A new era of energy or a pipe dream?
Japan has announced plans to send solar energy from space to Earth in 2025, two years after a similar achievement by American engineers. This development is a step towards a potential space-based solar power plant that could contribute to the abandonment of fossil fuels.
At the International Space Energy Conference held this week, Koichi Ijichi, an advisor to the Japanese Space Systems Research Institute, presented Japan's plan to create a miniature space solar power plant in orbit that will wirelessly transfer energy from low Earth orbit to Earth.
One kilowatt is the amount of energy required to operate a household appliance, such as a small dishwasher, for an hour, depending on its size. This is significantly less than the scale required for commercial use. In addition, the satellite will only be able to transmit energy for a few minutes, and then it will take several days to recharge.
The spacecraft will use an on-board photovoltaic panel with an area of 2 square meters to charge the battery. The stored energy will then be converted into microwaves and directed to a receiving antenna on Earth. Since the spacecraft is moving at a speed of about 28,000 km/h, the antenna elements must be spaced about 40 kilometers apart with an interval of 5 kilometers from each other to ensure the transmission of sufficient energy.
The mission, which is part of a project called OHISAMA (Japanese for "sun"), is preparing to launch in 2025. Researchers have already demonstrated wireless transmission of solar energy to earth from a stationary source, and in December they plan to carry out transmission from an airplane. According to Izichi, the aircraft will be equipped with an identical photovoltaic panel, which will be installed on the spacecraft, and will transmit energy over a distance of 5 to 7 kilometers.
The production of solar energy in space, first described in 1968 by former Apollo engineer Peter Glazer, has long been considered science fiction. Although this technology is theoretically feasible, it was considered impractical and too expensive, since it required assembling huge structures in orbit to produce the necessary power output. However, according to experts who spoke at the conference, the situation has changed as a result of technological advances and the urgency of decarbonizing the world's energy supply to prevent climate change.
Unlike most renewable energy production technologies used on Earth, including solar and wind energy, space-based solar energy can be available all the time because it does not depend on the weather and time of day. Currently, nuclear power plants or power plants powered by gas and coal are used to cover demand when the wind stops blowing or after sunset. Technology improvements may help partially solve this problem in the future. However, there are still difficulties in ensuring an uninterrupted zero-carbon energy supply by the middle of this century, as stipulated by international agreements on climate change.
The development of robotic technologies, increased efficiency of wireless energy transmission and the appearance of the SpaceX Starship rocket can make space solar energy a reality, experts said at the conference.
In 2022, the Space Solar Power Demonstrator mission, led by the California Institute of Technology, successfully demonstrated the transfer of solar energy from space. This achievement marked significant progress in the field of space solar energy.
A number of similar demonstration projects are currently being developed. Space agencies and research institutes such as the European Space Agency (ESA), the Defense Advanced Research Projects Agency (DARPA) and the U.S. Air Force are engaged in research on this technology. Commercial companies and startups are also developing concepts based on the capabilities of Starship and advances in space robotics.
However, the potential of space solar energy causes a mixed reaction. In January, NASA published a report expressing doubts about the feasibility of this technology. The report highlights the complexity and high energy costs associated with the construction, launch and assembly of orbital power plants. According to NASA estimates, the cost of electricity generated in this way will be 61 cents per kilowatt hour, which is significantly higher than the cost of solar or wind energy on Earth (5 cents per kilowatt hour).
In addition, the total carbon footprint of electricity production and greenhouse gas emissions generated by launch vehicles putting assemblies into orbit make such electricity less climate-friendly compared to ground-based technologies. For example, a space solar power plant with a capacity of one gigawatt, such as the conceptual CASSIOPeiA installation proposed by the British company Space Solar, will require 68 Starship launches to deliver components into space.