ORICHALCUM UNIVERSE Sidebar: Sunpower tubes...

[Johnny1A.2]

In the year 2121, Earth derives its energy from a combination of nuclear fission (and some fusion) reactors, some hydropower, but increasingly the largest slice of the energy budget is power direct from the Sun, which is used in two forms, 'solar' and 'sunpower'.

Solar power is power harvested directly from sunlight, using various collectors and methods. Their efficiency is sharply higher than is currently possible, and sometimes use other principles than photovoltaic panels, but otherwise 'solar power' in 2121 would be quite recognizable to a time traveler from 2021. Combined with fairly good energy storage technologies, solar panels of various sorts provide most residential power and much other power in 2121. Most houses have collector panels on the roof, many windows are covered by low-efficiency but very cheap 'spray on' solar collectors as well. A typical single-family house in an advanced region can store enough power for several days use, making solar power very practical for residential use.

The term 'sunpower', on the other hand, refers to a superscience technology that draws power directly from Sun via a field interaction called the Colman-Ling effect. It involves the miracle-material orichalcum, though fortunately (due to cost) in tiny albeit indispensable amounts. Sunpower energizers are extremely expensive to build, but very cheap to operate. They are suitable mainly for large-scale power uses, they do no scale down well.

Several corporations manufacture sunpower systems, but the most popular and reliable come from Benton-Ling Suntubes, Incorporated, an American company based in Denver. They manufacture sunpower tubes in various standard sizes, the smallest being a 25 megawatt unit, the largest standard units rated at 1 gigawatt. [1]

In appearance, a sunpower tube looks rather like an improbably large and elaborate vacuum tube, packed with complex machinery inside a semi-transparent casing. This resemblance is more than superficial, a sunpower tube is a giant vacuum tube, the power tap requires a vacuum to operate safely. For obvious reasons, the material of the shell is extremely strong, able to withstand the pressure difference and most impacts. [2]

Higher-rated sunpower tubes are larger, the 25 megawatt tubes are two meters long by three-quarters of a meter in circular diameter, with power connections or a spin-axle port at one end. Some sunpower tubes are designed to produce their power in the form of rotation of a shaft, others emit it as straight electrical current, some can do both. The 25 megawatt tubes mass about one ton. Larger tubes are proportionately larger in terms of mass and volume.

Because sunpower tubes are tapping into a large field that the Sun generates as a volume around itself, they work equally well day or night, and the field effect penetrates well enough that a sunpower tube is useful even at the bottom of the deepest ocean trenches on Earth. (Though far enough underground would begin to interfere with the effect.)

Once operational, a sunpower tube can generate its rated power output effectively indefinitely with no fuel or other input. The output is not particularly flexible, it can be adjusted up or down by about five percent or so, but not much more. The output is mostly set by the design of the sunpower tube, to reduce it much below the rated output requires a full shutdown. This can make sunpower tubes inconvenient for small-scale or highly variable power demands, though they can be used to charge storage systems that are in turn more flexible.

Though a sunpower tube requires no fuel, to start a cold sunpower tube requires that power equal to its rated output be fed in for about one minute. At that point it will begin generating its own output, rising over several minutes to full strength. The 'input power' must be scaled down in synch with the rising output, or the power tube will be damaged or destroyed. It generally takes about fifteen minutes to bring a cold 25 megawatt tube to full power, larger power tubes take longer.

Sunpower tubes have many advantages, a major one is that they produce relatively little waste heat. Most of the entropy associated with the energy production is produced in the Sun, rather than the tube. However, no machine is 100% efficient, and sunpower tubes do generate a small amount of waste heat in operation. The standard 25-megawatt tube produces about two percent of its rated output as heat, or half a megawatt. Larger tubes are actually more efficient, a 1 gigawatt power tube produces about ten megawatts of waste heat in operation. This heat does have to be removed, or the tube can overheat and fail. Usually this will consist of simply the tube overheating and going dead, but under unfortunate circumstances seriously overheated power tubes have been known to shatter with considerable force.

The field-effect that sunpower tubes use to draw energy out of the Sun decreases with distance from the Sun, but not in a linear way. Generally speaking, a sunpower tube will produce its rated power anywhere from about half an AU out to about six AU with little detectable difference. That means that a sunpower tube on Venus, Earth, Mars, or one of Jupiter's satellites will behave as rated. [3]

A sunpower tube closer to the Sun than half an AU will produce about ten times its rated power...until something overloads and the tube fails. Sunpower tubes meant for use that close to the Sun require special construction and preparation.

A sunpower tube farther out than six AU will produce about 1/5 its rated power. This will not damage the tube in any way. Note that starting a cold power tube that far out requires the full rated input power. That is, a 25-megawatt sunpower tube on Titan would only produce a steady five megawatts, but would still require 25 megawatts of input power (for a few minutes) to start. (Likewise, starting a 25-megawatt tube on Mercury would require only 25 megawatts of input power as well, even though the tube would generate ten times that...while it lasted.)

The next drop-off point is at about 100 AU. Past 75 AU from the Sun, a sunpower tube will have effectively no output at all. All the drop-off distances are very narrow, the output will increase or decrease over the course of no more than a million kilometers or so.

A sunpower tube will work to draw power from other stars, but it will require retuning. The power distances from a given star are proportional to its energy production, a sunpower tube will generate useful power much further from a class O supergiant than it will from the Sun. Conversely, such a tube would have to be much closer to a Class M red dwarf to produce useful power than the Sun would permit.

Sunpower tubes are extremely expensive kit. They require a tiny amount of orichalcum to operate, fortunately only a very tiny amount, given the expensive of that substance. [4]

Fortunately, the amount of orichalcum required does not scale up in a linear way with power output. A 25-megawatt power tube requires 1/20th a gram, which makes a 25-megawatt power tube about a 5 to 6 million dollar device. On the plus side, a power tube, if properly maintained and not misused, can operate reliably for decades, requires no fuel, and produces relatively little waste heat and no other direct pollution.

[1] Twenty-five megawatts is about the smallest sunpower tube that is practical. In theory smaller ones could be created, but in practice it is much more trouble than it is worth, and prohibitively expensive.

[2] The transparent material of the tube wall is about DR 150 per centimeter.

[3] That refers to power output and waste heat emission. Special case environments may require modification. For ex, a sunpower tube on Io would need extra protection to avoid having delicate components damaged by the high incident radiation. Extremes of temperature and pressure such as the surface of Callisto or Venus would need to be allowed for as well.

[4] Spot price of orichalcum on October 31, 2121: $90,124,404.34 a gram.

[martinl]

Originally Posted by Johnny1A.2

The next drop-off point is at about 100 AU. Past 75 AU from the Sun, a sunpower tube will have effectively no output at all. All the drop-off distances are very narrow, the output will increase or decrease over the course of no more than a million kilometers or so.

The above is technically correct (100 AU is about 75 AU) but looks kinda weird.

In any case, keep on keepin' on. The whole Orichalcum Universe project is kinda awesome, even if I'm only a fringy fan.

[Varyon]

Originally Posted by Johnny1A.2

Because sunpower tubes are tapping into a large field that the Sun generates as a volume around itself, they work equally well day or night, and the field effect penetrates well enough that a sunpower tube is useful even at the bottom of the deepest ocean trenches on Earth. (Though far enough underground would begin to interfere with the effect.)

From this, I take it this field behaves something like a sphere of water with the Sun in the center - so it can wrap around blockages to get through, but can't penetrate through them without loss. This makes me wonder how large of an opening is required - if an aspiring supervillain wants a deep underground base, is it possible to drill something akin to ventilation shafts down so the field can reach the base's sunpower generator?

Originally Posted by Johnny1A.2

The output is not particularly flexible, it can be adjusted up or down by about five percent or so, but not much more. The output is mostly set by the design of the sunpower tube, to reduce it much below the rated output requires a full shutdown.
(...)
It generally takes about fifteen minutes to bring a cold 25 megawatt tube to full power, larger power tubes take longer.

With this in mind, devices making use of sunpower tubes that have any variability in power requirements need either massive capacitors (so they can be shut down once full, then relied upon to continue to provide power while being drained for the startup process later) or some way to "vent" excess produced energy. For the later, lasers are probably a good option - you can readily aim them to not hit anything (or for military applications, to hit something you want to) and they have very high power requirements.

Originally Posted by Johnny1A.2

Fortunately, the amount of orichalcum required does not scale up in a linear way with power output. A 25-megawatt power tube requires 1/20th a gram, which makes a 25-megawatt power tube about a 5 to 6 million dollar device. On the plus side, a power tube, if properly maintained and not misused, can operate reliably for decades, requires no fuel, and produces relatively little waste heat and no other direct pollution.

Once a sunpower tube reaches the end of its life, can the orichalcum be readily reclaimed for building a new one?

Also, keep in mind these are going to be incredibly tempting targets for scrappers. There are a lot of issues in the modern day of people stripping copper wire and the like from remote locations to sell as bulk scrap, sometimes at great risk to themselves (as copper is often used in large quantities for power distribution, they tend to get electrocuted) and great cost to those maintaining such. With a device that has ~5 million dollars worth of scrap, you're going to need some protection for these things.

[warellis]

Are sunpower tubes often used as a sort or backup or supply of additional power for starships?

[Johnny1A.2]

Originally Posted by warellis

Are sunpower tubes often used as a sort or backup or supply of additional power for starships?

Occasionally. The problem with sunpower tubes for a starship, of course, is that once you get very far away from a star, they quit working, and it's hard to store enough energy to make up for that. So most starships end up relying primarily on fission or fusion or both. (There is a special case exception.)

But sometimes a starship will carry sunpower tubes to enable them to tap into the local star and save fuel (and ease heat dissipation issues) while they are in a star system.

[Johnny1A.2]

Originally Posted by Varyon

From this, I take it this field behaves something like a sphere of water with the Sun in the center - so it can wrap around blockages to get through, but can't penetrate through them without loss. This makes me wonder how large of an opening is required - if an aspiring supervillain wants a deep underground base, is it possible to drill something akin to ventilation shafts down so the field can reach the base's sunpower generator?

It doesn't usually arise, because 'deep enough underground' would be measured in miles. You'd probably have to get at least ten or fifteen miles below the surface before the sunpower tube began to sputter out. But yeah, if you dug a shaft that deep the power could reach you.

With this in mind, devices making use of sunpower tubes that have any variability in power requirements need either massive capacitors (so they can be shut down once full, then relied upon to continue to provide power while being drained for the startup process later) or some way to "vent" excess produced energy. For the later, lasers are probably a good option - you can readily aim them to not hit anything (or for military applications, to hit something you want to) and they have very high power requirements.

Actually, lasers wouldn't work well for that, for the same reason that Brin's infamous 'refrigerator laser' would not work. To get rid of the excess energy, you'd need heat radiators with plenty of surface area, or some kind of coolant that could be vented. OTOH, it's relatively easy to radiate away concentrated energy, it's the low-temperature heat that's hard to get rid of without enormous radiators.

Once a sunpower tube reaches the end of its life, can the orichalcum be readily reclaimed for building a new one?

Yes. Most of the manufacturers actually pay a substantial sum for damaged or worn out sunpower tubes, precisely so that they can reclaim the orichalcum. Or the owner can remove and sell the orichalcum himself if he has the necessary tools and technical skills to get it out.

Also, keep in mind these are going to be incredibly tempting targets for scrappers. There are a lot of issues in the modern day of people stripping copper wire and the like from remote locations to sell as bulk scrap, sometimes at great risk to themselves (as copper is often used in large quantities for power distribution, they tend to get electrocuted) and great cost to those maintaining such. With a device that has ~5 million dollars worth of scrap, you're going to need some protection for these things.

Oh yes! These things are usually under heavy lock and key and often armed guards, esp. when they are inactive.

When a power tube is running, it's relatively secure simply because most would-be scrappers don't have the necessary technical knowledge or tools to safely remove them or get into them. Even the smallest power tubes pump out a steady 25 megawatts, that's enough to dixie-fry a would be thief instantly if he makes a single error.

When the power tubes are turned off, though, they are vulnerable. Some tubes have internal capacitors that store enough energy to let a power tube 'self start' (see the start up power requirements in the original post). Some of these tubes are intentionally designed to discharge that power to kill anybody who tries to tamper with them. This option is illegal in American power tubes, but some jurisdictions permit it.

[johndallman]

Originally Posted by Johnny1A.2

The term 'sunpower', on the other hand, refers to a superscience technology that draws power directly from Sun via a field interaction called the Colman-Ling effect.

Were these inspired by the solar power tubes in the Venus Equilateral stories by George O. Smith?

[Rupert]

Originally Posted by Johnny1A.2

Yes. Most of the manufacturers actually pay a substantial sum for damaged or worn out sunpower tubes, precisely so that they can reclaim the orichalcum. Or the owner can remove and sell the orichalcum himself if he has the necessary tools and technical skills to get it out.

I expect that there'd be a market for rental tubes, given the high capital investment and low running costs. The whole-life cost of a tube should be easy to cover seeing as you (the company leasing them out) will be able to trade in the orichalcum when the tube dies.

At about $1 million for the tube, once the orichalcum's cost is removed (because you get that back when the tube dies), a 25MW tube produces power for $0.005 per unit (kW/hr) or less if it lasts for only one year. Any industry that needs constant power and doesn't have a large grid supply handy would find such a thing very economical and if they didn't have the up-front capital to buy one outright, renting would make a lot of sense, even with the inevitable mark-up in cost.

I expect grid supply probably uses the large ones to provide power to cover the constant demand levels, with something like stored hydro power to cover the surge periods.

[Varyon]

Originally Posted by Johnny1A.2

Actually, lasers wouldn't work well for that, for the same reason that Brin's infamous 'refrigerator laser' would not work. To get rid of the excess energy, you'd need heat radiators with plenty of surface area, or some kind of coolant that could be vented. OTOH, it's relatively easy to radiate away concentrated energy, it's the low-temperature heat that's hard to get rid of without enormous radiators.

I thought these didn't generate much waste heat? The reason a refrigerator laser wouldn't be feasible is largely just that there's too high of an energy cost (although at lower TL's the laser may produce more heat than it sheds) - but here we're basically looking for something with a high energy cost and a controllable effect. Unless the waste heat from the laser ends up being prohibitive (which is certainly possible), it seems like it would fit the bill - you can dump a lot of energy, and just aim it at the sun or deep space so as not to damage anything.

Originally Posted by Johnny1A.2

Occasionally. The problem with sunpower tubes for a starship, of course, is that once you get very far away from a star, they quit working, and it's hard to store enough energy to make up for that. So most starships end up relying primarily on fission or fusion or both. (There is a special case exception.)

But sometimes a starship will carry sunpower tubes to enable them to tap into the local star and save fuel (and ease heat dissipation issues) while they are in a star system.

Intra-system spacecraft could make pretty good use of them, as most traffic would be within the 0.5-6 AU* range for peak safe performance. Using the highest estimates for what a PP is worth (basing it off the output of an energy weapon, and assuming 30% efficiency**), each 25 GW sunpower tube would generate around 1.5 PP for an SM+7 vessel, despite being only 1/15th of a system for such a vessel (if output scales linearly with mass, a full-sized sunpowered power plant would produce 15 PP). The price is high - 5-6x the cost of an SM+7 Fission reactor (which costs $1M and produces 1 PP) - but it's only 1/15th the weight and most of that cost (~$4.5M, leaving around the cost of the Fission reactor) can be reclaimed via recycling the orichalcum. If you've got high-density capacitors (or some other method of storing large quantities of energy per ton), inter-system starships could fairly readily make use of sunpower tubes to recharge once they're in a system (I'm not certain what superscience you're using for interstellar travel, but a lot of the more interesting ones have ships spending a lot of their time in-system; depending on how good your capacitors are, it might be possible to have an exclusively-sunpowered starship). Note this assumes that a starship either spends a lot of its time in one system or that it can retune its sunpower tubes relatively quickly. It also assumes the vessels have consistent power requirements, a way to readily vent excess energy, and/or operate under conditions where it's safe to shut down (and later boot back up) the tubes as needed (that is, a scenario where you need power right now isn't something that is at all likely to crop up - you generally know when (and how much) energy you're going to need well in advance of needing it.

*Are the dropoff points dependent on the star, and if so what does it map to? Are higher-volume stars, more massive stars, brighter stars, or some other quality more "powerful" in terms of the Colman-Ling effect?

**I'll note this is pretty well in excess of what most of the non-superscience power plants could realistically provide (except for maybe the antimatter or total conversion plants, but honestly I think of those as "low superscience"). That is, 15PP for a full-size reactor is likely an underestimate for what these could produce. Not that many vessels would actually use a full-size reactor, mind you, as that would call for ~75% of your mass to be high-powered systems (you can get this a bit lower if you have systems that use more than 1 PP, like a Heavy Force Screen).

Originally Posted by Rupert

I expect that there'd be a market for rental tubes, given the high capital investment and low running costs. The whole-life cost of a tube should be easy to cover seeing as you (the company leasing them out) will be able to trade in the orichalcum when the tube dies.

This makes a lot of sense. Given the cost of the tubes, there's probably a market in insurance for these rentals, in case a tube is lost, stolen, or destroyed in a manner that leaves some of the orichalcum unrecoverable.

[Rupert]

Originally Posted by Varyon

I thought these didn't generate much waste heat? The reason a refrigerator laser wouldn't be feasible is largely just that there's too high of an energy cost (although at lower TL's the laser may produce more heat than it sheds) - but here we're basically looking for something with a high energy cost and a controllable effect. Unless the waste heat from the laser ends up being prohibitive (which is certainly possible), it seems like it would fit the bill - you can dump a lot of energy, and just aim it at the sun or deep space so as not to damage anything.

Just run it through a resistor that's allowed to run at a nice high temperature that's set up with a good radiator. If you're dumping most of the tube's power you clearly don't have anything else competing for use of the radiator. i.e. if it can handle to tube's entire output, the radiator won't find anything else's heat output hard to handle, except possibly waste heat from a rocket.

This makes a lot of sense. Given the cost of the tubes, there's probably a market in insurance for these rentals, in case a tube is lost, stolen, or destroyed in a manner that leaves some of the orichalcum unrecoverable.

I'd expect it to be mandatory and included in the rental.