
Power Water Networks - dredmorbius
http://www.lowtechmagazine.com/2016/03/hydraulic-accumulator-power-water-networks.html
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dredmorbius
Anyone who's studied some elementary hydraulics and electricity is aware of
some of the parallels between fluid flows and current flows. Some are direct
analogs, and the article mentions one: the fact that power water systems make
use of _slow_ fluid flows under _high pressure_ to minimise _friction losses_.
That's a direct analog to low-current (amperage), high-voltage currents to
minimise resistance losses in long-distance electric power transmission.

Other relationships are inverted. Electricity must be generated continuously.
Unused generation is wasted. Hydraulic pressure is retained in a system
(absent leaks) until tapped, a periodic re-setting of a concentrator load is
sufficient to re-charge the system. Tremendous forces can be made available
over wide areas with little energy input.

Oh: and city-wide grids of this existed. Until the 1970s in some cases.

~~~
adwn
> _Electricity must be generated continuously. Unused generation is wasted._

Not quite: You can use a capacitor to store electrical energy. In fact, a
capacitor corresponds to a water tower in the electricity/water analogy.

~~~
dredmorbius
I knew someone would mention that.

Turns out caps are kind of hard and expensive and finnicky. But yes, that's
the analogue.

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prions
As a water engineer I find this pretty fascinating. Some issues I see on how
this hasn't stuck throughout the 20th century:

700 psi is enormously high compared to current municipal water systems which
rarely go over 150 psi. Maintaining and working on a pipeline of this size and
pressure is more dangerous and very expensive. Over time, age will cause the
network to lose pressure(through leaking, scaling, etc). How can facilities
maintain power when a main line breaks? They would need their own water
supply, tank and pumps in lieu of a diesel generator.

Electrical systems are generally much easier to install and work on. Piping is
underground, large (compared to transmission wires) and much more prone to
failures. A powerline going down can cause an inconvenience for a few days at
most, but a broken water main will flood everything in its vicinity.

Also where will the water be sourced from? Municipalities are permitted to
only draw a certain amount from their water supplies. This will definitely
cause contention especially in drought conditions.

~~~
dredmorbius
Reading the article, several of these points are addressed.

As with electricity, hydraulic circuits are high-pressure, low-flow, and are
_largely_ self-contained. An advantage of water-based hydraulic systems over
synthetic hydraulic fluids is that the water _can_ be bled from the system
without contamination. But these are _pressure_ rather than _throughput_
systems. Actual water draw is minimal.

Pipelines themselves are small -- an inch or two in diameter. Not much larger,
if that, than electrical conduit.

You're almost certainly right that there would be ongoing maintenance issues
over time. Subcircuit isolation would have to be part of this, as well as
perhaps redundant pressure circuits.

Early designs were widely distributed because prime movers / energy sources
were scarce. We _do_ use hydraulic systems extensively today, but they're
largely small and self-contained. An automobile braking system, front-end
loaders or other construction equipment, elevator systems, and the like.

A thought is that such systems would be useful, on a localised scale, where
_energy_ inputs are variable, but uses are relatively occasional. A home or
factory power hydraulic system could operate small or occasional machinery
(lifts, presses, punches, door mechanisms) _without_ requiring 24/7 electrical
supply.

I also recall that the Amish make use of air-powered tools in certain
situations, possibly not unlike those described here.

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g8oz
I'm interested in raised weight hydraulic accumulators and their potential for
smoothing out peaks and troughs in the production of renewable energy. German
Prof.Dr. Eduard Heindl of Heidl Energy is developing the concept of a "rock
piston" where the lifting of a large rock mass will be done hydraulically to
store energy and then reversed to release it. Personally I believe this is a
much more scalable approach as compared to pumped hydro.

[http://www.heindl-energy.com/hydraulic-rock-
storage/overview...](http://www.heindl-energy.com/hydraulic-rock-
storage/overview.html)

~~~
dredmorbius
The difference between _force_ accumulation and _energy_ storage is ... that
gravitational potential energy just doesn't give you that much. The practical
instanciation of your idea would be pumped-storage hydro.

Another avenue is compressed-air energy storage (CAES). Here the problem is
Boyle's Law: compressing a gas heats it. Over time, that heat will leak out
through containment walls (even in underground spent gas field storage).
_Releasing_ the gas cools it, to the point that icing over of equipment is a
problem. One solution is to introduce a natural gas (or biogas) jet to the
release stream, with additional heat of combustion not for _energy_ so much as
to prevent icing.

This scales in theory, though it's still a tad complicated.

~~~
g8oz
>>"..that gravitational potential energy just doesn't give you that much"

To that point I'll respond with a quote from Hendl's site: _A storage with a
radius of 250 meters could store 124 GWh, which would correspond to the
worldwide storage capacity of all pumped storage power stations._

[http://www.heindl-energy.com/hydraulic-rock-storage/idea-
fun...](http://www.heindl-energy.com/hydraulic-rock-storage/idea-
function.html)

~~~
dredmorbius
Interesting, though I'm rather suspicious ths would work as stated.

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scotty79
Is there a modern version of hydraulic accumulator? One you could use to
prevent your pressure dropping sharply when neighbor opens valves at his
apartament?

~~~
Johnythree
It's called a header tank. Plus a pressure pump if you want high pressure.

There are literally millions of these in Asia, for exactly that reason
(pressure fluctuations).

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euroclydon
Low Tech Magazine has some great writing!

