From "precise feeding" for a single device to "even rain and dew" for a group of moving targets, China's "daily project" has taken a crucial step forward. Recently, Duan Baoyan, an academician of the CAE Member and professor of Xi'an University of Electronic Science and Technology, led the team to independently develop a ground verification system for microwave wireless energy transmission of a pair of multiple moving targets, which made a major breakthrough, achieving kilowatt level DC output power at a distance of 100 meters, with a DC DC transmission efficiency of 20.8% and a beam collection efficiency of 88.0%. How does this' great power heavy weapon 'aimed at space work? What can the future bring us? First question: Is the principle of space "big pot" the same as that of wireless charging for mobile phones? The "Daily Project" is a space solar power station project led by Xi'an University of Electronic Science and Technology, and its core technical solution is the "Omega" plan proposed by Academician Duan Baoyan's team. Visually speaking, it is like a "big pot" hanging in space. This' big pot 'consists of a spotlight and a photovoltaic array located in the center, responsible for collecting sunlight and converting it into electrical energy, which is then transmitted back to the ground in the form of microwaves through a transmitting antenna. So, is it the same principle as wireless charging for mobile phones? The principles are not exactly the same, and the technical difficulty is incomparable. One is' charging across the air ', and the other is' transmission from heaven to earth', which is a million times different, "explained Qian Sihao, associate professor of the School of Mechanical and Electrical Engineering at Xi'an University of Electronic Science and Technology. Wireless charging of mobile phones relies on electromagnetic induction, and the transmission distance is only a few centimeters; Space solar power stations use microwave radiation to transmit energy, with distances ranging from several hundred kilometers to tens of thousands of kilometers. Duan Baoyan once likened a space solar power station to a "space charging station" in orbit, but this "charging station" is not a plug to interface, but uses microwave beams to "illuminate" the target for power supply. Second question: How does the device "lose weight" and "clone"? According to public reports, the team has made key progress in the integration, miniaturization, and lightweighting of transmitting and receiving antennas, laying the foundation for the deployment of equipment in space. This concerns a core issue - how to "slim down" bulky ground equipment and send it to the sky? The ground verification system has a 75 meter high support tower, but the equipment in the sky must be light and small. ”Qian Sihao said that the team compressed multiple functional modules into a smaller space through integrated design, while significantly reducing weight, which made it possible to launch them into space by rocket. As for the "distributed" design, Professor Li Xun from the School of Mechanical and Electrical Engineering at Xi'an University of Electronic Science and Technology explained: "Initially, we envisioned a huge spherical spotlight, but once it was hit by space debris, the entire system could be scrapped." Now it has been changed to "distributed" - that is, breaking down a large system into several small modules and adopting formation flight mode. Even if individual modules are broken, it does not affect overall performance and greatly improves reliability. At the same time, distributed design can also reduce voltage and avoid the risk of high-voltage discharge in space, "said Li Xun. Question 3: What is the difficulty of "one to many" and what is the efficiency? In 2022, when Duan Baoyan led his team to develop the world's first full link and full system space solar power plant ground verification system and passed the acceptance inspection, the system still achieved one-to-one microwave power wireless transmission. Just a few years later, the team achieved a leap from "single goal" to "multiple goals". From 'one-to-one' to 'one to many', it is a comprehensive system level technological improvement. ”Qian Sihao introduced. In one-to-one mode, the receiving antenna is static, but once the targets become dynamic multiple, it means that the transmitting antenna must point to each moving target accurately in real time during the movement of the receiving antenna. In the early stages of the experiment, target loss and beam deviation were common occurrences. The communication delay caused the data to fall behind, and even though the receiving antenna was at this point, our beam hit that point, "Qian Sihao recalled. The team has developed a precise closed-loop control system based on reverse beam guidance for this purpose. Li Xun gave an analogy: "When a device 'cries hungry', the system will emit a guiding signal by itself. When the transmitting end receives the signal, it can calculate the relative angle of the device in real time and accurately 'throw' the energy. This technology enables the system to supply power to multiple moving targets, effectively avoiding energy competition. The data shows that under the conditions of a speed of 30 kilometers per hour and a distance of 30 meters, the drone has achieved stable reception of 143 watts of microwave wireless transmission. So, how much is the remote charging loss? The numbers 20.8% and 88.0% are the answers. From around 15% in version 1.0 to 20.8% in version 2.0, every percentage point increase requires tremendous effort, "said Qian Sihao. Li Xun added that efficiency improvement relies on two methods. One is "accurate shooting": The team achieved a beam collection efficiency of 88.0% through waveform optimization and high-precision beam pointing control, which means that the vast majority of the emitted microwaves are accurately captured by the receiving antenna without being wasted due to "deviation". Secondly, it is' able to withstand ': In the 1.0 era, they used silicon-based diodes. Once the beam was biased, the diodes on the receiving surface would burn out piece by piece, and they often stayed up all night to troubleshoot the problem. Now we have adopted gallium nitride diodes, which can withstand a wide power bandwidth, not afraid of high or low power, and have high efficiency, "said Li Xun. On May 6th, at the achievement evaluation meeting organized by Shaanxi Provincial Technology Transfer Center, the expert group unanimously agreed that the overall project achievements have reached the international leading level. We are the only country in the world that runs the entire chain of 'collecting sunlight - photoelectric conversion - microwave emission - space transmission - rectification output', "said Li Xun. Question 4: How much longer does it take to reach heaven and how can we change our lives? The successful ground verification is just the first step of the Long March. The team admitted that there are at least three "difficulties" in deploying a real space solar power station on a synchronous orbit 36000 kilometers away. The issue of "space survival" for devices is the first hurdle. The devices used on the ground may not work directly, "Qian Sihao said. The high radiation and extreme temperature differences in space pose a huge challenge to electronic components. Distance crossing is the second challenge. Qian Sihao said, "At such a long distance, if the beam divergence angle is slightly larger, it may be a few tens of kilometers square when it reaches the ground, and it cannot be received at all." How to achieve precise focusing at ultra long distances is a technical challenge that urgently needs to be overcome. The third challenge is precise control of high-speed moving targets. Both low Earth orbit satellites and space stations are flying at speeds of several kilometers per second. If we don't have precise control, it's likely that we'll just miss each other, "Qian Sihao said. So, when will this technology light up the lives of ordinary people? Many small and medium-sized satellites rely on their own solar panels for power supply, and once they reach the shadow area of the Earth, they run out of power. ”Qian Sihao said. With the 'space charging station', satellites can replenish energy at any time, and we are expected to enjoy more stable mobile phone signals and more accurate positioning services. At present, the team is actively connecting with application scenarios such as emergency power supply, microwave wireless power supply for drones and special robots. Duan Xuechao, Vice Dean of the School of Mechanical and Electrical Engineering at Xi'an University of Electronic Science and Technology, said, "Communication interruptions and power outages in disaster areas make temporary power supply facilities slow and expensive. In the future, through long-distance microwave wireless power transmission technology, emergency equipment in disaster areas can be wirelessly powered." He gave an example that a robot cleaning glass curtain walls is now dragging a long cable, which is both dangerous and troublesome. In the future, when exposed to a microwave, it will be able to charge while working. (Looking into the New Era)