From: ems@michael.apple.com (E. Michael Smith)
Newsgroups: sci.energy
Subject: Re: SOLAR efficiency
Date: 29 Sep 92 23:47:19 GMT
Organization: Apple Computer Inc, Cupertino, CA

In article <1a8f5tINN82t@gap.caltech.edu> carl@SOL1.GPS.CALTECH.EDU writes:
>In article <1992Sep28.213033.1123@michael.apple.com>, ems@michael.apple.com (E. Michael Smith) writes:
>>>Peaking capacity is also used
>>>when baseload plants are down for maintenance. 
>>
>>And it could still be so used.  If you need to have a nuke worth of
>>disaster coverage, you have a nuke worth of maintenance coverage or 
>>a nuke worth of 'loss of sun' coverage.
>
>I think you're missing an important point here:  

I didn't miss it at all, I just don't think it is as important as you do.

>When a baseload plant is taken
>down for maintenance, it's generally down for maintenance for at least several
>days (they do scheduled maintenance on them during the off-peak season).  

SYNOPSIS:  If it is off peak season, you have excess anyway.

	   I didn't say solar would eliminate all peaking plant from 
	   the face of the earth, only that the market size was what
	   was reasonably available for solar to try for in the future.

	   I think maintenance outage is a drop in the bucket.

If there was a nuke worth of disaster coverage available when you were
running full tilt at peak of season, there will still be a nuke worth
of coverage available off-season, and likely more.  You can argue that
the utility was running with no disaster coverage available at peak.
(Which means a lousy utility or a worse PUC).  You can argue that the
disaster coverage is still needed off peak (which then requires that
you show a 100% corelation of solar with seasonal peak), which is 
a reasonalble position, but I'd suggest that you need x% standby for
disasters and with total supply/demand down, the % standby would be
lower ... and you would have to show that other alternatives to 
cover outages were not available.

First, if it is 'off-peak season' then you will have some extra peak
capacity to use.  ONLY when solar has displaced ALL other sources 
would there be only solar peak available.  (This is a scenario you 
have claimed I've advocated which I have not.  I've advocated that
the magnetude of market available for solar to resonably compete in
is the size of the present peaking plant.  I've not advocated that
the existance of cheap solar will cause hydro dams to be distroyed,
for example ... In fact, I'd even posed it as a question, how MUCH
peak plant exists?  The reason?  To better estimate the quantity of
that peak plant that was amenable to replacement and the percent
that was needed for disaster coverage.)

Plus, if solar ever got REAL CHEAP, it would make sense to build 
excess solar and use conventional peaking type plant to cover the 
non-solar nightime peaks!  (i.e. when you reach a point where the 
captal cost of solar was low enough to make it cheaper than other 
baseload plant, it would make more sense to use it than to use a 
nuke to cover the days and spend the extra to pay for fuel for a 
low capital cost turbine.  In exact analogy to baseload/peak today, 
but with the unevenness of demand replaced by an unevenness of supply).  

Even if solar had displaced all the present fuel driven peak capacity 
from the market, there would still be hydro and pumped storage and 
throttling of nukes and ... to draw from.  

Am I saying that I think it is likely for solar to be cheaper than 
nukes?  No.  I AM saying that the limit on penetration of the power 
market is the cost of solar and at a low enough cost, solar capacity 
could theoretically exceed that of present day peaking plant.  I am
also saying that, as a first approximation, the present day size of
the peak plant market is about the same as what I think solar can
reasonably try for, since solar corelates strongly with this market.

The basic picture is this:  We have a highly uneven demand now.  There
is a big swing that happens daily in close sync with sunshine.  There is
a big swing that happens seasonally IN MOST PARTS OF THE COUNTRY that
is in close sync with sunshine.  We need peaking plant to cover both
the seasonal and daily swings and emergency standby.  (I would not 
expect utilities to run at 100% flat out with no ability at all to 
handle a loss of a plant if they have the option to avoid it...)

You assert that plant maintenance needs to use some of the capacity,
so ALL of it must be available.

I assert that plant maintenance needs to be covered by a small fraction
that can be met by 1)  Seasonal variance in demand that isn't exactly
in sync with solar.  2)  Extant plant that would not be displaced by 
solar but is only partly classed, or not classed at all, as peaking plant,
such as hydro, or using the other baseload plant at higher percents
of capacity (they DO throttle nukes, just not a whole lot...).  3)  Power
bought from other utilities that are not doing maintenance right now
or are in a different weather region that don't track solar as exactly
so they have non-solar peak or baseload capacity standing idle.  4) Using
the emergency standby if it really gets tight.  5)  Having the cogen
sites with whom they have load shedding agreements right now shed some 
load for a while.  6) ...

IF, as has been asserted by someone else, peak capacity is about 20%
of the total (and I have no idea if this is right, nor do I remember
who originally posted it, that's why I asked the quesiton that started
all this ...), then your assertion amounts to the statement that 
nearly 20% of capacity is needed to cover the typical baseload plant
being down for maintenance off season.  I find it a bit unlikely that
a single nuke plant would be 20% of the total capacity used in an entire
power sharing region.  Almost as unlikely that the total of all plants
that had to be down at the same time would be 20%.

IF, as is more likely, there are a couple of dozen baseload plants
in a power sharing region, then having each one down 'for a few days'
in rotation off season would impose about a 5% load increase to all
the others.  Since my voltage at home can vary from 105-125 at any
one time, I have to assume that 5% off season isn't a hard leap to 
make.  Since solar can't coorelate exactly with peak seasonal and
daily swings, I cheerfully grant you a 5% need for conventional
peaking plant.  (OR a 5% throtling of nukes/coal/hydro/... OR a need
for 5% standby gas burners at solar thermal plants OR a 5% load 
shedding agreement with cogeneration sites OR a 1% of each!)

So the picture of a nuke being down off-season doesn't in the least 
cause me to worry.  It should be made easily with a small fraction
of the available plant.

>This
>means that solar CANNOT be used to make up for this temporary loss of base-load
>capacity, unless you've either got a LOT of storage capacity or a global grid.

I grant you that solar isn't going to give you power at night in Chicago
in December.  I also assert that that doesn't make a damn bit of difference
to how viable solar is at taking significant chunks of market share from
conventional plant and that it doesn't change the ESTIMATE that solar 
has a market POTENTIAL about equal to PRESENT PEAK DEMAND/SUPPLY.

Having a market 'available' of a certain size does not mean you will 
own the whole thing.

Having a market penetration estimate that a given penetration potential
is about the same as a roughly competing product holds does not imply
that you will only sell to the same customers or for the same uses or
that your competitor will go out of business.  (i.e. they might move
to a NEW market, such as selling nighttime non-solar peaking plant ...
or big co-gen sites).


-- 

E. Michael Smith  ems@apple.COM

'Whatever you can do, or dream you can, begin it.  Boldness has
 genius, power and magic in it.'  -  Goethe

I am not responsible nor is anyone else.  Everything is disclaimed.