Scientists from Caltech have reported a significant milestone in their Space Solar Power Project (SSPP), successfully demonstrating the wireless transmission of power from space to Earth. A solar power collector was launched into space earlier this year aboard SpaceX’s Falcon 9 rocket, and has since begun operation.
The SSPP aims to harness clean energy in space, where solar collection devices can theoretically capture sunlight 24/7 all year round, without the influence of weather or day-night cycles. In fact, the potential solar energy per square meter in space is, in fact, eight times that of Earth.
However, such innovation comes at a high cost. To launch solar panels into space, the Levelized Cost of Electricity (LCoE) falls between US$1–2/kWh, which is approximately six times the retail electricity price in the US.
In January, Caltech launched a 50kg prototype Space Solar Power Demonstrator (SSPD-1) into orbit. The SSPD-1 consists of three key experiments:
- DOLCE (Deployable on-Orbit ultralight Composite Experiment): A structure measuring 6 feet by 6 feet that demonstrates the architecture, packaging scheme, and deployment mechanisms of the modular spacecraft.
- ALBA: Carries 32 different types of solar cells to determine which ones can survive in a space environment.
- MAPLE (Microwave array for Power-transfer Low-orbit Experiment): Demonstrates long-distance wireless power transmission in space.
Ali Hajimiri, Co-Director of the SSPP and Professor of Electrical Engineering and Medical Engineering at Caltech, revealed that experiments have proven that MAPLE can successfully transmit power to a receiver in space and, by programming the array, can also direct power to Earth. This has been detected at Caltech.
MAPLE includes two independent receiver arrays, about a foot away from the transmitter, primarily used to receive energy and convert it into direct current to illuminate a pair of LEDs. Current experiments in space are attempting to light each LED independently, testing in a harsh space environment that includes wide temperature fluctuations and solar radiation.
"To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space even with expensive rigid structures. We are doing it with flexible lightweight structures and with our own integrated circuits. This is a first," says Hajimiri.
The MAPLE device also includes a small window for energy emission. The team at Caltech detected the signal at the expected time and frequency, confirming the correct frequency shift from the orbital path.
In addition to proving that the transmitter can survive and maintain its performance, the experiment also incorporates a feedback mechanism. The power transmission antenna is divided into 16 sets, each driven by a flexible integrated circuit chip. Hajimiri’s team is currently evaluating the performance of individual components within the system using small-scale interference patterns and measuring the differences between combinations. This complex task may take up to six months to complete.
(Image Source: Caltech)
