Explainer: Space-based solar power & energy beaming — the concepts, the economics, and the decision checklist

In December 2025, Overview Energy emerged from stealth after successfully transmitting high-power energy from a moving aircraft to a ground receiver five kilometers below—the first demonstration of wireless power beaming in motion using the same optical systems planned for orbital deployment. This milestone, combined with Caltech's historic 2023 transmission of detectable microwave power from orbit to Earth and Japan's planned OHISAMA satellite launch in 2025, signals that space-based solar power (SBSP) is transitioning from theoretical concept to engineering reality. With the global SBSP market projected to grow from $3.54 billion in 2024 to $6.8 billion by 2040, and nations from China to the UK committing billions in development funding, sustainability leaders can no longer dismiss orbital energy as science fiction.

Why It Matters

Space-based solar power represents a fundamentally different approach to clean energy generation. Unlike terrestrial solar installations that operate at 15-25% capacity factors due to weather, atmospheric absorption, and day-night cycles, orbital solar arrays capture sunlight continuously at intensities up to 144% of Earth's surface maximum—yielding theoretical capacity factors approaching 99%.

The physics are compelling: a single two-gigawatt satellite could power approximately two million homes while requiring orders of magnitude fewer critical minerals than equivalent terrestrial solar-plus-storage systems. According to NASA's January 2024 SBSP assessment, space-based systems eliminate the intermittency challenge that currently drives 60-70% of grid-scale storage investment, potentially reducing total system costs for deep decarbonization scenarios.

For sustainability practitioners, SBSP addresses three structural limitations of ground-based renewables:

Geographic constraints: Orbital systems can beam power to any location on Earth, including regions with poor solar irradiance, remote industrial operations, or disaster zones lacking grid infrastructure. The UK Space Energy Initiative projects that SBSP could supply 30% of British electricity by the mid-2040s—a nation where ground solar achieves only 10-12% capacity factors.

Land use intensity: Terrestrial solar requires 5-10 acres per megawatt, creating competition with agriculture and biodiversity. SBSP consolidates generation infrastructure in orbit, requiring only compact ground receivers (5-10 meters for laser systems, larger for microwave).

Baseload compatibility: Unlike wind and solar that require expensive storage or gas backup for grid stability, SBSP delivers dispatchable power on demand, potentially serving as clean baseload complementing variable renewables.

Key Concepts

Wireless Power Transmission Technologies

SBSP systems convert collected solar energy into either microwave or laser beams for transmission to Earth:

Microwave transmission operates at 2-10 GHz frequencies, penetrating clouds and rain with minimal losses. Caltech's SSPD-1 demonstrator used 10 GHz phased arrays with custom integrated circuits enabling electronic beam steering without moving parts. Microwave intensity at ground receivers (~230 W/m²) is approximately one-quarter of midday sunlight, posing minimal safety concerns. However, microwave systems require large receiving antennas (rectennas)—potentially several square kilometers for gigawatt-scale installations.

Laser/optical transmission uses near-infrared wavelengths similar to fiber optic communications. Overview Energy and formerly Aetherflux pioneered this approach, enabling much smaller ground stations (5-10 meter apertures) and narrower beams. Trade-offs include weather sensitivity and more stringent pointing accuracy requirements over orbital distances.

Orbital Configurations

Geostationary orbit (GEO) at 36,000 km altitude allows satellites to remain fixed over a ground station, enabling continuous power delivery but requiring extremely high launch mass and cost. China's ambitious program targets GEO deployment with a one-kilometer-wide array by 2050.

Low Earth orbit (LEO) at 400-2,000 km reduces launch costs and enables smaller demonstration satellites but requires constellations of many satellites to maintain coverage. Japan's OHISAMA demonstrator operates at 400 km altitude with 40 km beaming range.

Key Performance Metrics

Metric	Current State (2025)	Commercial Target	Terrestrial Solar Benchmark
LCOE (levelized cost of energy)	~$0.61/kWh	<$0.10/kWh	$0.03-0.05/kWh
Capacity factor	Theoretical 99%	>90%	15-25%
Power density at receiver	230 W/m² (microwave)	500+ W/m²	1,000 W/m² peak
Transmission efficiency	60-80%	>85%	N/A (direct)
Satellite mass per GW	~10,000 tonnes	<2,000 tonnes	N/A

What's Working and What Isn't

What's Working

Wireless power transmission has been validated in space. Caltech's MAPLE experiment successfully beamed detectable power from orbit to its Pasadena campus in May 2023—the first confirmed space-to-Earth power transmission. The flexible phased array demonstrated electronic beam steering using constructive and destructive interference, proving that modular, lightweight architectures can replace expensive rigid systems.

Launch costs continue declining. SpaceX's Starship promises $10-100/kg to orbit, compared to $1,000-5,000/kg historically. This trajectory addresses SBSP's primary economic barrier: NASA's 2024 analysis identified launch costs as the dominant driver of current $0.61/kWh LCOE estimates.

Near-term applications provide revenue pathways. Military applications—powering remote forward operating bases, disaster response, and mobile operations—offer premium price tolerance that can sustain early-stage economics. The U.S. Air Force's SSPIDR program and Defense Department's Operational Energy Capability Improvement Fund are actively funding demonstrations.

Space-to-space power transmission is accelerating. Star Catcher's planned 200-satellite constellation at 1,500 km altitude would beam 100W-100kW to client satellites, addressing a growing market for on-orbit power services and validating transmission technologies at reduced regulatory complexity.

What Isn't Working

Economics remain challenging for terrestrial competition. At $0.61/kWh, current SBSP costs exceed terrestrial solar-plus-storage by 10-15x. While launch cost reductions and mass production could close this gap, skeptics argue that falling battery costs and improved grid flexibility will maintain terrestrial advantages.

Regulatory frameworks are immature. No international standards govern spectrum allocation for power beaming, laser safety corridors, or orbital debris from large structures. The lack of clear permitting pathways delays project timelines and increases investor uncertainty.

Scale demonstrations lag. While Caltech transmitted microwatts and Overview Energy demonstrated kilowatts, commercial systems require megawatt-to-gigawatt capacities. The engineering leap from current prototypes to operational scale involves unsolved challenges in km-scale coherent phased arrays and autonomous orbital assembly.

Investor patience is limited. SBSP requires decade-long development timelines and multi-billion dollar deployments—mismatched with typical venture capital exit horizons. Several startups, including Aetherflux's December 2025 pivot to space-based data centers, have shifted strategies when SBSP commercialization timelines proved longer than anticipated.

Key Players

Established Leaders

Northrop Grumman leads U.S. defense-funded SBSP development through its $180 million SSPIDR/ARACHNE program with the Air Force Research Laboratory. The company brings decades of space systems integration experience and government contracting relationships essential for early market development.

China Aerospace Science and Technology Corporation (CASC) executes China's state-directed SBSP program, targeting a 10 kW LEO demonstration by 2027-2028 and megawatt-scale GEO deployment by 2030. CASC's integrated approach combines heavy-lift rocket development (Long March-9), satellite manufacturing, and ground infrastructure.

European Space Agency (ESA) advances the SOLARIS program toward 2030 demonstrations and 2040 operational capability, incorporating the CASSIOPeiA design for 2 GW satellite arrays. ESA's multinational structure enables cost-sharing and technology pooling across European aerospace capabilities.

Emerging Startups

Overview Energy (Virginia, USA) emerged from stealth in December 2025 after demonstrating high-power near-infrared transmission from a moving aircraft. The company targets LEO demonstrations by 2028 and megawatt-scale GEO commercial operations by 2030, focusing on beaming power to existing terrestrial solar farms for grid integration simplicity.

Space Solar (UK) leads the CASSIOPeiA project under the Space Energy Initiative, coordinating over 90 organizations toward commercial SBSP deployment. The company received £1.5 million in UK government funding and recently demonstrated 360-degree power-beam steering with Queen's University Belfast.

Virtus Solis (USA) claims the first economically viable SBSP design, emphasizing cost optimization through manufacturing innovations and standardized satellite bus architectures. The company targets cost-competitive power delivery through modular GEO-based systems.

Solestial (USA) develops ultrathin silicon solar cells optimized for space deployment, partnering with NASA Glenn Research Center as of December 2025 to advance radiation-resistant photovoltaics critical for long-duration orbital operations.

Key Investors & Funders

Breakthrough Energy Ventures (Bill Gates) invested in Aetherflux, signaling climate-focused capital interest in frontier energy technologies despite long development timelines.

Lowercarbon Capital, Prime Movers Lab, and Engine Ventures backed Overview Energy, representing specialized climate-tech and deep-tech investors comfortable with hardware-intensive ventures.

UK Government committed £4.3 million to SBSP innovation challenges, with the Space Energy Initiative projecting commercial systems within six years of sustained investment.

U.S. Department of Defense provides critical early-market demand through OECIF grants and AFRL contracts, de-risking technology development for subsequent commercial applications.

Examples

1. Caltech Space Solar Power Project

Caltech's SSPD-1 mission, funded by $100+ million from the Donald Bren Foundation and $12.5 million from Northrop Grumman, demonstrated three critical technologies between January 2023 and early 2024. The MAPLE transmitter array beamed detectable power to Earth using flexible, lightweight construction an order of magnitude lighter than rigid alternatives. ALBA tested 32 photovoltaic cell types under space radiation, while DOLCE validated deployable structures for modular spacecraft. Professor Ali Hajimiri's team proved that phased array beam steering eliminates mechanical pointing requirements—a crucial simplification for scalable orbital systems.

2. Japan OHISAMA Program

Japan's OHISAMA satellite, scheduled for 2025 launch, represents the first national space agency demonstration of complete SBSP functionality. The 180 kg satellite in 400 km LEO orbit will transmit 1 kW via microwave to ground stations 40 km away—sufficient power for one dishwasher cycle during five-minute transmission windows. Ground tests and aircraft-based validations at 5-7 km range confirmed system performance. OHISAMA's modest scale enables rapid iteration and risk reduction before Japan's planned larger deployments through 2030.

3. China Bishan Test Facility

Since 2019, China has constructed a dedicated SBSP test facility in Bishan, Chongqing, validating ground-based microwave transmission systems before orbital deployment. Xidian University completed full system tests in June 2022, following a 300-meter line-of-sight microwave transmission in August 2021. This systematic ground-validation approach, combined with Long March-9 heavy-lift rocket development, positions China's CASC to attempt 1 GW orbital power stations by 2050—potentially the largest single energy infrastructure project in human history.

Action Checklist

• Assess organizational energy profiles for SBSP compatibility: remote operations, island nations, disaster response capabilities, and ultra-premium power applications represent near-term addressable markets
• Monitor regulatory developments in ITU spectrum allocation, national aviation authorities' laser safety frameworks, and space sustainability standards that will shape deployment timelines
• Evaluate supply chain implications for critical minerals if SBSP scales significantly—reduced demand for grid-scale batteries could affect lithium, cobalt, and rare earth investment assumptions
• Engage policy discussions through organizations like the Space Energy Initiative to shape standards, incentive structures, and procurement frameworks favorable to clean energy innovation
• Track demonstration milestones from Overview Energy (2028 LEO demo), Japan OHISAMA (2025), and China (2027-2028 LEO mission) as technical validation checkpoints
• Consider pilot partnerships with SBSP developers for disaster response, military, or remote industrial applications where premium pricing and operational urgency justify early-stage technology adoption

FAQ

Q: How does SBSP cost compare to terrestrial renewables, and when might it become competitive? A: Current SBSP LCOE estimates range from $0.61/kWh (NASA 2024) to over $1/kWh—roughly 10-20x terrestrial solar-plus-storage. Competitiveness depends primarily on launch cost reductions: if Starship achieves $50/kg to orbit and satellite mass decreases through manufacturing innovation, LCOE could approach $0.10/kWh by the late 2030s. However, SBSP may achieve competitiveness sooner in premium applications—remote military operations, disaster zones, and island nations—where delivered energy costs already exceed $0.30-0.50/kWh.

Q: Is wireless power beaming safe for humans, wildlife, and aircraft? A: Microwave transmission systems operate at intensities (~230 W/m²) approximately one-quarter of midday sunlight, well below safety thresholds established for telecommunications equipment. Laser systems require designated exclusion zones and aviation coordination but use wavelengths similar to fiber optic networks with well-understood safety protocols. Regulatory frameworks remain immature, but no fundamental safety barriers prevent deployment with appropriate operational controls.

Q: What happens during cloudy weather or at night—doesn't SBSP have the same intermittency as ground solar? A: No. Satellites in geostationary orbit receive continuous sunlight except during brief eclipse seasons (totaling less than 1% of annual hours), and even LEO constellations can provide near-continuous coverage through multiple satellites. This fundamental physics advantage enables 90%+ capacity factors compared to 15-25% for terrestrial solar. Microwave transmission penetrates clouds with minimal losses; laser systems experience weather sensitivity but can switch between multiple ground stations to maintain delivery.

Q: Why hasn't SBSP been deployed already if the concept has existed since the 1960s? A: Three barriers have historically blocked deployment: prohibitive launch costs ($10,000+/kg historically), immature lightweight materials for large orbital structures, and electronics limitations for efficient power conversion and beam steering. All three constraints are now easing: SpaceX targets $50-100/kg to orbit, advanced composites and deployable structures have matured through ISS and commercial satellite programs, and integrated circuit advances enable the flexible phased arrays Caltech demonstrated in 2023. The current wave of startups and national programs reflects genuine technological readiness rather than mere renewed enthusiasm.

Q: How does SBSP compare to other clean baseload options like nuclear or geothermal? A: SBSP offers unique advantages: no fuel requirements, no radioactive waste, no geographic limitations of geothermal, and minimal land use. However, advanced nuclear (SMRs) and enhanced geothermal are further along commercialization pathways with clearer regulatory precedents. For sustainability portfolios, SBSP represents a 2035-2045 option worth monitoring rather than a near-term deployment candidate, except in niche premium applications.

Sources

• NASA Office of Technology, Policy, and Strategy. "Space-Based Solar Power." January 2024. https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf

• Caltech Space Solar Power Project. "Space Solar Power Project Ends First In-Space Mission with Successes and Lessons." 2024. https://www.caltech.edu/about/news/space-solar-power-project-ends-first-in-space-mission-with-successes-and-lessons

• World Economic Forum. "Why we need space-based solar power (SBSP)." October 2025. https://www.weforum.org/stories/2025/10/space-based-solar-power-energy-transition/

• PV Magazine. "U.S. space solar startup proves wireless power system works in motion." December 2025. https://pv-magazine-usa.com/2025/12/11/u-s-space-solar-startup-proves-wireless-power-system-works-in-motion/

• IEEE Spectrum. "Caltech's SSPD-1 Is a New Idea for Space-Based Solar." 2024. https://spectrum.ieee.org/space-based-solar-power

• UK Space Energy Initiative and Space Solar. Industry reports and government funding announcements, 2024-2025.

• RatedPower. "Japan's groundbreaking solar power experiment: solar power from space." 2024. https://ratedpower.com/blog/japan-solar-power-from-space/

• Emergen Research. "Top 10 Companies in Space-Based Solar Power Market." 2024. https://www.emergenresearch.com/blog/top-10-companies-in-space-based-solar-power-market