As the global energy landscape undergoes a transformative shift toward sustainability, space-based solar power (SBSP) has emerged as a groundbreaking solution with the potential to redefine clean energy production. In 2025, two pivotal initiatives—Japan’s orbital power transmission tests and the U.S. Air Force’s upcoming microwave energy trials—are poised to accelerate this vision, bringing us closer to a future where abundant, uninterrupted solar energy is beamed from space to Earth.

Japan’s Orbital Power Transmission Breakthrough

Japan’s ambitious Ohisama program (Japanese for “sun”) represents a significant leap forward in SBSP technology. Slated for launch in 2025, the program will deploy a 180-kilogram satellite equipped with a 2-square-meter photovoltaic panel in low Earth orbit (LEO) at an altitude of 400 kilometers . The satellite will convert solar energy into microwaves and transmit approximately 1 kilowatt of power to a ground-based receiving antenna spanning 40 kilometers—a critical test of wireless energy transmission over interplanetary distances.

Central to Japan’s approach is its focus on scalability. By using small satellites and modular designs, the program aims to overcome the challenges of cost and complexity that have long hindered SBSP development. For instance, the satellite’s energy transmission will occur within minutes, but recharging its battery will take days, highlighting the need for advanced energy storage solutions . To address this, Japan plans to conduct mid-air trials in December 2024, using an aircraft-mounted photovoltaic panel to beam power over 5–7 kilometers, refining the technology before its orbital debut .

U.S. Air Force’s Microwave Energy Trials

Concurrent with Japan’s efforts, the U.S. Air Force is advancing high-power microwave (HPM) technology through its Chimera system, developed in partnership with Raytheon. While primarily designed for defense applications—such as neutralizing drone swarms—the system’s underlying technology has dual-use potential for SBSP . In 2024, Chimera demonstrated end-to-end fire control, successfully targeting and disabling aerial threats using concentrated microwave pulses, showcasing its precision and scalability .

The Air Force’s research into HPM aligns with broader SBSP objectives, particularly in optimizing energy transmission efficiency and minimizing atmospheric interference. For example, the system’s ability to rapidly adjust beam direction and power output could be adapted to track moving satellites and compensate for orbital dynamics . Additionally, the U.S. is exploring Thor, another HPM weapon capable of neutralizing multiple targets simultaneously, further refining the technology’s reliability and cost-effectiveness .

Technological Synergy and Challenges

Both Japan and the U.S. are leveraging complementary innovations to address SBSP’s core challenges: energy conversion, transmission, and cost. Japan’s focus on lightweight materials and modular satellite design , combined with the U.S.’s advancements in HPM beam control , could enable more efficient and resilient SBSP systems. However, significant hurdles remain, including:

Cost: Current estimates suggest that a gigawatt-scale SBSP system would cost upwards of $7 billion, primarily due to launch expenses and materials .

Efficiency: While space-based solar panels generate 3–5 times more energy than ground-based systems, wireless transmission losses and atmospheric absorption must be minimized .

Infrastructure: Ground-based receiving stations require vast arrays of antennas, posing logistical and land-use challenges .

The Path to Commercialization

Despite these challenges, 2025 marks a critical inflection point. Japan’s Ohisama program and the U.S. Air Force’s HPM trials are not isolated efforts but part of a global race to unlock SBSP’s potential. China, for instance, plans to deploy a 1-megawatt space-based solar station by 2030 , while the European Space Agency is exploring robotic assembly for orbital infrastructure .

Key advancements—such as SpaceX’s Starship reducing launch costs to $800 per kilogram and breakthroughs in microwave transmission efficiency —are narrowing the gap between ambition and reality. By 2035, the International Energy Agency projects that SBSP could supply 19% of global electricity if costs continue to decline .

Conclusion

The year 2025 will be a defining moment for space-based solar power, with Japan and the U.S. spearheading technological milestones that could reshape the energy sector. While challenges like cost and infrastructure persist, the convergence of satellite miniaturization, microwave beam control, and reusable rocket technology offers unprecedented hope. As these innovations move from the lab to orbit, they carry the promise of a future where clean, reliable energy is no longer bound by Earth’s limitations—a future where the sun’s power is truly within our reach.

（Writer：Lorik）