"... these were painted with a tasty candy coating. Unfortunately, through an "oversight" at a sub-contracter, lead paint was mixed in and children around the region are a little dimmer. "
hmmm... In my last posting "(fluid liquid)" (in the first paragraph) is supposed to say "fluid" does not equal "liquid". I had the less-than and greater-than symbols in there but the posting s/w drops them out... must think they are control characters for HTML or something...
linuxamp - Well, you may not be a civil engineer, but the issues involved don't pertain to civil engineering anyhow... it's Mechanical Engineering or Aeronautical Engineering, ME's fluid mechanics-heavy brother. The turbine design resembles a wind turbine because the goals are similar. Air and water are BOTH fluids (fluid liquid).
The design is more influenced by the expected tip speed and available real estate. On a boat, the propshaft turns very very fast (much too fast for a big diameter prop) and available real estate under the boat is limited anyhow. The situation is different with these guys. Also, efficiency is much more important here than with a typical propellor design as well (big slow turbines can be very efficient). Furthermore, these guys can be optimized to have a much more narrow band of operation. A boat prop, by its nature, will see a greater variation in its rotational speed.
Don't lose sleep over this ... Something tells me that the people who design these things use some high powered computational fluids dynamics modeling packages to get the design pretty good.
Becki- The diesel engines you are looking at are the old technology indirect injection ones. Modern common rail direct injection diesels used in current passenger vehicles are a WHOLLY different animal entirely. The NOx emissions are slightly higher than gasoline engines, but the hydrocarbons and carbon monoxide are much better. With particulate traps and NOx aftertreatment, they have much better emissions than the toughest Federal standards. CO2 (if you believe in global warming) and fuel economy are better as well and the engines have much better torque than gasoline engines.
As for the noise issue with old-tech diesels, that comes from very high rates of combustion; electronic injection on modern engines allows the fuel pulse to be metered out more slowly, "rate shaping" the combustion. Works good! On common rail engines with electronic injection noise has been 90% improved -- you'd probably have to put the hood up to notice it's a diesel.
Modern automotive diesels produced in Europe are very nice engines with gobs of torque, good emissions, and excellent fuel economy. I wouldn't put on in a pure sports car like a Porsche (not quite as high revving as an Otto engine), but for even sporty sedans like Mercedes and BMW they are excellent. The key is common rail direct injection. Except for the few diesels sold by Mercedes and VW in the US (well, 45 states of the US), the rest of US Diesels (pickups and big trucks) are old tech and not too impressive. If you stuck one of the modern diesels in a very light car like a Honda Insight (throwing out the stupid hybrid powertrain), you'd wind up with a lighter, cheaper, better performing, and handling car that gets comparable fuel economy. A side benefit of diesels is that they are relatively easy to run on all kinds of kooky bio-fuels like this bean juice. The Diesel cycle is a lot less fussy than the Otto cycle as to fuel properties. That doesn't mean biofuels are "the answer", but the diesel cycle is more efficient to start with and more amenable to alternate fuels -- it's a better place to start.
Bah. Science teachers were teaching this junk decades ago when I went to school (the same time they taught us the earth was cooling and their was an ice age fast on the way ... make up your minds!) and it was disproved then. In the late 80s my Materials Science prof in college chuckled over the common misconception of waviness from window glass flowing in old buildings.
Ignorant, lazy teachers continue to spout such absurdities, but with the easy access of information we have today, it's unforgivable. No excuses for lazy deadwood teachers! Pay the good ones more and fire the rest. Take that useless Masters of Education degree and go flip burgers. If you were any good, you would have gotten a real Masters in (choose one) science, history, math, etc.
The whole thing is a gimick to get rap stars out on the town to part with cash whilst impressing their lady friends. The place envisions Fiddy Snoop Puffy Didling Tupac Dawg rolling up in his Hummer Limo with his posse (and model babes on each arm) and ordering "all the best" because he's a big shot with unlimited green. It's kind of a (large) step up from the old days of impressing folks by buying bottles of Dom Perignon. The idea is the same, though.
Unlike most kooky forms of alternative energy (like photovoltaic solar cells), the underwater turbine idea (river or tidal) has some merit. If they can make it work without government welfare (subsidies, research $, or taxing of their competition), than it is worth exploring. If private $ is interested in doing it w/o government teat involved, it usually makes sense. If they need government teat to make it fly, it was stupid to do in the first place.
I forgot to add one thing... If you look at the picture, you'll note how smooth, mossy and free from debris the forest floor is. I've been to the Black Forest and the Ardennes and I don't remember them from being that different from typical North American forests, i.e. full of tangles of vines/underbrush and varied rocks, fallen treelimbs, and big piles of leaves. Their robo-bug friendly forest in the pictures seems pretty optimistic.
I had to chuckle about Floyd's high school science teacher comments. Yes, a lot of really bad information comes from teachers who are nitwits and speak from their butts. Don't get me wrong, an awesome teacher (and I've had some) really make a huge difference in kids' lives. The problem is those awesome ones (in the U.S. anyhow) don't get paid any more than the urban legend spreaders. It wouldn't be "fair" after all... Ugh. :-P
Some folks are bringing up the scale of time we are considering. Well the argument is made that glass in 200 year old buildings (like my house) has flowed under the force of gravity. That is the timescale. To be safe, take it out 1000 years or so and look at some old cathedral window glass. It would be pretty tough to find any examples of installed window glass older than that, so speaking of flow rates in geologic timeframes is extrapolating WAY beyond the limits of available samples. The assertion is that glass is visibly thicker in the bottom of old windows because of flow. That has been proven false by gifted material scientists. Any visible waviness was an artifact of production techniques. Done.
Well, you may not be a civil engineer, but the issues involved don't pertain to civil engineering anyhow... it's Mechanical Engineering or Aeronautical Engineering, ME's fluid mechanics-heavy brother. The turbine design resembles a wind turbine because the goals are similar. Air and water are BOTH fluids (fluid liquid).
The design is more influenced by the expected tip speed and available real estate. On a boat, the propshaft turns very very fast (much too fast for a big diameter prop) and available real estate under the boat is limited anyhow. The situation is different with these guys. Also, efficiency is much more important here than with a typical propellor design as well (big slow turbines can be very efficient). Furthermore, these guys can be optimized to have a much more narrow band of operation. A boat prop, by its nature, will see a greater variation in its rotational speed.
Don't lose sleep over this ... Something tells me that the people who design these things use some high powered computational fluids dynamics modeling packages to get the design pretty good.
The diesel engines you are looking at are the old technology indirect injection ones. Modern common rail direct injection diesels used in current passenger vehicles are a WHOLLY different animal entirely. The NOx emissions are slightly higher than gasoline engines, but the hydrocarbons and carbon monoxide are much better. With particulate traps and NOx aftertreatment, they have much better emissions than the toughest Federal standards. CO2 (if you believe in global warming) and fuel economy are better as well and the engines have much better torque than gasoline engines.
As for the noise issue with old-tech diesels, that comes from very high rates of combustion; electronic injection on modern engines allows the fuel pulse to be metered out more slowly, "rate shaping" the combustion. Works good! On common rail engines with electronic injection noise has been 90% improved -- you'd probably have to put the hood up to notice it's a diesel.
Modern automotive diesels produced in Europe are very nice engines with gobs of torque, good emissions, and excellent fuel economy. I wouldn't put on in a pure sports car like a Porsche (not quite as high revving as an Otto engine), but for even sporty sedans like Mercedes and BMW they are excellent. The key is common rail direct injection. Except for the few diesels sold by Mercedes and VW in the US (well, 45 states of the US), the rest of US Diesels (pickups and big trucks) are old tech and not too impressive. If you stuck one of the modern diesels in a very light car like a Honda Insight (throwing out the stupid hybrid powertrain), you'd wind up with a lighter, cheaper, better performing, and handling car that gets comparable fuel economy. A side benefit of diesels is that they are relatively easy to run on all kinds of kooky bio-fuels like this bean juice. The Diesel cycle is a lot less fussy than the Otto cycle as to fuel properties. That doesn't mean biofuels are "the answer", but the diesel cycle is more efficient to start with and more amenable to alternate fuels -- it's a better place to start.
Ignorant, lazy teachers continue to spout such absurdities, but with the easy access of information we have today, it's unforgivable. No excuses for lazy deadwood teachers! Pay the good ones more and fire the rest. Take that useless Masters of Education degree and go flip burgers. If you were any good, you would have gotten a real Masters in (choose one) science, history, math, etc.
Straight talk from Sid.
Straight talk from Sid.
Perhaps people should get nervous when these 2 powers start scheming along the same lines again...
Some folks are bringing up the scale of time we are considering. Well the argument is made that glass in 200 year old buildings (like my house) has flowed under the force of gravity. That is the timescale. To be safe, take it out 1000 years or so and look at some old cathedral window glass. It would be pretty tough to find any examples of installed window glass older than that, so speaking of flow rates in geologic timeframes is extrapolating WAY beyond the limits of available samples. The assertion is that glass is visibly thicker in the bottom of old windows because of flow. That has been proven false by gifted material scientists. Any visible waviness was an artifact of production techniques. Done.