ritilan: Water powered cable trains

Water powered cable trains: "

Cable
trains (or funiculars) are one of the most energy-efficient modes of
transport out there. A large portion of the power required to pull up the ascending
car is delivered by the counterweight of the descending car. Many
historical systems used this efficiency and took it one step further with systems exclusively powered by water and gravity.

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Cable trains first appeared within the second half of the 19th century. Many of them have survived and continue to be utilised
(mostly in a modernized form) and new systems are being developed. A cable train system is operated on a steep slope with a
gradient of up to 55 percent and consists of two passenger cars which are
connected by a steel cable. Both cars travel on the same single track,
which is undoubled in the middle so that they can pass each other.

Cable trains prove extremely energy efficient because a large share of the power
required to pull up the ascending car is delivered by the counterweight
of the descending car. Since the system only needs one track and can go
straight up a mountain, it also saves a lot of materials and space (some systems use
two tracks but follow the same principle).
A funicular should not be confused with a cog wheel train - even though
many older cable cars applied a similar mechanism, as a braking system and speed governor, not as a traction
method.

Water powered cable trains

Originally, cable train systems were even more energy-efficient than they are
today. Instead of using an engine to pull the cable, the extra power
required to overcome friction and to pull up the ascending car was
delivered by filling the water reservoir of the upper car (see an
example of the mechanism below).

Before
departure, the employee in the upper station was informed of the number
of passengers that had entered the ascending car. He then knew exactly
how much water the reservoir of the descending car should contain
(around 80 litres per passenger).

From the moment the
descending car became heavier than the ascending car, the brakes were
loosened and both cars were set in motion powered solely by gravity.
Once the descending car arrived, its water reservoir was emptied and
the process was repeated.

Most cable trains using water counterbalanced energy have been replaced
by systems that utilise engines. One famous example is the Funiculaire de Montmartre in Paris, France,
which was operated by water power from 1900 to 1930 and
transported one million passengers per year (illustration below).

Thankfully, a few water powered cable cars continue to be in service, and have remained so for over a century. The Elevador do Bom Jesus in Braga, Portugal, has been in use since 1882. The Nerobergbahn in Wiesbaden, Germany, has been working since 1888, the Lynton & Lynmouth in North Devon, UK since 1890, and the Funiculaire Neuveville-St.Pierre in Fribourg, Switzerland since 1899 (see picture intro, note the water filling system on the side of the car).

Perpetuum mobile

Most water powered cable cars
require energy to operate the pump that transports the water up the
hill again, so of course, perpetual motion does not exist. There are however some exceptions to this. The 120 metre track in
Fribourg, Switzerland, operates without a pump.
It makes use of the natural flow of water along the track, more
specifically the waste water infrastructure which connects the upper
and the lower part of town.

How it works is this (illustration above, source):
The
waste water flows into a reservoir of 100,000 litres. From there it
flows in the water tank of the rail car . Around 1,500 litres of water
is required to pull up the other car from 60
meters below, and it takes 3 minutes to fill up the tank. After
approximately 1.5 minutes, you will have arrived at the ground station.
The reservoir is
then emptied and the water continues its way downwards through the
sewer
system. The train route was designed as a (very creative) way to lower
the flow of the fountains in the lower part of town.

Gravity

To add to this, in
the case of the Lynton & Lynmouth Cliff Railway, no water is pumped
from the bottom to fill the tanks at the top station - the water is
taken from a nearby river. Moreover, at this track the method is reversed.
Both car tanks are full of water, the tank of the bottom car is
partially discharged until the bottom car becomes lighter than the top
car, and gravity takes its course (source & more info). The Centre for Alternative Technology built a similar system in 1992 with a lake at the top of the mountain supplying the railway with water.

The
main disadvantage of a water-balanced railway (just like any other use
of hydro power) is that it cannot be operated when the water freezes
over. Bummer.

You need a mountain as well, of course.

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