Wikipedia:Reference desk/Archives/Science/2019 June 9

= June 9 =

Space-based solar power
Would a Molniya orbit be suitable for a (theoretical) space-based solar power plant? 2601:646:8A00:A0B3:E143:3EF:8DB:B5B7 (talk) 01:37, 9 June 2019 (UTC)


 * As described in space-based solar power, most proposals have the transmitters in geosynchronous orbit, where they will see the sun ~99% of the time and aiming at the receiver is relatively easy. However, further down in the "non-typical" section, it also describes and links to a proposal for using more exotic orbits, including Molniya, in part because it could be relatively cheaper. Someguy1221 (talk) 02:07, 9 June 2019 (UTC)


 * Transmitting the power back to Earth seems impractical, as whatever the gain is from placing the solar panels in space (subtracting the losses of transmitting through the atmosphere), that gain can't possibly be worth the extreme cost of placing the solar panels there. That is, you could just use a small fraction of that money to place far more solar panels and energy storage facilities on Earth. Of course, eventually the space costs will come down and we may run out of places to put solar panels on Earth, but by then hopefully we will have fusion reactors working. So, solar panels in space really only make sense for powering devices right there (which does include sending signals back to Earth). SinisterLefty (talk) 03:28, 9 June 2019 (UTC)
 * At microwave frequencies the atmospheric absorption is considered not that bad. There are all kinds of artist conceptions of cows grazing under the ground antennas, planes flying through the microwave beam without the aircraft or passengers being heated, etc.  There is math behind all of it but I have to wonder about public acceptance if the schemes got anywhere near practicality and someone wanted to actually launch them.  The lyrics of Home on Lagrange allude to this. 173.228.123.207 (talk) 05:48, 9 June 2019 (UTC)
 * someone wanted, a century ago. It failed. Wireless_power_transfer Gem fr (talk) 11:39, 9 June 2019 (UTC)
 * Transmitting the power back to Earth IS impractical indeed, and, moreover, the energy cost to send things in orbit is so great it kills the payback. But we also need energy in space. So, maybe, for space application? Gem fr (talk) 11:39, 9 June 2019 (UTC)


 * Absolutely, solar panels are widely used to power satellites and space ships, at least in the inner solar system. But whether it would ever be practical to send solar power from one collecting station to a remote location, both in space, is questionable. What would be the advantage, instead of just attaching the solar panels directly ? If there are no big advantages, then it just adds complexity, inefficiency in changing energy forms, and potential for accidents, for little benefit. I suppose one advantage would be that the solar collector could be in an orbit that never or rarely passes into the Earth's shadow, but just tripling the size of the solar panels on the station using the power (which does pass into the Earth's shadow), and adding some batteries, might be a more practical fix. However, if the remote station is used, perhaps just using mirrors to aim light at the destination's solar panels when it's in shadow (or even to boost power when it's in light) would be the simplest fix. SinisterLefty (talk) 13:19, 9 June 2019 (UTC)


 * More (well, OK, less) to the point, following the logic above, why doesn't Earth send the power to space routinely? I'd think that, apart from backing up the most critical systems, a satellite could use that same power transfer tech to get a signal, especially since it would unfurl a very light net of delicate antennae a long way. Wnt (talk) 14:33, 9 June 2019 (UTC)


 * What would be the advantage ? Any device designed to receive the power source on the satellite would likely weigh as much as the solar panels. And then bad things might happen to planes flying through the power stream, so you'd probably need to put it on top of a mountain to minimize that risk (and atmospheric scattering), with high associated costs. And unless the satellite was in geostationary orbit (rather distant and directly over the equator), it would lose the power stream at least as often as it would lose sunlight. SinisterLefty (talk) 17:30, 9 June 2019 (UTC)


 * current solar panel don't have impressive power-to-weight ratio: ~100 W/kg. And, funnily, one of the best way to transmit power to space seems to make use of... solar panel (the source is a laser instead of the sunlight); efficiency is greater, and it can be more intense that the petty 1kW/m² of the sun. Now, any risk to lose power is a no-no, and you don't want to rely on heavy batteries or fuel consuming device, so, self-power it (currently) is. Gem fr (talk) 18:43, 9 June 2019 (UTC)


 * The power-to-weight ratio is infinite, since it's weightless while in orbit. :-) But seriously, the entire lifespan of the solar panels should be considered, so we look at power generated over the entire lifespan (kWh, for example) divided by mass. Batteries, voltage converters, etc., should be included. For the alternatives, like nuclear power, the fuel and all the equipment and shielding would need to be considered. If the satellite or ship mission is only planned for X number of years, then the calculations should only take that amount of time in consideration. SinisterLefty (talk) 00:43, 10 June 2019 (UTC)


 * Proposals for solar power satellites that I remember involved making the solar panels from lunar material so there was no need to launch it from Earth. Laser propulsion has been proposed as a way to launch spaceships, possibly using light sails.  But a high powered microwave beam could be hard to focus on a geostationary satellite.  You'd need multiple ground stations, etc.  The hope of spaceflight buffs was to just make launching stuff to LEO a lot cheaper, and have high efficiency space tugs to move stuff to GEO.  Project Orion (nuclear propulsion) was the most extravagant of the cheap launch schemes.  "We could have brought barber chairs" is the quotation I remember. 173.228.123.207 (talk) 23:04, 9 June 2019 (UTC)


 * Yes, moving production to the Moon would be one necessary step, but to bring the production costs down, the system has to be highly automated, so we don't need the expense of sending people there, and ultimately we need self-replicating robots, so we don't need to keep sending them there, either. All this is decades or perhaps centuries off, though. SinisterLefty (talk) 15:38, 10 June 2019 (UTC)


 * [un-indent] Folks, let's not get sidetracked here -- I was asking about the advantages and drawbacks of a Molniya (or better yet, Tundra) orbit compared to the traditional proposals for solar power in equatorial orbit (presupposing for the sake of the argument that space-based solar has become feasible, which IRL it hasn't), not about the feasibility of space-based solar power as such! 2601:646:8A00:A0B3:C5E:C820:3A44:3500 (talk) 01:04, 11 June 2019 (UTC)
 * hum, sorry for the sidetracking. Satellites on those orbit have a changing position and a changing distance to a station on Earth, and, unless I am mistaken, a higher energy cost than on a geostationary orbit. All this rank as drawbacks, while i struggle to see any advantage. If such a power plant were to exist, it most sensible and first use would be to power space objects, and for that, you don't need geosynchonism, but rather synchronism with the objects to be powered, that is, a lower, less costly, orbit. Gem fr (talk) 17:08, 11 June 2019 (UTC)

bird net around wind turbine?
Would it be that difficult/costly to cover wind turbines with nets to prevent them killing birds and bat? Any idea why this is not done?Gem fr (talk) 18:54, 9 June 2019 (UTC)
 * How fine would the mesh need to be? ←Baseball Bugs What's up, Doc? carrots→ 19:21, 9 June 2019 (UTC)
 * Just like nets used as pest control for orchard, I guess. Gem fr (talk) 20:04, 9 June 2019 (UTC)
 * Googling "bird friendly wind turbine" yields a number of theoretical and practical approaches. ←Baseball Bugs What's up, Doc? carrots→ 19:30, 9 June 2019 (UTC)
 * indeed, but saw only designs that, for all practical purpose may solve the issue in the future. And I never saw nets mentioned. There must be some reason Gem fr (talk) 20:04, 9 June 2019 (UTC)

What's the business case? Mostly, anything that reduces the efficiency of the turbines would need a good business argument (e.g. reduces bird strikes by X% which in turn reduces maintenance costs by £Y million, at a cost of £Z million in the reduction of electricity generated). If it was good business sense to do so, it would be happening already. The Rambling Man (talk) 20:09, 9 June 2019 (UTC)
 * It obviously cost something to prevent bird kills. And it seems that it was cheaper (better business) to convince administration to turn a blind eye on those kills. Now, what if the administration required those safety net, so the business had no choice? would that kill it, or just imperceptibly dent profits? Gem fr (talk) 20:36, 9 June 2019 (UTC)
 * I don't think for a moment that wind turbine operators care about the death of birds, just the ability to maintain turbines creating as much electricity as possible. Putting a net around the turbines (and I'm still unclear as to how that is possible) would inevitably cost money and reduce efficiency.  It's obvious that the payback in reduced maintenance is not worth it.  Hence they don't do it. The Rambling Man (talk) 20:39, 9 June 2019 (UTC)
 * I think you have more faith in the intelligence of business people than I do. :-) But I share your curiousity in how such a thing would even work. Would they essentially all get turned into box fans? Matt Deres (talk) 20:58, 9 June 2019 (UTC)
 * boxed fan, yes, that's the idea. although maybe just covering the most dangerous part (the tip) could be enough (again: if possible and if this doesn't make thinks worse, which could be. I don't know, hence the question) Gem fr (talk) 07:54, 10 June 2019 (UTC)


 * Maybe it would make sense in the rare case of a bird nearing extinction being threatened by a wind farm. But, in general, the surviving birds will learn to avoid turbines, just as the surviving varmints learn to avoid being hit by cars. SinisterLefty (talk) 00:39, 10 June 2019 (UTC)

This article claims windmills kill far fewer birds than most people think. It cites this article (paywalled), which claims that, per unit of energy generated, fossil-fueled power stations kill something like 15&times; as many birds. Adrian J. Hunter(talk•contribs) 00:59, 10 June 2019 (UTC)


 * Unfortunately, from a publicity POV, the windmills are worse. That is, if they can install a camera to monitor a turbine, and capture a bird being sliced in half, and put that on the news, that will garner far more outrage than if 15 birds, miles from the coal-fired plant emitting pollution, die from no apparent cause. Even worse, those plants also kill many people, but it's never obvious who would have lived had the air been a bit cleaner. SinisterLefty (talk) 15:31, 10 June 2019 (UTC)
 * The fact that no such video ("killer windmill brutally slices cute seagull in half") has been produced yet, despite political incentive to do so, tells you enough about the frequency of such incidents. (Also, as the original article (paywall) says, not all mortality is not due to gruesome slicing: there are also collisions with static parts, electricity lines etc.). Tigraan Click here to contact me 10:36, 11 June 2019 (UTC)


 * Any bird that manages to kill itself by flying into a stationary object deserves the Darwin award, for improving the gene pool. :-) SinisterLefty (talk) 17:53, 11 June 2019 (UTC)
 * As others have brought up, lots of man-made things kill more birds, and often more graphically. (Environmental impact of wind power has a table.) Bird strikes are a constant issue for aircraft, and there are plenty of videos of them, but there doesn't appear to be any big movement to ban or heavily restrict aircraft. Many have argued (example) that the concern about windmills and concentrated solar power killing birds is really just NIMBYism. People don't want the things built near them, and then they look around for other justifications to try to sway people, and choose the impact on charismatic megafauna as one. --47.146.63.87 (talk) 00:10, 12 June 2019 (UTC)

There is experience of audio and visual means of scaring birds away from airports. A loudspeaker mimics actual bird distress calls or makes frightening noises. It can broadcast species specific distress cries that scare flocks away. Visual deterrents, such as representations of owls and other natural predators, frighten birds away.See Bird control for airports. Special measures that can be employed include lasers, drones and radio-controlled hawks. DroneB (talk) 15:59, 10 June 2019 (UTC)