Since the 1970s, some of the brightest scientific minds have been working to materialize what is known as space-based solar power (SBSP). Unlike traditional solar harvesters whose efficiency is heavily dependent on prevailing weather conditions, this concept refers to the incredibly futuristic technology of gathering solar energy in space, with the help of specially-engineered solar power satellite (SPS). Given the inexhaustible and environment-friendly nature of solar energy, Tokyo-based Japan Aerospace Exploration Agency (JAXA) has undertaken an ambitious project that promises to deliver 1 gigawatt of solar power, from space to the Earth, no later than 2030s. Last week, Mitsubishi Heavy Industries and JAXA successfully conducted ground testing of one of the major components of SBSP: long-distance wireless power transmission.
The technology, currently under development, seeks to eliminate the hitherto-necessary cable connections for transmitting power and electricity. In order to be able to deliver 1 gigawatt of solar power, one needs to build a solar power system, measuring a few kilometres in diameter and weighing up to 10,000 metric tons. Launched into the geosynchronous orbit, the satellite will be revolving at a distance of 36,000 kilometres from the Earth. Hence, researchers across the world are looking for ways to wirelessly transmit the power, collected by the satellite, back to Earth. Earlier tests of the same technology resulted in only a minuscule fraction of the assimilated energy being sent from one island to another.
On March 12, this year, scientists at JAXA managed to transfer 1.8 kW of energy wirelessly to a rectenna located 55 meters (170 feet) away. The researchers sent the power using carefully-targeted microwaves, which were then converted to DC electricity by means of a rectifying antenna. The demonstration, which marks the first time that such high-output power has been transmitted through microwaves, actually focused more precision than the amount of power transferred. According to a JAXA official, the technology will, in the future, prove to be indispensible to a resource-deficient country like Japan. He said:
This was the first time anyone has managed to send a high output of nearly 2 kilowatts of electric power via microwaves to a small target, using a delicate directivity control device… But it could take decades before we see practical application of the technology — maybe in the 2040s or later. There are a number of challenges to overcome, such as how to send huge structures into space, how to construct them and how to maintain them.
On the same day, last week, Mitsubishi conducted a similar test at its Kobe Shipyard and Machinery Works, in collaboration with Japan Space Systems. In it, the company successfully sent 10 kW of power wirelessly, over a distance of 500 meters (1640 feet). The experiment was part of the “2012 Solar Power Wireless Transmission Technology Development Project”, as authorized by METI (Japan’s Ministry of Economy, Trade and Industry). The transmitted energy was then used to illuminate a bunch of LED lights, present at the receiving unit of the system. While the exact percentage of the delivered power has not yet been revealed, Mitsubishi’s officials believe that the technology will eventually lead to the development of advanced solar power systems, capable of collecting and transmitting enormous amounts of solar energy.
The technology, used by Mitsubishi to precisely transfer power via microwaves, is known as radio emission technology. Unlike lasers that cannot penetrate clouds easily, microwaves can work even under unfavourable weather conditions. According to the company’s spokesperson, the wireless power transmission technology will aid in sending energy to places where installing power cables is burdensome. Furthermore, it can likely be used to transmit usable power from oceanic and offshore wind turbines. When fully developed, the technology can be used to wirelessly charge electric cars; a step that can help decrease our dependence on fossil fuels. On the other hand, JAXA is gearing up to send the first ever solar power satellite into space, by 2018. If everything goes according to plan, the agency might be able to launch a 100kW solar collector into orbit by 2021, and an advanced 200kW satellite no later than 2028.
Here’s to hoping for the best!