Re: [Phys-l] black start

[John Denker <jsd@av8n.com>]

On 05/03/2011 06:59 AM, Edmiston, Mike asked:

> [1] Would a single 10 MW gas turbine installed as part of the 
> cold-start procedure be of any value as a "peaking generator" for a 
> power plant that has 400 MW steam-generated power capacity?

I have no idea.  My note was meant as an existence proof.  If
anybody wants to take it as a starting point and do some optimization,
that's fine.  I am quite willing to believe that making the peakers
several-fold bigger and/or several-fold more numerous would be an 
improvement.

One key idea that was implicit in the numbers I gave that should
be made explicit is that the energy and power required to start
a gas turbine is small.  The required power is on the order of 0.1% 
of the rated output power in the examples I am familiar with.  This 
stands in contrast to the 10% number claimed for a coal-fired steam 
engine.  This changes the black start calculation by two orders of 
magnitude.

> [2] How does the cost of a small gas turbine generator compare to
> the same-sized diesel generator?  I think the gas turbine costs a
> lot more.  Is that correct?

Not if you plan on running it on natural gas.  Diesels don't like
natural gas too much.

The point here is that 
  a) If you are only going to use the generator during black start
   operations, which are rare, then all you care about is reducing
   the capital cost.
  b) OTOH if you are actually going to use it to generate peak power
   then you care about fuel cost and fuel efficiency.  Natural gas 
   is relatively cheap fuel at the moment.

Also you can get "dual fuel" turbines (natural gas and/or fuel oil) 
which offers additional advantages for peaking and/or emergency 
operation.  It is easy to store lots of fuel oil on-site.  For
that matter, you can store a nontrivial amount of natural gas
on-site for peaking and/or emergency operation.

> [3] How many steam-turbine power plants have a natural-gas pipeline
> available; particularly a natural-gas pipeline large enough to power
> a gas-turbine having 10% of the capacity of the smallest
> steam-generator it needs to start?  If such a pipeline does not
> already exist, how much would it cost to run one to the plant?

That's another part of the capital cost.  The capital cost of 
a pipe is not zero, but the operating cost is verrry small.

Again:  The spirit of the idea is 
 a) The turbine is easy to start, and 
 b) we can defray the capital costs by operating the turbine 
  a nontrivial fraction of the time.

As a result, we get black start capability essentially for free
... by which I mean the cost is negligible compared to the benefit.

Note that I have used a rather general engineering principle:
    If there is something you want, find a way to get it as
    a by-product or co-product with something else of value.
That can dramatically improve the cost/benefit ratio.

====

I consider black start to be a "homeland security" issue.  We 
want to be secure against 
 a) natural disasters 
 b) engineering disasters
 c) natural disasters exacerbated by bad engineering
 d) enemy attack
 e) et cetera.

Note that enemy attack is not the only thing on the list.
IMHO it's not even the #1 thing on the list.  On a worldwide 
basis, since 2001 (inclusive), tsunamis have killed two orders 
of magnitude more people than terrorist attacks.