Harnessing the Cosmos: Space-Based Solar Power Technology Breakthroughs Illuminate a Future of Unlimited Renewable Electricity

Rajesh Uppal May 11, 2024 Energy & Propulsion, Space Comments Off on Harnessing the Cosmos: Space-Based Solar Power Technology Breakthroughs Illuminate a Future of Unlimited Renewable Electricity 672 Views

Introduction:

In the quest for sustainable and efficient energy sources, scientists and engineers have set their sights on the cosmos, unlocking the potential of Space-Based Solar Power (SBSP or SSP). Recent breakthroughs in this revolutionary technology are paving the way for a new era in renewable energy, promising unlimited, clean electricity beamed down from space. In this article, we’ll explore the cutting-edge advancements that are propelling SBSP into the forefront of the renewable energy landscape.

Understanding Space-Based Solar Power:

Space-Based Solar Power involves capturing sunlight in space using solar panels or other collecting devices and then transmitting the harvested energy to Earth. This ambitious concept offers a solution to the limitations faced by traditional solar power systems on Earth, such as weather-dependent energy production and nighttime darkness.

Space-based solar power (SBSP) — in which Miles-long satellites covered with solar panels capture the Sun’s radiation, convert it to electricity and then transmit it back to Earth in the form of either microwaves or lasers could form the basis of unlimited, renewable electricity.

The advantage of collecting solar energy in space is a higher collection of energy due to the lack of reflection and absorption by the atmosphere, and the possibility of placing a solar collector in an orbiting location where there is no (or very little) night, and better ability to orient to face the sun. A considerable fraction of incoming solar energy (55–60%) is lost on its way through the Earth’s atmosphere by the effects of reflection and absorption.

SBSP is considered a form of sustainable or green energy, renewable energy, and is occasionally considered among climate engineering proposals. It is attractive to those seeking large-scale solutions to anthropogenic climate change or fossil fuel depletion (such as peak oil).

The SPS would also be useful for disaster missions, a thin, portable rectenna can be unfolded and deployed to receive microwaves from space, which can be converted into electrical energy.

In addition to providing constant renewable energy to the planet, a space solar power plant could, in theory, focus its beam outward and power spacecraft, obviating the need for solar cell wings and greatly increasing power levels and control accuracy.

That power could also used in space to meet the energy demands of future space mining and resource extraction operations. NASA is examining how space solar power could support robotic mining operations on the moon or asteroids–a stepping stone toward enabling long-term human space exploration and possible colonization of the solar system beyond Earth. The energy beams could also direct power to remote areas or even dissipate destructive weather systems like typhoons.

Global Race for SBSP

SBSP is being actively pursued by Japan, China, Russia, India, the United Kingdom and the US. In 2008, Japan passed its Basic Space Law which established space solar power as a national goal and JAXA has a roadmap to commercial SBSP.

In 2015, the China Academy for Space Technology (CAST) showcased their roadmap at the International Space Development Conference. In February 2019, Science and Technology Daily (科技日报, Keji Ribao), the official newspaper of the Ministry of Science and Technology of the People’s Republic of China, reported that construction of a testing base had started in Chongqing’s Bishan District. Chinese scientists were reported as planning to launch several small- and medium-sized space power stations between 2021 and 2025. In December 2019, Xinhua News Agency reported that China plans to launch a 200-tonne SBSP station capable of generating megawatts (MW) of electricity to Earth by 2035.

The US Military has also become interested in this concept as it would save their billions in fuel costs as well as provide ultimate flexibility in their expeditionary missions as solar power could be redirected anywhere on the planet. Ralph Nansen from the US-based advocacy group Solar High, urges the US to act on this because he believes that whoever develops SBSP first, will have a monopoly position in the world economy, just like England did during the industrial revolution because of coal.

Technology requirements

Space-based solar power faces major challenges including economic feasibility and manufacturing costs, cheap and reliable launch services, and efficient and safe energy transmission.

Besides the cost of implementing such a system, SBSP also introduces several technological hurdles, including the problem of transmitting energy from orbit to Earth’s surface for use.

Since wires extending from Earth’s surface to an orbiting satellite are neither practical nor feasible with current technology, SBSP designs generally include the use of some manner of wireless power transmission with its concomitant conversion inefficiencies, as well as land use concerns for the necessary antenna stations to receive the energy at Earth’s surface.

The collecting satellite would convert solar energy into electrical energy on board, powering a microwave transmitter or laser emitter, and transmit this energy to a collector (or microwave rectenna) on Earth’s surface.

Various SBSP proposals have been researched since the early 1970s, but none are economically viable due to the expense of launching material into orbit with present-day space launch infrastructure.

Contrary to appearances of SBSP in popular novels and video games, most designs propose beam energy densities that are not harmful if human beings were to be inadvertently exposed, such as if a transmitting satellite’s beam were to wander off-course. But the vast size of the receiving antennas that would be necessary would still require large blocks of land near the end-users to be procured and dedicated to this purpose. The service life of space-based collectors in the face of challenges from long-term exposure to the space environment, including degradation from radiation and micrometeoroid damage, could also become a concern for SBSP.

What once seemed impossible, space policy analyst Karen Jones of Aerospace Corporation says, may now be a matter of “pulling it all together and making it work.” Today, both space and solar power technology have changed beyond recognition. The efficiency of photovoltaic (PV) solar cells has increased 25% over the past decade, Jones says, while costs have plummeted. Microwave transmitters and receivers are a well-developed technology in the telecoms industry. Robots being developed to repair and refuel satellites in orbit could be turned to building giant solar arrays.

Space-based solar power essentially consists of three elements:

collecting solar energy in space with reflectors or inflatable mirrors onto solar cells or heaters for thermal systems
wireless power transmission to Earth via microwave or laser
receiving power on Earth via a rectenna, a microwave antenna

The space-based portion will not need to support itself against gravity (other than relatively weak tidal stresses). It needs no protection from terrestrial wind or weather, but will have to cope with space hazards such as micrometeors and solar flares. Two basic methods of conversion have been studied: photovoltaic (PV) and solar dynamic (SD). Most analyses of SBSP have focused on photovoltaic conversion using solar cells that directly convert sunlight into electricity. Solar dynamic uses mirrors to concentrate light on a boiler. The use of solar dynamic could reduce mass per watt. Wireless power transmission was proposed early on as a means to transfer energy from collection to the Earth’s surface, using either microwave or laser radiation at a variety of frequencies.

If a space-based power station ever does fly, the power it generates will need to get to the ground efficiently and safely. In a recent ground-based test, Jaffe’s team at NRL beamed 1.6 kilowatts over 1 kilometer, and teams in Japan, China, and South Korea have similar efforts. But current transmitters and receivers lose half their input power. For space solar, power beaming needs 75% efficiency, Vijendran says, “ideally 90%.”

The safety of beaming gigawatts through the atmosphere also needs testing. Most designs aim to produce a beam kilometers wide so that any spacecraft, plane, person, or bird that strays into it only receives a tiny—hopefully harmless—portion of the 2-gigawatt transmission. Receiving antennas are cheap to build but they “need a lot of real estate,” Jones says, although she says you could grow crops under them or site them offshore.

Orbital location

The main advantage of locating a space power station in geostationary orbit is that the antenna geometry stays constant, and so keeping the antennas lined up is simpler. Another advantage is that nearly continuous power transmission is immediately available as soon as the first space power station is placed in orbit, LEO requires several satellites before they are producing nearly continuous power.

Power beaming from geostationary orbit by microwaves carries the difficulty that the required ‘optical aperture’ sizes are very large. For example, the 1978 NASA SPS study required a 1-km diameter transmitting antenna, and a 10 km diameter receiving rectenna, for a microwave beam at 2.45 GHz. These sizes can be somewhat decreased by using shorter wavelengths, although they have increased atmospheric absorption and even potential beam blockage by rain or water droplets. Because of the thinned array curse, it is not possible to make a narrower beam by combining the beams of several smaller satellites. The large size of the transmitting and receiving antennas means that the minimum practical power level for an SPS will necessarily be high; small SPS systems will be possible, but uneconomic.

Earth-based receiver

The Earth-based rectenna would likely consist of many short dipole antennas connected via diodes. Microwave broadcasts from the satellite would be received in the dipoles with about 85% efficiency. With a conventional microwave antenna, the reception efficiency is better, but its cost and complexity are also considerably greater. Rectennas would likely be several kilometers across.

Heavy lift launch vehicles

A solar power satellite big enough to replace a typical nuclear or coal-powered station will need to be kilometers across, demanding hundreds of launches. “It would require a large-scale construction site in orbit,” says ESA space scientist Sanjay Vijendran.

It took dozens of launches to construct the International Space Station in low-Earth orbit, and would likely require an order of magnitude more launches to assemble a solar power satellite that weighs in at many thousands of tonnes. In the past, due to the high costs of launch, solar power satellites were not deemed to be economically competitive with terrestrial solutions.

“We need a cheap heavy-lift launch vehicle,” says Wang, who designed China’s first carrier rocket more than 40 years ago. “We also need to make very thin and light solar panels. The weight of the panel must be less than 200 grams per square meter.” He also points out that the space solar power station could become economically viable only when the efficiency of wireless power transmission, using microwave or laser radiation, reaches around 50 percent.

A single solar power satellite of the planned scale would generate around 2 gigawatts of power, equivalent to a conventional nuclear power station, able to power more than one million homes. It would take more than six million solar panels on Earth’s surface to generate the same amount.

However, falling costs of space launches – Musk’s company plans to slash the cost of launching into space to $1,100/kg ($500/lb) from currently $20,000/kg ($10,000/lb) through reusable launch vehicles, improvement of the efficiency of solar cells from 10 to 40% over the last four decades, advancements in space robotics, development of new lightweight materials – including graphene and advanced polymers have brought back the interest in the concept of SPS once again.

A SpaceX Falcon 9 rocket lofts cargo at about $2600 per kilogram—less than 5% of what it cost on the Space Shuttle—and the company promises rates of just $10 per kilogram on its gigantic Starship, due for its first launch. “It’s changing the equation,” Jones says. “Economics is everything.”

To bypass launching the heavy station from Earth, researchers are considering having a robot factory in space to build the power station in orbit instead. Its construction would also present huge logistical issues. “(An) SSP would be assembled piece-by-piece over repeated launches and dockings,” according to the JAXA. “The construction of the structure by crew members would be prohibitively expensive and unsafe. A key phase of the program will be to develop robotic systems capable of assembling all of the components of the large orbital structure autonomously.”

NRL conducts first test of solar power satellite hardware in orbit

The U.S. Naval Research Laboratory (NRL) has achieved a significant milestone in the development of space-based solar power (SBSP) technology by conducting the first test of hardware designed specifically for solar power satellites in orbit. The Photovoltaic Radio-frequency Antenna Module (PRAM), launched aboard an Air Force X-37B Orbital Test Vehicle in May 2020, is a “sandwich” module consisting of a photovoltaic panel, an electronics system, and an antenna. The module aims to harvest solar energy in space, convert it into radio frequency (RF) energy, and transfer it to a target on the ground. NRL envisions assembling multiple modules in space using robots to create a powerful satellite, potentially providing an innovative solution to Earth’s energy needs.

PRAM’s 12-inch square tile module tests the efficiency of harvesting power from its solar panel and transforming it into RF microwave energy. The experiment focuses on the energy conversion process and thermal performance, providing valuable data for the design of future space solar prototypes. Depending on the results, NRL aims to build a fully-functional system on a dedicated spacecraft to test the transmission of energy back to Earth. This breakthrough in SBSP technology could have wide-ranging applications, from providing energy to remote installations like forward operating bases to supporting disaster response efforts. The development of space solar capabilities represents a futuristic approach to addressing global energy challenges and harnessing the untapped potential of solar power from space

Air Force makes breakthrough in space-based solar power reported in Dec 2021

Air Force researchers, in collaboration with Northrop Grumman Corp., have achieved a significant breakthrough in space-based solar power, paving the way for a revolutionary renewable energy source for military applications and beyond. The Arachne mission, initiated in 2018 with a funding of over $100 million, explores the feasibility of capturing solar energy in space through panels and transmitting it to Earth wirelessly. Recent tests of a solar panel prototype, known as a “sandwich tile,” demonstrated the capability to convert intense solar radiation in outer space into radio frequency (RF) energy, which can be beamed back to Earth. This breakthrough, deemed scalable for large space-based solar operations, holds the potential to provide a continuous and abundant supply of solar energy day and night. The success of the prototype marks a critical step in achieving the Arachne mission’s objectives, with plans to launch an experimental satellite in 2025 for comprehensive testing of power collection, conversion, and transmission aspects.

China’s developments

China’s Xidian University in June 2022 completed a 75-meter-high steel structure facility which it calls the world’s first full-link and full-system ground test system for SBSP. In another possibly related development, research into construction of kilometer-scale objects in orbit received funding last year. Such work could help to address the major challenge of assembling the giant arrays needed for solar power collection and transmission arrays.

If we choose to encourage solar power satellites (and nuclear power, another central station technology) to serve the market as a matter of public policy, we must also assure the existence of a grid that will carry that power to market. Otherwise, why waste the $20 billion?, says LEONARD S. HYMAN, Managing Director, Energy Resource Capital, LLC

Arachne Mission’s Solar Panel Prototype

One of the most significant breakthroughs in SBSP comes from the Arachne mission, a collaboration between the Air Force Research Laboratory and Northrop Grumman Corp. The mission focuses on harnessing solar energy through space-based panels and transmitting it wirelessly to Earth. Recent tests of a solar panel prototype, known as a “sandwich tile,” successfully converted intense solar radiation in outer space into radio frequency (RF) energy. This achievement represents a scalable and lightweight architecture, marking a critical step toward realizing the Arachne mission’s objectives.

NASA / LaRC “SpiderFab” for automated on-orbit construction

Company called Tethers Unlimited (TUI) is currently developing architecture and a suite of technologies called “SpiderFab” for automated on-orbit construction of very large structures and multifunctional space system components, such as kilometer-scale antenna reflectors.

This process will enable space systems to be launched in a compact and durable ’embryonic’ state. Once on orbit, these systems will use techniques evolved from emerging additive manufacturing and automated assembly technologies to fabricate and integrate components such as antennas, shrouds, booms, concentrators, and optics.

Under a NASA/LaRC Phase I SBIR contract, TUI is currently implementing the first step in the SpiderFab architecture: a machine that uses 3D printing techniques and robotic assembly to fabricate long, high-performance truss structures. This “Trusselator” device will enable construction of large support structures for systems such as multi-hundred-kilowat solar arrays, large solar sails, and football-field sized antennas. The development of economically viable SPS now depends more on the availability of adequate budgets; finally the vision of a ring of satellites in orbit to provide nearly unlimited energy for the earth’s needs may become reality.

Caltech’s Ambitious Self-Assembling Space Solar Power Dream

The project, nicknamed the “Space Solar Power Demonstrator” (SSPD), recently achieved a major milestone in January 2023 when a prototype launched aboard a SpaceX rocket. Now, researchers are eagerly analyzing data as the system undergoes a painstaking self-assembly process in orbit.

The SSPD is essentially a robotic origami masterpiece. Individual units unfold from compact packages into flat squares once released from the rocket. Each square boasts solar cells on one side and wireless power transmitters on the other. As these units connect and align using a combination of magnets and robotic arms, they create a larger, energy-gathering surface.

The ultimate goal is to build a vast, self-assembling solar array in space, capturing the sun’s energy with its expansive photovoltaic surface. This energy is then converted to microwaves and beamed down to Earth via specialized antennas, ultimately reaching designated receivers and transforming into electricity for our homes and cities.

Adavanges are Scalability and efficiency: The modular design allows for gradual expansion of the solar array in space, potentially generating vast amounts of clean energy.

3D printing in space

Another solution to the transportation issue could be 3D printing. “Additive manufacturing is now widely available for the aeronautics industry,” says Nobuyoshi Fujimoto, a spokesman for the Japan Aerospace Exploration Agency (JAXA), the country’s equivalent of NASA. “Therefore, this new manufacturing technology will be used for SSPs as well.” The NSS believes the necessary technologies are “reasonably near-term” and the costs involved are smaller than paying the price of global warming — particularly when the long-term environmental benefits are considered.

3D printing has been developed at a fast pace in recent years, It is thought that by sending up special 3D printers into space to manufacturer the solar panels in orbit, the installation costs can be drastically reduced, compared to sending up pre-made solar panels. In 2014 an astronaut on the International Space Station used a 3D printer to make a socket wrench in space, hinting at a future when digital code will replace the need to launch specialized tools into orbit.

Scalability for Large-Scale Operations

The success of the Arachne mission’s prototype indicates scalability for large space-based solar operations. This scalability is crucial for creating expansive solar arrays that can capture substantial amounts of sunlight and transmit it consistently to Earth. As the technology matures, it holds the promise of providing a continuous and abundant supply of solar energy, offering a strategic advantage for military operations and paving the way for broader civilian applications.

Challenges and Future Prospects:

While SBSP presents a promising vision of unlimited renewable electricity, challenges remain. Material development for high-temperature environments and addressing the cost and scalability of 3D-printed components are areas that require continued innovation. Additionally, rigorous testing, like the upcoming launch of an experimental satellite as part of the Arachne mission, will be crucial in refining and validating SBSP technology.

While the potential of space-based solar power is undeniable, overcoming the technical hurdles is no small feat. Key challenges include:

Assembly and maintenance: Ensuring flawless self-assembly in the harsh space environment and developing efficient repair mechanisms for potential issues are crucial.
Microwave beam transmission: Optimizing the efficiency and safety of beaming concentrated microwave energy over long distances requires further research and development.
Cost and infrastructure: Building and maintaining such a system in space will be expensive, necessitating international collaboration and innovative cost-reduction strategies.

The Future of Space-Based Solar Power:

Space-Based Solar Power not only addresses Earth’s energy needs but also opens the door to a multitude of possibilities. Imagine a future where satellites equipped with advanced solar panels orbit the Earth, beaming down clean energy to remote areas or disaster-stricken regions. The scalability of SBSP could also facilitate the development of large-scale power stations in space, reducing dependence on finite terrestrial resources.

Conclusion:

Space-Based Solar Power technology breakthroughs are unlocking the potential for a future where clean, renewable electricity knows no bounds. The successful conversion of solar radiation into RF energy and the scalability of the technology mark significant strides toward making SBSP a reality. As scientists and engineers continue to push the boundaries of innovation, the dream of unlimited, space-borne solar energy inches closer to becoming a transformative force for our planet’s energy landscape. The cosmos, it seems, holds the key to a brighter and more sustainable future.