Opinion by Dale Skran
A big thanks to John Mankins for some key ideas and examples. Note that one section as noted was updated a day after posting.
Casey Handmer, formerly with Hyperloop and recently a software developer at JPL, loves to opine on space-related topics. He is a big fan of StarShip/SuperHeavy and Musk’s city on Mars but a deep skeptic of space solar power (SSP), space mining, and a bunch of other things. His first anti-SSP essay appeared on his blog in August.
Why should you pay any attention to what I have to say about this? Although I don’t claim to be an electrical power systems professional, I am at least in the ball park in terms of having relevant expertise as the holder of Electrical Engineering degrees from Michigan State (BSEE) and University of Michigan (MSEE), a veteran of 17 years at Bell Labs, a member of the management team at two highly successful networking equipment startups (one on the East coast, Sonus Networks, and one on the West coast, Ascend Communications), and a telecom expert.
To play fair and avoid accusations that I am quoting Handmer out of context, I am including his entire “physics based” anti-SSP argument, interspersed with my responses. However, his entire approach suffers from an enormous flaw which makes it virtually useless, namely that you can’t just look at the cost of a rectenna in isolation from system costs, nor can you look at the costs of ground based solar just as the costs of the panels in the desert. You need to do a best-case analysis of each system but with the same ground rules, which Handmer does not even remotely attempt. By best case I mean that you can’t make pessimistic assumptions for one approach and optimistic assumptions for the other to get things to come out the way you think they ought to come out.
What would an apples-to-apples comparison look like? First, it would only focus on baseload electric power. Ground solar is a great solution for day-time peaking electricity to power air conditioners since the sunlight itself drives the need for air conditioning, and no batteries would be required, nor would any transmission system beyond the current grid required. But a baseload electric power analysis needs to look at all system level costs.
For ground solar this includes:
- The cost of the basic solar panels
- The cost of the extra panels to provide extended duration, full-load backup and the cost of the accompanying batteries; this will vary depending on the location and the season—perhaps 1-2 days (Arizona), perhaps 1-2 weeks (Illinois) and possibly more.
- The cost of the land for the above panels.
- The cost of regular cleaning of the panels (and the distilled water required).
- The cost to connect the panels with the batteries and the existing network.
- Any new transmission lines needed to connect remote panel farms to the network.
- An honest account of the likely impact of weather on the system, including funds needed to repair storm damage over the lifetime of the system.
- A backup plan for when the batteries run out during the winter or during the storm season.
- Consideration of network transmission losses.
For space solar power this includes:
- The cost of the panels and in-space microwave transmitters.
- The cost of assembling the panels and transmitters in space.
- The cost of launch.
- The cost of the rectenna, including land.
- The cost of connecting the rectenna to the network.
One of the many advantages of SSP is the ability to send the power to where it is needed to minimize transmission costs. I’ve seen anti-SSP arguments where the Sahara Desert is covered in rectennas, and huge transmission costs are assumed. These kind of “straw man” models are not representative of real systems.
Another common error in anti-SSP arguments is to assume that all SSP components are built on Earth and lifted at great expense to space. Although the first SPS will be built from Earth-manufactured components, there is no to reason to assume that this will always be the case.
So, let’s get to it!
[Handmer] In this blog we’re going to avoid reasoning by analogy which, in space, will lead us astray. Space is so different from the familiar here on Earth that the only way to be sure we’re on the right track is to think like physicists and use first-principles reasoning.
[Skran] I am all for first-principle reasoning, but when economics are involved, you need to consult more than just the physicists.
[Handmer] My view is that space-based solar power is impossibly expensive and will never be used on Earth. There are no shortage of prominent and qualified people on both sides of this issue – my purpose here is to show why it’s hard and attempt to illustrate some limits on the concept.
To get the obvious out of the way, solar power is an obvious and vital source of electrical power for space-based applications, such as powering satellites and rovers, probes and space stations. It is, and will remain, the de facto source of energy for applications in space well into the foreseeable future.
[Skran] Handmer is right here, but if anything understates the value of solar power in space. The ability to transmit power to an ion-drive or mass-driver craft via a laser opens up the potential of very high-ISP craft with much higher thrust to weight ratios than conventional vehicles. Such vehicles could be key to the industrialization of cis-lunar space.
[Handmer] What of Earth? Space-based solar power is not a new idea. Indeed, it was popularized by Gerard O’Neill in his visionary book “The High Frontier”, which I have reviewed. O’Neill advocated the construction of gigantic space stations in Earth orbit, and saw solar power as the killer product to pay for construction.
In another blog I will explore the detailed reasons why mining the moon or asteroids is a commercially tricky proposition, but fundamentally it’s due to the enormous expense of flying rockets to and from space, combined with their desperately limited cargo capacity.
[Skran] This is a bit out of scope, but there is virtually no area where sillier arguments are advanced than by those who think space mining is not possible. For starters, Handmer believes that we will never mine commodity products in space and return them to Earth. Couldn’t agree more, but no space mining advocate seriously suggests bringing lunar aluminum to the surface of the Earth. This is another “straw man” argument. Of course, we could mine “rare” materials in space in such large quantities that they become commodities when returned to Earth.
[Handmer] Solar power, on the other hand, could be beamed to Earth using microwaves, which have no intrinsic mass and so only require rockets to install the systems in the first place. In addition, a gigantic solar array built in space could receive solar power 24 hours a day, unobstructed by clouds, night time, or the atmosphere. In California we are spoiled by solar availability, but much of northern Europe receives pitifully small quantities of solar power, particularly in winter.
The principle of wireless power transfer, first practically demonstrated by Nikola Tesla, is well understood physics. The underlying technology for space-based solar power has existed since the 1970s. Oil has been considered scarce since the same period, so why haven’t gigantic solar space stations been built to provide us with power?
As Elon Musk has concisely pointed out, the fundamental problem with space-based solar power is that it’s obtaining a commodity, power, somewhere where it’s expensive and selling it somewhere where it’s cheap. This is not a good business. Indeed, it might make more sense to beam power from Earth to space stations, if they needed it.
[Skran] This is just rhetoric without any analysis. The idea that power in space is expensive appears to be based on the cost of power on the ISS, which is in fact really high. But fundamentally power in space is cheap and reliable—just put up the solar panels and you are done.
[Handmer] But why is power in space so much more expensive than Earth? Remember, there is 3-50x more solar power in space than Earth, depending on the location. If my opinion is valid, then we should expect ancillary system costs to outweigh the improved solar resource in space.
What are the extra costs? Broadly, they fall into the following categories: Transmission losses, thermal losses, logistics costs, and space technology penalty. Individually, any one of these issues cancels out the benefits, and combined they leave space-based solar power at least three orders of magnitude more expensive than the terrestrial equivalents. Because it’s not even close, I don’t have to be persnickety about decimal places – instead I can rely on generously drawn bounds.
[Skran] As I said in my intro, this approach is fundamentally wrongheaded. Handmer looks in isolation at cherry picked elements, but you need to consider the entire system.
[Handmer] For a baseline comparison, consider a GW-scale power station. For terrestrial solar, this consists of standard panels on single axis mounts, covering about 10 square miles. For the space-based solar case, an identical area of land is covered instead with an antenna, a mesh of conductive wire held above the ground, to absorb the transmitted microwaves and convert them to electricity. An identical area implies similar overall energy fluxes, which is correct. Even if it were physically possible (it is not) to transmit microwaves in some focused narrow beam with power densities of MW/m^2, it would be unacceptably dangerous to do so. In some orbit far above, a space station covering, say, 2 square miles, receives the sun’s light and converts the power to microwaves, transmitting to the ground through an antenna of similar size, necessary to keep the beam focused.
[Skran—updated Dec. 19] This is not an apples-to-apples comparison. Space solar power is 24/7, while the cost of ground solar is based on power generation capacity at peak sunlight. Ground photovoltaic (PV) requires over-sizing and a vast energy storage system to provide comparable baseload power. Let’s look at a specific case. The July insolation in Chicago is 4.7 kWh per meters-squared per day—with a peak insolation of roughly 700 watts per square meter. With 20% efficient PV panels, that yields a peak power generated of 140 Watts per meter-squared (and a cost of about $140/meter-squared since solar panels cost about $1.00 per Watt-installed average), but produces only about 940 watt-hours per day of energy per meters-squared. Delivering 1 kW of baseload power—24 kWh over one full day—would hence require about 26 square-meters of PV array, at a cost of about $3,600.
Moreover, in December, the total insolation drops to an average of about 3 kWh per square-meter per day. Again with 20% efficient PV, in December that yields about 600 watt-hours per square-meters. On average, a 24/7 ground PV system in December in Chicago would need to be sized at about 41 square-meters to provide the 1 kW of baseload power. That’s if every day is clear. If you have 10 days of overcast (not unusual in Chicago in December), then in the day before the clouds you need to generate 240 kWh of energy—which totals about 400 square-meters for 24/7 power, at which point, the cost of the PV array is about $56,000.
Note that clearly you could make this calculation look better by generating the “extra” power over a period longer than one day. This does not change the amount of storage needed, but it does reduce the extra panel area required. It can be argued, however, that 1 day is actually a realistic requirement, since it is perfectly possible to have 10 days of overcast, 1 day of sun, and 10 more days of overcast. Regardless of the work that might be done to optimize these calculations in favor of ground-based baseload solar electricity, that optimization will not change the fact that ground-based baseload electricity generation is much more expense that is often claimed.
And, you must add storage to the ground PV system to cope with the 10 days of overcast. A typical cost for long-term battery storage as documented by the U.S. Energy Information Agency (EIA) in 2020 is about $750 per kWh. That works out to a total of roughly $240,000 for each 1 kW of 24/7 baseload power. This mathematics is why ground PV is not used for baseload power in most of the world. Rather it is used in conjunction with dispatchable baseload power—such as natural gas turbines—that can take up the load when the sun is not shining.
For the city of Chicago, the total cost for a conventional PV array system plus the required energy storage to deliver 2GW of baseload power in December becomes about $480B, with dedicated land area of 800,000,000 square-meters (a circle about 32 miles across). For a similar 2 GW of baseload power, SSP delivering an average 90 Watts/square-meter of receiver would require only 28,000,000 square-meters (a circle of only 3.6 miles), plus the space system, which is discussed elsewhere. Moreover, the power from a single SPS could be delivered in the northern hemisphere in December, but in the southern hemisphere in June; and shifted from East coast to west coast as demand shifts during each day. All-in-all, this is why SSP might well make a fabulous partner for conventional solar power—rather than a competitor.
[Handmer] Transmission losses: The process of converting sunlight to electricity is about 20% efficient, depending on the type of panel – and this is a loss common to both systems. In addition
[Skran] Although it may seem fair to assume the same efficiency in space and on the ground, this doesn’t really make sense. If you have to lift the solar cells to space, it may work out to make more sense to use a more expensive, but more efficient cell in space to save on launch costs. Also, current solar cell maximum efficiency is more in the 40% range than 20%, which is often given as what can be expected out of a ground based solar panel. One must also consider the use of concentrators on both the ground site and in space (where concentration is almost certainly easier than on the ground). Of course on the Earth weather and the tilt of the axis has a big impact on the amount of sunlight on the panel, while in space you get direct sun all the time. The point of all this is not to quibble about 20%, but to suggest how complex a real analysis needs to be.
[Handmer] space-based system has to convert the electrical power back into EM radiation, which is converted back into power on Earth. Proponents think that it should be possible to perform each conversion with 90% efficiency, but even beam-forming that well is not possible without a much larger antenna. My personal opinion is that the end-to-end microwave link efficiency would be lucky to exceed 40% efficiency, which erodes the competitive advantage substantially.
[Skran] It is unclear to me how this kind of off-the-cuff opinion amounts to “first principal reasoning.” The use of “my personal opinion…” makes it clear that Handmer has no knowledge in the field. As it happens, experiments by Brown and Dickinson in the 1970s demonstrated rectenna RF-to-DC conversion efficiencies of up to 93%. Credible estimates put the end-to-end efficiency (DC to DC) at roughly 55-65% for state-of-the-art microwave devices.
[Handmer] Thermal losses: The conversion efficiency of the high-power microwave transmitter has a nasty side-effect, namely that what isn’t transmitted is wasted as heat, and that heat has to go somewhere. If the transmitter is 80% efficient (which is being very generous), then it will have to radiate 200MW of thermal power. This is a different problem to the thermal losses in the solar panels, which are more like 4GW but spread over a huge area that is in radiative thermal equilibrium with its environment. Instead, the microwave power electronics will need a huge cooling system. If the electronics can operate at 350K, then the radiator power will be 850W/m^2, so the radiator will need a total area of 23ha, comparable to the total size of the solar array and the microwave transmission antenna. In contrast to the usual claims of perfect scaling efficiency with solar arrays in microgravity, a large space-based solar power system will also need a huge antenna and cooling system, which don’t scale quite as nicely.
[Skran] There is little doubt that the main technical complaint that can be raised about SSP is whether or not waste heat can be radiated away fast enough to allow the electronics to keep working and cheaply enough that the cost of the radiator doesn’t sink the entire idea. There is, however, an element of “garbage in garbage out” in the above analysis. Clearly, the amount of waste heat depends directly on the efficiency of the conversion of electricity to radiated microwaves. Since ordinary house microwaves are typically 82%, but range up to 88%, the selection of 80% as being “generous” seems deceptive, and the efficiency of solid-state power amplifiers continues to increase steadily. Since Handmer has done only a superficial analysis of the cost and area of the radiator needed, and since this analysis is strongly impacted by the assumed low conversion efficiency, he is not making a “knockout” argument. It is possible he is correct, and excessive requirements for heat dissipation will doom SSP, but the reality of things remains to be seen. In particular, he seems to be assuming that a very large and cumbersome radiator will be needed, and that the system will be designed in such a fashion that the radiator is not modular and does not scale well. There are a number of SPS concepts—like that tested recently by the Naval Research Laboratory—that use the antenna as the radiator, allowing passive cooling. What Handmer refers to are just assumptions, not physical limits
[Handmer] Logistics costs: Consider transportation cost. Today, SpaceX has crushed the orbital transport market with a price of around $2000/kg. Compare this to the worldwide network of intermodal containers, which can transport anything in 20T units almost anywhere on Earth for about $0.05/kg. Even if all of Elon Musk’s wildest Starship dreams come true, transport costs will dominate the total capex of any space-based solar system, by many orders of magnitude. A factor of 10x improvement in resource does not make up for transport costs which are more than 10,000x higher. If logistics costs are more than 0.1% of current solar farm costs (they’re more like 20%), then increased transport costs completely negate the improved solar resource. It’s not even close.
[Skran] One flaw in this reasoning is the assumption that the entire mass of the SPS must be lifted from Earth. However, the more basic flaw is that you can’t compare the weight of the ground solar panels with the weight of the space solar panels. You need to look at specific cases, and not just assume, for example that the panels have the same efficiency, or that the size of the panels is the same, etc. Then you have to do a complete system comparison, not just examine transportation in isolation.
Transport to space will always be more expensive than transport from Michigan to New Jersey. But transport to space may be similar to the cost of flying from New Jersey to Australia. So, you can’t just assume that transport costs will dominate the cost of SSP. In particular, the cost of launch via Starship as promised by Elon Musk will be roughly $200 per kilogram or less—much less depending on the source. If the mass of an SPS delivering 1 GW were 5,000,000 kg (not a bad number), then a simple calculation of the contribution to the Levelized Cost of Energy (LCOE) represented by the cost of launch yields less than 0.3¢ per kilowatt-hour. Even if the cost of launch were increased by 10-fold (to the current launch price of Falcon 9R) the cost of launch would still only represent 3¢ per kilowatt-hour—hardly the ‘orders of magnitude’ erroneously asserted by Handmer.
Finally, we need to keep in mind that Musk’s current 9m StarShip/SuperHeavy is the beginning of cost reductions, not the end. The future lies with bigger rockets—18m diameter and more—that will drive still lower costs
[Handmer] One further aspect of logistics bears closer examination. In our baseline case, we considered an array of panels strung up on posts, compared to a mesh of wire strung up on posts. It turns out that (as of 2019) a substantial fraction of the overall cost of a solar PV station is the mounting hardware, which is also required by the microwave receiver. So, if the mounting hardware costs
[Skran] This argument assumes, without any references or meaningful analysis, that the cost of mounting hardware for a solar panel and for a rectenna will be the same. Even if this were true, we are comparing highly refined mounting hardware for ground solar panels with lab-demo rectenna mounting hardware. Modest engineering efforts will almost certainly reduce the costs of rectenna mounting hardware, since rectennas promise to be lighter than solar panels, and should need less bulky mounting hardware. Consideration needs to be given as well to the labor cost of solar panel installation vs rectenna installation. Also, rectennas are more likely to survive storms than solar panels, so post-storm repair needs to be part of the equation.
[Handmer] 20% of the overall deployment cost for terrestrial solar, that places a strong upper bound on total system cost allowable for space-based. In other words, does anyone seriously believe that the microwave receiving antenna could cost 20% of the overall system capex, the other 80% to be used to launch thousands of tonnes of high-performance gear into space? Put another way, the most cost-effective way to get a GW of power out of a microwave receiving antenna is obviously to tear down the wire mesh and sling up a bunch of solar panels, which can be ordered with a lead time of weeks from any of dozens of suppliers worldwide with widely available financing.
[Skran] This is just rhetoric since it is not based on whole-system analysis. The cost structures for ground vs. space solar are entirely different, as are the use cases.
[Handmer] Finally, the space technology penalty. On Earth, we are living in an extremely exciting time for energy. Hundreds of major companies are competing on development cycles measuring only months to provide solar panels in an industry that’s growing at 20% a year. As a result, costs have fallen by 10% a year, and in the last few years, solar and batteries have neared, equaled, then utterly crushed all other forms of electricity generation. Initially, this process occurred on remote islands with high fuel import costs. Then the sunnier parts of the US. The rampage continues northwards at about 200 miles a year. The industry can sustain 30% deployment growth rate worldwide for another decade at least, before saturation occurs.
Today, I can pick up the phone and any of dozens of contractors in the LA market can fill hundreds of acres with panels, each built to survive 30 years under the harsh sun and sized perfectly for deployment using the latest tech, which is men in orange vests with forklifts.
In contrast, space technology has not benefited from such breakneck levels of growth, demand, and investment. Prohibitive maintenance costs demand perfect performance, and low rates of deployment ensure a slow innovation feedback loop. The result is that none of the current incredibly cheap solar panels could work in space, where thermal and vacuum, not to mention stresses of launch, would destroy their operation in days.
[Skran] There is no magic in the low cost of ground solar panels, only the common magic of markets and mass-production via automated plants. This same ‘magic’ will benefit space solar power systems as well—at least those that are designed to exploit it. While his “space technology penalty” argument may have appeared true to Handmer in 2019, it seems vastly less true in 2020, as SpaceX launches the Starlink mega-constellation 60 satellites at a time, around 900 so far on the way to 42,000. Moreover, Silicon Valley engineering practices, fast prototyping, a willingness to fail, and changed assumptions about cost-effective satellite lifetimes have brushed aside Handmer’s “space technology penalty” argument. Modern SPS designs like SPS-ALPHA are based on mass production of pizza-box sized common elements, not on the sort of 1970s engineering described in The High Frontier and that appears to be assumed by Handmer.
[Handmer] Instead, space operators rely on more traditional supply chains, with the result that building anything for space takes years and costs billions. Right now, a billion dollars invested will buy about 100MW of solar panels on the Earth, or 100kW of solar panels in space. This is a factor of 1000, and it also erases the advantages of more sunlight in space.
[Skran] SpaceX has led the way toward ignoring the “traditional supply chains,” with others following. Handmer is in effect arguing that if NASA builds SSP, it will be as expensive as the ISS solar panels. This may even be true, but no SPS advocate suggests that NASA or “Oldspace” defense contractors should be tasked with putting gold-plated equipment in orbit to beam power back to Earth. As noted above, the current revolution being accomplished by SpaceX through the manufacture of 1000s of Starlink satellites (120 and 30 metric tonnes fabricated and launched per month, at only about $2,000 per kilogram is well on the way to SSP logistics—still shy of the requirement, but well on the way).
[Handmer] These four elements, transmission, thermal, logistics, and space technology, inflate the relative cost of space-based solar power to the point where it simply cannot compete with terrestrial solar. It’s not a matter of 5% here or there. It’s literally thousands of times more expensive. It’s not a thing.
[Skran] In fact, Handmer’s argument is totally bogus, and demonstrates nothing about SSP.
[Handmer] I can relax assumptions all day. I can grant 100% transmission efficiency, $10/kg orbital launch costs, complete development and procurement cost parity, and a crippling land shortage on Earth. Even then, space-based solar power still won’t be able to compete, because the antenna receiver alone is basically a solar plant in disguise.
[Skran] Contrary to Handmer’s assertation, a rectenna is not a solar plant in disguise, something that becomes obvious when a total system comparison for baseload electricity is done.
[Handmer] I can grant a post-scarcity fully automated luxury communist space economy with self-replicating robots processing asteroids into solar panels, and even then people will still prefer to have solar panels on their roof, to avoid supply interruptions and utility bills. Or maybe they’ll all be post-humans living in some data center orbiting Jupiter. Let’s reel it back in a bit.
[Skran] This above makes it even more clear that Handmer just doesn’t understand the uselessness of solar panels on the roof by themselves except as sources of peaking power. Without very significant energy storage—much more than even the most dedicated solar enthusiast ever installs—ground solar is not a good source of baseload electricity on a global scale, even in the most favorable conditions. The ground solar advocate may then suggest that the entire electrical network be rebuilt to move solar electricity from place to place, and to transport wind and wave electricity from remote areas so that a virtual baseload can be maintained. This is all fine and dandy, but it needs to go into the analysis to compare ground solar to space solar. Handmer hasn’t even got the basic assumptions correct, and apparently lacks any real knowledge of how electrical networks work or what they cost.
[Handmer] There is one additional reason why space-based solar power won’t be built, and that is investment risk. It is the same reason why nuclear power won’t solve climate change. Power plants traditionally front load much of their costs, and space-based solar is no exception. So what, advocates say, all infrastructure costs a huge amount up front, and that investment is paid off gradually over decades of use by everyone. Let’s say that despite all the above issues, a business plan emerges which can justify borrowing the necessary capital to build and deploy a bunch of space-based power stations, backed by a “purchase power agreement”, where a utility agrees to buy all the power at a currently acceptable price for some number of decades. Like nuclear power, which requires 50 or more years of operations to pay off construction and decommissioning costs, signing such an agreement in 2019 is an enormously risky thing for a utility to do, because of future price uncertainty.
[Skran] Here Handmer is making a basic error in assuming that there will be a large up-front capital cost before there is any meaningful payback for SSP. Modern SPS designs are totally modular and can be incrementally constructed to arbitrary size, while providing power back to Earth from the first launch. This makes a comparison to nuclear power or coal/natural gas plants inappropriate. In fact, an SPS launched on a single Falcon Heavy could become almost immediately profitable by selling electricity to islands in competition with imported—and expensive—oil.
[Handmer] Indeed, just last month a major solar farm was announced in Nevada with a power price of $35/MWh, including storage. This price would have seemed impossibly low even last year, and yet I am certain that we will not have to wait long to see solar projects built for less than $10/MWh. For the first time in nearly 50 years, energy is rapidly getting cheaper and there’s no limit in sight. Against a backdrop of supply costs dropping by 10%/year, it will not be possible to find financial backers for projects that have a ROI time measured in decades. It is simply not possible to predict whether they will be able to make any money.
[Skran] As near as I can tell from following the links, the actual price per Kw/Hr is lower than Handmer reports, but does not include battery storage. Without sufficient storage—weeks at full power—these prices can’t be compared to baseload electricity from SSP. I have seen various reports of solar utilities with storage, but the amount of storage is modest, often hours, and far short of what is needed to be a true baseload electricity source. Also, this project received a 30% subsidy from the government, and made use of existing transmission equipment already installed for a coal plant. With all these caveats, the example demonstrates nothing about real costs.
[Handmer] This is not a bad thing! Sure, I would love to see a vibrant cis-Lunar economy, enormous space stations, and thousands of people living in space. It’s a beautiful vision. But if it occurs, it will not be funded by electricity, because climate-friendly energy has gotten very cheap here on Earth. If I had to choose between terrestrial solar power crushing coal and gas, or giant space cities, I would choose the former. So has the market.
[Skran] It is easy for those like Handmer to make half-baked arguments against SSP that are outside their area of professional expertise—Handmer is a mathematician and software designer who only recently started working at JPL. Of course, like a broken clock that is right twice a day, Handmer may be correct that SSP will never be “a thing” for providing electricity to the Earth. Among SSP circles, I’m a bit of a skeptic myself. For example, I allow that if some kind of cheap, high-current, high energy density battery is developed (think quantum batteries), it may be sufficient to allow ground-based solar to provide true baseload electricity. Even in this case, SSP may be advantageous for providing carbon-free power to remote locations and disputed areas.
The bottom line is that to do useful economic comparisons we must do full system comparisons, and not use the cherry-picking approach that Handmer takes.
Great rebuttal Dale. Toss that femur vertically.
Thanks for the post. I was reading Casey’s blog because I don’t have a physics or aerospace background, but I started to see read flags with how their posts are pepper with phrases like: “only way”, “exactly zero”, “absolutely”, “totally”, “basically”, etc.
I would like to live in his word of absolutes and zero probabilities, but that’s not reality. Thanks for the constructive post and the call for level-headed analysis.
For SPS to be a reality, efficient power transmission must be a reality.
If efficient transmission is a reality, then transmission up must work, not just down.
So you can leave the panels on the ground, beam the power up, and then back down to where it’s needed. It’s always sunny somewhere, so power is available 24/7, so that’s one black mark against ground solar gone. No storage is needed as it can be beamed wherever it’s needed, so that’s another gone. They can be sited near the equator, so the issues you raised about Chicago and other high latitude sites are gone. They can be sited on cheap ground, so that’s another black mark gone.
So the technology that is absolutely required for SPS to work, means it can never compete with ground panels. Power relay, yes, but SPS, no.
Conceptually, for this orbital power relay scheme to work, you need to have on each side of the Earth 2x the ground solar cells needed, so that you can send half the power to the shadow side. So you need to build 2X the global power load from ground solar, plus add to that the same number of receiving antennas as would be needed if you used SSP to provide all electricity. And then you need to have a large number of orbiting receiving antennas and microwave relay stations in geosynchronous orbit, or possibly LEO. And this is assuming that this arrangement is competitive technically and economically with ground based transmission approaches. This seems so much more complex and expensive than just putting solar power satellites in orbit that it does not appear to be a real option. Note that if it did work,it would be a very large in-space construction project similar in magnitude to SSP, but the ground segment would be much more work – and cost – than is required for SSP.