Homestead mailing list

[Bill Jones <billj AT harborside.com>]

EarthNSky wrote:

> Bill Jones wrote:
>
>  
>
> > Never mind, I had it right the first time.  Sorry.  Nowadays I would be 
> > one of those special "dyslexic" kids with an excuse for failing.
> >
> > Bill
> >
> >    
>
> Dang Bill...methinks you need some sleep, too!
>
> Bev
>  
I was really rushing before going out to get lunch.  It's also the sort 
of sentence you could easily reword in the opposite way..."if the pump 
is below ground...," etc.

Anyway, there's one other source of inefficiency I haven't considered: 
the electric generator.  If our choices for creating "action at a 
distance" (way down in the well) are between electricity and compressed 
air, then a generator is required to do it electrically (starting from a 
source of rotary motion).  It's only fair to evaluate all the energy 
losses.  The generator is analogous to the compressor, in that it also 
converts rotary motion (from a windmill presumably) to "portable 
power".  The pneumatic pump itself is 100% efficient; push 1 liter of 
cooled compressed air into it, and 1 liter of water emerges.  Nearly all 
the losses occur in the compressor itself, or in the connecting air tube.

By contrast, the generator and the pump motor are both less than 50% 
efficient.  Although they tried to make it as abstruse as possible, you 
can calculate the efficiency of my electric well pump right from the 
label; it's about 35%.  If the generator's efficiency is similar, that 
takes us down to about 15% efficiency.  To illustrate this, you may have 
wondered why there's no product being sold to consumers where you turn a 
crank to run a generator, and the resulting electricity runs a motor: 
not even so much as a doorbell.  That's because you could then tell how 
much energy is wasted.  This morning I thought of one exception.  Have 
you ever used an old hand crank telephone?  You turned a generator 
handle, and it powered a ringer somewhere else.  Fairly furious cranking 
was required to get the ringer hammer to move even a little, but 
fortunately only a small tap rings the bell audibly.

I'd honestly estimate the overall efficiency of my pneumatic system, 
from the turning shaft to the water leaving, at around 40% (for a slow 
trickle into a storage tank).  If I run it on a compressor whose motor 
is similar to the well pump's, the whole system will definitely be less 
efficient than the existing well pump.  But electricity is still very 
cheap for us; I never noticed any bump in the bill due to water use.  
The point is that we'll have a system that _we_ control, one that can be 
easily modified.

More broadly, I think the advantages of a pneumatic system lie not in 
efficiency (which will nevertheless surpass the generator-motor 
combination for harnessing wind power), but in the fact that it really 
puts power back in the hands of the people, almost any of whom could 
make one even more easily than I.  I'm also partial to the _durability_ 
of the hardware involved.

Bill
S. Oregon coast