Jaffe’s vision for the project is a one-kilometer array of modules, along with sun reflectors, which would span about nine football fields. Up until now, the only space satellite to date that even comes close to this scale is the International Space Station, which is a bit longer than an American football field.
While it may seem a bit out there (literally) right now, the Navy’s work to explore alternative solar options for energy isn’t surprising. It’s part of a trend by the US military to explore the use of and deploy alternative energy sources to achieve its mission.
The Army already has erected a number of
key solar arrays as part of microgrids to power its installations, finding that renewable energy can be more cost-effective than using generators or hooking up to the regular electricity grid.
Indeed, the Navy said using solar arrays according to Jaffe’s design could deliver energy at about 10 cents per kilowatt-hour. Eventually such an idea might even be extended to the commercial sector to power cities.
This idea, to me, seems both very complicated and simple at the same time. Satellites already use solar energy, and where better to harvest energy from the sun than the place where the sun is located. While what Jaffe has already designed and built is promising, it also will take a significant amount of investment and technology to get it where it needs to be for this to become a reality. Still, this is fascinating stuff and could one day revolutionize renewable energy, at least that from the sun.
Ha, yes, TJ, it does seem the stuff of scifi and I am sure there will be naysayers that claim it's dangerous and it shouldn't be done. I personally think it's a great idea and, given the fact that we use solar energy naturally anyway, it would be hard to argue that this is dangerous for humans. But I guess you're right in that the transition from solar energy to radio waves that will be "beamed" down will spur panic among some!
Elizabeth, one thing you don't mention is how much energy the proposed array will produce. What is the efficiency of the whole system?
On another note, why use robots to assemble this. Why not the International Space Station (ISS)? It has a robotic arm and people to do the work. This would have lots of benefits. First, there is cost. The whole robotic assembly is not a part of the technology of power generation. It is a whole other program requiring diffent skills and really raises the cost and complexity of the system. I expect that a demonstrator would be built (a single satellite) and then a larger array, then the full envisioned array. That's a lot of steps. Getting rid of the robotics in the early stages would speed things along.
Lou, those are good questions, but as to your first I don't think the research has gotten that far. I would have to check with Jaffe. I think the answer may be a bit further down the line, as it hasn't really been tested yet.
And as for the robots, that's also a question for Jaffe. I am sure he has a good reason for including robotic assembly, but I completely see your point that it seems like a lot of effort for something that doesn't contribute to the ultimate goal of the system.
I would think that robots would be far more desirable than humans because of the added cost and risk associated with life support. This is supported by our government use of aircraft drones. These drones are actually robots controlled by humans, as would be the robots constructing the space array. The space station certainly is not designed to perform array construction, and it would be far to difficult and costly to manuver its own solar arrays around a huge construction site.
How is the energy harvested to be transferred? Solar panels have greater efficiency and longer life due to lack of atmosphere. However, is it enough to outweigh the efficiency lost in transmission through the atmosphere?
Can we deliver the sun's energy to earth more efficiently than nature does now?
Robots are much cheaper to support in space than humans. Humans need food, water, air, companionship, and an environment with tightly controlled temperature range and air pressure. All of this means a lot of weight being sent to space consistently which is really expensive. Robots are more durable. Robots can withstand greater temperature ranges and higher levels of exposure to radiation. Robots don't get tired, bored, or disgruntled. Robots don't have to be brought back to Earth after a relatively short stay.
It looks like most of the other posts broach the question, "how much power?". This is certainbly a valid question. I also wonder about the cost figure of 10 cents per Kwh. I'd certainly like to see how this was calculated ... i.e. what assumptions were made. On the logistics side, I think it might be imprudent to quickly discount the "death rays from space" argument. The article talks of RF and then seems to move on to microwaves. If this is the case, then I must logically conclude that there would be a transmitting antenna array/dish for directing the energy toward some receiving station on the ground. What will be the size of the energy "beam"? Probably most important, how accurately can/will this be directed between orbit and the ground? Let's consider some numbers. In the desert SW of the US (and even sometimes in the SE regions), the insolation can reach 1000w/(sq meter). In space, where there is no atmospheric attenuation, that number will certainly be higher ... but let's just use 1Kw/m^2. If the collector array is 1Km x 1Km (implied from the article), then we could expect an array output of 1Mw. For the sake of argument, let's also assume a DC power - to - beam conversion efficiency of 25%. Further assuming a uniform distribution of power across the beam cross section, that would give us a total cross sectional beam power of 250Kw. For a beam diameter of 1m, the power would be approximately 333Kw/m^2. This number would go up for smaller beam diameters and down for larger beam diameters. The positioning of such a beam would need to be VERY carefully controlled.
It isn't clear what type of beam will be used. RF does not seem very efficient as there is too much atmospheric loss, the beam power you calculated is way beyond the capability of any present day RF amplifier, which would need power to operate. Such a process would require a passive device that can convert the collected energy and convert it into a beam (like a magnifying glass).
On another note, what are the environmental effects of the beam in question?
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