Beaming Power from Space
Published on Oct 11, 2007 at 9:09 pm.
3 Comments.
Filed under solar energy, space businesses, space exploration.
For about five months, a collaborative study on Space Based Solar Power (SBSP) was conducted for the National Security Space Office. The text of that report is available here. You might wonder what solar power has to do with national security. Well, I’ll get to that a bit later. Suffice it to say that this report is the work of well over a hundred people working together on considering the feasibility of collecting solar power in space and sending it back to Earth.
Now, the idea of using solar power in space dates back to the earliest days of spaceflight. In space, solar power is not bothered by weather like on Earth, and there are no atmospheric effects to worry about. The sunlight is more intense above the atmosphere, too. So, solar power is a natural. It is free and easy. (Free referring to the sunlight itself, not the solar collectors, which can be quite costly.) The early solar cells were quite low efficiency by today’s standards. However, with the newer high efficiency solar cells, it is easy to generate all the electricity that you need for a spacecraft or space station using solar panels. In fact, you can quite easily have solar panels large enough to provide far more power than is needed for a space station.
On Earth, if you power your home with solar panels or a wind turbine, any excess electricity that you make is generally sold to the electric company. I once knew a guy who had a wind turbine. On months when the wind did not blow enough, his electric bill was about $50. But, in the months when it was windy, his electric bill could be -$75, meaning that the electric company paid him $75 for the month! On the whole, he said that he ran a profit having the turbine and being hooked up to the electric grid. But, a space station isn’t hooked up to any external electric grid, so there is no option for selling the surplus electricity. Or, is there?
There was an idea put forth in the 1960s to build orbital solar power stations and to beam the energy down to the ground. This idea would likely have not gone anywhere had it not been championed by Peter Glaser (project manager for laser ranging retroreflector arrays place on the Moon during the Apollo Program, and later president of the International Solar Energy Society and the editor in chief of the Journal of Solar Energy). While certainly wires can’t run between an orbital space station and a ground based power grid, it was suggested that the solar energy could be converted into electromagnetic radiation and then beamed to the ground, where it could then be converted into electricity. Though the idea of solar power stations beaming energy down to Earth has been an occasional feature in science fiction novels, nothing ever came of the idea in real life. Studies done in the 1970s showed that the cost of such a program would be prohibitive. Furthermore, the efficiency with which solar energy could be collected, turned into microwave radiation, beamed to the ground, collected again, and turned into electricity was very poor. The conclusions of those studies suggested that while SBSP was a cool idea, particularly in light of the attitude towards solar power by the environmental movement of those times, it was not practical at the time.
Then, in the 1990s, more studies were performed. By then, the technology had improved considerably. It was by then technically possible to build SBSP stations. Furthermore, by the 1990s, there was some concern over greenhouse gas emissions from fossil fuel consumption, and these SBSP stations would produce no direct greenhouse emissions. However, the cost of the project was prohibitive. Building such a station would require as many Space Shuttle flights as building the International Space Station, or more. With the price of oil at about $15 per barrel, there was little financial incentive to build SBSP stations, or any other form of alternative energy for that matter. Even though we use far more than oil to power our society, the prices of other fossil fuels (natural gas and coal) tend to track the price of oil. Furthermore, even biofuels use diesel machinery to produce, making even their production dependent upon the price of oil.
Though proponents of SBSP don’t like to admit it, these studies also showed that these orbital power stations are not really as environmentally neutral as had been first assumed. For one thing, they would require massive solar panels. Production of these panels involves some environmentally unfriendly chemicals. Of greater concern, though, was the environmental impact of the beamed microwave radiation. In order for the system to be economically feasible, the intensity of the microwaves would have to be rather high. There was no data available for the biological impact of such microwave exposure in the vicinity of the ground station if the beam were to drift off target.
But now, things may be different, as seen in this latest report to the National Security Space Office. In the post September 11, 2001, world, the government is now more concerned about international affairs. The United States’ heavy dependence upon foreign oil is perceived as a potential weakness in our national security. Now, I have full confidence in the United States Navy to protect shipping in international waters. So, we don’t have to worry about a blockade or someone torpedoing tankers heading to the USA. But, as has been demonstrated over the last few years, disruptions can occur at the wellhead in foreign nations. And, of course, we could face an embargo of oil, as happened in the 1970s. So, there has been a greater openness to pursuing alternative energy sources from national security considerations, aside from economic and environmental factors.
Economically, SBSP is not as far fetched as it seemed just ten years ago. For one thing, the efficiencies of the solar energy collectors are vastly superior to what they were two decades ago. Also, the efficiency of the ground station microwave receivers is far higher. There will be some loss, of course, but far less than before. Furthermore, the study participants believe that Shuttle flights could be altogether eliminated and the orbiting platform built entirely by robotic craft. This would save enormously on costs. Furthermore, there have been a number of commercial launch companies coming onto the scene in the last few years, and this has the potential to also drive the assembly costs down. Furthermore, with oil now near $80 per barrel, alternative energy sources are more economically viable than they were before.
Even so, however, it is estimated that the cost of electricity beamed to Earth from SBSP stations would be on the order of $1 to $2 per kilowatt-hour. Now, that seems excessive compared with the current cost of about 15 cents per kilowatt-hour here in Texas. But, lets consider that right now, forward military bases in Iraq and Afghanistan are dealing with unreliable local power grids, necessitating their requirement for on site electrical generation. The estimates for the cost of that on site electrical power is in the neighborhood of $1 to $2 per kilowatt-hour. It would be far easier and safer for a military base to deploy portable microwave collectors than to build a generator station and then convoy fuel to the generator through potentially hostile territory. If the cost is the same, then the SBSP option seems to be a major benefit. So, the report proposes that to get the first SBSP stations online, the Department of Defense should be an anchor customer for space based solar energy. As the technology developed, and as more SBSP stations came online, the overall cost would drop.
This would not be the first time that the government spent money on something that at first seemed an excessively expensive way to get something done that could be done other ways. The Hoover Dam, for example was built at a time when it seemed unlikely that the full extent of the hydroelectric power produced by that dam could ever be profitable. An improved ferry system would have been cheaper than the Golden Gate Bridge, but today the bridge seems to have been a wise investment. And, Global Positioning Satellites (GPS) seemed a bit excessive at first just to provide the military with ease in navigation, but the GPS technology has proven to be well worth the tax dollars spent on the system. Likewise, if SBSP were to actually work, then it may well turn out to be money wisely spent.
But, there are other issues to be worked out. For one thing, the environmental impact of beaming microwaves to a target on Earth is still not clear. How much scatter would there be? What impact would this have on migratory birds flying through the beam? How would it affect plants and animals in the vicinity of the collectors?
And, where would you put the orbital SBSP stations? If they were built in low Earth orbit (LEO), then they would be continually moving across the sky as seen by an observer on the ground. Each station would only provide beaming for a minute or two to any one ground site. It would take an enormous number of stations to provide adequate coverage. Furthermore, the moving station would require complex guidance and tracking systems for the receivers. Another possibility, though, would be to put the SBSP stations in geosynchronous orbits. Geosynchronous orbits are those that are at a sufficient altitude that the satellites orbit Earth in the same period of time that it takes Earth to execute a complete rotation. So, if the satellite is over Earth’s equator, then it will seem to hang in one point in the sky. That makes tracking the satellite easy. In fact, there is no tracking. You just point the antenna at it and forget about it. This is how satellite television works. But, that brings up a big problem. Geosynchronous orbits are prime orbital real estate for communication and weather satellites. In fact, those orbits are already getting crowded. A station such as this would take up even a lot of orbital space. Furthermore, you would want to restrict any other satellites from being too near to the SBSP station in case debris from one satellite were to impact the station and damage it. Also, the geosynchronous orbits are very high. Other satellites, and almost all manned spaceflight activities, occur in lower orbits, and the SBSP station would have to beam its microwaves to the ground through the altitudes at which these other satellites orbit. This could become a problem, particularly as more satellites are launched and more SBSP stations are built.
So, clearly there are issues left to deal with. However, even though SBSP has been championed for decades, this is the first time that it looks like technology would begin to make the idea really feasible. Furthermore, the national security issues and potential military utilization of such a system may make the government more willing to spend the money to investigate the idea of solar energy from orbital space platforms.
So now, there needs to be even more serious studies of this idea, and the concept needs to be actively promoted. That is where organizations such as the Space Solar Alliance for Future Energy (SSAFE) comes in. So, obviously there needs to be more work on the matter. And, let us not forget the astronomical implications. What would this do the sky sky if it were filled with giant power stations with huge solar panels? That needs to be addressed to. This is an interesting topic, and I’ll be blogging more about it later. I don’t want to make this single entry too long.
 -Astroprof
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Images © Mafic Studios, and courtesy of the National Space Society
Darnell Clayton on October 12, 2007 at 1:36 pm: 1
You forgot to mention one thing. Weather.
Forget the animals. What would enormous microwaves piercing our atmosphere do to our weather system?
It would over time (if not instantly) heat things up, which could create a chaotic weather pattern throughout the area.
Just my two cents.
Lokesh on October 17, 2007 at 2:16 pm: 2
On a serious note, a more advanced civilisation in some distant universe may be generating energy by using distortion in space-time produced by their Sun… Beaming Power from space “may be” a step forward in that direction as we have just begun on a daring expedition to explore energy options outside our home and in our neighbourhood star *
Sorting Out Science » Blog Archive » Carnival of Space #25 on October 18, 2007 at 7:07 am: 3
[…] Space Law Probe discusses the legal ramifications of solar power satellites, Space Solar Power describes the approach taken to compiling the study, and Astroprof goes into depth describing the history and workings of the technology. Shorter discussions come courtesy of Space Pragmatism, Out of the Cradle, Really Rocket Science, and Spaceports. Meanwhile, MSM coverage comes by way of Space.com, the Los Angeles Times, Aviation Week, New Scientist, and MSNBC. […]