Space solar power plant: China plans to build a first photovoltaic power plant in space by 2035.
To face its colossal energy challenges, China leads the way
The idea of capturing the sun's rays in space to produce energy is not new. Already in 1925, the Russian scientist Konstantin Tsiolkovsky had imagined the project of permanently capturing the energy of the sun's rays and returning it to Earth in the form of a beam of waves.
In 1970, NASA demonstrated that it was technically possible to produce electricity in space and transmit this energy to Earth by radiation, laser, or microwave. But 50 years ago, such a project was unthinkable economically.
Half a century later, advancements, both technological and economic, have been so dramatic that space-based solar power projects are falling out of the box. The current energy and climatic context is not for nothing and has only increased interest in this objective, judged yesterday as utopian and unachievable.
In space, solar radiation is not attenuated or filtered by the atmosphere and clouds: it is four times more intense than that which arrives at the surface of the Earth. In addition, if the power station is positioned far enough from our planet it will never pass in its shadow and the energy captured will therefore not be intermittent. The idea is to place this station in a stable geostationary orbit at an altitude of about 36,000 kilometers above the earth's surface. For the same area, such a space installation could, in the end, capture eight times more energy than a terrestrial photovoltaic farm.
Initiatives around the world
While JAXA (the Japanese space agency) has been working since 2009 in collaboration with seventeen private companies on a solar power plant project of 1,000 megawatts (the equivalent of a large nuclear reactor) by 2030, The California Institute of Technology (Caltech) announced in 2018 the creation of a space prototype allowing the collection of solar energy and its transmission to Earth, wirelessly.
Russia and India are working on similar projects, and China recently announced that it, too, has firm plans to put its first space solar power plants into orbit by 2035. The country seems to have a head start, thanks to its many technical skills in space, photovoltaics, and wireless energy transmission.
Among the progress made in recent years, the reduction in the weight of solar modules is a major development. For its space prototype, Caltech is working on modules weighing 800 grams per m², while it takes between 9 and 12 kg for 1 m² of a conventional photovoltaic panel. The recent development of organic photovoltaic films also opens up the field of possibilities in terms of space solar power plants.
Then, the performance of the modules has changed significantly in recent years. This can now reach 24% thanks to heterojunction solar cells, or even 46% with the most efficient cells in the laboratory, while the efficiency is still on average only about 15% for a conventional monocrystalline panel.
An astronomical cost, but constantly falling
The cost per tonne of material transported is a fundamental factor in the feasibility of building a space solar power plant, but may soon no longer be a major obstacle.
With its Ariane 5 launcher, Arianespace currently charges between 8,300 and 18,700 dollars per kilogram of material put into orbit. The future Ariane 6 launcher, still in development, should make it possible to lower this price to 10,000 dollars per kilo.
Elon Musk's SpaceX launcher came to play the spoilsport by offering between $ 4,700 and $ 12,600 per kilo of on-board equipment, a price of 33 to 43% lower.
In the longer term, the European Space Agency, ArianeGroup, and CNES are working together to develop a reusable launcher. It should be operational by 2030. The consortium will then be able to offer 5,000 dollars per kilo launched into orbit, ie a price half the price of Ariane 6.
But at 10,000 dollars per kilo, the cost of assembling a one-megawatt station, the weight of which is estimated by Chinese engineers at 1,000 tonnes for a 5 km² plant, would still amount to 10 billion dollars.
And the carbon footprint in all of this?
Although there is no precise study on this subject, the question of the carbon return time remains unresolved for this project: how many launchers will it take to propel into space to transport 1,000 tons of material? With what fuel, and with what impact in terms of greenhouse gases?
It is very likely that the carbon footprint will be much less positive than that of the simple installation of photovoltaic panels on our good old shed roofs.
However, the situation in China allows us to consider the project from a different perspective. In 2018, China's coal-fired power plants produced 1,027 gigawatts, representing 4.6 billion tons of coal.
While it is the leading consumer of coal (50.5% of global consumption), and its use increased by 4% in 2019, China will no longer be able to ensure its economic development from this fossil fuel. for reasons that are both economic (renewable is now less expensive), health (more than 3 million premature deaths are caused by a level of fine particles higher than that recommended by the WHO), but above all climatic. The Middle Kingdom is in fact responsible for 30% of global emissions of greenhouse gases of human origin. The environmental impact of space photovoltaic power plants should, therefore, be compared to the significant CO 2 emissions caused by coal power plants.
Moreover, we are not unaware that in addition to the enormous needs of China in terms of energy production, space solar power plant projects make it possible to green up the country's image, but above all also meet a geostrategic need for asserting its power at the global level, and become a key supplier of clean energy.