Re: Renewables in power cuts

In message <8oc8k1hq7hqdga8j0v5i9p6j6vtsu0nf0t@xxxxxxx>, AJH <sylva@xxxxxxxxxxxxx> writes 
On Wed, 5 Oct 2005 00:45:52 +0100, John Beardmore
<wookie@xxxxxxxxxxxxxxxxxx> wrote:


What particular level of demand do you have in mind ?  As far as I can
see there should be two rules,

       micro generators should contribute as much energy as
       practicable,

Sounds good 

and

       MGs should not be able to go off line at such a rate that
       alternative sources are unable to go on line to meet the
       instantaneous demand.


Could put people of using micro generation from renewables (or good
CHP). It addresses my concern but puts a condition on the use of MG.

Not really, because in aggregate, their all going off line quickly is extraordinarily unlikely.


At the end of the day it comes down to maths.  How fast can they go off
line, and how long does it take to spool up the reserve ?


Yes but there are a number of ways of providing this reserve, one is
to keep the generator hot and spinning, like in a coal plant, another
is to start from cold, like in the aero derived gas turbines plus of
course hydro which I take to be the fastest to react. Each has
different efficiencies.


Yes, but from memory, coal is the worst !


We're debating how much "conventional" generation capacity we can
afford to shed as micro renewable schemes come on line, and
concomitant to that what the energy cost per kWhr of renewable energy
produced is "wasted" on spinning reserve.

Was it you suggesting 0.1p / kWh ? 

Yes I mooted it as a figure I had seen mentioned but with no evidence
to back it up.


OK.  Well, it's not much anyway then...


Is so, I'm not sure I'm excited about the spinning reserve cost anyway.

Problem is that cost may be a poor measure of environmental effect.

Don't see why. Cost is proportional to fuel + O&M costs. If the 0.1p/kWh figure is right, then neither fuel or O&M costs can be that big.


I have not suggested they should be denied, I am simply asking the
energy cost of maintaining a supply which they may or may not make use
of.

There may not be much cost. Do you have a figure in mind ? 

No but convince me there is no cost, I'd love to hear it as this is
often cited as a detraction from small scale renewables.

I'm not saying there is NO cost, but if it's as low as 0.1p/kWh, then it's a lot less than the cost of the same kit while generating, and presumably reduces net environmental impacts.


And that the aggregated contribution from many such sites is far less
likely to fluctuate as much.

Yes it does appear so from David's post,

And any sort of back of envelope mathematical model.

Not from me, David cited some erudite study 

OK.


I would still like to see a
years worth of figures from a matrix of anemometers over the country.
I'll bet the met office are capable of supplying this if needed.


I'll bet they want you to pay for detailed data, but as I recall there
is some wind data on line.  Go google ?


I will one day, in the meanwhile I suppose I should stick an
anemometer on the telly aerial, I've been talking about it for a
while. Any suggestions for something that could be logged via a serial
cable (old style or usb) or self contained data logger? otherwise I'll
go and ask some weather watchers.


Cheap anemometers are a tricky proposition.

We got three of the £110 ones from Proven but their readings were wildly divergent.

Maplin used to do a very good kit, but you had to calibrate it yourself, and is now no longer available.

Ask the weather watchers ant let us know what they say ?


Cheers, J/.
--
John Beardmore
.

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