How Do I Make My Dog-Bone Love My Steam Engine.
In which certain principles are supposed true.
*The principles:*(I do not say these things are true, only that they
seem to be, given what we've been reading...)
1. After Dog-Bone startup is achieved, power output is increased as
temperature is increased, and vice versa. Presumed monotonic, but
probably not linear.
2. This defines an operating range bounded by too cold -no power, and
too hot -destruction.
3. To get into the operating range external heat (power) must be applied.
4. The power generated in the upper end of this range is a generously
larger than any applied power. Thus turning off this applied power input
-in this upper range- /could never reduce/ the temperature.
5. A further point is required by our premise:
We are trying to run a steam engine, not a co-generation plant or an
endless sink for fire extinguisher bottles, and therefore the only
logical cooling source is the steam engine itself, that is, the boiling
process that feeds it.
*Howthen?*
Let us start by ignoring the steam engine. How do we stabilize our Bone
at some desired temperature, and thus power level?
Our operator, a nimble nerd with three hours on a simulator, has a
single control, the valve for the feed water. The simulator has already
taught him that the fire goes out if fed too much water, and he risks
his chance for continued employment if he feeds too little.
The Bone has already been brought up, steam is being generated, the
plant engineer is hovering. Carefully our tyro replaces the current
shift's hand with his own, notes that the temperature is increasing, and
gingerly increases the water flow, then a little more.. Good! Wait, back
it off, now it's getting cold! A few tense minutes go by, the training
takes hold, and the plant engineer relaxes.
The boss says "Increase generated steam 20%". Our tyro glances at the
current power/temp table, and eases /down/ the flow to cause a moderate
rate of temperature rise -then, slightly panicked as the temperature
increases more and more, throws more water on and overshoots. The Bone
turns off. Or would have, but the plant engineer has used the override.
Fifth time this month -"Gotta fine tune that simulator." he thinks.
An analog for all this is a sloping alley and a broom stick. You must
transport the broom stick up the alley (toward the high -hot end)
balanced on end, on your hand. Stopping and hovering where required,
moving hotter or colder as required. If you intend to go one way, you
must first move the other, to get the stick falling the right way. Much
like steering a bicycle. Hardly tricky! And yes a controller can easily
be made to do this, but that would ruin my story!
*Add the steam engine back in -and it gets harder.*
(Here I assume I want electricity.)
Your steam is there and plentiful, the engine runs really pretty, the
generator generates. Now double the load: throw another big light bulb
across the wires.
Yuck! The steam engine slows down, and voltage and frequency drop. But
the steam pressure does rise, which slows the rate of heat transfer from
the Bone, raises the Bone's temperature and thus increases power
generation. Nice: negative feedback, tending to stabilize Bone
operation. Unless wild overshoot... (the Bone /is /probably grossly
non-linear)!
Our nimble nerd now has a much harder job: not only does the broom stick
always want to fall over, but there are external disturbances -the
unpredictable load changes- which are like sudden breezes/winds/gales on
the upper end of his stick, which he must account for. Probably we'd
better get him, beside the bone temperature meter, meters for steam
pressure, engine speed, output watts. A little advance warning! But no
matter what, he cannot keep the /voltage/output acceptably flat for the
modern household.
Well some of this, you may point out, can be mitigated by a
steam-governor on the engine, a large steam reservoir, a bigger
flywheel, feedback on the generator windings (to correct the voltage).
Note that the increases in energy storage (flywheel, reservoir) are
equivalent to adding capacitance to a circuit within a loop, and so may
be very helpful, or problematic, depending on loop parameters.
The governor and the winding feedback are themselves control loops,
inside the larger nerd-loop*. They both work to speedup the change in
energy transfer (which poorly expresses what's going on). Note for now
that the governor causes (in our current example of a large load
increase) the steam flow to quickly /increase/, rather than decrease.
Result: the Bone's temperature decreases, not increases, and we have
positive (bad) feedback. Possible fatal to our nimble nerd's composure,
especially for the opposite case of a sudden load decrease.
*Or maybe not inside the nerd loop after all: our nerd is fighting to
control the Bone's operating point primarily, and only secondarily is he
tasked with accommodating changing load demands.
All this supposes “off-grid”; grid independence. If the generator is
tied tightly to the grid it rotates synchronously, even to the point of
driving the steam engine if there's no steam. Everything is simpler -but
you still need the nerd to balance that broomstick.
There's another solution if you want off-grid and can't afford much
complexity. That is to give up on tight voltage and frequency control,
and modern plug-and-run electricity. Just use the electricity for
battery charging. Very like solar then.
I hope I have made my two main points: that the LENR characteristics I
assumed make for a tricky control problem, and this in turn makes
“Gracious Living” electricity more expensive then we may have thought.
Comments welcome!
Ol' Bab, who was an engineer.
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