The increasing energy demands to support continued (and sustainable) global economic growth, thrust for renewable power because of environmental/climate concerns, has inspired researchers to look for fundamentally new energy technologies. Space-Based Solar Power (SBSP) uses solar panels in space (specifically in an equatorial Geosynchronous Earth Orbit) to beaming energy to earth using either microwaves or lasers could form the basis of unlimited, renewable electricity.
Even as early as 1960s, Dr. Peter Glaser of Arthur D. Little invented Solar Power Satellite (SPS) concept: a large platform, positioned in geostationary orbit in space continuously collects sunlight, converts it into microwaves or laser beams, and transmits these to the ground; and a power receiving facility on the ground, converts it into electricity and hydrogen for practical use.
A satellite in Geosynchronous orbit receives 5-15 times as much solar energy per year as any place on earth, there are no efficiency reductions due to the day-night cycle, seasonal variation, or weather conditions. Such a plant would be up to six times more efficient than comparable technologies on Earth.
Paul Jaffe, spacecraft engineer at the U.S. Naval Research Laboratory, declared that if there are solar panels in space, they are going to be illuminated 24 hours a day, seven days a week, 99% of the year. Due to the fact that Earth’s axis of rotation is tilted, the solar satellite could pick up sunlight almost all the time only going offline when the Earth eclipses the sun. Jaffe continues by explaining that individual space-based solar arrays would be able to produce 250 megawatts, and go up to 5 gigawatts of energy. As an example, Jaffe has given New York City, which needs around 20 gigawatts of power. By his calculations, the system required would consist of four arrays, each providing 5 gigawatts, thus being able to power the entire city.
Energy could be beamed to Earth via microwaves or lasers. But Pang Zhihao, a researcher at the China Academy of Space Technology, warned that the hazards potentially posed to humans, plants and animals by that process must be examined.
While an endless source of renewable energy is the holy grail in tackling climate change, some fear that lasers produced at an SSP could potentially be weaponized to give Beijing a lethal military instrument. “Coherent radiation from a laser is so far different from the microwave or radio wave approach — (if weaponized) a laser could burn a city to the ground in a matter of minutes or hours,” says Schubert. Schubert says that a satellite in geostationary orbit has a view of about one third of the Earth’s surface, which would present a huge tactical advantage — the ultimate “high ground,” he says. “It is my opinion that no large nation would allow another nation to put a 5 GW laser in (goestationary orbit). As everyone knows, there is no such thing as an unhackable system. Huge power lasers are just too much of a risk to put in space.”
The technology for harnessing solar power in space has been around since the 1960s, says Peter Schubert, director of the Richard G. Lugar Center for Renewable Energy at Indiana University-Purdue University Indianapolis. But there are several technical hurdles, he says. These include finding a low-cost, environmentally-friendly launch vehicle to take the solar plant into space, combating the huge in-orbit operation and construction costs, and working out how best to transmit the power back to Earth.
The construction has long been a challenge for scientists because its weight and size are way beyond the current carrying capacity of spacecraft. Many studies and experiments in the past have found the concept to be too costly in terms of space transportation, billions of dollars to send a rig that could be several kilometers across and weigh several thousand tons; and too complex to assemble a structure in space which is ten times the size of the International Space Station that itself is about the size of a football field.
Microwave transmitting solar satellites would need to go about 35,000km into space from Earth to optimize functionality, making them virtually impossible to repair in a timely or regular manner. Also, a single solar power station may have to cover as much as 5 square miles – equivalent to 1,400 football fields. While laser-emitting solar satellites only need to venture about 400 km into space, their relatively small generation capacity would mean hundreds, or even thousands, would need to be launched in order to make a substantial impact. Microwave beaming systems could provide upwards of 1 GW of energy to terrestrial receivers, which is enough to power a large city. Laser systems produce 1-10MW per satellite, and would theoretically be deployed in constellations of hundreds.
Researchers estimate that lightweight designs of space solar panels could produce 1 kW per kilogram, thus requiring 4,000 metric tons of solar panels to produce 4 gigawatts of power. Energy captured in space-based solar panels would be transmitted back to Earth based antennas wirelessly. “It’s a lot of money to put one of these things up in space,” said Ian Lange, assistant professor of economics and business and director of the Mineral and Energy Economics Program, “You need more than a model that says nuclear power is 15 cents per kilowatt hour and this is 14.”
In addition a broad range of technical challenges must be addressed in order to establish the economic feasibility of SPS like synchronizing the phases of microwaves produced by more than billion antennas, that would be installed on a single SPS, to produce a single precisely focused beam; the efficiency degradation of wireless power transmission (WPT) due to diffraction of energy through the water vapor absorption, the need of very light materials for the mirror structures to allow for the formation flight. Power generation, and power management, including extremely high-voltage power transmission cables that could channel the power from the solar panels to the transmission unit with minimal resistive losses.
The urgent need for green energy, cheaper access to space, and improvements in technology could finally change that, proponents of space solar power believe. “Once someone makes the commercial investment, it will bloom. It could be a trillion-dollar industry,” says former NASA researcher John Mankins, who evaluated space solar power for the agency a decade ago. The International Academy of Astronautics recently stated that space-based solar power would be viable within 30 years.
The strategic race between countries like US, Japan, China, and Russia
This has driven a new strategic race between countries like US, Japan, China, and Russia who have all made a huge investment in this area, and the space departments of India, South Korea, and Europe are also conducting related research.
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 be 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.
NASA recently tweeted that it has teamed with five companies – including Northrup Grumman and Lockheed Martin – to design “vertically deployable solar arrays” for use on the Moon. The solar arrays would be able to autonomously deploy up to 32 feet high and retract for relocation. The technology is meant to serve as the foundation for future extraterrestrial solar arrays that could be used to power anything from lunar habitats, to rovers, to future robotic or crewed missions
Remote power should be an obvious benefit to a military looking to power a base in a remote location. Other potential customers would be remote energy exploration – like shale or Arctic exploration – that is far from any electric grid.
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. 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. 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.
The U.S. Naval Research Laboratory (NRL) is building a “sandwich” module; the top side is a photovoltaic panel that absorbs the Sun’s rays. An electronics system in the middle converts the energy to a radio frequency, and the bottom is an antenna that transfers the power to a target on the ground. Ultimately, the idea is to assemble many of these modules in space by robots — something the NRL’s Space Robotics Groups is already working on — to form a one kilometer, very powerful satellite.
The world has recognized the need to replace fossil fuels with clean energies. However, the ground-based solar, wind, water and other renewable energy sources are too limited in volume and unstable. “The world will panic when the fossil fuels can no longer sustain human development. We must acquire space solar power technology before then,” Wang, an academician of the Chinese Academy of Sciences (CAS) and a member of the International Academy of Astronautics, says. “Whoever obtains the technology first could occupy the future energy market. So it’s of great strategic significance,” Wang says.
Li Ming, research fellow of China Academy of Space Technology (CAST) has claimed that China now holds a leading position in the research of space-based solar power after decades of research which has narrowed the gap between itself and leading countries. Space-based solar power will ease environmental and energy pressure in China, and also spur the country’s innovation and emerging industries, Wang added.
The state-owned China Aerospace Science and Technology Corporation hopes to be operating a commercially viable solar space station by 2050, according to a recent report in the country’s official newspaper Science and Technology Daily. Scientists had previously thought space solar plants (SSPs) would be prohibitively expensive. China has already pledged to invest 2.5 trillion yuan ($367 billion) in renewable power generation — solar, wind, hydro and nuclear — by 2020.
Japan, where the disastrous Fukushima meltdown heightened the search for safe, sustainable alternative energy, is also looking at space based space power. Japan Aerospace Exploration Agency (JAXA), which leads the world in research on space-based solar power systems, now has a technology road map that suggests a series of ground and orbital demonstrations leading to the development in the 2030s of a 1-gigawatt commercial system—about the same output as a typical nuclear power plant.
JAXA has already demonstrated wireless microwave transmission of solar power in space by beaming 1.8 kilowatts of electricity via microwave transmission 55 meters to a pinpoint target on a receiver. The microwave was successfully converted into direct electrical current at the receiving end. The experiment was conducted in March 2015. If implemented, microwave-transmitting solar satellites would be set up approximately 35,000 kilometers from Earth. Jaxa says that a receiver set up on Earth with an approximately 3-kilometer, or 1.9-mile, radius could create up to one gigawatt of electricity, which is about the same as one nuclear reactor.
It will be many years before that happens, if it ever does. Researchers “are aiming for practical use in the 2030s,” Yasuyuki Fukumuro, a researcher at Jaxa, said on its website. While the energy is transmitted in the same microwaves used in microwave ovens, it doesn’t fry a bird or an airplane traveling on its path because of its low-energy density, according to the Jaxa spokesman
China is planning to build the world’s first solar power station in space to provide “inexhaustible clean energy” according to a story in Science and Technology Daily, the official newspaper of China’s Ministry of Science and Technology. A testing facility in Chongqing’s Bishan district is being built that will be used to test the theoretical viability of a space-based solar power station. A 33-acre test facility will develop space transmission technologies while studying the effect of microwaves beamed back to Earth on living organisms.
China intends to use its newly-completed Tiangong space station to test key technologies required for space-based polar power, according to a senior space official. Robotic arms already operating on the outside of Tiangong will be used to test on-orbit assembly of modules for a space-based solar power test system, Yang Hong, chief designer of the Tiangong space station said in a presentation at the ongoing China Space Conference.
A model power station at Xidian University in Shaanxi province captures sunlight high above the ground and converts it into microwave beams. It then transmits through the air to a receiver station on the ground, where it can be converted back to electricity. While the model only sends the energy 55 meters through the air, the researchers hope the technology could one day be expanded to send power from orbiting solar panels to Earth. The research team behind it recently conducted tests in front of a panel of outside experts, who verified its success on June 5, the university said in a press release.
Taking space-based solar power as a key research program since 2008, China has made a number of major breakthroughs in wireless energy transmission and proposed various energy-collecting solutions. China Aerospace Science and Technology Corporation plans to launch small solar satellites that can harness energy in space as soon as 2021. Then it will test larger plants capable of advanced functions, such as beaming energy back to Earth via lasers.
A receiving station will be built in Xian, around 500 miles northeast of the Chinese city of Chongqing. The city is a regional space hub where a facility to develop the solar power farms has been founded. By 2050, the company plans that a full-sized space-based solar plant would be ready for commercial use, the Chinese media report said.
The China Academy of Space Technology (CAST), the country’s main, state-owned spacecraft maker which made the modules for Tiangong, earlier stated that it plans to conduct a “Space high voltage transfer and wireless power transmission experiment” in low Earth orbit in 2028.
This first phase test is to be followed by a second phase experiment conducted in geostationary orbit, requiring accurate energy transmission over a distance of 35,800 kilometers to Earth, according to earlier presentations.
Phases 3 and 4, in 2035 and 2050 respectively will aim for energy generation of 10 MW and 2 gigawatts, requiring leaps in capabilities in power transmission, orbital assembly capabilities, beam steering accuracy and transmission architecture.
Long Lehao, chief designer of China’s Long March rocket series and a SBSP advocate, said in June 2021 that the potential project would use the in-development Long March 9 super heavy-lift rocket to send the requisite infrastructure into geostationary orbit.
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.
China Association for Science and Technology (CAST) revealed more details of a 100kW SBSP demonstration, which it plans to put in low earth orbit is expected by 2025, followed by a fully-operational SBSP system in geostationary orbit by 2050. The project, which is still in the conceptual stage, would involve a satellite that weighs more than 10,000 lbs., dwarfing anything previously placed into orbit, including the International Space Station, according to the China-based Xinhuanet, part of the Xinhua News Agency.
A Chinese ground-based facility for converting solar energy bounced to Earth is scheduled for completion by the end of 2021 and has already conducted energy transfer tests up to 300-meter altitudes, a key project member told state-run media China Science Daily. The Earth-based station is designed to collect solar energy wirelessly from solar panel power stations in orbit.
“The approach that the Chinese have announced looks very reasonable to me,” says Schubert. “Because the ultimate goal of this is to get very large power stations, doing that all in one go is not practical — there are a lot of things you learn along the way.” “Construction of a space solar power station will be a milestone for human utilization of space resources. And it will promote technological progress in the fields of energy, electricity, materials and aerospace,” says Wang.
A division of the Russian Federal Space Agency (Roscosmos) revealed that it has a working prototype of a 100kW SBSP system in development; although no launch date was announced.
India – who has begun a significant investment into a ‘solar mission’ – has expressed interest in partnering with the United States on a SBSP program.
In Nov 2020, the UK government commissioned new research into space-based solar power (SBSP) systems that would use very large solar power satellites to collect solar energy, convert it into high-frequency radio waves, and safely ‘beam it’ back to ground-based receivers connected to the electrical power grid. The study, led by Frazer-Nash Consultancy, will consider the engineering and economics of such a system – whether it could deliver affordable energy for consumers, and the engineering and technology that would be required to build it.
Frazer-Nash space business manager Martin Soltau added: “Frazer-Nash is studying the leading international solar power satellite designs, and we will be drawing up the engineering plan to deploy an operational SBSP system by 2050. “Historically, the cost of rocket launches and the weight that would be required for a project of this scale made the idea of space-based solar power unfeasible. But the emergence of privately-led space ventures has brought the cost of launch down dramatically in the last decade.
In Sep 2022, engineers at the European aerospace firm Airbus showed off what might be the future of clean energy. They collected sunlight with solar panels, transformed it into microwaves, and beamed the energy across an aircraft hangar, where it was turned back to electricity that, among other things, lit up a model of a city. The demo delivered just 2 kilowatts over 36 meters.
For now, Europe is where public agencies are taking space solar power most seriously. Last year, ESA commissioned two cost/benefit studies of space solar. ESA space scientist Sanjay Vijendran says they concluded it could conceivably match ground-based renewables on cost. But even at a higher price, comparable to nuclear power, its around-the-clock availability—unlike conventional solar or wind—would make it competitive.
In November 2022 , ESA asked member states to fund an assessment of whether the technical hurdles can be overcome. If the news is good, the agency will lay out plans for a full effort in 2025. Armed with €15 billion to €20 billion, ESA could put a megawatt-scale demonstration facility in orbit by 2030 and scale up to gigawatts—the equivalent of a conventional power station—by 2040.
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