Wikipedia:Reference desk/Archives/Science/2015 May 29

Science desk
< May 28	<< Apr | May | Jun >>	May 30 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

May 29

Why would the North Pole be full of oil (alledgedly)? Was is not always a cold place where life couldn't thrive?

A bathymetric/topographic of the Arctic Ocean and the surrounding lands.

Why would the North Pole be full of oil (alledgedly)? Was is not always a cold place where life couldn't thrive?--82.159.164.102 (talk) 17:29, 29 May 2015 (UTC)

The North Pole is not full of oil. The oil is in Northern Alaska, places like Barrow, Alaska and the Arctic National Wildlife Refuge and places like that. Still, assuming you mean the oil in Northern Alaska, remember that plate tectonics is a thing. No patch of the Earth's crust has been where it is now forever, it all moves and drifts around quite a bit; there are also dramatic changes in climate; at times in the past there have been temperate conditions near the poles and no ice caps, for just one example during the period of the Paleocene–Eocene Thermal Maximum. Petroleum#Formation also makes clear, most of it comes from zooplankton and algae, i.e. tiny critters living in the sea. Most oil reserves are under the locations of former seas. So, the notion that oil currently exists in the frigid, low-life areas of earth doesn't mean that those parts of earth were always frigid, and didn't used to support a lot of life, especially of the kind that forms oil. Indeed the existence of the oil is one of the ways that we know what the earth USED to look like. --Jayron32 17:39, 29 May 2015 (UTC)

Much of Alaska's oil is outside of ANWR. You might find these keywords helpful in your search: the North Slope and the Prudhoe Bay Oil Field (among many others). The State of Alaska has a great website full of resources, North Slope Regional Geology (there is even a full-length book for interested readers) and the US Geological Survey's Energy Resources program has a website, Alaska Regional Studies with a lot of accessible information on the geology and geological history of Alaska as it applies to energy resource exploration.

Even Prudhoe Bay's petroleum service terminal has greenery.

Although these regions are quite northerly, and many of the famous oilfields of Alaska are above the Arctic Circle, they are still quite distant from the geographic north pole: the Earth is quite large. Furthermore, Alaska is quite green: more of Alaska is green than you might expect, and very little of the state actually experiences permafrost. When I visited Fairbanks in the summer, I found the climate to be very similar to that in Northern California; when I visited Kodiak in the winter (in Southern Alaska, although out at sea and quite cold), I found the winter storm weather to be milder than certain winters I experienced in Upstate New York. Life thrives in Alaska; wildlife and vegetation is nearly everywhere - mostly because there are very few people to ravage it.

Nimur (talk) 18:11, 29 May 2015 (UTC)

I'm not sure if there has been much oil exploration at the actual North Pole. There wouldn't be much point in a company searching for oil there, as the constantly moving ice pack on top would make for difficult drilling, either exploratory drilling or for production purposes. Global warming may soon melt the ice in summer, but having wells you could only tap in summer would still be problematic. Perhaps some system could be devised to send the oil via pipelines to the nearest land, but that sounds like an enormously expensive proposition. A continuous attack by ice breakers might also be able to keep the ice pack from destroying a drilling platform, but again that would be prohibitively expensive. StuRat (talk) 18:39, 29 May 2015 (UTC)

(I'm just speculating, but so are you...) I think it is conceivable to imagine having manned or automated submersibles fuel from a site well beneath the ice at any time of year. The ballasting issues would be a bitch, especially if you're not allowed to exchange the oil tanks with seawater + air for environmental reasons, but I imagine they'd think of something. Wnt (talk) 20:24, 29 May 2015 (UTC)

The arctic is a very productive ecosystem during the summer. See insolation - the region does receive less than other places on Earth, but not by a huge factor, and not relative to places you think of as having oil. Also, bear in mind that living organisms have no actual purpose in becoming part of hydrocarbon deposits. You can have a peat bog in one spot and a barren hillside close by, both receiving the same amount of sun and rain, but one is just better recycled than the other. In the case of the Arctic, plankton are well evolved to survive freezing; nonetheless the yearly cycle might cause some loss to the sea floor (however, I have absolutely no idea if that is really a factor). Last but not least, remember that in geological time all the features of the Earth's crust have moved due to plate tectonics. Wnt (talk) 20:22, 29 May 2015 (UTC)

• Ocean drilling is done on the continental shelves, not normally in deep oceanic basins. Deep ocean basins are area where new crust has been created by sea-floor spread, as along the Mid-Atlantic Ridge. Most oil deposits are from land plants that were sequestered on land during the Carboniferous, and which a now usually buried at some depth under continental surface. The North Sea beds, for example are flooded continental shelves, not deep-sea crust. μηδείς (talk) 05:02, 30 May 2015 (UTC)

@Medeis: By "North Pole", people mean the Lomonosov Ridge, which various countries are trying to connive to make into their national waters. According to our article the ridge comes up to within 400 meters of the surface. I suppose what comes next is for somebody to dump 400 meters of debris on top of some part of it and fortify a military base there to help argue their claim... Wnt (talk) 11:17, 30 May 2015 (UTC)

Yes, you're pointing out an example of the principle I was discussing. As the Lomonosov Ridge actually is part of a bit of unusual submerged continental crust, it may indeed have oil deposits. μηδείς (talk) 19:19, 30 May 2015 (UTC)

Windmill without blades

I saw a news report at http://www.theengineer.co.uk/energy/news/spanish-firm-proposes-bladeless-wind-turbine/1020399.article

Some questions:

• 1) Is this actually going to be substantially quieter than bladed windmills (including at 'subsonic' frequencies) or not?

• 2) Will this actually avoid harming birds?

• 3) Will this provide power under as wide a range of conditions as a bladed windmill?

• 4) Why does it actually have to move back and forth, rather than just experiencing the force of the wind in place?

Wnt (talk) 20:14, 29 May 2015 (UTC)

I think the real problem is that the device will have a hard time generating a megawatt (as claimed). Hooke's law tells us:

Energy = 1/2 k x²

...for displacement x and spring constant k.

If we assume the wind can repeatedly move the device to displacement x, then we can calculate an energy extraction rate per unit of time, and deduce a maximum possible power (assuming perfect mechanical and electrical transduction). Obviously, a real thermodynamic system will have conversion loss.

The spring equation also tells us how fast the device will naturally oscillate, as a function of its mass.

You can crunch these numbers yourself, if you don't already have an intuition that this is implausible... and I think you will find that it is unreasonable to assume we can extract a million watts from oscillation unless the device is swinging great distances at high speeds. If it does these things, what material will it be built from? The developers claim fiberglass...

(I should emphasize that these back-of-the-envelope calculations are not hard physical limits: strictly speaking, a rod forced to oscillate by the wind could theoretically extract any amount of energy on each swing. These calculations do, however, provide context for the energy scales that are characteristic to this setup).

You can read about the physics of wind turbines. There is a reason that wind turbines like to use very large, very long blades: the power extraction and the efficiency increase dramatically as the blades are built at larger length scales.

If you aren't intuitively familiar with dynamic analysis of oscillating beams, also read about elastic beam equations. This is a standard problem in engineering dynamics or advanced mathematics. You can find thousands of worked examples online; here's an introductory lecture note from San Jose State University on Applications of Second Order ODEs. Once you work this math out (and repeat about a million times), you'll have a good quantitative intuition about energy and power in these scenarios.

Nimur (talk) 23:08, 29 May 2015 (UTC)

I numbered your Q's above so I could reply to each:

• 1) Vibrations in the ground might be more of a problem than audible sound. People and animals living nearby might not like that.

• 2) It shouldn't harm birds unless they fly into it or try to nest nearby. I'd paint them a bright color (not sky blue) to make them less likely to fly into it.

• 3) It might work better in low winds that a traditional windmill, since there's no friction to overcome to get it going.

• 4) You can't generate electricity in this device without some motion. Compare with a bicycle pump. Can you get it to work just by pushing on it harder and harder, without ever reversing direction ? StuRat (talk) 02:47, 30 May 2015 (UTC)

The physics of this does confuse me. I understand that mechanical work requires that the work be done over a distance that the object is moved; otherwise you could do work just sitting on the couch! Also that if you're going to reduce the energy of the wind by slowing it down (relative to your rest frame) you also have to take some momentum and put it somewhere. Even so, well... there are ridiculously inefficient mechanisms by which some energy clearly can be extracted. If the wind happens to be blowing at atmospheric reentry speeds, we know the tower would glow cherry red and could power steam boilers inside it. If the tower is made of aqueous gel, separated by a barrier, the higher pressure of O2 means that there would be more oxygen molecules on one side than the other, and you could use that to power a symporter to create a proton gradient and generate electricity (in some absolutely miniscule amount). I feel as if there is precedent, then, for somehow evading the need for the seemingly required motion, and so then the question is whether there's an actual limit to how clever a method someone potentially could devise. Wnt (talk) 13:43, 30 May 2015 (UTC)

Yes, this limiting factor is determined by thermodynamics. If we return to basic theory, we can describe every energy extraction machine as a heat engine. In this case, the hot reservoir is the wind itself, which has kinetic energy. We could construct an effective characteristic temperature to describe the kinetic energy in the wind. This will not be the gas temperature; rather, it is a theoretical temperature that represents the amount of extractable energy. This type of "fictitious temperature" representation is sometimes used in radiometry (see antenna temperature), semiconductor physics (see junction temperature), and so on: any place where we want to use statistical methods of thermodynamics in other-than-textbook-circumstances. We have to be careful in formulating this parameter, but once it is set up, we can use simple heat engine equations to express the extraction of work from the hot reservoir (the kinetic energy of the wind) and the cycle to the cold reservoir (the output from our machine after it extracts energy). The key take-away is that work is only extracted if the input has more energy than the output; and we can never beat the statistical limitations imposed by Carnot efficiency.

If you extracted kinetic energy by aerodynamically interacting with the wind (slowing the wind velocity on the other side of your machine), you could represent extractable power as the change in the energy per unit volume per unit time. You could calculate all of these parameters from the fluid equations, and plug in the maximum achievable change (I think dropping the wind to zero velocity on the output!) Whether you could build such a machine is a secondary question. Even if you satisfy thermodynamic laws, you must also satisfy all other physical laws. For example, I think Gauss's law (conservation of mass flux) (as it applies to the gas equation) is inconsistent with bringing wind to a dead stop! Either pressure will build up ad infinitum, or the gas has to move somewhere else! So, if you construct an overly-narrow representation for your energy extraction - say, by fixating only on the kinetic energy of the bulk transport of the gas molecules, ("wind speed"), you are neglecting all kinds of realities that will preclude efficient energy extraction. In the same way that we might "ignore" friction to simplify the problem, we must recognize that when we add these annoying extra constraints back in to our problem, they will always reduce efficiency from our "peak acheivable theoretical limit." Nimur (talk) 14:37, 31 May 2015 (UTC).

Interesting links for this windturbine (not actually a turbine though) might be the Kármán vortex street, which is what I suppose this machine uses. For the theoretic maximum efficiency of normal windmills, see Betz's law. Rmvandijk (talk) 08:23, 1 June 2015 (UTC)

• Isn't one of the missing premises above that the arms will oscillate sideways in an oblique wind as the Tacoma Narrows Bridge did in the famous video? The wind won't be pushing the arm forward, then pulling it back. It will be setting up a harmonic oscillation. Also, birds can see in ultraviolet, so markings in ultraviolet on a neutral blue-grey should be feasible. Also, birds don't usually fly into swaying trees or the towers of windmills. It's the hazard of swiftly rotating bladetips with which they have no familiarity, not tall things that sway. μηδείς (talk) 04:55, 30 May 2015 (UTC)

• Birds do fly into windows, so stationary objects can be a problem, if they can't see them. The UV reflective paint is a good idea, but there might not be much UV to reflect at dawn and dusk, and there's also the concern of low flying prop planes etc., so they still should be painted bright colors, for those reasons. StuRat (talk) 15:11, 30 May 2015 (UTC)

That's just an easily solvable engineering question, not a point of actual disagreement between us. And while birds do fly into windows fatally (I have discussed it here before from experience), how many documented deaths are there from birds flying into trees?

I do not believe that windmills harm birds. At least, not in any meaningful way. A bat could hit its head against anything, even in a familiar environment. However, bats reproduce like rats, and so this is not a problem. Birds are definitely quite intelligent and have a better perception of their environment as us. --Llaanngg (talk) 13:14, 30 May 2015 (UTC)

It's estimated that a few 100,000 birds a year are killed by wind turbines. Were they more common, the death toll could be much higher. Perhaps the solution is to use housecats as biofuel. μηδείς (talk) 19:09, 30 May 2015 (UTC)

Good reference... excellent suggestion. :) Wnt (talk) 19:16, 30 May 2015 (UTC)

(edit conflict) Estimates tend to be between 5 and 20 birds per turbine per year, or several hundred thousand bird deaths per year in the US. Whether or not this is significant is a matter of perspective. Cats are estimated to kill more than a billion birds in the US per year. On the other hand, cats probably don't kill many adult bald eagles or golden eagles or other large endangered species, which has been a problem at a number of wind farms, e.g. [1]. Dragons flight (talk) 19:11, 30 May 2015 (UTC)

Mitigating dengue fever in US flooded areas with mosquito bits

I was looking at [2] and have questions about [3], in particular how often do BtI mosquito treatments need to be applied? Months or years and how many between applications? 2001:558:1418:31:ED6B:3F1F:8C10:4F0E (talk) 20:19, 29 May 2015 (UTC)