China to engineer a gigawatt-scale PV plant – in space


A few decades later than Russia and the U.S., but with no less ambition, China’s space race is fully into gear.

The nation’s latest reported project: a multi-gigawatt solar plant to orbit the Earth and transmit energy in the form of microwaves down to a land-based receiver. Such a supply would be theoretically uninterrupted by nightfall or seasonal change, according to an article published in Chinese tech newspaper the Science and Technology Daily.

The monumentally ambitious project fits right into the same stable as the world’s longest bridge, from Hong Kong to Zhuhai; the world’s largest hydropower station – the Three Gorges Dam; and the huge ‘One Belt One Road’ infrastructure project.

The solar plan would also serve to underline China’s capabilities in space after the landing of the Lunar 4 spacecraft on the dark side of the Moon.

The experimental stages of the first space-based solar plant have reportedly been launched in Chongqing. If successful, the project would also see solar technology come full circle, as PV’s first field of application, decades ago, was to generate electricity for satellites and space stations orbiting the earth.

Geostationary orbit

The Chinese plan would position a solar power station 36,000 km above the Earth, in geostationary orbit, fixed above a certain spot on the Earth’s surface. Seasonal changes in solar irradiation and day and night changes would be negligibly minute and project researchers expect solar energy could be produced 99% of the time, representing a sixfold increase on utilization rates on the ground. Higher yields would also be likely due to a lack of atmosphere to absorb solar energy.

The fields of application for the project would not just be limited to the delivery of largely uninterrupted solar power. A space-based solar power station could supply remote areas on Earth as well as spacecraft and satellites and long-term, Moon-based space stations with electricity, the researchers suggested.

In recent years, great strides in the power conversion efficiency of solar cells and microwave conversion efficiency have been made, potentially rendering such an ambitious project feasible. Scaling is important and the project would need to reach a considerable size in the early stages. During the initial phases, the team would work towards a multi-megawatt application, with a solar panel field stretching across several square kilometers.

Such a power station would outweigh the largest man-made orbiter by a significant margin. The international space station weighs about 400 tons and required a joint international effort to be built. With a projected weight of several thousand tons, any space power station would require a considerably bigger effort. A gigawatt-scale power plant could weigh around 10,000 tons, providing severe logistical challenges.

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3D printing

The research team has reportedly suggested the plant be 3D-printed in space and assembled by robots. Even so, new earth-to-orbit vehicles, materials and energy conversion devices would have to be developed. Combined with the technical challenges related to remote control, in-orbit assembly and maintenance procedures, the project would face huge challenges.

Having been embedded in the nation’s twelfth five-year plan, in 2008, the key technology research and support for the project has come from the National Defense Science and Technology Bureau of China.

The team in Chongqing reportedly started work last year and will build a small-to-medium-sized solar plant to be based in the stratosphere between 2021 and 2025. According to the plans, the stratospheric plant would have a wireless, microwave-based grid connection to transmit energy it produces.

The newspaper report stated Chinese engineers have proposed a roadmap for realizing the ambitious project. Under the plan, after 2030 a megawatt-scale test station would be built. By 2050, the plan would be to have a gigawatt-scale solar power plant in space.

We’ve been here before…

The idea of transmitting solar energy from an area where it is abundant to where it is needed has made headlines before. Northern parts of Africa were to have hosted massive solar parks with transmission lines through the Mediterranean to Europe at one stage. That idea has faded amid concerns over price and security of supply, among other reasons.

In a – literally – more down to earth sense, PV’s golden hour arrived when the price of solar power fell below that of coal and gas in several markets.

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