Very interesting. :thumbs_up: However, the article doesn't mention fuel storage and supply. I wonder how big a container would be needed for 15-20 hours of laptop operation, and where it would be carried...a backpack, maybe??? I wonder how the turbine's sound level and frequency would compare to that of the CPU's cooling fan? Possibly a turbine of such a small size would rotate so fast that its sound frequency would be above that which most people could hear. On the other hand, you might have a pack of dogs following you around the airport or Internet cafe.mg: :teeth: Maybe somebody could put it in an N- or Z-Scale loco.....:shade:
I.e. engine and fuel are the same weight as a laptop battery. Presumably any production model would be a slot in replacement for any laptop battery so that dictates the size and weight. Obviously you don't need a model loco to run continuously for 15-20 hours so it wouldn't need nearly as much fuel. The turbine itself and enough fuel for a couple of hours should easily fit into an HO loco. Cheers David
Hopefully they are going to concentrate on the hydrogen-powered ones... I would HATE to be in a room full of people with laptops that run off carbon-based fuels! (carbon monoxide poisoning, anyone?)
Why? 20 laptops with micro turbines would produce less emissions than a cake with 20 candles on it. Presumably you have no qualms about being in the same room as a birthday cake? Carbon monoxide is a product of incomplete combustion, i.e. too much fuel or not enough oxygen. Gas turbines typically have an air/fuel radio of over 60:1 and only a small fraction of the air is required for complete combustion. It's very difficult for a turbine to run rich unless there is a fault with the compressor. Even CO2 wouldn't be that much of a problem. A turbine that small would release less CO2 into the room than you would through normal breathing. Cheers David
I've worked IT, and I know for a fact a typical laptop today on average needs a steady 60-70W to drive the LCD screen, the CPU, GPU, RAM, motherboard, HDD, etc. (your typical Centrino Core 2 Duo laptop with say a 15" TFT LCD screen). So you are talking about 70-watt-hours of electricity to drive an average laptop. Can 20 birthday candles produce 70W/H to power even just 1 laptop? Give me some numbers because I'm still kind of skeptical.
I was talking about carbon monoxide emissions, not power. For specifics of the power output of microengines you'd have to ask MIT. Cheers David
If one of those turbines as you say releases the same amount of CO2 as one birthday candle yet generates a steady 70 watts of electrical power to run a laptop for 15-20 hours, it is implying that the fuel has at least a comparable amount of carbon as a birthday candle (which is not much). Can such a small amount of fuel be enough to run a laptop for 15-20 hours, which means 15h x 70W = 1.05 Kilowatt-hours? Since you can't answer the power question (which is of course related to the carbon content of fuel), we'll put that aside for now... We have all seen plenty of instances where jet engines leave trails of smoke. I'm not so sure if most typical gas turbines (with faulty compressors or not) are that complete in combusting fuel. I'm skeptical, but I remain convinceable if you can find some numbers to back it up. Thanks!
Naked flames are extremely inefficient as they rely on convection. This is why candles frequently release soot which, by definition, means the air/fuel ratio is less than 1 (compared to 50-60 in a typical gas turbine/jet engine). I don't know the exact fuel efficiency of a candle but naked flames are generally only a few percent. Some large gas turbine power plants (e.g. GE's H series) running at constany duty have fuel efficiencies as high as 50-60%. Small gas turbines used by aero modellers are around 20-25%. Jet engines are generally around 30-35%. Incomplete combustion can also occur if the fuel is too heavy or dirty. Heavier fractions don't become vapour quick enough (or at all) and hence aren't burnt. Try running a small bore/high rev diesel engine on No.4 diesel and you'll see a similar effect, but a large bore/low rev diesel will quite happily burn No.4. You'd have to ask MIT for specifics about their micro engine. Cheers David
I found the published paper: http://microfluids.engin.brown.edu/Breuer_Papers/Conferences/AIAA97-1773_Microengine.pdf A quick glance through it says the fuel usage rate on is 0.44g per watt per hour on the models they currently have working (page 3). They expect to be able to decrease the specific fuel consumption rate down to .28g per watt per hour using a hydrocarbon fuel. So if you are talking about powering a laptop for 15 hours, which require 70W per hour, you will need 0.28g x 70W x 15h = 294g of hydrocarbon fuel. I don't know man, that sounds like A LOT MORE than 1 stick of birthday cake candle to me! If you got 20 laptops in a room, you are burning (294g x 20)/15 = 38.6g of hydrocarbon fuel per hour.. That's definitely a lot more than a birthday cake with 20 sticks of candles on it. I think the carbon dioxide content would actually be significant. The CO release of course is the big question, since we don't know for sure just how complete the combustion is on those microengines. Time will tell, but for now I think I need to hold my breath..
Once again, I was talking about carbon monoxide in response to the comment about poisoning. And I wouldn't worry about carbon dioxide emissions either. The average adult human exhales 30g of carbon dioxide per hour. Presumably you've got no qualms about being in the same room with 30 other people while they were breathing? I'll resist the temptation to discuss other gases emitted by humans. Cheers David
As I said, we don't know exactly how much CO the microengines produce. I find no mention of it in the paper anywhere on how efficiently it combusts the fuel, or even what effects different fuels would have. This is simply an unknown right now (any new technology brings with it new unknowns), and I think it would be premature (edited to add: foolhardy perhaps) to dismiss it as negligeable without real-world testing. And as far as the CO2 goes, it's definitely a LOT more CO2 than burning a stick of birthday candle than you presumed. I don't know about you, but if I'm stuck in a conference room designed for a maximum occupancy of 20 people but they all got laptops running on those things giving you a total of 40 people's worth of CO2 being emitted in the room, in addition to all the other noxious gases you mentioned that we humans emit (heh), I'd be taking VERY frequent trips out of the room for fresh air (or finding ways to avoid such meetings altogether.) But hey, if you enjoy being in such meetings, more power to ya. Like I said, I'll hold my breath for now and see how this technology plays out.
Reading this conversation has been fascinating, and entertaining.:teeth: Doesn't hydrogen have a higher energy content than the run-of-the-mill hydrocarbon, say RP-1, JP-4, or even JP-7? Also, since we're talking about a micro-turbine, I assume that fuel molecule size would be a consideration. A di-atomic hydrogen molecule is much smaller than the smallest hydrocarbon molecule, so pump and burner clogging should be less of a problem. Speaking of emissions in crowded meeting rooms, I would much rather be subjected to turbine exhaust from 20 or so laptops than to a cloud of onion and garlic breath during the after-lunch session.:sad:
It's micro scale, not nano scale. The MIT paper says the compression chamber is about the size of a pea and the fuel injectors are pin point holes. A pin hole is maybe 1mm diameter, 10^8 times the Van der Waals radius of hydrogen. I don't think clogging is going to be a problem. Cheers David
Emissions aside, it's a fascinating piece of technology that makes me think about the possibilities. Each quarter sized wafer can output 10 Watts under these infant stages of the technology - once they perfect the mechanics of such a small motor then they can work on alternative fuels for it... one step at a time And I'm sure that if it becomes an off the shelf item, one of us is going to cram it into a scale loco just to say they did it! Regards, -Mike
I am visualizing an N-Scale model of UP's Big Blow hammering up Sherman Hill or someone's helix.....:shade: P.S. You're right, I was thinking "Nano", while all along you guys were saying "Micro".:embarassed:
