..and Roald Dahl wrote a nice little story about it - the title of which escapes me, unfortunately.
A brilliant but control-freak scientist ends up as a supported-brain-in-the-jar (with a single remaining eye floating on top) in the care of his wife...who proceded to aim the eye and force him to watch all the sorts of behaviour he'd abhored whilst mobile;)
..but it depends where you are (local average wind speed, depends heavily on topography) and how much power you need.
If you can find a way of levelling the load (e.g. batteries) with only moderate conservation you'd need the equivalent of a constant 1kW output, about 1.4 Hp. Power abstracted from a windmill follows the formula k*0.5*A*V^3, where A is the area of the blade disc, V the windspeed, and K is the fudge factor. There's a theoretical limit of about 59% efficiency, due principally to retaining enough momentum to carry the air on the downwind side away from an axial turbine.
Anyway... say you have a mean wind speed locally of 10mph, which is constant, because you have the device up a tower. That equates to 4.45ms^-1, so working backwards, and assuming 50% efficiency for the 'k' factor - hey, we're geeks, we'll buy th every best - you'd need a blade disc, um, 5.4 metre diameter. Of course the conversion to electricity incurs losses, sy 80% overall... so a (*very* efficient) wind genny rated for1Kwh output at 10mph would imply a 5.9m diameter swept area. Pretty small!
In fact, in the interests of minimising noise and improving part-speed efficiency, you'll find 1kW rated wind generators are slightly bigger, and rely on rather higher mean windspeeds. Beware the windspeed measurement though, that V^3 term will kill ya. If the mean windspeed locally turns out to be just half what you measure, you'll get, at best, only 1/8th the output expected. The actual design considerations for wind turbines (disc solidity, operating range windspeed etc) are wonderfully technical and pretty interesting in their own right.
As to why not...well small wind gens are rather expensive , and Planning control (local ordinances, US) tend to restrict the possibility to rural areas.
It's all about efficiency, and therefore running cost. Optimum cruising speed is set by considerations of wave drag for a given hull - there's a sharp curve, whereby faster cruises become *incredibly* inefficient. Big marine diesels providing this motive effort are far and away the most efficient prime movers on the planet, because economies of scale and the singular nature of the task lends itself very well to such optimisation - which the owners take advantage of.
The bottom line is that every single %age point gained represents a huge saving to the owners in fuel cost. If it can be done with a lighter/more efficient propulsion package, so much the better - that's extra cargo that's free to carry, but the prime incentive is fuel cost - you may not realise we're talking *thousands* of tons for oil bunkers on big ships...
I'm not at all surprised that marine propulsion is the first major application of high-temp superconductors in this regard.
So where is the necessary cheap energy going to come from? Keeping things in mid-air will always extract a toll in fuel consumption over just resting on the ground - and we're inefficient enough at that as it is.
We've already reached the condition of waging proxy wars over energy supplies to support our existing ways of life, and now without addressing the practicalites of making it sustainable (let alone welcoming the other 95% of the world up to our standard of living) the ad-men are trying to sell the idea of a bigger, better, faster tomorrow.
The little boy in me would really, really like my own flying machine; but as an adult all I see is down sides. Christ, flying soccer-moms should be enough to put any one off....
Realise that man tends to create gods in his own image, and Randy Newman expressed the issue best:... The Christians and the Jews were having a jamboree The Buddhists and the Hindus joined on satellite TV They picked their four greatest priests And they began to speak They said "Lord the plague is on the world Lord no man is free The temples that we built to you Have tumbled into the sea Lord, if you won't take care of us Won't you please please let us be?"
And the Lord said And the Lord said
"I burn down your cities--how blind you must be I take from you your children and you say how blessed are we You must all be crazy to put your faith in me That's why i love mankind You really need me That's why i love mankind
The best way to wean people onto such renewables is to do it in a way that seamlessly replaces what they are used to. Look, electric cars have been in use for 110+years, in fact at one time an electric car set the landspeed record (Jenatzy's 'Le Jamais Contente') - so where are the electric cars? Right, limited range, severe performance:range tradeoffs etc. This doesn;t change just by using the magic word ' fuel cell'. They are heavy, have complex control regimen and are too fragile for mainstrean use.
The infernal combustion engine is old-tech, well known and *thoroughly* well understood. The best performance-per-pound-carried is obtained by running an ICE on hydrogen. It's a natural development, allows dual-fuel use for the interim (whilst that hydrogen infrastructure is built as the price of oil climbs), and buys time for the fuel cells to develop - I can foresee those being used for trolling about town, but that's about it for a few years yet.
BTW dual-fuel hydrogen/gasoline is something BMW have been working on for at least 18 yeasr to my knowledge. Apparently it's a seamless transition and can be done on the fly. The driver doesn't notice, except the ICE tends to run quieter on hydrogen...
It's a little bit O/T, but there is no point pursuing the liquid-filled beam/column idea - there are much, much better ways (read : both cheaper *and* more effective) of fire-protecting steel.
The basic issue, as you note, is that steel loses flexural strength at an alarming rate when heated. At 500degrees C, the flexural modulus is reduced over 50%, and that's enough to destabilise structures - after which loads get concentrated, and progressive collapse ensues. No need for actual melting.
So: how to keep structural temperatures down. There are a few basic approaches. One, occasionally used when the steel is BIG, is just to rely on Hp/A: if the exposed surface area is small compared with the cross-section, the rate of heating will be acceptaby low. The second is insulation: either a spray-on insulating coating (usually vermiculite-based), encapsulation in concrete, or enclosing with insulative board materials. There are also intumescent coatings, but these are expensive, and so limited to areas where the steel is exposed for aesthetic reasons - lobbies and the like. The third, proposed here, is essentially filling the structure with liquid. But a polymer like this, apart from expense, is never going to abstract enough heat to do any good. There is are only two structures I know of which do this, both exposed tubular structural members: the Cannon Stret office building (Ove Arup & Partners, London, 1973) and the Swiss Re building (Foster & Partners, London, 2003). In both cases the fluid is water with anti-corrosives and a bunch of other chemicals, and is continually pumped. Not cheap, but only water has a high enough specific heat capacity to be useful.
Note further, the point of fire protection is NEVER to save the building. The *only* criterion is to buy time to get people out, and safe. The building can fall, indeed should - after a major fire there will be all sorts of latent damage that could endanger future inhabitants. The two coincided at the WTC: it wasn't just the extraordinary fire load that brought the building down - but the impact which shook loose flaky insulative materials, fatally exposing the (lightweight floor) structure to high rates of heating.
Building in frozen ground is fine. Building in unpredictably-wet climes, with unpredicatable days below freezing, certainly isn't. Canada, like most of the civilised world, often uses lightwieght construction and prefab elements; homebuyers in the UK have an unhealthy obsession with bricks-and-mortar...
Nasty finds can be geological as well as archaeological - the UK has some pretty amazing (and locally-varying) geology, and a 3000yr+ history of mining. Bottle mines turning up unannounced? Yep, catches everyone out. BTW a bottle mine is named for its cross-section- basically , someone found an expensive mineral resource locally, and dug out as much as possible. Creates a subsidence hazard 3-400 years later, with nothing to mark the spot because the hole at ground level is 1-person-size, and long since back filled...
As for using spoil across the site - yep, hats the obvious solution, but UK housing developers aren't that creative...
You're quite right about what to do with spoil, but you have to think like housing developer (cheeeeeeap!)
That's 1.2Kw steady-state design heat loss, indicative of c.29KwH consumption per day on the coldest days for space heating only. Actual peak consumption will be higher, because no construction is perfect, there will be excess air infiltration etc. It also ignores the dynamic condition - what really happens whe the sun shines, gets covered, someone opens a window etc. Over a year though, totals are quite low, becuase peak heat / cooling is quite infrequent. That gets *really* interesting, and it's one area I keep a beady eye on. If you want to know more about predicting building energy useage, you could start with a search on 'BRE degree day method'. The accessible bible on the subject is Littler and Thomas on 'Design and Use of energy in Buildings'. An oldie but a goodie.
60% of heat loss in a typical house in the UK climate is *purely* down to ventilation, both wanted and unwanted - hence the plug for heat exchangers in grandparent post. Based on 1 air change per hour, two thirds of your heating/cooling bill is quite simply adapting incoming air to room temperature, because that energy is displaced outside by incoming air! Deal with draught-stripping, use a small plate-type heat exchanger, get that loss down to
BTW, in the US the same principles will apply for heating,and for cooling. To effect a given change in room temperature uses one unit of energy to heat, but three to cool. Consider insulation, air-tightness and heat-exchange carefully!
Oh,/. tech content: CFD is going to be *real* big for commercial architecture, hint hint - make me a nice package that I can use like I use Excel after importing a CAD model, with output pretty enough to sell energy-saving to clients, and we'll be minted. I'm serious.
You might want to check out the price of digging holes in the UK by the time you include the landfill tax that applies to such spoil. Also, a cellar is effectively another storey (of retaining wall no less) to build, which delays the developer's programme. Everybody hates groundworks - too prone to weather-reklated delay and nasty finds - and the sooner he can get out of the ground and offsite, the better his margins - he's borrowing the money to build,and wants payback ASAP. IOW, sure you can have a cellar; just don't expect it fer free in a new-build.
Housing Developers' margins are far and away the healthiest in UK construction - they aim for a inimu of 20% vs a general contractor's 7-12%
Very common, but usually used for acoustic reasons - the minimum of bridging kills flanking transmission. Figure on ~80% more expense though -you're doubling the number of studs and construction time, though prob. using smaller timber sizes.
this region which is said to be the cause of
> peculiar 'shooting stars' seen in the visual field of astronauts.
I'm damn sure I've seen these too. Probably only notice once or twice a year. Anybody comment?
I'm in Southwest UK, BTW , have good eyesight and was given all clear again at last exam a few weeks ago.
Simply not true. Autarkic housing can be achieved simply, and the result need not look like a pudding. Their usual issue is actually overheating in spring and autmn seasons (low-angle sunlight comes in through windows, during seasons of near-minimum heating requirement).
Even 'regular' houses have no excuse not to be more efficient. Heat reclaimation units deal with pre-heating incoming air with the outgoing (hey, Wickes in the UK sell a packaged unit suitable for retrofit to an average UK house for less than 160quid last I checked; payback is 15-18months ). That also deals with odour, air moisture content etc. It's quite easy to get a 3-bed UK semi (say 100sq.m.) down below 1.2Kw design heatloss for a 19degC interior / -1degC exterior temp difference.
At which point, you might note, overheating can actually become an issue with typ. family (2 adults at 135W each @average activity, two kids at 100w each, modicum of household gizmos). Your only real losses are top-up heating overnight and domestic hotwater.
Actually, try checking-out allowances from your local power company. In many States your service providers offer 30-50% buy-down i.e. generous rebates on completed installations. And they have to buy your surplus power:-)
Check out www.homepower.com, they're pretty good on thi ssort of thing.
Another consideration that governs energy payback is surface temeperature. If you use panels, mount them well clear of the roof finish / substrate below for convective cooling. Photovoltaic activity drops off markedly with high panel temps, increasing payback time.
Note most panels are rated at 25degC surface temperature, but under standard illumination, and depending on ambient temps, will typically be running at 55-65degC. That's one reason it's difficult to achieve rated output.
Finally, the panels don;t die after 25years - they wil continue producing electricity until physically destroyed, but the amount tails off on an exponential curve. 25-35years is usu. given as alifetime, becasue at that point rated output is expected to have have dimished 20-25% (depends on rating method)
Okay, so I expect you've posted in jest...but if not, you've completely overlooked the lifetime's work that makes the good Doctor credible material for an Expert Witness.
..more particularly, it's the spectrum of the distortion.
Tube amps usually display quite large amounts of added 2nd harmonic, which is euphonic, or 'warming' and musically concordant. However tube amps usually show far, far less odd harmonics than solid-state amps, and have a distortion spectrum that rarely extends beyond the 5th/6th harmonic at all. In contrast, solid state amps, esp. those with high negative feedback, can produce harmonics a lot further out, even though the total summed is less than the tube amp, the result has a different sound and many people can tell the two apart on this basis. BTW it is *not* due to simple differences in signal:noise ratio and the like. It appears the ear/brain hearing mechanism has a FFT component - check how the ear works, and look closely at what the cilia do.
The bottom line really is that there's a *lot* the ear/brain hearing mechanism does that bald figures like 'hearing response' and 'THD' are inadequate to describe.
Slashdot Mirror
...I'm gonna kill you. ;)
..and Roald Dahl wrote a nice little story about it - the title of which escapes me, unfortunately.
;)
A brilliant but control-freak scientist ends up as a supported-brain-in-the-jar (with a single remaining eye floating on top) in the care of his wife...who proceded to aim the eye and force him to watch all the sorts of behaviour he'd abhored whilst mobile
Be careful what you wish for!
*hic*
..but it depends where you are (local average wind speed, depends heavily on topography) and how much power you need.
If you can find a way of levelling the load (e.g. batteries) with only moderate conservation you'd need the equivalent of a constant 1kW output, about 1.4 Hp. Power abstracted from a windmill follows the formula k*0.5*A*V^3, where A is the area of the blade disc, V the windspeed, and K is the fudge factor. There's a theoretical limit of about 59% efficiency, due principally to retaining enough momentum to carry the air on the downwind side away from an axial turbine.
Anyway... say you have a mean wind speed locally of 10mph, which is constant, because you have the device up a tower. That equates to 4.45ms^-1, so working backwards, and assuming 50% efficiency for the 'k' factor - hey, we're geeks, we'll buy th every best - you'd need a blade disc, um, 5.4 metre diameter. Of course the conversion to electricity incurs losses, sy 80% overall... so a (*very* efficient) wind genny rated for1Kwh output at 10mph would imply a 5.9m diameter swept area. Pretty small!
In fact, in the interests of minimising noise and improving part-speed efficiency, you'll find 1kW rated wind generators are slightly bigger, and rely on rather higher mean windspeeds. Beware the windspeed measurement though, that V^3 term will kill ya. If the mean windspeed locally turns out to be just half what you measure, you'll get, at best, only 1/8th the output expected. The actual design considerations for wind turbines (disc solidity, operating range windspeed etc) are wonderfully technical and pretty interesting in their own right.
As to why not...well small wind gens are rather expensive , and Planning control (local ordinances, US) tend to restrict the possibility to rural areas.
It's all about efficiency, and therefore running cost. Optimum cruising speed is set by considerations of wave drag for a given hull - there's a sharp curve, whereby faster cruises become *incredibly* inefficient. Big marine diesels providing this motive effort are far and away the most efficient prime movers on the planet, because economies of scale and the singular nature of the task lends itself very well to such optimisation - which the owners take advantage of.
The bottom line is that every single %age point gained represents a huge saving to the owners in fuel cost. If it can be done with a lighter/more efficient propulsion package, so much the better - that's extra cargo that's free to carry, but the prime incentive is fuel cost - you may not realise we're talking *thousands* of tons for oil bunkers on big ships...
I'm not at all surprised that marine propulsion is the first major application of high-temp superconductors in this regard.
We've already reached the condition of waging proxy wars over energy supplies to support our existing ways of life, and now without addressing the practicalites of making it sustainable (let alone welcoming the other 95% of the world up to our standard of living) the ad-men are trying to sell the idea of a bigger, better, faster tomorrow.
The little boy in me would really, really like my own flying machine; but as an adult all I see is down sides. Christ, flying soccer-moms should be enough to put any one off....
..what someone describes as 'blasphemous' reveals more about their own insecurities or psychology, than it says about the $Deity potentially offended.
Realise that man tends to create gods in his own image, and Randy Newman expressed the issue best: ...
The Christians and the Jews were having a jamboree
The Buddhists and the Hindus joined on satellite TV
They picked their four greatest priests
And they began to speak
They said "Lord the plague is on the world
Lord no man is free
The temples that we built to you
Have tumbled into the sea
Lord, if you won't take care of us
Won't you please please let us be?"
And the Lord said
And the Lord said
"I burn down your cities--how blind you must be
I take from you your children and you say how blessed are we
You must all be crazy to put your faith in me
That's why i love mankind
You really need me
That's why i love mankind
I'm not so sure.
The best way to wean people onto such renewables is to do it in a way that seamlessly replaces what they are used to. Look, electric cars have been in use for 110+years, in fact at one time an electric car set the landspeed record (Jenatzy's 'Le Jamais Contente') - so where are the electric cars? Right, limited range, severe performance:range tradeoffs etc. This doesn;t change just by using the magic word ' fuel cell'. They are heavy, have complex control regimen and are too fragile for mainstrean use.
The infernal combustion engine is old-tech, well known and *thoroughly* well understood. The best performance-per-pound-carried is obtained by running an ICE on hydrogen. It's a natural development, allows dual-fuel use for the interim (whilst that hydrogen infrastructure is built as the price of oil climbs), and buys time for the fuel cells to develop - I can foresee those being used for trolling about town, but that's about it for a few years yet.
BTW dual-fuel hydrogen/gasoline is something BMW have been working on for at least 18 yeasr to my knowledge. Apparently it's a seamless transition and can be done on the fly. The driver doesn't notice, except the ICE tends to run quieter on hydrogen...
...the power density of current fuel cells wouldn't allow the track performance achieved.
Given ther is hydrogen on-board allows the use of a fuel cell for the electronics because it's a technology showcase - not a practical car.
It's a little bit O/T, but there is no point pursuing the liquid-filled beam/column idea - there are much, much better ways (read : both cheaper *and* more effective) of fire-protecting steel.
The basic issue, as you note, is that steel loses flexural strength at an alarming rate when heated. At 500degrees C, the flexural modulus is reduced over 50%, and that's enough to destabilise structures - after which loads get concentrated, and progressive collapse ensues. No need for actual melting.
So: how to keep structural temperatures down. There are a few basic approaches. One, occasionally used when the steel is BIG, is just to rely on Hp/A: if the exposed surface area is small compared with the cross-section, the rate of heating will be acceptaby low. The second is insulation: either a spray-on insulating coating (usually vermiculite-based), encapsulation in concrete, or enclosing with insulative board materials. There are also intumescent coatings, but these are expensive, and so limited to areas where the steel is exposed for aesthetic reasons - lobbies and the like. The third, proposed here, is essentially filling the structure with liquid. But a polymer like this, apart from expense, is never going to abstract enough heat to do any good. There is are only two structures I know of which do this, both exposed tubular structural members: the Cannon Stret office building (Ove Arup & Partners, London, 1973) and the Swiss Re building (Foster & Partners, London, 2003). In both cases the fluid is water with anti-corrosives and a bunch of other chemicals, and is continually pumped. Not cheap, but only water has a high enough specific heat capacity to be useful.
Note further, the point of fire protection is NEVER to save the building. The *only* criterion is to buy time to get people out, and safe. The building can fall, indeed should - after a major fire there will be all sorts of latent damage that could endanger future inhabitants. The two coincided at the WTC: it wasn't just the extraordinary fire load that brought the building down - but the impact which shook loose flaky insulative materials, fatally exposing the (lightweight floor) structure to high rates of heating.
Yes. It's what one finds under the bonnet of router*
*pronounced 'root-er'
Fancy a scone?
Building in frozen ground is fine. Building in unpredictably-wet climes, with unpredicatable days below freezing, certainly isn't. Canada, like most of the civilised world, often uses lightwieght construction and prefab elements; homebuyers in the UK have an unhealthy obsession with bricks-and-mortar...
Nasty finds can be geological as well as archaeological - the UK has some pretty amazing (and locally-varying) geology, and a 3000yr+ history of mining. Bottle mines turning up unannounced? Yep, catches everyone out. BTW a bottle mine is named for its cross-section- basically , someone found an expensive mineral resource locally, and dug out as much as possible. Creates a subsidence hazard 3-400 years later, with nothing to mark the spot because the hole at ground level is 1-person-size, and long since back filled...
As for using spoil across the site - yep, hats the obvious solution, but UK housing developers aren't that creative...
You're quite right about what to do with spoil, but you have to think like housing developer (cheeeeeeap!)
60% of heat loss in a typical house in the UK climate is *purely* down to ventilation, both wanted and unwanted - hence the plug for heat exchangers in grandparent post. Based on 1 air change per hour, two thirds of your heating/cooling bill is quite simply adapting incoming air to room temperature, because that energy is displaced outside by incoming air! Deal with draught-stripping, use a small plate-type heat exchanger, get that loss down to BTW, in the US the same principles will apply for heating,and for cooling. To effect a given change in room temperature uses one unit of energy to heat, but three to cool. Consider insulation, air-tightness and heat-exchange carefully!
Oh, /. tech content: CFD is going to be *real* big for commercial architecture, hint hint - make me a nice package that I can use like I use Excel after importing a CAD model, with output pretty enough to sell energy-saving to clients, and we'll be minted. I'm serious.
You might want to check out the price of digging holes in the UK by the time you include the landfill tax that applies to such spoil. Also, a cellar is effectively another storey (of retaining wall no less) to build, which delays the developer's programme. Everybody hates groundworks - too prone to weather-reklated delay and nasty finds - and the sooner he can get out of the ground and offsite, the better his margins - he's borrowing the money to build,and wants payback ASAP. IOW, sure you can have a cellar; just don't expect it fer free in a new-build.
Housing Developers' margins are far and away the healthiest in UK construction - they aim for a inimu of 20% vs a general contractor's 7-12%
Very common, but usually used for acoustic reasons - the minimum of bridging kills flanking transmission. Figure on ~80% more expense though -you're doubling the number of studs and construction time, though prob. using smaller timber sizes.
..means 'the act of estimating as worthless.'
-To you and me, it means calling something shit.
(teehee. finally found a way to post that one)
I'm damn sure I've seen these too. Probably only notice once or twice a year. Anybody comment? I'm in Southwest UK, BTW , have good eyesight and was given all clear again at last exam a few weeks ago.
Simply not true. Autarkic housing can be achieved simply, and the result need not look like a pudding. Their usual issue is actually overheating in spring and autmn seasons (low-angle sunlight comes in through windows, during seasons of near-minimum heating requirement).
Even 'regular' houses have no excuse not to be more efficient. Heat reclaimation units deal with pre-heating incoming air with the outgoing (hey, Wickes in the UK sell a packaged unit suitable for retrofit to an average UK house for less than 160quid last I checked; payback is 15-18months ). That also deals with odour, air moisture content etc. It's quite easy to get a 3-bed UK semi (say 100sq.m.) down below 1.2Kw design heatloss for a 19degC interior / -1degC exterior temp difference.
At which point, you might note, overheating can actually become an issue with typ. family (2 adults at 135W each @average activity, two kids at 100w each, modicum of household gizmos). Your only real losses are top-up heating overnight and domestic hotwater.
(yes I am an architect)
Actually, try checking-out allowances from your local power company. In many States your service providers offer 30-50% buy-down i.e. generous rebates on completed installations. And they have to buy your surplus power :-)
Check out www.homepower.com, they're pretty good on thi ssort of thing.
Another consideration that governs energy payback is surface temeperature. If you use panels, mount them well clear of the roof finish / substrate below for convective cooling. Photovoltaic activity drops off markedly with high panel temps, increasing payback time.
Note most panels are rated at 25degC surface temperature, but under standard illumination, and depending on ambient temps, will typically be running at 55-65degC. That's one reason it's difficult to achieve rated output.
Finally, the panels don;t die after 25years - they wil continue producing electricity until physically destroyed, but the amount tails off on an exponential curve. 25-35years is usu. given as alifetime, becasue at that point rated output is expected to have have dimished 20-25% (depends on rating method)
Anyway, beyond payback, all that power is FREE.
That's why , to IBM, he's worth $550 an hour.
..country I ever heard of. They speak English in What?
..more particularly, it's the spectrum of the distortion. Tube amps usually display quite large amounts of added 2nd harmonic, which is euphonic, or 'warming' and musically concordant. However tube amps usually show far, far less odd harmonics than solid-state amps, and have a distortion spectrum that rarely extends beyond the 5th/6th harmonic at all. In contrast, solid state amps, esp. those with high negative feedback, can produce harmonics a lot further out, even though the total summed is less than the tube amp, the result has a different sound and many people can tell the two apart on this basis. BTW it is *not* due to simple differences in signal:noise ratio and the like. It appears the ear/brain hearing mechanism has a FFT component - check how the ear works, and look closely at what the cilia do. The bottom line really is that there's a *lot* the ear/brain hearing mechanism does that bald figures like 'hearing response' and 'THD' are inadequate to describe.
Doh.