieve it. Hence, space-based solar power (SBSP) is being considered as an alternative source of limitless clean and renewable energy.

Space-based solar power (SBSP) is a rather ambitious concept that revolves around putting stupendously large solar power plants into the geostationary orbit that can harvest Sun’s raw energy and beam it down to Earth. Theoretically, SBSP is better at energy generation than current nuclear power plants. The potential of this idea can be imagined by the statement of Martin Soltau the Co-chairman of the Space Energy Initiative (SEI), “A narrow strip around geostationary Earth orbit receives more than 100 times the amount of energy per year than all of humanity is forecast to use in 2050.”

If this ‘too good to be true’ idea proves to be viable then unimaginable success can be achieved not only in space exploration missions but  the goals of achieving net zero-carbon emissions and shifting from fossil energy to all clean energy also won’t be looking unattainable in future. The notion of generating electricity in space and then beaming it on earth by conversion into microwave or laser energy has fascinated researchers since long ago.

A figment of imagination of a fiction writer Isaac Asimov in 1940s has now brought significant attention from space agencies, governments, and private companies due to its potential to provide a limitless source of energy. In recent years, interest in SBSP has grown due to concerns that the shot humanity is taking at achieving 2030’s Sustainable Development Goals (SDGs) might miss the mark by a couple thousand miles in actuality.

Peter Glaser conducted the first serious study of SBSP in 1968 and proposed the idea of sending a satellite equipped with large solar arrays into space that could capture sunlight and send it down to Earth using microwaves or lasers. Despite being deemed too expensive and technologically challenging at the time, NASA showed positive interest in the idea and introduced Solar Power Satellite (SPS) project. Japan and Russia followed suit and even started developing small-scale SBSP systems to be tested in space.

The superiority of SBSP over traditional terrestrial solar power systems is literally in the fact that it is timeless unlike the intermittent system on ground which gets limited by the Earth’s atmosphere or geography. SBSP can generate baseload energy in space throughout the clock neither being obstructed by clouds, pollution, nighttime nor by the concerns of land availability.

The proposal of using flexible and lightweight solar cells is also being tested which should produce 50 times more energy on the basis of power to weight ratio as the conventional silicon solar cells on do Earth. Additionally, the idea of detachable power can be achieved easily as energy transmission from space can be directed to specific locations that need it the most, including remote or isolated communities, disaster areas, or areas with inadequate power infrastructure.

However, significant technological and financial obstacles still need to be overcome before SBSP becomes a reality. The financial costs of launching payloads into space are prohibitively expensive, with current estimates ranging from $5-10K per kilogram. Alongside the weight, the size of panels poses an additional issue because launching 100s of meters long structures in 1 piece is currently not possible.

Alongside high energy losses, the problems of inefficiency of conventional silicon photovoltaic cells at high temperatures of space and the scattering of microwaves and laser beams through atmosphere need to be tackled because the specific type of solar cells currently being used in spacecrafts are far too expensive to be deployed as huge arrays and for efficient capturing of scattered waves, kilometers long receiving stations are needed on land. Another challenge is the probable environmental impact of the building, developing and launching of these solar farms to space. The increasing space debris due to these launches can also pose threat to long term sustainability of space exploration.

Despite the long list of challenges, the researchers are hard at work to make SBSP come to life. The efforts of Japan, China, Europe and USA are commendable in this regard. To tackle the issue of sending wide structures to space, experimentation with flexible, foldable and lightweight solar panels has started. California Institute of Technology (Caltech) is testing its tightly folded structures, roughly the size of a table, which can unfurl to about 60 meters long in space. China is trying to generate crown-shaped solar collectors. Even Japanese origami model has been the inspiration of some of the tests where flexible solar panels are folded into an origami shape and sent to space.

Even ideas of autonomous assembly of small modules in space via robots where  micro-satellites would be sent to space on a weeks’ time intervals where they would then gather to create a formation just like a constellation are being tested by The Cassiopeia project of Space Energy Initiative (SEI) and Caltech Space Solar Power Project (SSPP). Testing different materials for solar cells in space including gallium, arsenide, indium, silicon, thin-film solar cells, and nanowire solar cells has also begun. Caltech SSPP has sent 32 different types of solar cells in space to check the best one out of them.

Space Solar Power Incremental Demonstrations and Research (SSPIDR) by US Air Force Laboratory has carried out ground-based tests of equipment for in-space flight experiment called Arachne, where beams power military missions. Orb-Shape Membrane Energy Gathering Array (OMEGA) of Xidian University in China has started tests on ground for the full-way process of complete working of SBSP.

First Space Solar Power Demonstrator (SSPD-1) was sent to space by Caltech and the results are giving a positive outlook to the bright future of this amazing and fascinating concept called Space Based Solar Power.

Author:  Ayesha Israr   
An enthusiast of renewable energy and a researcher of materials for energy storage and conversion