#255226 - Thu Jan 27 2005 06:40 PM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Electricity can be produced in a number of ways; eg. batteries, solar cells, generation. From your question I assume you are referring to the latter. Commercial electricity is mainly produced by rotating electrical conductors at high speed within a powerful magnetic field. There are a variety of complex formulae used to calculate the amount of electricity which can be derived from a given magnetic field strength.
The rotation of the generator conductors can be achieved from various primary sources; eg, windpower, water (hydro) power, gas or steam. The most commonly used primary source is steam, and this can be produced again from various sources; eg, coal, oil, gas, or nuclear energy. All of these sources are simply used to produce heat which turns water into superheated steam, which in turn drives the turbines which in turn drive the electrical generators. Another type of turbine driven generator is the 'gas turbine', which is an expensive form of generation utilising aero engines which exhaust into a power turbine connected to the electrical generator.
Please come back if you'd like anything clarified! I'm off to Egypt next week by the way, and may get to visit the Aswan damn while I'm in that area!
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#255227 - Thu Jan 27 2005 06:59 PM
Re: Generating Electricity
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Prolific
Registered: Sat Sep 15 2001
Posts: 1050
Loc: Adelaide SA Australia
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Yeah i know all that, I was thinking a little more in depth. Coal you say, wow!
What do the magnets actually do, is it magnetic drag causing electricity. Hit me with the nitty -gritty. Is speed the most important thing or the strength of the magnets involved or what?
What is to stop somebody palcing a bunch of "wind turbines" on the roof of the car to generate electicity while they drive around? They could clock up a decent speed but the magnetic field would be pretty small, is there a ratio?
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#255228 - Thu Jan 27 2005 09:18 PM
Re: Generating Electricity
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Prolific
Registered: Fri Jun 06 2003
Posts: 1336
Loc: Mumbai India
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Quote:
What is to stop somebody palcing a bunch of "wind turbines" on the roof of the car to generate electicity while they drive around?
Because the drag caused by the effort required turn the turbines can be overcome only by using MORE fuel: so what you're doing is just converting the energy stored in your car's fuel (petrol, diesel, CNG or whatever it may be) into mechanical energy of the turbines on its roof, which can be used to generate electricity. And, of course, this process is not exactly "energy-efficient".
A much better way to make optimum utilisation of the kinetic energy possessed by your vehicle is by installing dynamos in the wheel mechanism- parts which rotate anyway. This is how a "bicycle lamp" works; the cyclist pedals to accelerate the bike, and the turning of the wheels generates electricity which can be used to power a lamp: no extra effort is needed.
Hope this helps.
{Edit}
Quote:
Is speed the most important thing or the strength of the magnets involved or what?
After a bit of research, this is what I found:
Quote:
For a coil of wire in a changing magnetic field, Faraday's law of electromagnetic induction states that
Epsilon = -N(dPhi/dt)
where
Epsilon is the electromotive force (emf) in volts
N is the number of turns of wire
Phi is the magnetic flux in webers
Further, Lenz's law gives the direction of the induced emf, thus:
The emf induced in an electric circuit always acts in such a direction that the current it drives around the circuit opposes the change in magnetic flux which produces the emf.
Lenz's law is therefore responsible for the minus sign in the above equation.
from here
From the (dPhi/dt) in Faraday's expression, I would assume that the EMF produced at an instant is proportional to the magnetic flux. Based on what I have learnt in school, my guess is that for every rotation, a fixed amount of EMF is induced, which produces the current; and so the more the rotations, the more the total current produced. However, I am not all that sure about this, and confirmation by someone more knowledgable would be appreciated.
Edited by achernar (Thu Jan 27 2005 09:36 PM)
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#255229 - Fri Jan 28 2005 12:40 AM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
This is how a "bicycle lamp" works; the cyclist pedals to accelerate the bike, and the turning of the wheels generates electricity which can be used to power a lamp: no extra effort is needed.
You've clearly never pedalled a bike with a dynamo if you think that 'no extra effort is needed'. In fact it requires considerable extra effort. The only time you will get 'free' electricity is when freewheeling downhill, and even this isn't really free as the primary driving force is gravity - as is the case with a hydro-electric power station.
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#255230 - Fri Jan 28 2005 01:08 AM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
Yeah i know all that, I was thinking a little more in depth. Coal you say, wow!
What do the magnets actually do, is it magnetic drag causing electricity. Hit me with the nitty -gritty. Is speed the most important thing or the strength of the magnets involved or what?
What is to stop somebody palcing a bunch of "wind turbines" on the roof of the car to generate electicity while they drive around? They could clock up a decent speed but the magnetic field would be pretty small, is there a ratio?
Without resorting to a lot of complex formulae it's difficult to answer your question, and my keyboard hasn't got the formulae symbols anyway. The magnetic strength increases as the speed and load increase because the magnetism required is electro-magnetism derived from coils or windings, not from fixed magnets. the generator comprises two main parts, the static part being called a 'stator', and the moving part a 'rotor'. A direct current is fed into the windings of the rotor from an external source. This produces a magnetic field and as the rotor spins at high speed the lines of this field cut across the windings of the stator inducing in them an electric current. The stator windings are connected via various types of equipment to the external load, and the electrical current then flows round the whole network. As the external load increases or decreases, so must the primary driving force increase or decrease accordingly. The operating speed of the rotor remains constant, and as this speed is what sets the supply frequency, it is imperative that it is maintained within very strict limits.
Virtually all commercial networks utilise alternating current (usually at 50 or 60 hertz), but the generation principle is the same for DC (direct current) generation.
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#255232 - Fri Jan 28 2005 07:05 AM
Re: Generating Electricity
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Prolific
Registered: Sat Sep 15 2001
Posts: 1050
Loc: Adelaide SA Australia
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hmm might have to reading up on it, interesting stuff.
_________________________
Never moon a werewolf.
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#255236 - Fri Jan 28 2005 06:17 PM
Re: Generating Electricity
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Forum Champion
Registered: Sat Apr 13 2002
Posts: 5473
Loc: South of England
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But there's also not much chance of escape from global warming due to burning fossil fuels. Even if we don't live near a source of the cause of this, we might all end up being affected by it. If the scientists are right, the effects of global warming will pose more of a threat to life than if we lived near a nuclear power station. That's why I think nuclear power could be the lesser of two evils. Neither option is good admittedly.
Where there are no natural ways to generate enough power, other ways have to be found. I think wave power and wind turbines will only ever be able to provide supplementary contribution to the huge amount of power we demand (nobody wants wind turbines near them either). Nuclear power stations can be an accident waiting to happen if not properly run. Global warming due to what we're doing may be an accident silently happening right now. Power generation using fossil fuels must be a contributing factor to that.
In practice, I can't see any nuclear power stations being built because of the objections to them. So, I expect we will go on burning fossil fuels until the effects of doing so really come and bite us. I think my generation may live it out. I worry about future ones though.
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#255237 - Fri Jan 28 2005 06:42 PM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
You might not think that if you lived within spitting distance of a nuclear power station, and a nuclear reprocessing plant with no possible chance of escape if there should be an accident. 
Most people who live close to Nuclear power stations aren't too worried about them, and many welcome them as they derive their livelihood from them either directly or indirectly. In some countries people living close to a nuclear power station get reduced price electricity. Statistically you're in far greater danger living or working downstream of a hydro-electric station. Other facilities such as chemical plants, refineries, and some factories are also statistically a far greater hazard than a nuclear power station, the Union Carbide plant in Bhopal, India and the Nypro UK plant in Flixborough, England to name but two examples.
If you live, as millions do, in a low lying area such as the Maldives or similar areas to those so tragically affected by the recent tsunami, you are more likely to be concerned about global warming than by potential risks from nuclear generation.
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#255238 - Sat Jan 29 2005 02:27 PM
Re: Generating Electricity
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Administrator
Registered: Sun Dec 19 1999
Posts: 38005
Loc: Jersey
Channel Islands
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I suppose we are in a strange position, the above mentioned plants are not in the same country as us. The reason for our concern is that we are on an island so in the event of an accident we cannot be evacuated. Also ships carrying nuclear waste travel very close to our shores. For good measure the French are now talking about building a wind turbine farm within sight of us too.
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#255239 - Sat Jan 29 2005 02:48 PM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
I suppose we are in a strange position, the above mentioned plants are not in the same country as us. The reason for our concern is that we are on an island so in the event of an accident we cannot be evacuated. Also ships carrying nuclear waste travel very close to our shores. For good measure the French are now talking about building a wind turbine farm within sight of us too.
Sue, I don't think it will be too long before your own electricity utility builds wind farms, either onshore or offshore - or both, so you should then get your own back on the French! Actually islands are the best sites for wind generation of electricity. French nuclear power stations are situated in many bays on the English Channel, as most yachtsmen (of which I'm one) can attest. They make good navigation aids, especially at night! Don't worry too much though as the quality of engineering is extremely good, and in no way can such power stations be compared with those such as Chernobyl. In fact you are still in greater danger from old Russian and East European power stations than you are from French ones.
by the way, I'm very familiar with your island, and indeed all the Channel Islands, they being a regular destination for British yachtsmen. Sark is my favourite, and Alderney my least favourite!
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#255240 - Sat Jan 29 2005 03:08 PM
Re: Generating Electricity
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Administrator
Registered: Sun Dec 19 1999
Posts: 38005
Loc: Jersey
Channel Islands
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Ah, in which case you will know where I mean when I say the French intend siting the wind farm just off the Ecrehous.
There is little chance of us building anything as the island sold out a number of years back and stopped generating its own electricity - yes we import that nasty nuclear-generated stuff from France! Our own generating station runs on oil so was too costly, French electricity is very cheap. Personally I would prefer to pay more for my electricity and get rid of the French plant.
Then there are all the spent fuel rods, what happens to them? Why they get shipped either to Sellafield or to Cogema (the French reprocessing plant just across the way).
Edited by sue943 (Sat Jan 29 2005 03:09 PM)
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Many a child has been spoiled because you can't spank a Grandma!
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#255241 - Sat Jan 29 2005 06:09 PM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
Ah, in which case you will know where I mean when I say the French intend siting the wind farm just off the Ecrehous.
There is little chance of us building anything as the island sold out a number of years back and stopped generating its own electricity - yes we import that nasty nuclear-generated stuff from France! Our own generating station runs on oil so was too costly, French electricity is very cheap. Personally I would prefer to pay more for my electricity and get rid of the French plant.
You're answering your own argument! If the French think it economical to build a wind farm when they have surplus nuclear power, then it should be economical for the Channel islanders to do so too. It all depends on the tarriff the French are giving you, and there may be penalties for under-usage. Offshore would I think be best for Jersey and Guernsey, but Alderney would be about as ideal as could be for an onshore windfarm. If the technology could be successfully developed, and it hasn't been yet, the Alderney race would be excellent for a tidal generation scheme.
England, by the way, also imports large quantities of nuclear generated electricity from France - about 2,000 megawatts (or 2 gigawatts for connoisseurs) almost continuously. The flow can go either way, but usually is from France to England.
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#255242 - Sun Jan 30 2005 06:29 AM
Re: Generating Electricity
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Administrator
Registered: Sun Dec 19 1999
Posts: 38005
Loc: Jersey
Channel Islands
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I am paying 7.581p per unit. As I said, I would willingly pay more to not live in the shadow of a nuclear power station and reprocessing plant.
_________________________
Many a child has been spoiled because you can't spank a Grandma!
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#255243 - Sun Jan 30 2005 10:05 AM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
I am paying 7.581p per unit. As I said, I would willingly pay more to not live in the shadow of a nuclear power station and reprocessing plant.
Ah but Sue, would you willingly accept living in the noise and visual shadow of a windfarm?
I've no problem with nuclear power stations as such, except for their capability of producing the ingredients for nuclear weapons. Fossil fuel burning stations are IMHO overall a far greater hazard.
Unfortunately a huge amount of generated energy is wasted, Better conservation would be a better answer to the world's climatic problems than simply building 'cleaner' stations. Actions such as widespread fitting of solar panels on roofs, especially in areas with a good sunshine record could have a massive effect on energy production and reduction of greenhouse gases.
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#255244 - Sun Jan 30 2005 12:07 PM
Re: Generating Electricity
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Administrator
Registered: Sun Dec 19 1999
Posts: 38005
Loc: Jersey
Channel Islands
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Visual I could live with, noise I cannot. I live on a small private estate with no main road nearby, I am used to absolute silence in the night. Having said that I guess we get used to certain sounds and don't notice them, I find traffic noise unbearable in the night, friends of mine complained about the noises here, the foghorn at Corbiere, cockerels at daybreak, cows mooing, tractors in the fields, even the occasional peacock.
I find it difficult to sleep in high winds now, I dread to think of what extra noise there could be with a wind farm.
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Many a child has been spoiled because you can't spank a Grandma!
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#255245 - Sun Jan 30 2005 01:13 PM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
I find it difficult to sleep in high winds now, I dread to think of what extra noise there could be with a wind farm.
One of the lesser known disadvantages of windmill generators is they cannot operate at high wind speeds - so provided it was windy enough you'd be OK! Your roof might blow off and you wouldn't have any lights but the windmill would be fairly quiet!
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#255247 - Sat Feb 12 2005 01:04 AM
Re: Generating Electricity
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Multiloquent
Registered: Tue Dec 28 2004
Posts: 2813
Loc: Hertfordshire<br>England UK
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Quote:
Statistically you're in far greater danger living or working downstream of a hydro-electric station.
Sadly, my posting made only a few weeks ago has already become reality. The Shadikor dam in Balochistan province, Pakistan has burst causing flooding over a huge area. So far there are 70 confirmed deaths, but many 100's still missing, and at least 30,000 people have been affected by this tragedy. I suspect there's likely to be little world reaction to this incident, but if 70 people had been killed in a nuclear incident I reckon it would be headline news throughout the world!
Edited by aramis (Sun Feb 13 2005 01:42 AM)
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)
. Many lamps use LEDs now rather than bulbs with filaments inside. An LED is less demanding on the battery.
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