Saturday Night Science: The Case for Space Solar Power

 

The Case for Space Solar Power by John C. MankinsAs world population continues to grow and people in the developing world improve their standard of living toward the level of residents of industrialised nations, demand for energy will increase enormously. Even taking into account anticipated progress in energy conservation and forecasts that world population will reach a mid-century peak and then stabilise, the demand for electricity alone is forecasted to quadruple in the century from 2000 to 2100. If electric vehicles shift a substantial part of the energy consumed for transportation from hydrocarbon fuels to electricity, the demand for electric power will be greater still.

Providing this electricity in an affordable, sustainable way is a tremendous challenge. Most electricity today is produced by burning fuels such as coal, natural gas, and petroleum; by nuclear fission reactors; and by hydroelectric power generated by dams. Quadrupling electric power generation by any of these means poses serious problems. Fossil fuels may be subject to depletion, pose environmental consequences both in extraction and release of combustion products into the atmosphere, and are distributed unevenly around the world, leading to geopolitical tensions between have and have-not countries. Uranium fission is a technology with few environmental drawbacks, but operating it in a safe manner is very demanding and requires continuous vigilance over the decades-long lifespan of a power station. Further, the risk exists that nuclear material can be diverted for weapons use, especially if nuclear power stations proliferate into areas that are politically unstable. Hydroelectric power is clean, generally reliable (except in the case of extreme droughts), and inexhaustible, but unfortunately most rivers that are suitable for its generation have already been dammed, and potential projects which might be developed are insufficient to meet the demand.

Well, what about those “sustainable energy” projects the environmentalists are always babbling about: solar panels, eagle shredders (wind turbines), and the like? They do generate energy without fuel, but they are not the solution to the problem. In order to understand why, we need to look into the nature of the market for electricity, which is segmented into two components, even though the current flows through the same wires. The first is “base load” power. The demand for electricity varies during the day, from day to day, and seasonally (for example, electricity for air conditioning peaks during the mid-day hours of summer). The base load is the electricity demand which is always present, regardless of these changes in demand. If you look at a long-term plot of electricity demand and draw a line through the troughs in the curve, everything below that line is base load power and everything above it is “peak” power. Base load power is typically provided by the sources discussed in the previous paragraph: hydrocarbon, nuclear, and hydroelectric. Because there is a continuous demand for the power they generate, these plants are designed to run non-stop (with excess capacity to cover stand-downs for maintenance), and may be complicated to start up or shut down. In Switzerland, for example, 56% of base load power is produced from hydroelectric plants and 39% from nuclear fission reactors.

The balance of electrical demand, peak power, is usually generated by smaller power plants which can be brought on-line and shut down quickly as demand varies. Peaking plants sell their power onto the grid at prices substantially higher than base load plants, which compensates for their less efficient operation and higher capital costs for intermittent operation. In Switzerland, most peak energy is generated by thermal plants, which can burn either natural gas or oil.

Now the problem with “alternative energy” sources such as solar panels and windmills becomes apparent: they produce neither base load nor peak power. Solar panels produce electricity only during the day, and when the Sun is not obscured by clouds. Windmills, obviously, only generate when the wind is blowing. Since there is no way to efficiently store large quantities of energy (all existing storage technologies raise the cost of electricity to uneconomic levels), these technologies cannot be used for base load power, since they cannot be relied upon to continuously furnish power to the grid. Neither can they be used for peak power generation, since the times at which they are producing power may not coincide with times of peak demand. That isn’t to say these energy sources cannot be useful. For example, solar panels on the roofs of buildings in the American southwest make a tremendous amount of sense since they tend to produce power at precisely the times the demand for air conditioning is greatest. This can smooth out, but not replace, the need for peak power generation on the grid.

If we wish to dramatically expand electricity generation without relying on fossil fuels for base load power, there are remarkably few potential technologies. Geothermal power is reliable and inexpensive, but is only available in a limited number of areas and cannot come close to meeting the demand. Nuclear fission — especially modern, modular designs — is feasible, but faces formidable opposition from the fear-based community. If nuclear fusion ever becomes practical, we will have a limitless, mostly clean energy source, but after 60 years of research we are still decades away from an operational power plant, and it is entirely possible the entire effort may fail. The liquid fluoride thorium reactor, a technology demonstrated in the 1960s, could provide centuries of energy without the nuclear waste or weapons diversion risks of uranium-based nuclear power, but even if it were developed to industrial scale it’s still a “nuclear reactor” and can be expected to stimulate the same hysteria as existing nuclear technology.

This book explores an entirely different alternative. Think about it: once you get above the Earth’s atmosphere and sufficiently far from the Earth to avoid its shadow, the Sun provides a steady 1.368 kilowatts per square metre, and will continue to do so, non-stop, for billions of years into the future (actually, the Sun is gradually brightening, so on the scale of hundreds of millions of years this figure will increase). If this energy could be harvested and delivered efficiently to Earth, the electricity needs of a global technological civilisation could be met with a negligible impact on the Earth’s environment. With present-day photovoltaic cells, we can convert 40% of incident sunlight to electricity, and wireless power transmission in the microwave band (to which the Earth’s atmosphere is transparent, even in the presence of clouds and precipitation) has been demonstrated at 40% efficiency, with 60% end-to-end efficiency expected for future systems.

Thus, no scientific breakthrough of any kind is required to harvest abundant solar energy that presently streams past the Earth and deliver it to receiving stations on the ground that feed it into the power grid. Since the solar power satellites would generate energy 99.5% of the time (with short outages when passing through the Earth’s shadow near the equinoxes, at which time another satellite at a different longitude could pick up the load), this would be base load power, with no fuel source required. It’s “just a matter of engineering” to calculate what would be required to build the collector satellite, launch it into geostationary orbit (where it would stay above the same point on Earth), and build the receiver station on the ground to collect the energy beamed down by the satellite. Then, given a proposed design, one can calculate the capital cost to bring such a system into production, its operating cost, the price of power it would deliver to the grid, and the time to recover the investment in the system.

Solar power satellites are not a new idea. In 1968, Peter Glaser published a description of a system with photovoltaic electricity generation and microwave power transmission to an antenna on Earth; in 1973 he was granted U.S. patent 3,781,647 for the system. In the 1970s NASA and the Department of Energy conducted a detailed study of the concept, publishing a reference design in 1979 that envisioned a platform in geostationary orbit with solar arrays measuring 5 by 25 kilometres and requiring a monstrous space shuttle with payload of 250 metric tons and space factories to assemble the platforms. Design was entirely conventional, using much the same technologies as were later used in the International Space Station (ISS) (but for a structure 20 times its size). Given that the ISS has a cost estimated at US $150 billion, NASA’s 1979 estimate that a complete, operational solar power satellite system comprising 60 power generation platforms and Earth-based infrastructure would cost (in 2014 dollars) between $2.9 and $8.7 trillion might be considered optimistic. Back then, a trillion dollars was a lot of money, and this study pretty much put an end to serious consideration of solar power satellites in the U.S.for almost two decades. In the late 1990s, NASA, realising that much progress has been made in many of the enabling technologies for space solar power, commissioned a “Fresh Look Study”, which concluded that the state of the art was still insufficiently advanced to make power satellites economically feasible.

In this book, the author, after a 25-year career at NASA, recounts the history of solar power satellites to date and presents a radically new design, SPS-ALPHA (Solar Power Satellite by means of Arbitrarily Large Phased Array), which he argues is congruent with 21st century manufacturing technology. There are two fundamental reasons previous cost estimates for solar power satellites have come up with such forbidding figures. First, space hardware is hideously expensive to develop and manufacture. Measured in US$ per kilogram, a laptop computer is around $200/kg, a Boeing 747 $1400/kg, and a smart phone $1800/kg. By comparison, the Space Shuttle Orbiter cost $86,000/kg and the International Space Station around $110,000/kg. Most of the exorbitant cost of space hardware has little to do with the space environment, but is due to its being essentially hand-built in small numbers, and thus never having the benefit of moving down the learning curve as a product is put into mass production nor of automation in manufacturing (which isn’t cost-effective when you’re only making a few of a product). Second, once you’ve paid that enormous cost per kilogram for the space hardware, you have to launch it from the Earth into space and transport it to the orbit in which it will operate. For communication satellites which, like solar power satellites, operate in geostationary orbit, current launchers cost around US $50,000 per kilogram delivered there. New entrants into the market may substantially reduce this cost, but without a breakthrough such as full reusability of the launcher, it will stay at an elevated level.

SPS-ALPHA tackles the high cost of space hardware by adopting a “hyper modular” design, in which the power satellite is composed of huge numbers of identical modules of just eight different types. Each of these modules is on a scale that permits prototypes to be fabricated in facilities no more sophisticated than university laboratories and light enough they fall into the “smallsat” category, permitting inexpensive tests in the space environment as required. A production power satellite, designed to deliver 2 gigawatts of electricity to Earth, will have almost four hundred thousand of each of three types of these modules, assembled in space by 4,888 robot arm modules, using more than two million interconnect modules. These are numbers where mass production economies kick in: once the module design has been tested and certified you can put it out for bids for serial production. And a factory that invests in making these modules inexpensively can be assured of follow-on business if the initial power satellite is a success, because there will a demand for dozens or hundreds more once its practicality is demonstrated. None of these modules is remotely as complicated as an iPhone, and once they are made in comparable quantities shouldn’t cost any more. What would an iPhone cost if they only made five of them?

Modularity also requires the design to be distributed and redundant. There is no single-point failure mode in the system. The propulsion and attitude control module is replicated 200 times in the full design. As modules fail, for whatever cause, they will have minimal impact on the performance of the satellite and can be swapped out as part of routine maintenance. The author estimates than on an ongoing basis, around 3% of modules will be replaced per year.

The problem of launch cost is addressed indirectly by the modular design. Since no module masses more than 600 kg (the propulsion module) and none of the others exceed 100 kg, they do not require a heavy lift launcher. Modules can simply be apportioned out among a large number of flights of the most economical launchers available. Construction of a full scale solar power satellite will require between 500 and 1,000 launches per year of a launcher with a capacity in the 10 to 20 metric ton range. This dwarfs the entire global launch industry, and will provide motivation to fund the development of new, reusable, launcher designs and the volume of business to push their cost down the learning curve, with a goal of reducing cost for launch to low Earth orbit to US $300–500 per kilogram. Note that the SpaceX Falcon Heavy, under development with a projected first flight in 2015, already is priced around US $1000/kg without reusability of the three core stages that is expected to be introduced in the future.

The author lays out five “Design Reference Missions” that progress from small-scale tests of a few modules in low Earth orbit to a full production power satellite delivering 2 gigawatts to the electrical grid. He estimates a cost of around US $5 billion to the pilot plant demonstrator and $20 billion to the first full scale power satellite. This is not a small sum of money, but is comparable to the approximately US $26 billion cost of the Three Gorges Dam in China. Once power satellites start to come on line, each feeding power into the grid with no cost for fuel and modest maintenance expenses (comparable to those for a hydroelectric dam), the initial investment does not take long to be recovered. Further, the power satellite effort will bootstrap the infrastructure for routine, inexpensive access to space, and the power satellite modules can also be used in other space applications (for example, very high power communication satellites).

The most frequently raised objection when power satellites are mentioned is fear that they could be used as a “death ray.” This is, quite simply, nonsense. The microwave power beam arriving at the Earth’s surface will have an intensity between 10–20% of summer sunlight, so a mirror reflecting the Sun would be a more effective death ray. Extensive tests were done to determine if the beam would affect birds, insects, and aircraft flying through it and all concluded there was no risk. A power satellite that beamed down its power with a laser could be weaponised, but nobody is proposing that, because it would have problems with atmospheric conditions and cost more than microwave transmission.

This book provides a comprehensive examination of the history of the concept of solar power from space, the various designs proposed over the years and studies conducted of them, and an in-depth presentation of the technology and economic rationale for the SPS-ALPHA system. It presents an energy future that is very different from that which most people envision, provides a way to bring the benefits of electrification to developing regions without any environmental consequences whatsoever, and ensures a secure supply of electricity for the foreseeable future.

This is a rewarding, but rather tedious read. Perhaps it’s due to the author’s 25 years at NASA, but the text is cluttered with acronyms—there are fourteen pages of them defined in a glossary at the end of the book—and busy charts, some of which are difficult to read as reproduced in the Kindle edition. Copy editing is so-so: I noted 28 errors, and I wasn’t especially looking for them. The index in the Kindle edition lists page numbers in the print edition that are useless because the electronic edition does not contain page numbers.

Mankins, John C. The Case for Space Solar Power. Houston: Virginia Edition, 2014. ISBN 978-0-9913370-0-2.

Here is a presentation by the author and other speakers at the National Press Club on the study which is the basis for this book.

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There are 61 comments.

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  1. Stad Thatcher

    I love these posts!

    I have always liked the idea of “renewable” energy, but there is a weakness often ignored—we are at the mercy of the thing that is doing the renewing. Solar energy—clouds and night. Hydroelectric power—drought. Wind energy—well, lack of wind. I won’t even mention the fact that threatened or endangered species are killed by some renewables (I guess I just did mention it—sorry!).

    There is a base load (variable daily and seasonally) that needs a reliable source of power, a source independent of the elements. That source must be: coal, nuclear, natural gas, fuel oil, even wood . . .

    Beaming energy from space has always been more of a sci-fi dream than reality. Even if the practical problems were solved, there are safety issues—what if the energy beam moved away from its target and irradiated a playground?

    Nonetheless, the potential is there—multiple power receptors and repeaters to avoid cloud cover. The problem? Everything always looks good on paper—the cost, the efficiencies, but ultimately reality takes over. When do we learn if a new energy source is not practical—after we’ve spent billions?

    Again, keep up the great posts!

    • #1
    • June 28, 2014, at 1:28 PM PDT
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  2. John Walker Contributor
    John Walker Post author

    If you prefer a less detailed introduction to space solar power than the press conference video in the original post, here is a 20 minute TEDx talk by author John Mankins which provides an overview for those unfamiliar with the concept, “Space Solar Power: The Tipping Point”:

    • #2
    • June 28, 2014, at 1:41 PM PDT
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  3. John Walker Contributor
    John Walker Post author

    Stad: Beaming energy from space has always been more of a sci-fi dream than reality. Even if the practical problems were solved, there are safety issues—what if the energy beam moved away from its target and irradiated a playground?

    Nonetheless, the potential is there—multiple power receptors and repeaters to avoid cloud cover. The problem? Everything always looks good on paper—the cost, the efficiencies, but ultimately reality takes over. When do we learn if a new energy source is not practical—after we’ve spent billions?

    I discuss the beam safety issue in the third from last paragraph. The intensity of the microwave beam is no more than 20% of that of summer sunlight, and has been tested to be safe for birds, insects, and aircraft which fly through the beam. Further, the beam is directed toward the receiver antenna by an uplink beam which aims it. If lock is lost, the beam would be immediately cut off since it lost its aim point.

    The downlink from the satellite to the Earth is in the microwave band with a wavelength between 1 and 10 centimetres. At this wavelength the Earth’s atmosphere is transparent, so clouds and precipitation do not affect the beam; there is no need for multiple receivers.

    It would not take billions of dollars to establish the practicality of space solar power. If something is going to fail, it will almost certainly be detected in one of the earlier design reference missions, at which point the sunk investment is much smaller. The production system uses precisely the same modules as the earlier missions, just (many) more of them.

    Note that US$ 150 billion has been spent on the International Space Station with no benefit comparable to space solar power.

    • #3
    • June 28, 2014, at 2:04 PM PDT
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  4. Bryan G. Stephens Thatcher

    If there is no way to focus the beam in to a death ray, I am not for it. 

    • #4
    • June 28, 2014, at 2:27 PM PDT
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  5. Stad Thatcher

    John Walker: The downlink from the satellite to the Earth is in the microwave band with a wavelength between 1 and 10 centimetres. At this wavelength the Earth’s atmosphere is transparent, so clouds and precipitation do not affect the beam; there is no need for multiple receivers.

    Now it sounds like the energy density is too low to be useful. Nonetheless, anything should be looked at, just examine the technology thoroughly before commiting the money!

    In Asimov’s “I Robot” book, one of the short stories dealt with a robot in charge of keeping an energy beam focused from (IIRC) a satellite in Mercury orbit to Earth for the purpose of power transmission . . . a great read. The story was called (again, IIRC) “Reason”.

    • #5
    • June 28, 2014, at 2:54 PM PDT
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  6. AIG Inactive
    AIG

    I don’t buy it. If electricity demand is supposed to quadruple over the next century, I’m not sure this would be a “problem”. US energy consumption has increased over….8 times…in the last 60 years. We’ve managed quite nicely, while also improving considerably the environmental impact of energy production.

    The author compares the hypothetical $20 billion cost for a hypothetical 2GW solar “power plant” to the $26 billion Three Gorges Dam. Except the Three Gorges Dam has a capacity of 22GW, more than ten times larger. 

    There is no comparison on the cost-benefit analysis: existing energy sources will out-compete any such schemes in every scenario.

    But, NASA scientists doing what NASA scientists always do: dream up totally useless and hugely costly ideas for no particular reason.

    • #6
    • June 28, 2014, at 3:19 PM PDT
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  7. John Walker Contributor
    John Walker Post author

    Stad: Now it sounds like the energy density is too low to be useful.

    The low energy density of the microwave beam (100–200 watts per square metre) means the receiving antenna on Earth will be large: on the order of 10 kilometres diameter. This is big, but the antenna will be composed of millions of identical very simple elements and is estimated to account for only about 5% of the cost of the entire system. The antennas can be mounted on elevated poles and since they are almost completely transparent to sunlight, the land beneath them can be used for grazing land or agriculture. Almost none of the microwave energy will reach the ground beneath the antenna, so prolonged exposure of crops and animals beneath is it not a problem.

    There is a trade-off: if you make the antenna in space larger, you can increase the energy density of the beam and reduce the size of the receiving antenna on Earth, but that ends up costing more and may create hazards due to the beam intensity. Many studies done in the last three decades have worked out the sweet spot as 100–200 W/m² for the beam.

    The land used for space solar power receiving antennas is less than intermittent power generated by terrestrial solar panels or wind power, and has the advantage compared to terrestrial solar that the land can be dual use.

    • #7
    • June 28, 2014, at 3:28 PM PDT
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  8. John Walker Contributor
    John Walker Post author

    Stad: In Asimov’s “I Robot” book, one of the short stories dealt with a robot in charge of keeping an energy beam focused from (IIRC) a satellite in Mercury orbit to Earth for the purpose of power transmission . . . a great read. The story was called (again, IIRC) “Reason”.

    Asimov’s “Reason” is considered the first suggestion of space solar power, and envisioned wireless power transmission by microwaves, just as contemporary solar power satellite designs do. There is one aspect of the story which may be considered blasphemous by those inclined to cut off heads these days.

    • #8
    • June 28, 2014, at 3:33 PM PDT
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  9. AIG Inactive
    AIG

    Current capital costs for a 2GW installed capacity natural gas plant…estimated at under $1.5 billion. (according to 2013 US energy information administration estimates). 

    • #9
    • June 28, 2014, at 3:41 PM PDT
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  10. John Walker Contributor
    John Walker Post author

    AIG: The author compares the hypothetical $20 billion cost for a hypothetical 2GW solar “power plant” to the $26 billion Three Gorges Dam. Except the Three Gorges Dam has a capacity of 22GW, more than ten times larger.

    There is no comparison on the cost-benefit analysis: existing energy sources will out-compete any such schemes in every scenario.

    The $20 billion estimate covers all R&D, infrastructure, and intermediate steps through the first 2 GW power satellite entering revenue service. Once that investment is made, the marginal cost to produce additional power satellites is much lower, since you already have the launch, in-space transportation, module manufacturing, and operations infrastructure in place. By comparison, if one wished to build a second Three Gorges Dam, assuming a suitable river on which to build it existed (it does not), you would essentially start from scratch and expect the civil engineering costs to be roughly equal to the first dam.

    I wouldn’t be surprised if the cost projections for the first operational solar power satellite were underestimated by a factor of two or three, but then that happens with many other civil engineering projects which involve much more mundane technologies: the Channel Tunnel experienced an 80% cost overrun.

    As to “existing energy sources will out-compete any such schemes in every scenario” (we can’t properly quote and interleave comments here), wouldn’t that have been said for every transition in energy production in human history? Each new technology (coal vs. wood, oil vs. coal, natural gas vs. oil, etc.) must compete and demonstrate its superiority in the marketplace.

    • #10
    • June 28, 2014, at 3:50 PM PDT
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  11. AIG Inactive
    AIG

    John Walker: Each new technology (coal vs. wood, oil vs. coal, natural gas vs. oil, etc.) must compete and demonstrate its superiority in the marketplace.

     Of course. And there’s no reason to believe that this solar satellite power plant is anywhere close to be feasible, economically. 

    The cost estimates are fantastical, at best. But even if we assumed they were right, and after trillions of dollars of R&D…decades of R&D…probably hundreds or thousands of rocket launches needed to deliver it into space…this “best case” scenario only promises to deliver a system that costs about 10 times more than existing technologies, and delivers 10 times less energy. 

    Sounds like pure science fiction. Of course, once you get NASA into it, and the rocket launchers, you don’t exactly have a “market” situation. 

    Another oversight: even if energy consumption is forecast to increase 4 times in the next century (which is much lower than it has increased in the past 50 years), this increase is mostly going to happen in places which already have abundant natural resources and nuclear technology: China, India, Asia, Latin America, US. They all can build nukes for a tiny fraction of the cost of this scheme.

    • #11
    • June 28, 2014, at 4:01 PM PDT
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  12. AIG Inactive
    AIG

    Also, assuming all of this away, and you can get something that is cost-efficient, somewhere 30-40 years down the line: how is this going to help places which don’t have the capacity to create such a system? Is the US going to build a constellation of these, and then sell the energy to…Angola? And by the “US”, do we mean the US government? 

    I don’t think maintenance costs are going to be trivial here. Something as massive as that is going to have to deal with a lot of space debris and micro-meteoroids, probably requiring routine replacement of damaged parts. Space Shuttle 2.0. How does that compare to maintaining a nuclear plant or a coal plant on earth?

    • #12
    • June 28, 2014, at 4:08 PM PDT
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  13. John Walker Contributor
    John Walker Post author

    AIG:

    Current capital costs for a 2GW installed capacity natural gas plant…estimated at under $1.5 billion. (according to 2013 US energy information administration estimates).

    Sure, but a solar power satellite has economics comparable to a hydroelectric plant, not a fossil fuel thermal plant. According to this EIA document, the fuel cost in mills per kW/h for fossil steam plants (mostly natural gas) was 24.17 versus zero for hydroelectric. The fossil steam plants spent 3.73 mills per kW/h on operation compared to 6.71 for the hydro plants, while maintenance costs were comparable at 3.99 for fossil steam and 4.63 for hydro. Total costs were 31.89 for fossil steam and 11.34 for hydro.

    It costs a lot more to build a dam than a natural gas power plant, but once you’ve built it it just keeps on producing power as long as you do the maintenance. So it is for solar power satellites. To compare, you have to compute the cost for power delivered over a period sufficiently long to amortise the capital cost of the plant.

    Space, especially geostationary orbit, is a relatively benign environment as long as you understand the requirements for operating there. Communication satellites routinely operate for in excess of 15 years with no maintenance whatsoever. With robotic maintenance and refueling, there is no reason a power satellite could not operate for as long and as reliably as a hydroelectric dam.

    • #13
    • June 28, 2014, at 4:10 PM PDT
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  14. Al Sparks Thatcher

    There is no way to implement something like this without government involvement. And since you bring up NASA, I found them to be a big disappointment when it comes to space travel (I was eleven years old during the first moon landing).

    And the centralization required is immense. Smaller countries would probably cede the management of their power grid to some international organization. What kind of mischief would that bring about?

    In the contiguous United States, where we have three major power grids (East, West, and Texas) there have been some major power outages because of some power switch going bad in one area, and causing a domino affect across several states as other switches overloaded. Nor was it simple to restore power.

    There has been a movement afoot to create smaller more decentralized power plants that might service large neighborhoods instead of whole cities. And easily transportable generation would probably benefit 3rd world countries than this proposal.

    Lastly, I don’t accept the premise that the human population will continue to grow. It seems that good economies, which includes cheap power, mean less population growth. It probably won’t happen in my lifetime, but I suspect that worldwide population will probably start to decrease, just as it has in western first world countries.

    • #14
    • June 28, 2014, at 4:17 PM PDT
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  15. John Walker Contributor
    John Walker Post author

    AIG: The cost estimates are fantastical, at best. But even if we assumed they were right, and after trillions of dollars of R&D…decades of R&D…probably hundreds or thousands of rocket launches needed to deliver it into space…this “best case” scenario only promises to deliver a system that costs about 10 times more than existing technologies, and delivers 10 times less energy.

    Nobody is talking about trillions of dollars of R&D, or decades. The estimate is that a proof of concept pilot plant could be done within 15 years for about 5 billion dollars, and there are multiple milestones along that path where the project could be stopped if it failed to meet them on time.

    • #15
    • June 28, 2014, at 4:19 PM PDT
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  16. John Walker Contributor
    John Walker Post author

    AIG: I don’t think maintenance costs are going to be trivial here. Something as massive as that is going to have to deal with a lot of space debris and micro-meteoroids, probably requiring routine replacement of damaged parts.

    Yes, this has been studied in detail, and we have decades of experience from operating communication satellites in geostationary orbit (GEO). There is little or no space debris in GEO—there is simply so much space there (that’s why they call it “space”) and so few objects that the probability of a collision is very small. (This is not the case in low Earth orbit, but that isn’t where power satellites will operate.) Meteoroid damage and other attrition of elements, based upon communication satellite experience, is estimated at about 3% of modules per year. Replacing them is included in the operating budget in the cost estimations.

    This is comparable to the ongoing maintenance cost for hydroelectric dams and their power generation plants.

    • #16
    • June 28, 2014, at 4:27 PM PDT
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  17. blank generation member Inactive

    Just a few thoughts – 
    There will be a concern with background microwave radiation. For example remote control of home power meters by the local power company was a topic here recently, although a typical person won’t blink an eye at using a cell phone. I can see an opponent saying that there’s a microwave oven in space nuking your house.
    Would competition for prime geostationary orbital slots make this too costly?
    Also while not a good weapon, would a tunable downlink transmitter with a steerable antenna make a good jammer?

    • #17
    • June 28, 2014, at 4:39 PM PDT
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  18. RushBabe49 Thatcher

    Asimov’s robot novels, specifically Robots and Empire (1985) posited that space solar power was the main source for all of Earth. Of course, he also predicted that most humans inhabited huge underground cities (caves of steel), leaving the surface mostly empty.

    • #18
    • June 28, 2014, at 4:44 PM PDT
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  19. John Walker Contributor
    John Walker Post author

    Al Sparks: Lastly, I don’t accept the premise that the human population will continue to grow. It seems that good economies, which includes cheap power, mean less population growth. It probably won’t happen in my lifetime, but I suspect that worldwide population will probably start to decrease, just as it has in western first world countries.

    I’m not a great fan of the United Nations and its agencies, but in this case I agree with their forecast for human population, which is as you stated. As populations become more prosperous, birth rate falls, and this seems to be independent of other social factors. The U.N. Medium population forecast shows global population reaching around 10 billion (we’re already around 7 billion) and then leveling off at that number.

    This makes sense: the parents of the next three billion are already alive, and most of them live in traditional societies which technology and the culture it diffuses will be slow to reach.

    Since energy use per capita is an excellent proxy for development and hence reduction in fertility, providing the ten billion energy comparable to that available to residents of the developed world isn’t just a feel-good measure, it’s survival for everybody.

    • #19
    • June 28, 2014, at 4:51 PM PDT
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  20. AIG Inactive
    AIG

    John Walker: To compare, you have to compute the cost for power delivered over a period sufficiently long to amortise the capital cost of the plant.

     Yes of course. So how long is this for such a hypothetical solar plant? Far longer than it is for a conventional power plant. Are these satellites going to operate for 50 years? Probably not. 

    Nobody is talking about trillions of dollars of R&D, or decades. The estimate is that a proof of concept pilot plant could be done within 15 years for about 5 billion dollars

    That’s just fantasy. 15 years down the line, just the rocket launchers won’t cost that much. 

    Meteoroid damage and other attrition of elements, based upon communication satellite experience, is estimated at about 3% of modules per year. Replacing them is included in the operating budget in the cost estimations.

    This thing will be considerably bigger than a satellite, so the risk of damage is much greater. The cost estimates are pure fantasy.

    • #20
    • June 28, 2014, at 4:53 PM PDT
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  21. AIG Inactive
    AIG

    Here’s a simple estimate. If there’s 400,000 modules making up one of these power plants, and there’s an expected 3% attrition rate per year, of a module weighting about 100kg….that comes out to about 12,000 modules needing to be delivered per year, or about 1,200 tons. 

    A Falcon 9 Heavy (which doesn’t exist yet) is estimated to cost about $125 million per launch, and deliver about 21 tons to geostationary orbit. 

    So yearly replacement costs for damaged modules would run about…$7 billion

    That’s not counting launching the “robotic modules” to assemble them, and assuming that the full payload of a Falcon 9 Heavy is composed of these modules.

    I really doubt that in 15 years time the cost of space launchers will be so low today’s prices as to make any of these remotely feasible. I have no idea how they think they can launch 400,000 modules, with an estimated weight of 100kg each, for “$20 billion”.

    At estimated prices for the state of the art launcher today, Falcon 9 Heavy (which does not exist yet)…just launching such a system into GTO would cost…$238 billion

    Are we assuming that in 15 years the cost will be reduced by 10 times, forgetting the R&D cost of all of this? 

    Pure fantasy.

    • #21
    • June 28, 2014, at 5:00 PM PDT
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  22. AIG Inactive
    AIG

    John Walker: Construction of a full scale solar power satellite will require between 500 and 1,000 launches per year of a launcher with a capacity in the 10 to 20 metric ton range. This dwarfs the entire global launch industry, and will provide motivation to fund the development of new, reusable, launcher designs and the volume of business to push their cost down the learning curve, with a goal of reducing cost for launch to low Earth orbit to US $300–500 per kilogram. Note that the SpaceX Falcon Heavy, under development with a projected first flight in 2015, already is priced around US $1000/kg without reusability of the three core stages that is expected to be introduced in the future.

     Falcon Heavy is estimated at about $6,000/kg to GTO. 

    How long will it take to drive the price down to $300-500/kg? Not 15 years, that’s for sure. Maybe 150 years. 

    1,000 launches per year of a Falcon Heavy class rocket? Just for a 2GW capacity power plant? WOWWWWW!!!! 

    The US launches about 15-20 rockets per year. 

    • #22
    • June 28, 2014, at 5:08 PM PDT
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  23. John Walker Contributor
    John Walker Post author

    blank generation member:

    (1) I can see an opponent saying that there’s a microwave oven in space nuking your house.

    (2) Would competition for prime geostationary orbital slots make this too costly?

    (3) Also while not a good weapon, would a tunable downlink transmitter with a steerable antenna make a good jammer?

     We can’t interpolate comments in quoted messages, so I have numbered them and will respond by numbers.

    (1) The downlink power beam will be largely confined to the area of the receiver antenna, which will probably be in a rural area so that the ground beneath it can be used for agriculture. Microwave radiation outside the footprint of the antenna will be minimal, and will have no plausible consequences for those nearby (which doesn’t mean, of course, that they won’t come up with imaginative lawsuits). But the microwave radiation outside the antenna area will be negligible by any biological measure.

    (2) Providing all the world’s electricity requirement may create crowding in geostationary orbit, but this isn’t a problem because power satellites can be placed in geosynchronous orbits inclined to the equator. As seen from the Earth, they make a figure of 8 every day, moving above and below the equator. Because the power beam from the satellite is directed by a pilot beam from the antenna, it will continue to arrive at the antenna as the satellite moves in the sky relative to it.

    (3) I’m not sure I completely understand this, but the pilot beam sent by the receiving antenna would be encrypted and very difficult to spoof. It could be jammed, but jamming it would cause power transmission to be shut down, which would get the immediate attention of people whose lights went out to identify and deal with the jammer.

    • #23
    • June 28, 2014, at 5:15 PM PDT
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  24. John Walker Contributor
    John Walker Post author

    AIG: Are we assuming that in 15 years the cost will be reduced by 10 times, forgetting the R&D cost of all of this?

    Pure fantasy

    Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and weigh only 1½ tons.
    Popular Mechanics, March 1949

    • #24
    • June 28, 2014, at 5:24 PM PDT
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  25. John Walker Contributor
    John Walker Post author

    AIG: The US launches about 15-20 rockets per year.

    Yes, and fixing that totally changes the economics of launch to orbit, as I described in 1993.

    • #25
    • June 28, 2014, at 5:26 PM PDT
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  26. AIG Inactive
    AIG

    John Walker: Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and weigh only 1½ tons. — Popular Mechanics, March 1949

     Yes, and you’re assuming the technology curve for space launchers is going to be comparable to electronics? 

    That’s even greater science fiction than the technology of this solar plant.

    • #26
    • June 28, 2014, at 5:30 PM PDT
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  27. AIG Inactive
    AIG

    John Walker: Yes, and fixing that totally changes the economics of launch to orbit, as I described in 1993.

    In the entire history of the US space program, 57 years, the US has launched a total of 1,127 rockets into space. Majority have been small LEO payloads. 

    This system would require over 2,000 rockets of the heaviest type, just to install. And triple the current launch rate per year, just to maintain operational. 

    And this capacity will exist in 15 years? Science fiction.

    And all this effort… launching double the number of rockets the US has ever launched in the previous 60 years, for a budget that will likely be the equivalent of the entire DOD budget, with likely trillions of R&D development costs…just to get a 2GW power plant? 

    A natural gas plant will get you the same result for 0.01% of the cost.

    • #27
    • June 28, 2014, at 5:40 PM PDT
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  28. John Walker Contributor
    John Walker Post author

    AIG:

    John Walker: Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers in the future may have only 1,000 vacuum tubes and weigh only 1½ tons. — Popular Mechanics, March 1949

    Yes, and you’re assuming the technology curve for space launchers is going to be comparable to electronics?

    That’s even greater science fiction than the technology of this solar plant.

    Yes, I am. Developing technologies follow an exponential growth curve. Have you looked at the cost per kilowatt of photovoltaic solar panels, whether for Earth- or space-based applications? Exponential growth. The price of launching a kilogram into orbit has been falling exponentially with the advent of cubesats. Exponential growth. The same kind of autonomous robotics which enable self-driving cars will permit assembly of complex structures in orbit without humans to assist them.

    You call exponential growth “science fiction”. Hey, I write science fiction—punch me in the middle of my market demographic!

    • #28
    • June 28, 2014, at 5:42 PM PDT
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  29. AIG Inactive
    AIG

    John Walker: Yes, I am. Developing technologies follow an exponential growth curve. Have you looked at the cost per kilowatt of photovoltaic solar panels, whether for Earth- or space-based applications? Exponential growth. The price of launching a kilogram into orbit has been falling exponentially with the advent of cubesats. Exponential growth.

     1) Cubesats have nothing to do with the cost of…launching. Costs of launching have to do with rocket technology.

    2) The most advanced rocket technology we have today was developed in the…1960s. NASA relies on refurbished Russian rocket engines produced in the 1960s, because still today, we don’t have anything that is better than that.

    3) VERY FEW technologies follow an “exponential” growth curve. Extremely few. Rocket technology, certainly, is not one of them.

    • #29
    • June 28, 2014, at 5:45 PM PDT
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  30. AIG Inactive
    AIG

    John Walker: The same kind of autonomous robotics which enable self-driving cars will permit assembly of complex structures in orbit without humans to assist them.

     They have absolutely no relation to each other. One has to do with detection via radar or ladar or some other sensor…the other has to do with sending tons into space. The technology to remotely assemble stuff in space isn’t particularly challenging. But it costs astronomically. 

    • #30
    • June 28, 2014, at 5:48 PM PDT
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