Hydro power dam is a good example of energy store in pressurized liquid.
Hydraulic reciprocal motors are used in powerful low speed
Higher speed is most feasible with the Quasiturbine low inertial flow
Quasiturbine - (Water) Hydraulic
Water Hydraulic Limits
Consider a water dam, where say a ton of water is slowly
taken down into an elevator from the top to the bottom of the dam: All the
gravitational energy can be recovered by the elevator pulleys and cables, but
because this water is moving slowly, the power produced will be modest. To get
more power, more water must go down every minute, which means that the final
speed of the water at the bottom of the dam will not be zero anymore.
Consequently, to get power one has to increase the flow and discard some kinetic
energy at the exit. At the other extreme, if you let the water makes a free
fall, you recover of course little power as most of it energy end up in kinetic
energy at the bottom. This is a paradox where "call for power" destroy
efficiency! Conversely, pump efficiency is optimum when the exit is at near
zero flow speed (volume out with no kinetic energy), and where here it is the
"call for flow-rate" which destroys the efficiency. If the speed of a water free-flow in a
conduct at the bottom of the dam is V (containing all the gravitational energy
in kinetic), maximum power is taken when that speed is reduced to about half
(V/2), which for incompressible fluid means that only about 3/4 of the potential
gravitational energy is
harvested this way at maximum power condition. Closed loop hydraulic may avoid
some of this limitation if exit kinetic energy is useful at intake?
To further increase the conversion efficiency, the kinetic
energy of the flow past the turbine wheel need to be recovered. The momentum of
the flow pass the turbine wheel can be used to create a powerful vacuum (source
of cavitations) when forced to slowdown through a rapid increase of the conduct
section (Aspirateur - Draft tube - Thanks to Bernoulli), which vacuum
accelerates the flow upstream of the turbine in excess of V. This way, hydro turbines
up to 95% of the potential gravitational energy in a narrow range (by design).
Mainly because the pump inefficiency, the reversibility of an hydro-pumped
storage do not exceeds 70 %, even
when pumping slowly over 22 hours (efficiently because of low flow-rate kinetic
energy lost) and producing maximum power for 2 hours a day. This flow
problematic is far different from a fix weight moving up and down a hill, where
complete reversibility is possible because energy and power management required
the weight to be at rest once down hill. This hold for all type of engine,
turbine and even the Quasiturbine, where the lost of efficiency end up in heat
Hydraulic motor limitations have to do essentially with
(heat), flow reciprocal (rate), draft tube, operational range and check-valves. In a
piston chamber, the flow goes to a complete inversion of direction from
entering to exit, whereas in the rotary engines, only a part of flow goes
to some reversal at each one of these 2 stages. The hydraulic
(incompressible) case is more symmetrical with regard to the admission and
exit than compressible fluids, and obviously imposes a lower speed,
but the continuity of flow is appreciably better in the rotary engines,
which also make better use of the forces on the perimeter.
Conventional turbines have narrow working range in
term of flow speed, torque and power, while the Quasiturbine has a much
wider range, specially in the low-flow-speed domain where much higher
efficiency can be reach at reduced power, without the need of draft tube.
Superior to conventional hydraulic motor?
Conventional hydraulic motors use a set of pistons on a plate which is not
at the maximum external diameter, and moreover these pistons are very
limited in speed. The Quasiturbine uses the largest maximum diameter of the external perimeter and also all its width.
The Quasiturbine produces a larger specific motor torque and can moreover
turn at a higher speed, since the fluid flow does not reciprocate but
runs almost always in the same direction, producing consequently more power
by volume and unit of weight. With comparable dimensions, one can operate
a Quasiturbine at lower pressure. Moreover, the Quasiturbine is more
homo-kinetic and the torque is better angularly distributed. A set of 2
Quasiturbines with 45 degrees of phase out gives a more
linear angular torque. Quasiturbine is reversible and can also to
be used as pump.
Modulated Hydro-Electric Power
hydroelectric Quasiturbine is mainly superior for
modulated power needs and for torrential flow conditions.
Conventional hydroelectric turbines are very effective
when they turn at their speed of design under a determined water head,
and under design load. Their effectiveness falls quickly when moved
away from one or more of these 3 conditions. (Each conventional turbine
is designed and built specifically for a dam according to these 3
conditions, and it cannot be inter-changed with other hydro-electric
The Quasiturbines hydro-electric
present several advantages on the conventional turbines:
- They preserve a better effectiveness at all the RPM,
and since they are without leak at low revolution, they could save water.
- They preserve better effectiveness independently of
- They preserve their effectiveness independently of the water head,
and as they do not have to be built for a specific water head, they can
be manufactured in series and kept in inventory. They are thus replaced
quickly in the event of damage.
- Not having power shaft, they allow
more compact and less heavy units.
- As they have a broad speed range and load with
high efficiency, they can directly actuate industrial
- As Quasiturbines are reversible and allow to pump with
a high effectiveness, they are desirable for pumped
storage station, and particularly for energy storage in urban environment.
Because of its great specific power density and of its most homo-kinetic
geometry, the Quasiturbine is well suitable for small engines, but can also be dimensioned for very
powerful units. As an example, preliminary calculations indicate that
a Quasiturbine for hydroelectric dam having a rotor of 1 m of
diameter by 0,5 m thickness, operated under a differential of 33 bars (500 psi),
could produce up to 33,000 CV (25 MW) at only 1800 RPM! (power to be
reduced linearly for reduced pressure
differentials - Flow viscosity may however no permit to reach such a rpm?).
However, conventional water hydraulic turbines are doing a good job at fix
design value, and for the
time being, the Quasiturbine should be used mainly where power demand
varies and water stream saving can result of rpm variation.
Water Hydraulic to Pneumatic Conversion
waves sweeping through a fix caisson pressurizes the confined air,
relaxes it. These pressure variations can be directed toward both a
pressurized tank and a vacuum tank. This conversion from hydraulic to
pneumatic allows to conveniently drive pneumatic Quasiturbine (almost in
closed loop) between both
reservoirs, avoiding dirty water flow or icing conditions into the energy
system. A similar pneumatic conversion can be done from any water head dam
by dropping the water in a closed tube, and so compressing the confined
air, and later letting the water go while creating a vacuum (Essentially
still a fix caisson which is alternatively flooded and drained to simulate
a large amplitude wave effect). A very efficient way is to use water
pressure at the bottom of a water dam to fill a closed air reservoir,
compressing the capture air; this way, 100 % of the water potential energy
is converted into compressed air. If this closed air reservoir is a long
horizontal tube (U-turn at the end and back to the dam, so that all valves
and pressure take-out be in only one location - Can be slightly uphill to keep the water under the air),
the water kinetic energy can further be used to obtain some extra
pressure! Horizontal tube design requires a rotary 3 ways valve at intake,
and both a air pressure check valve and atmospheric check valve at the end
of the tube. Active ports management when at high and low
pressure water level (opening the loop when the air flow becomes negligible) can further improve the efficiency.
Other systems using Venturi water draft tube (siphon type) can also produce high vacuum
air flow. These can be a very attractive solution for energy independence
in vicinity of small rivers, where all the energy system equipments can be located
Since a water head of 32 feet (10 m) correspond to 1
atmosphere pressure (14 psi), this water head dam
conversion generally involve pressure
in the range of 20 to 60 psi, a secure level where efficiency is fairly good
Quasiturbine Hydraulic (in French)
Pump and Turbo-pump