What is Space-Based Solar Power?
Space-based solar power (SBSP, also referred to as SSP) is the concept of collecting solar power in outer space and distributing it to Earth. The idea is attractive because space does not have the atmospheric or seasonal limitations that can hinder solar energy collection on Earth. The sunlight in space is also more intense, as it hasn’t been filtered by Earth’s atmosphere.
SBSP Overview, Benefits, AND Challenges
How It Works
The basic idea behind SBSP involves three key elements:
- Collectors: These are large solar panels or arrays that are placed in space to collect sunlight. These collectors convert the sunlight into electricity.
- Converters: The electricity generated by the collectors is then converted into a form that can be transmitted back to Earth, typically as microwave or laser energy. This process is necessary because it’s currently not feasible to transmit electricity directly through space.
- Receivers: These are located on Earth and are designed to capture the transmitted energy and convert it back into electricity. These receivers are often referred to as ‘rectennas’ (short for ‘rectifying antennas’).
The entire process is as follows: the sunlight is collected in space, converted into microwave or laser energy, transmitted to Earth, and then converted back into electricity. This electricity can then be fed into the existing power grid.
There are several benefits to SBSP. The most significant advantage is that sunlight in space is available 24/7, unlike on Earth where sunlight availability depends on the time of day and weather conditions. Moreover, the intensity of sunlight in space is constant and much higher than on Earth due to the lack of atmospheric interference.
There are also several challenges to implementing SBSP:
- Cost: The cost of launching and installing solar panels in space is incredibly high. Currently, the cost of launching anything to space is thousands of dollars per kilogram, making it financially unfeasible for large-scale deployment of solar panels.
- Efficiency: The conversion of solar energy to microwave or laser energy, transmission through space, and reconversion back to electricity on Earth all involve energy losses. The overall efficiency of this process would need to be significantly improved to make SBSP viable.
- Safety: Transmitting high-energy beams from space to Earth poses safety risks. If a beam were to stray off target, it could potentially cause damage or harm.
- Infrastructure: Large-scale ground infrastructure (like rectennas) would need to be built to receive the power beamed down from space. This could require significant land use and could have environmental impacts.
Despite these challenges, ongoing research and development in space technology and solar power are making the prospect of SBSP more feasible. Innovations in wireless power transmission, cheaper and more efficient space launch systems, and advanced solar panel technology could all contribute to making SBSP a reality in the future.
ESA SBSP infographic
Non-Military Research Activities
Research and Development Activities
Research into SBSP has been conducted by a number of organizations, including government agencies, research institutions, and private companies. Here are a few notable examples:
- NASA: NASA has conducted, and continues to conduct, studies on the viability and technology needed for SBSP, including:
- 1970s and early 1980s: Studies were prepared as part of the Satellite Power System Concept Development and Evaluation Program.
- 1995-1996. A Fresh Look at Space Solar Power updated the findings of previous NASA work on this topic. The study examined whether SPS could be a viable alternative to terrestrial electrical power, including economic, environmental, and safety perspectives.
- 2012: NASA Innovative Advanced Concepts (NIAC) study examined various concepts and supported Solar Power Satellite Arbitrarily Large Phased Array (SPS-ALPHA), including detailed studies of technology readiness and economic viability.
- Caltech’s Space Solar Power Project: The California Institute of Technology (Caltech) has a dedicated research project for SBSP. Their approach involves the creation of lightweight, ultra-thin, high-efficiency solar cells. These cells would be launched into space, where they would form a modular array capable of generating and transmitting power back to Earth.
- JAXA: The Japan Aerospace Exploration Agency (JAXA) has been a major proponent of SBSP. They have conducted several advanced studies and practical experiments on wireless power transmission, a key technology for SBSP. They have a roadmap that envisions the deployment of a 1 GW SBSP system by the 2040s.
- China: In 2015, China announced plans to launch a test SBSP satellite by 2025, and has been investing heavily in research and development. Their plans include a megawatt-level space solar power station by 2030, and a gigawatt-level space solar power station by 2050.
- ESA (European Space Agency): The ESA has conducted several studies on SBSP, assessing the potential for the technology and the feasibility of its implementation. To prepare Europe for future decision making on SBSP, ESA has kicked-off a preparatory initiative, called SOLARIS, for which funding was approved at the ESA Council at Ministerial Level in November 2022. The goal of SOLARIS is to prepare the ground for a possible decision in 2025 on a full development programme by establishing the technical, political and programmatic viability of SBSP for terrestrial clean energy needs.
These examples illustrate the range of research being conducted into SBSP and the ongoing interest in harnessing the potential of space-based solar power.
SBSP systems could be used for a variety of military purposes:
|SBSP Military Application||Description|
|Remote Power Supply||One of the most significant potential military uses of SBSP is the ability to supply energy to remote or difficult-to-reach locations. This could include forward operating bases, remote surveillance equipment, or other isolated assets. This could reduce the logistical challenges and vulnerabilities associated with traditional fuel supply chains.|
|Power for Unmanned Systems||SBSP could potentially provide energy for unmanned systems, such as drones or autonomous vehicles. This could allow these systems to operate for extended periods without needing to refuel.|
|Resilience and Redundancy||Having a space-based source of power could provide a valuable backup in case of disruptions to terrestrial power grids, whether from natural disasters, cyber attacks, or physical attacks on infrastructure.|
|Support for Space Assets||SBSP could be used to power satellites and other space-based assets. This could potentially extend the lifespan of these assets, or allow for the use of more power-intensive technologies.|
|Directed Energy Weapons||The US and China have both deployed terrestrial-based directed energy weapons, and are reported to be working on space-based directed energy weapons. SBSP systems could potentially be used to power terrestrial or space-based directed energy weapons.|
Military Research Activity
SBSP has a wide range of potential military and defense applications; So it is not surprising that there are US defense organizations known to have interest, and working to advance SBSP technology:
- US Department of Defense (DoD): The DoD has expressed interest in SBSP as a way to improve the resilience and security of military energy supplies. The National Security Space Office (NSSO) of the DoD released a report in 2007 exploring the potential of SBSP for national security. It concluded that the US should begin a coordinated national SBSP program.
- Strategic Studies Institute (SSI): SSI published a 2015 report Space-based Solar Power: A Technical, Economic, and Operational Assessment. The report examines the questions: Is there compelling evidence that space-based solar power systems will provide the best energy solution? How does the Army’s current approach to incorporating a diverse portfolio of renewable energy sources in distributed locations compare with the potential of enterprise ventures that beam energy from solar collectors in space? This report found that, while space-based solar power systems may be technically feasible, there is no compelling evidence that such systems will be economically or operationally competitive with terrestrial-power generation systems in use or in development. The report also found that there may be some utility in the limited application of space-based solar power to enable operations in remote and forward operating locations.
- US Air Force Research Laboratory (AFRL): AFRL initiated the Space Solar Power Incremental Demonstrations and Research Project (SSPIDR) in 2020. The project is focused on developing the technology needed to harvest and beam solar power from space.
- US Naval Research Laboratory (NRL): NRL has been/Is involved in the following SBSP research activities:
- Space-Based Solar Power: Possible Defense Applications and Opportunities for NRL Contribution: This 2009 report reviews some of the critical technology issues for SBSP and highlights relevant research areas, particularly those that NRL is technically qualified to address. The focus of the study was on defense applications. Conclusions include the following: SBSP concept is technically feasible but that there remain significant system risks in many areas; SBSP offers one of several possible solutions to the energy independence and dominance of our country and our military and that those alternative solutions (including terrestrial solar, nuclear, and wind) must be an integral part of the solution; Safe power densities for wireless energy transmission generally restrict applications to large, relatively immobile receiver sites; and capital, launch, and maintenance costs remain significant concerns in the economics of fielding a practical SBSP system.
- Opportunities and Challenges for Space Solar for Remote Installations: This 2019 study report extends previous efforts exploring the concept of providing power to military and remote installations via solar power satellites. The goal of the study was to determine the feasibility of a coordinated development effort for this capability. Included are key findings of opportunities and challenges, as well as recommendations for advancing the development of technologies applicable to space solar for remote installations. The report determined that there remain significant unresolved technological, economic, legal/political, operational/ organizational, and schedule challenges inherent in the development of the capability. Important questions regarding the most promising approaches and prospective utility for operationally relevant contexts have yet to be definitively answered because of technological immaturity and uncertainties in non-technical areas. Because of the potential game-changing nature of space solar, investments in several critical areas are recommended, the foremost of which is power beaming technology.
- Power Transmitted Over Laser (PTROL). NRL conducted a successful demonstration of a land-based power beaming system using an infrared laser during 2019.
- Photovoltaic Radio-frequency Antenna Module (PRAM): The first orbital experiment was launched on the X-37B space plane in May 2020. Its purpose was to test the viability of space-based solar power systems by converting sunlight to microwaves outside the atmosphere and analyzing the energy conversion process and resulting thermal performance.
- Lectenna: A light-emitting rectifying antenna converted a wireless network signal into electric power. This experiment was conducted on the ISS during February 2020.
Note that this list is not exhaustive. Also, due to the sensitive nature of defense research, some projects related to SBSP may not have been publicly disclosed.
What Does the Future Hold?
The ability to collect and distribute power from space may provide a significant strategic advantage in a range of military scenarios. However, the implementation of SBSP systems also presents significant technical, economic, and regulatory challenges, and there are important ethical and security considerations related to their potential military use. Military and non-military research is ongoing, and it is reasonable to expect that implementation challenges will be resolved over a period of time.