Space-based solar energy, rather than controlled nuclear fusion, will completely solve human energy problems?

solar panel. (Xinhua News Agency reporter Xie Han/photo)

On April 7, 2022, Elon Musk said on social media: "Compared to the huge energy that reaches the earth from the sun, the solar energy used by humans is minimal! Solar power per square kilometer is about 1GW. In terms of the current energy efficiency ratio of solar power generation units, it can produce about 200MW of power generation power per square kilometer. In other words, a small corner of Texas (covered with solar panels) can meet the electricity demand of the entire United States.

Musk's words are promoting his Solar City company, and he does not explicitly say that he will launch the "space-based solar" project. But combined with some of his recent scattered remarks and the industrial layout in recent years, he is likely to dabble in this novel area.

In 2021, Musk said; he doesn't think "controlled nuclear fusion" is that important, because the sun is the largest and most perfect nuclear fusion reactor, so why not make full use of its energy and start a new one?

At the end of the year, when attending the International Astronautical Congress, some "environmentalists" asked: Why do you launch so many rockets and emit so many greenhouse gases every year? Just because you personally want to go to Mars? Musk replied: Solar energy is the clean energy, and the energy density of space-based solar energy is greater, and the current development process will be conducive to the long-term environmental protection in the future... A word poked at the heart of the "environmentalist".

Earth's energy comes from space, mainly from the sun: the total solar power received by the earth is about 1.7 × 10^14KW, of which 47% passes through the atmosphere to the surface, and the rest is attenuated by the reflection and scattering of the atmosphere, and these energies account for only one-billionth of the total radiation energy of the sun. But the other side of the extremely low utilization rate is that the potential is huge.

But the existing solar ground power station is not ideal, first of all, its footprint is too large, human beings also need land for farming, living. And on Earth, half the time of the day is night, and only half of the time of work.

Cloud layer and air pollution, the blocking and attenuation of sunlight, are the main factors affecting the efficiency of solar power generation: particle pollutants in the bottom atmosphere form an aerosol, which will block sunlight transmission and deposit on solar panels, in more polluted areas, and even lead to a decline in solar power generation efficiency of more than 50%.

Space-based solar energy, which does not occupy the ground, saves rare earth resources; there is no atmospheric reflection and scattering effect, and the solar radiation acceptance rate reaches 100%; there is no day and night rotation in the sun-synchronous orbit, and the continuous work is 24 hours a day; there is no change in cloudy winter and summer, and the working conditions are constant for 365 days a year; and there is no problem of gradually reducing the power generation efficiency due to sand and dust accumulation and material oxidation. At the current level of science and technology, the power generation efficiency of solar panels per unit area is 5 times higher than that of ground stations.

Considering the scientific and technological progress in the next few decades: the quality of the "solar film" based on the development of graphene, nanomaterials and so on will be reduced to the fraction of the current "solar panel"; the energy efficiency of the solar power generation medium will be increased by 20%-30%; if the space-based solar base station is pushed in the direction of the orbit of Venus to make it closer to the star, the "solar constant" obtained will be higher, and its unit area power generation efficiency will be increased by 10 times, which is a vision, not a dream.

Perhaps, "space-based solar energy" is a means to replace most of the fossil energy consumption on the earth, reduce pollution and greenhouse gas emissions, and greatly meet environmental demands.

Japan, which is energy-poor, is very concerned about "space-based solar energy". In September 2009, Mitsubishi Electric and IHI partnered to start a 2 trillion yen ($21 billion) project to build a large solar farm in space over 30 years and transmit energy back to Earth.

In 2014, Japan's "Shimizu Construction" announced the "Moon Ring" plan: solar panels orbiting the moon's equator, with a length of nearly 11,000 kilometers, generating about 13,000 TW (terawatts, 10^12W) of energy, and the current global annual electricity consumption is about 15 TW.

In March 2015, Japan's Mitsubishi Corporation made a breakthrough in energy wireless transmission: scientists successfully used microwaves to transmit 1.8kw of electrical energy to a distance of about 55 meters. Although it is still very far from practical, the first step has finally been taken, laying the scientific and technological foundation for transferring energy from space to Earth.

However, the progress of Japan's "space-based solar energy" research and development will not be too smooth. Because the cost of space launch is very expensive, if there is no low-cost launch technology, all space development can only stay at the level of science fiction. The Japanese Ministry of Trade and the Japan Aerospace Exploration Agency acknowledged that the cost of "space-based solar energy" is extremely expensive, and the cost of a rocket per launch is about $105 million. At present, the shortcomings of Japan's aerospace are that they have not yet mastered the reusable rocket technology.

NASA and the energy sector, over the past 30 years, have spent more than $80 million to intermittently study "space-based solar energy," but little progress has actually been made. The reason is: First, NASA itself has not mastered low-cost launch technology, and second, the United States is an energy exporter, and the demand for "space-based solar energy" is not urgent and strong.

China, a large country with a large population and little energy, is certainly more interested in solar energy. In 2016, the mainland has begun to conduct "space-based solar" research and has developed a "four-step" strategy, envisaging the construction of its own experimental space-based solar power plants between 2036 and 2050, with an operating life of about 30 years.

Musk has great advantages: he has aerospace companies, solar energy companies, has the advantage of unified decision-making and management, and integrates resources within his own system. Competitors, on the other hand, need cross-industry, cross-sectoral, and administrative coordination. As a result, Musk's businesses are always able to respond to the market at a faster pace and at a lower cost.

Its competitors have not yet mastered the reusable rocket technology, and SpaceX has been "eating alone" in this market for nearly 6 years. According to the research and development progress of its competitors, this "eat alone" state will continue for another 3-4 years. Even if competitive products emerge in a few years, SpaceX's second-generation reusable rocket will have a technological and cost advantage of a leading generation.

Musk has the required advantage, the closest to "space-based solar", will he abandon this future field that has no actual competitors? Give up the opportunity to take the lead in "eating alone" again? Perhaps, he just keeps a low profile in this field, does not formally open his own plans, and the only words in the media and self-media show that he is not completely devoid of ideas in "space-based solar energy".

For the entire human race, standing on the threshold of the "interstellar era", interstellar voyages, dark matter dark energy, space-time warping, etc., are too sci-fi, too far away, "space-based solar energy" is one of the most realistic near-future space development projects.

Energy is the most realistic pursuit of wealth. If, in the next few decades, this huge project will begin to start construction and continue for hundreds of years, it will become one of the greatest projects of mankind in the future, and it will also provide tens of millions of new jobs for aerospace, solar energy, AI, electric power, manufacturing, infrastructure and other related industries, and these new jobs will be passed on for generations and even longer.

Mei Yijun