Harnessing Solar Power From Where There Is No Night—Space  

Srikanth Ramakrishnan

Apr 16, 2017, 04:30 PM | Updated 04:30 PM IST

The Suntower Concept by NASA
The Suntower Concept by NASA
  • Wireless transmission of energy from space may be closer in future than you imagined
  • There is talk of wireless transfer of electricity. Space has 24x7 sunlight. Imagine the possibilities. These were Piyush Goyal’s words at the Mail Today Energy Conclave last week (12 April).

    This technology, called ‘Space-based Solar Power’ or SBSP has been proposed since the 1970s, but was never practical due to the large payload that would be required to be launched into outer space.

    As far as traditional solar energy is concerned, the most common thing one hears is that India is a large tropical country with sunlight 365 days a year. However, in most places, this sunlight is available only for half a day and sometimes, well, the moon gets in the way.

    So what makes SBSP practical?

    Simply put, there is virtually no ‘night time’ in outer space. Night time occurs on Earth due to its rotation. The side facing away from the sun, experience night. But if one were in space, the sun would perennially be shining, unless something comes in between the sun and any object.

    However, Solar Power Satellites (SPS) are not that far into the future. The Japan Aerospace Exploration Agency (JAXA) has actively been working in the field, going so far as to come up with a 25 year roadmap that aims to set up an orbital solar farm with a capacity of 1 gigawatt power that can be sent back to the earth by the 2030s. Of course, the fact that it will require a large payload of equipment is a hindrance. JAXA estimates that in order to generate one gigawatt of power, it would require a solar collector unit weighing at least 10,000 metric tonnes, in a geosynchronous orbit, 36,000 km away from the Earth.

    The Roadblock

    There is however, one major roadblock in this whole concept. Getting the power back to Earth. There is no way that a cable can be used to transmit this power back. While proposals have been made (again by the Japanese) to build a ‘space elevator’, that would use carbon nano-tubes to transmit power, this concept is further away than the SBSP.

    Electromagnetic induction is completely out of the question since it would require a large magnetic field which would have unwanted side-effects. Lasers cannot be used since they cannot penetrate through clouds, much like sunlight. So what is left? Microwaves.

    Microwaves are radio waves with a frequency between one metre and one millimetre. Its short wavelength allows it to transmit energy over long ranges. In March 2015, JAXA successfully managed to transmit 1.8 kilowatts using microwaves across a distance of 55 metres, while a Mitsubishi-JAXA partnership simultaneously transmitted 10 kilowatts of power over 500 metres. JAXA states that transmission efficiency is high with losses in transmission being close to 20 per cent of the total power being beamed across.

    Further Applications?

    This whole beaming of energy concept, although no longer a concept, is not restricted to any sector alone. Mitsubishi has stated its intentions of using it to transit power to charge electric vehicles in the future. It can be used in many scenarios, including the generation, transmission and distribution of power. It could reduce the need for high-tension power cables, thus enabling a more efficient transmission grid. In the long run, it could result in cheaper and more reliable electricity supply.

    So, is it possible?

    Yes, why not? Research is ongoing at a rapid pace and Japan isn’t the only one in the field. The National Aerospace and Science Administration (NASA) proposed its Suntower Concept in 2001. China’s Central Military Commission too has proposed exploiting the ‘Earth-Moon space for industrial development’. The National Space Society (NSS) of the United States proposed a joint forum with ISRO, named the NSS-Kalam Initiative to work on an SBSP framework. China too, proposed a similar joint venture with India after former president APJ Abdul Kalam visited the country in 2012. With so many entities in the sector, it isn’t long before we get a working prototype ready. The largest bottleneck in the project is to get the heavy payload into space. With both ISRO and Elon Musk’s SpaceX working full-time on improving launch capabilities, this is set to be the least problematic of all requirements.

    Figuring out how to send the power back to Earth will certainly take time, but it can be done. The evolution of transmission of power and associated technology has come a long way in the last century. To quote Neil Armstrong, “Mystery creates wonder and wonder is the basis of man’s desire to understand.” This mystery (sending the power down to Earth) too will be solved, there is no doubt about that.

    The associated research and opportunities the sector offers presents us a major opportunity. It would help solve the everyday power crises, and at the same time create more research oriented jobs.

    Piyush Goyal was certainly not joking when he spoke of wireless transmission of energy from space and when he said, ‘Imagine the possibilities’, we must realise that the possibilities are vast.

    Srikanth’s interests include public transit, urban management and transportation infrastructure.

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