Solar power satellites: Orbiting solar arrays could make electricity, convert it to microwaves and then beam that energy to a ground antenna where it would be converted back to electricity. But to make 10 trillion watts of power would require about 660 space solar power arrays, each about the size of Manhattan, in orbit about 22,000 miles above the Earth (Hoffert).
Some doubt that space solar power will ever prove economically competitive for terrestrial use. “The tasks are formidable, and it’s not clear you can identify a path that you know will solve the technology problems,” says Richard Schwartz, an electrical engineer and dean of engineering at Purdue University in West Lafayette, Indiana, who chaired the NRC panel.
The U.S. National Research Council noted: “providing space solar power for commercially competitive terrestrial electric power will require breakthrough advances in a number of technologies.”
There’s also the problem of getting the necessary equipment into space. Both NASA and NASDA have programs to develop low-cost launch technologies based on either reusable rockets or inexpensive expendable rockets. Both will probably be needed to build a workable power grid: The NRC committee estimates that it would take 1000 space shuttle payloads to deliver the necessary material, an order of magnitude more than the number of missions needed to construct the international space station. Without breakthroughs in launching technology, space solar power “would be impractical and uneconomical for the generation of terrestrial base load power due to the high cost and mass of the components and construction,” the NRC report concludes (Normile).
Besides the cost of implementing such a system, SBSP also introduces several new hurdles, primarily 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. The collecting satellite would convert solar energy into electrical energy on board, powering a microwave transmitter or laser emitter, and focus its beam toward a collector (rectenna) on Earth’s surface. Radiation and micrometeoroid damage could also become concerns for SBSP.
There are many other problems.
- The large cost of launching a satellite into space
- Inaccessibility: Maintenance of an earth-based solar panel is relatively simple, but performing maintenance on a solar panel in space incurs the extra cost of transporting a team of astronauts into space.
- The space environment is hostile; panels suffer about 8 times the degradation they would on Earth.
- Space debris is a major hazard to large objects in space, and all large structures such as SBSP systems have been mentioned as potential sources of orbital debris.
- The broadcast frequency of the microwave downlink (if used) would require isolating the SBSP systems away from other satellites. GEO space is already well used and it is considered unlikely the ITU would allow an SPS to be launched.
- The large size and corresponding cost of the receiving station on the ground.
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.
To give an idea of the scale of the problem, assuming a solar panel mass of 20 kg per kilowatt (without considering the mass of the supporting structure, antenna, or any significant mass reduction of any focusing mirrors) a 4 GW power station would weigh about 80,000 metric tons, all of which would, in current circumstances, be launched from the Earth. Very lightweight designs could likely achieve 1 kg/kW, meaning 4,000 metric tons for the solar panels for the same 4 GW capacity station. This would be the equivalent of between 40 and 150 heavy-lift launch vehicle (HLLV) launches to send the material to low earth orbit, where it would likely be converted into subassembly solar arrays, which then could use high-efficiency ion-engine style rockets to (slowly) reach GEO (Geostationary orbit). With an estimated serial launch cost for shuttle-based HLLVs of $500 million to $800 million, and launch costs for alternative HLLVs at $78 million, total launch costs would range between $11 billion (low cost HLLV, low weight panels) and $320 billion (‘expensive’ HLLV, heavier panels).To these costs must be added the environmental impact of heavy space launch emissions, if such costs are to be used in comparison to earth-based energy production. For comparison, the direct cost of a new coal or nuclear power plant ranges from $3 billion to $6 billion per GW (not including the full cost to the environment from CO2 emissions or storage of spent nuclear fuel, respectively); another example is the Apollo missions to the Moon cost a grand total of $24 billion (1970s’ dollars), taking inflation into account, would cost $140 billion today, more expensive than the construction of the International Space Station.
SBSP costs might be reduced if a means of putting the materials into orbit were developed that did not rely on rockets. Some possible technologies include ground launch systems such as Star Tram, mass drivers or launch loops, which would launch using electrical power, or the geosynchronous orbit space elevator. However, these require technology that is yet to be developed. Project Orion (nuclear propulsion) is a low cost launch option which could be implemented without major technological advances, but would result in the release of Nuclear fallout.
Alice Friedemann comment on the Berkeley Blog:
The issue with launching anything into space is the energy resource – fossil fuels are a non-renewable resource, but that’s the only way we have of getting objects into space. Nuclear power is unacceptable because there’s always the risk of an explosion and radioactive particles spread across a vast area. Wind, solar, hydrogen, hydropower, geothermal, etc., to launch an object into space? Not possible due to the laws of physics.
To get to the stars, an unknown type of energy would have to be found, and ask any physicist if there are any unknown types of energy to be discovered. There are no anti-gravity, teleportation launches of spacecraft in our future.
So then it boils down to the “cost”, as if printed money was more meaningful that the energy that makes anything possible.
A contracting engineer at NASA’s Marshall Space Flight Center in Huntsville, Alabama made the following points on a forum that’s been discussing Energy Returned on Energy Invested (EROEI) for over a decade.
It’s hard to calculate the cost per pound of deliver to the geosynchronous orbit (GSO), but Futron Corporation is paid by the companies that actually launch satellites to make estimates (www.futron.com).
In 2003, Futron estimated GSO launch vehicles cost per pound at $17,000 (Western) and $7,000 (non-Western). In 2000, the costs were around $12,000 per pound. Low Earth Orbit, (LEO) is much cheaper.
At $7,000 per pound, it would cost $42 billion to launch a 3,055-ton satellite into geosynchronous orbit, and another $4.2 billion for every refueling run.
These costs are for UNMANNED objects.
Many use the argument that because we put a man on the moon we can do anything. Or like the late Napoleon Hill put it, “Whatever the mind of man can conceive and believe, it can achieve”.
But no one ever came up with a way to make nuclear powered airplanes, which the Air Force tried to build from 1946 to 1961, for billions of dollars. They never got off the ground. The idea was interesting – atomic jets could fly for months without refueling. But the lead shielding to protect the crew and several months of food and water was too heavy for the plane to take off. The weight problem, the ease of shooting this behemoth down, and the consequences of a crash landing were so obvious, it’s amazing the project was ever funded, let alone kept going for 15 years.
The costs of launching orbital solar arrays would be astronomical:
Orbiting solar arrays could make electricity, convert it to microwaves and then beam that energy to a ground antenna where it would be converted back to electricity. But to make 10 trillion watts of power would require about 660 space solar power arrays, each about the size of Manhattan, in orbit about 22,000 miles above the Earth.
Futron estimates it “would take about $42 billion in launch vehicle costs to put a 3,055-ton satellite in the geosynchronous orbit, and another $4.2 billion for every refueling run. That is just for one 2,500-megawatt satellite”. Ron Patterson. 14 Jan 2003. Energyresources msg 28631
“What happens when the triple redundant onboard mission computer allows the downlink beam to drift off target by a few degrees, slewing the beam across the countryside adjacent to the ground station and barbequing same with a few gigawatts of microwave radiation ? It is also difficult / impossible to maintain against the backdrop of a global decline in energy availability and the concomitant economic dislocation imposed by same. Keeping the flight hardware operating at peak efficiency would let’s just say require 2 shuttle flights a year”. Mark Petrie. 8 Nov 2000. Space Power. Energyresources msg 3511.
Hoffert, Martin, et al. 1 Nov 2002 Advanced Technology Paths to Global Climate Stability: Energy for a Greenhouse Planet, Vol 298
Normile, D. SPACE SOLAR POWER. Japan Looks for Bright Answers to Energy Needs 9 November 2001: Science. Vol. 294 no. 5545 p. 1273
30. In space, panels suffer rapid erosion due to high energy particles,“Solar Panel Degradation” whereas on Earth, commercial panels degrade at a rate around 0.25% a year.“Testing a Thirty-Year-Old Photovoltaic Module”
31. “Some of the most environmentally dangerous activities in space include […] large structures such as those considered in the late-1970s for building solar power stations in Earth orbit.“The Kessler Syndrome (As Discussed by Donald J. Kessler)”. Retrieved 2010-05-26.
32. Hiroshi Matsumoto, “Space Solar Power Satellite/Station and the Politics”, EMC’09/Kyoto, 2009