Last night we had lightning, not flickering street lights -- and there
were power cuts also. Do you live near any rail system? The shoe
on the third rail makes some pretty impressive lightning which lights
up the clouds - especially in a fog or snow storm.
When I lived in Massachusetts, the only times my lights flickered was
during lightning storms. Most of that occurred when demand was almost
equal to capacity.
Can you describe the flickering? Were the lights really flickering
or was the snow so bad that snow blown sideways blotted out the light
Demand is always almost equal to capacity. If it would be more, it would be
a waste, if less there would be serious stability issues. That's the problem
with wind turbines, you just don't know when the wind blows, and you have to
cover each MW of wt with at least of 700 kW conventional reserve, because
when the wind stalls what? Stop everything?
major in electrical engineering
Please check the definitions of demand and capacity - as the above is
Ideally the capacity should exceed the demand by some optimal margin but as
adding and dropping on line capacity is in blocks corresponding to the
capacity or rating of individual generators, and demand is up to the
customers (predictable but not controllable) the capacity will normally
exceed the demand by a fairly large margin at times- there is no "stability"
problem. As for waste by having extra on-line generation- economic dispatch
optimization is a common procedure.
If demand exceeds capacity, then problems can occur- not necessarily
As for the wind turbine reserve, you are being a bit over optimistic. You
are assuming 30% availability of wind capacity. In practice, from recent
data it appears that 10-15% is a better figure and this is a statistic based
on an annual average, which means nothing if wind fails. In other words.
reserve capacity must be available for the worst case situation- 100%
failure of any generation source, concentrated as in a 500MVA fossil plant
or distributed as in 500-1MVA wind units in a region where wind diversity is
Most of the generators have variable power output, not simply on
Frequency drops below nominal, and conversely when supply exceeds
demand, frequency increases above normal. There's a requirement in
the UK for frequency to average out correctly long-term (so things
like synchronous clocks don't drift long-term), consequently,
supply has to exactly match demand long-term. However, since the
demand and supply can't exactly track each other short term due to
inherent lags, there are periods of both demand exceeding supply,
and supply exceeding demand. These are both inevitable due to the
supply lag with different types of plant and unexpected plant
failures on some occasions, and deliberately forced to correct for
earlier drifts on other occasions.
There is contingency reserve in addition to the supply - additional
plant spinning sychronous online ready when needed due to either an
increase in demand or an unexpected loss of supply, and yet more
plant offline ready to run up and cut in with a bit more notice.
A longer article I wrote on this some years back, with some examples
of how it was applied in the UK to some specific historic events,
and how it went wrong on one occasion...
The BBC did a programme about the wind power in Denmark, one of
the highest users of wind power. In spite of installing lots of
turbines and being able to point to all the power they get from them,
they haven't been able to spin down any conventional generating
station, because they need them when the wind stops. When the wind
blows, they have an excess of conventional electricity which they
sell, but for their neighbours, it's effectively as unreliable as
the wind, since its export stops as soon as the wind stops, so it
only commands a low price as an unreliable source. This combined
with a failure of a transmission circuit, plunged much of central
Europe into darkness a couple of years ago when supply suddenly
fell well short of demand, and emergency load shedding was initiated.
[email address is not usable -- followup in the newsgroup]
In no way did I imply otherwise. However a generator is either on line or
off line as a unit so that the system "capacity" changes in blocks depending
on the rating of the machine added or removed from the system. The system
"demand" depends on the load and this demand is split between the units on
line- generally through some economic dispatch scheme.
I am quite familiar with the concepts and practice involved.
Again I have no problem with this- this is normal . Possibly there are
some word usage problems
I take capacity as the total available generation on line That is,
(ignoring power factor as it affects unit capability), if there are 2- 100MW
units and a 50MW unit on line the capacity is 250MW . The load and losses
(again ignoring pf) may be 200MW leaving 50MW on-line reserve.
I take demand in this case as the load +losses 200MW which has to be
delivered to the system. Except for transient periods when loads change the
supply and demand are the same. Only during acceleration or deceleration
will they be unbalanced. Typically generator droops, essential to proper
load sharing between units, will result in speed changes. These lead to
frequency errors and the need to correct the long term average frequency.
In my opinion, wind is to be used when available- reducing the load on other
sources at that time- but it doesn't replace the other sources for the good
reasons that you have given. The fact that wind energy is available on
nature's timetable, not man's, is one that many wind advocates appear to
The refutation of his, and any windmill enthusiast's claim that windmill
are going to reduce CO2 emissions is to look at countries which have an
aggressive policy of installing windmills. Say Germany.
Compare Germany (lot so windmills) to France (very few windmills, lots
of nuclear power). Germany emits about 10 tonnes of CO2 per person per
year. France about 6.5 tonnes per person per year.
Similar levels of industrialisation, similar climates, similar
everything. What the Germans have found (surprise, surprise) is that
wind power is unreliable and must be supplemented by conventional
The UK could meet all its Kyoto obligations by going nuclear to the same
extent as France. Politicians in the UK are too wet to go for it.
British citizens nowadays carry drugs into China to get themselves
executed; they have good ol' Gaelic, Cymru or Anglo-Saxon
names like "Akmal Shaikh". I'm surprised Gordon Brown isn't
wearing a turban to get himself re-elected.
I know this is going to be hard for you to understand. But the use of
the plural in that phrase was inappropriate, and the use of "citizen" is
dubious. I think the term you were looking for was "subject", singular.
I think you will find his aim was to make lots of money, not to get
As opposed to good old American names like "Nidal Malik Hasan",
"Mohammed Ali", "Barak Obama" or "Androcles" you mean?
Turbans are worn by a very small proportion of the UK population,
notably Sikhs who are not Moslems and who are not even the majority in
the immigrant population. Your own coutnry appears to have an immigrant
population of about 250 million. So if you're one of those tossers who
bases their entire politics on the status of someone as "an immigrant"
then I suspect you'll have to start by hating yourself.
Oh look. You already do.
Mr Shaikh was a subject. Perhaps you should try to remember what you are
I see you dodged away from the fact that he was an individual, not a
group. Is coping with the difference between singular and plural
something that confuses you?
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