Satellite Transmits Space-Based Solar Power to Earth

Caltech Scientists Successfully Transmit Solar Power from Satellite to Earth

Solar power has long been hailed as a promising renewable energy source, and recent breakthroughs at the California Institute of Technology have taken this technology to new heights by demonstrating that space-based solar energy can be gathered and transmitted from space to the Earth's surface. Space-based solar energy is now a reality.

In an unprecedented achievement, Caltech's Space Solar Power Project (SSPP-1) has successfully demonstrated the wireless transmission of solar power in space and, moreover, from a satellite in space to receivers on the planet's surface. The roof of the Moore Engineering building on the Caltech campus.

Betty Moore engineering building space-based solar
Detected: Roof of Betty Moore Engineering Building, Pasadena. Caltech

The Space-Based Solar Power Demonstrator (SSPD-1)

Caltech's Space Solar Power Demonstrator (SSPD-1) is a groundbreaking, decades-long project developed by Caltech to harvest the sun's rays in space and transmit it wirelessly in space and more importantly to Earth's surface.

Launched into orbit in January 2023, slightly behind schedule in a Momentous Vigoride spacecraft, the SSPD-1 was carried into space in a SpaceX heavy rocket into orbit.


One of three key technologies tested within SSPD-1 payload is the Microwave Array for Power-Transfer Low-Orbit Experiment (MAPLE). MAPLE consists of an array of flexible lightweight microwave power transmitters that run so far with custom electronic chips built using cost-effective silicon technologies.

This array enables the transmission of energy potentially millions of miles in space and also to desired remote regions of Earth's surface.

MAPLE was developed by a Caltech team led by Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering and a project manager and director of SSPP. The other projects, DOLCE and Alba complement MAPLE.

DOLCE, the Deployable on-Orbit ultraLight Composite Experiment, is a structure measuring approximately 1.8m square that demonstrates the architecture, packaging scheme, and deployment mechanisms of a modular solar spacecraft.

Dolce Unfolding: Credit: Caltech
DOLCE module unfolding: Caltech

ALBA: A collection of 32 different types of photovoltaic (PV) cells, to enable an assessment of the types of PV cells that are the most effective in the punishing environment of space.

MAPLE, DOLCE, Alba are part of SSPD-1

To achieve an engineering and economically feasible system to power terrestrial electrical energy from energy gathered in space, SSPP-1 aimed to minimize the mass on-orbit, leading to a unique instantiation of the space power station.

SSPP employed a modular, scalable architecture based on an ultra-lightweight unit of functionality called a tile.

Wireless Power Transmission and Its Feasibility

Wireless power transfer was successfully demonstrated on March 3rd. MAPLE scientists can transmit from satellite to satellite. Moreover, the array was programmed to direct its energy toward Earth, and the power was detected or received at Caltech's Betty Moore Laboratory of Engineering, validating this remarkable experiment a success. The prototype demonstration proved the capability to beam detectable solar-based power to Earth using wireless power transfer.

SSPD utilizes the concept of constructive and destructive interference between individual transmitters to shift the focus and direction of the energy it beams out, all without the need for any moving parts. Alba is the array that collects it and DOLCE integrates it together.

By employing precise timing-control elements, the transmitter array dynamically focuses the power on the desired location using the coherent addition of electromagnetic waves. This technique ensures that the majority of the energy is transmitted to the intended destination, maximizing efficiency.



Advantages of Space-Based Solar Power Transmission

The first successful transmission of solar power from a satellite to Earth signals immense potential and offers several advantages over traditional terrestrial solar power generation. Here are some of the key benefits:

1. Continuous Availability

Collecting solar power in space ensures its availability throughout the day, unaffected by weather conditions or the time of day. Unlike ground-based solar farms that rely on sunlight, space-based solar power is continuously accessible, providing a reliable and constant energy source.

This energy can be transmitted to darkened areas of the earth, war zones, or to an electric to vehicle charging stations or even to a self-driving electric vehicle if properly equipped.

2. Weather Independence

Traditional solar power generation is influenced by weather patterns, such as clouds or rain, which can significantly impact energy production. By harnessing solar power in space, we can overcome these limitations and ensure a stable power supply regardless of local weather conditions. The weather is a series of events in the atmosphere that worsens an existing decline in energy when harvested on the surface of the planet.

3. Unlimited Potential

Space solar power has virtually unlimited potential for expansion. By leveraging the modular assembly of ultralight and foldable integrated elements, the scalability of space-based solar power is unmatched. This approach also minimizes the impact of local element failure on the overall system.

4. Reduced Weight and Complexity

Integrating solar power and radio frequency wave (RF) conversion into a single element eliminates the need for a complex power distribution network throughout the structure. This design simplifies the system, reduces weight with less gravity, and enhances overall efficiency.

Learning from SSPD-1: The Future of Space-Based Solar Power

Caltech's groundbreaking achievements in wireless solar power transmission pave the way for an exciting future in space-based renewable energy. While the mission will require more experiments and other challenges to overcome, such as scaling up the technology and ensuring cost-effectiveness, the potential benefits are too significant to ignore.

"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,"

Government agencies including NASA and private enterprises worldwide have already started exploring space solar power initiatives, with companies like Airbus and countries like China, Japan, South Korea, and the United States making significant strides in this field.

project manager and directors sspd space based solar
SSPD Team Leaders: Caltech

Continued research and development in this area promise a future where space solar power becomes a mainstream and indispensable source of clean energy. The successful transmission of solar power from the SSPD-1 to Caltech's campus in Pasadena marks the first major milestone in the pursuit of space-based renewable energy.

This breakthrough technology has the potential to revolutionize the way we generate and distribute power, offering continuous availability, and weather independence, and is certain to alter the way we view energy storage and transmission from now on.

Space-based Solar Deomonstration Has the Attention of Congress

A decades-long dream of a sustainable and greener future powered by space solar energy is coming closer and Congress is showing an interest. During a meeting of the Science, Space, and Technology Committee last week, overwhelmingly bipartisan passage of an amendment to House Resolution 2988. It is a small but definitive step to make space-based solar energy a national priority which it hasn't been since the 1970s,

HR 2988 is a bill expected to pass that instructs the US Department of Energy and NASA to collaborate on key areas of research and development including: propulsion, artificial intelligence, astrophysics, Earth science, and quantum computing.

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