Space Based Solar Power 10 Watt Demos in Space Now and Beaming and Other Demos Now to 2023

The US military tested a pizza box sized solar power module – Photovoltaic Radiofrequency Antenna Module (PRAM) in space. It was first launched in May 2020, attached to the Pentagon’s X-37B unmanned drone.

Orbital Demonstrations for Large-Scale Deployable SPS

The Air Force Research Laboratory (AFRL) is executing a major demonstration project with the goal of beaming power collected in space to expeditionary forces on Earth. The motivation for this capability is clear: assured energy supply with reduced vulnerabilities and lower-cost logistics. The AFRL project created to achieve this capability is Space Solar Power Incremental Demonstrations and Research (SSPIDR). SSPIDR is methodically pursuing rapid, demonstration-driven activities with increasing performance and integration level to reduce risk for an operational space solar power system.

SSPIDR has two major thrust areas:
(1) incremental demonstrations and
(2) developing critical technology elements (CTEs).

Three initial in-orbit prototype demonstrations are being developed in Phase I to advance the TRL of the needed component technologies to enable an operational space solar power system.

(1) Arachne,
(2) SPINDLE, and

Arachne will be the world’s first space-to-ground power beaming demonstration of a solarto-RF modular panel with in-situ surface-shape measurement to optimize beam formation. The solar-to-RF panel technology is designed to scale to very large apertures and to support high volume, low-cost manufacturing. Arachne is planned to fly in 2023. SPINDLE will test on-orbit structural deployment of a sub-scale version of the operational system. SPINDLE is designed to test deployment kinematics and deployed structural dynamics. Finally, SPIRRAL will test thermal management approaches to ensure a long-lasting, high-performance system. The SPIRRAL experiment is planned to launch in 2023 via Alpha Space’s MISS-E platform for rendezvous with the International Space Station.


The Photovoltaic Radiofrequency Antenna Module (PRAM), 12×12-inch panel, is capable of producing about 10 watts of energy for transmission.

IEEE Journal of Microwaves – Microwave and Millimeter Wave
Power Beaming

Abstract – Power beaming is the efficient point-to-point transfer of electrical energy across free space by a directive electromagnetic beam. This paper clarifies the basic principles of power beaming in simple terms, and proposes a benchmarking methodology for improving the comparative assessment of power beaming systems and technology. An in-depth historical overview tracing the worldwide progress in microwave and millimeter wave (mmWave) experimental demonstrations over the past 60 years shows clear evidence of a significant increase in activity during the last 5 years. In addition, a review of progress in scalable rectenna arrays for the reception of microwave power beaming shows sufficient maturity for new research to initiate on the ruggedization, productization, and system integration aspects of the technology. A review of regulatory issues including spectrum management and safety indicates the need for additional technical solutions and international coordination.

Breaking results reported in this paper include
1) data from the first in-orbit flight test of a solar-to-RF “sandwich module”,
2) the construction of multiple US in-orbit demonstrations, planned for 2023 launch, that will demonstrate key technologies for space-based solar power, and
3) a 100-kW mmWave power beaming transmitter demonstrating inherent human life safety.

Increased Areal Absorption per Diode

In 2018, the University of Waterloo and Prince Sattam University collaborated on ways to increase the absorption efficiency per unit area to near unity in order to channel more RF to the rectifying diodes. Using detailed Floquet analysis, they designed the 3.4 GHz energy harvesting rectenna array. This array used asymmetric dipoles covered by a high-permittivity TMM-10i superstrate to increase the incident power delivered to the diodes. An overall array RF-to-DC conversion efficiency of 76% was obtained experimentally, which the authors claim is the highest ever recorded for an energy harvesting surface.

Broad Bandwidth, MMWAVE Operation

In 2019, Shanghai University researchers developed a novel 35 GHz millimeter-wave rectenna designed for broadband performance. The array was
composed of 16 subarrays. Each subarray had a 2 × 2 array of slot coupled patch antennas backed by substrate integrated waveguide (SIW) cavities and a single rectifier. The antennas worked well from 31 to 40 GHz. Each 2 × 2 rectenna subarray had an RF-to-DC conversion efficiency of 51% when 13 dBm was incident upon a 550 load.

Progress and creativity in rectenna array technologies shows sufficient maturity for new work to begin productization of the technology for low cost, environmental resiliency, and compatibility with real-world power systems in support of future large-scale infrastructure and other real world deployments.

Caltech has active development of many aspects of space based solar power. They are advancing lightweight structures and are progressing to inspace demonstrations. Nextbigfuture will have separate articles covering their work and the recent 2021 SSSP conference.

SOURCES – USNRL, Caltech, IEEE microwave journal
Written by Brian Wang,