"The Natural Philosopher" wrote in message
...
Franz Heymann wrote:



I have read a report one experimental fuel cell unit installed in
Holland,
where it was mentioned that "At the point of shutdown, the unit was also
sustaining a power generating efficiency of more than 46 percent, well
above
a conventional combustion-based power plant that typically generates
electricity at efficiencies of 33 to 35 percent".


That is typical of an old station running coal or gas, built to 60's
standards. Noit a modern set.

The report was quite recent, like a couple of years old.


That does not sit well with whoever it was who recently said something
about
conventional power stations operating at 60%.

Depends on what you mean by conventional.

The key to efficiency is getting your working fluids temperature and
pressure way up, and the final exhaust way down.

Steam turbines with ultra superheated steam going through multistage
turbines with condensors on the back end to get the back end temp way
down will do better than 50%. Gas turbines with extremely high
combustion temperatures, whose exhaust then heats water to drive a steam
turbine, do even better. If the coolant water at around 40-60C is then
fed to housing next door for heating purposes...you are getting up
towards 75-80% usage of thermal energy released.

But if it is true that a conventional power station can in fact run at over
60%, why were folk so pleased with that fuel cell power source of which I
spoke, when it ran at only somewhat above 46%?



And the last little bit goes to help you farm fish in the cooling tanks
:-)

In viiew of the latest newspaper reports, that is not to be counted as being
on the side of the angels.

So, two points

- in an overall energy and fuel conservation analysis, efficiency is not
the primary problem. If you can use waste heat to save heating oil being
burnt - example, build a bakery next door and use the heat to run the
proving process, and bake bread at the edge of the furnace, or use waste
heat to heat greenhouses to grow vegetables, or to farm fish or whatever
- then you have an *ovearall* more efficient system anyway.

It would be most surprising if that could be done at more than a minority of
the power stations of the world.

- in an overall carbon neutral scenario, you want to reduce the
conversion BY ANY MEANS of fossil fuel to carbon dioxide. I am not sure
what fuel cells produce, but the carbon has to end up somewhere. If they
are running on fossil fuels they don't really solve the problem. Whereas
burning waste paper in a combined heat/power set can be extremely
inefficient, as long as the heat ends up reducing fossil fuel usage and
generateing SOME power. Because paper comes from carbon that has been
taken OUT of the air by trees.

The trouble is that neither the governments nor the power industry has
any real incentive to either do the OVERALL analsysis, nor to embark on
co-operative projects to utilise e.g. waste heat.


If someone could only come up with a plant that I simply stuffed full of
junk-mail and which heated my house, generated most of my electricity,
and allowed me to run a few pipes rund the garden to grow vegetables in
winter from....at similar cost to an oil boiler...

I am truly surprised that some such object has not yet been developed. I
wonder if anybody has reckoned the energy economics in my case, where I have
to take my newspapers and junk mail by car to the nearest collection point.

Franz