Re: Roger Ford on Electrification

On 13 May 2006 07:22:03 -0700 someone who may be RBCatlow@xxxxxxx
wrote this:-

I am interested that this debate so far has centred around generating
electricity rather than transmitting and distributing it.

The debate can centre around generation, especially in the mass
media. Other aspects have been considered in great detail, but tend
not to make it into the mass media. All they tend to cover is bogus
claims by the anti-wind lobby on the subject of the variability of
wind generated electricity.

Loads are predictable,

Only to a certain extent. For example dark clouds do cause an
increase in lighting loads as they pass over cities, heating loads
vary with the weather.

generating station output and availability are known

Again only to a certain extent. It's a good job we don't rely on
nuclear for electricity for in February according to
http://business.scotsman.com/utilities.cfm?id=290562006 "the company
has been dogged by a series of unplanned outages, the latest only
last weekend, when technical hitches took a fifth of its generating
capacity offline."

that is until renewables with
unpredictable outputs become a larger component of the energy mix.

There is a good discussion of the issues involved at
http://www.ukerc.ac.uk/content/view/258/852

Wind is so fickle and
variable that you cannot accurately forecast the duration or output of
the generation, all you will know a day ahead is, for example, that it
will be windy in the north of the UK and thus you can expect a lot of
wind energy. Which areas will generate for what and for how long is an
unknown quantity.

I disagree. There are two timeframes that are important. The first
timeframe is the next hour or two. Over this timeframe forecasting
is already highly accurate, even for individual locations. This
allows wind operators to be part of the normal one hour gate closure
process. Obviously forecasting is not 100%, but that is true for all
other forms of generation and there are ways of dealing with that.

The other timeframe is the next day or so. This is obviously less
accurate, but does give time for slow to react reserves to be made
ready if it looks like there will be a large reduction in wind
output, or the same reserves to be prepared to be stood down if it
looks like there will be a large increase in wind output. While the
wind does not blow evenly over the UK it does blow somewhere all the
time.

The anti-wind lobby place great store by reports of problems
integrating wind into the electricity system in Germany. However,
they fail to mention that the resource is somewhat different and the
electricity system is somewhat different, in particular firm
forecasts need to be made much further ahead then in the UK.

The net effect of this during the time that non baseload renewables are
becoming a larger part of the energy mix is that coal and gas fired
power plants' outputs have to be ramped up and down to accommodate the
constantly changing mix of power generated by renewables, exactly what
these plants were NOT designed for, their efficiency and thermal stress
suffers and their emmissions actually increase per kW/hr.

Since the dash for gas that is how these plants have been used, in
order to meet the variable demand, long before any significant
amount of renewables. Adding significant renewables means they are
operated in this way a little more, but not much.

It would indeed be more sensible to run these plants more steadily
and this can be done by changing the role of some gas fired plants,
making more use of hydro and so on.

Nowadays, along comes a wind farm
developer with a few megawatts worth of peak output wanting to be
connected to the 33kV pole line in the next field.

In the past most were connected to the 11kV system, as this is the
most cost effective for the outputs concerned. The detailed study of
the effect of Delabole on the surrounding system looked largely at
its effect on the 11kV system.

However, some of the larger ones are now being connected at 132kV,
an example being Black Law which has 13km of 132kV line leading to
the substation at Wishaw.

Only this pole line
isn't capable of accommodating the extra load, nor is the 132kV to 33kV
tapchanger in the grid substation used to regulating power in more than
one direction. The consequence is that the wind farm has to be
connected (often) at 132kV which can kill the scheme off financially.

It can certainly be a financial problem for some schemes. What is a
scandal is the large upfront charges developers are expected to pay
to their friendly local electricity monopoly, for which they may get
nothing. A number of developers have withdrawn or are going to
withdraw schemes because of this. There has been a little movement
on this, but not enough. This scandal has a number of parallels with
Railtrack.

The lower the connection voltage at which CHP schems are connected, the
bigger the headaches become. They don't cause problems at the moment
because they are few and far between, when they become commonplace at
the 240V level, the voltage regulation of the LV network will be all
over the place because their AVR's will beat against each other (trials
have already proven this).

One of the skills most of those in electricity need to gain is
running a system with a large number of small generators, which only
exist to a large extent in the north of Scotland.

Microgeneration does add problems, but these are also an opportunity
to convert the system from an inflexible one based on what was
possible in the past to a 21st century system. That would be world
beating engineering. One of the objections to yet more nuclear power
is that it would fossilise the system on the 20th century.

Once again, becuase these schems don't have 100% availability,

Neither does any other form of generation.

more
thermal power generation will be have to kept on line at low output
levels or having to meet a more rapidly changing load than they were
optimised for,

The question is whether there are other more attractive ways of
dealing with the situation and if there are not how much extra
variability there will be. There is actually a reasonable
relationship between micro CHP operation, wind speeds and the
increasing lighting and heating loads in winter.

As is already the case, this is a matter of statistical analysis.
Renewables add some variability, but this can already be modelled
and accommodated.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
.

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