System for the regulation of a water flow passing through a hydroelectric turbine

DESCRIPTION Field of the invention

[0001] The present invention relates to the field of hydroelectric power generation within canals.

[0002] In particular, the invention relates to a system for the regulation of a water flow passing through a hydroelectric turbine.

Description of the prior art

[0003] As well known, the canals for the flow of water are of the irrigation or energy type. The former are used to distribute water in the cultivated fields and can be gravity-fed or pumped, while the latter are created to feed power plants or to convey water into the natural riverbed, once the jump of the canal has been exploited upstream. Both categories of canal, with the exception of pumped irrigation canals, can be further exploited from the energy point of view by recovering kinetic energy through flowing water turbines.

[0004] However, the existing canals are very little exploited from the energy point of view due to a strong variability of level and scope during the year. [ 0005] In fact, since hydroelectric turbines need to have the blades constantly immersed in the flow and to make the rotor rotate at a speed as constant as possible, the installation of a traditional type turbine inside one of these canals would produce a very variable yield and on average insufficient to justify the running costs.

[ 0006] Furthermore, these canals are designed and sized according to a maximum flow rate which, although present in the canal only for short periods of the year, would in such periods lead to flooding of the canal due to the excess volume of the turbine immersed in the canal and not foreseen in the design phase, entailing significant safety problems, both for the operators and for the canal and the turbine itself. [ 0007] The document W02011095240 discloses a hydroelectric power station comprising at least one rotor, a rotor-driven generator, a floating body and a nozzle assembly for increasing the flow rate in the rotor area. In particular, the nozzle assembly has at least one adjustable wall. The purpose of W02011095240 is to vary the inclination of the adjustable walls so as to keep the flow speed constant in proximity to the rotor and, therefore, to keep the rotation speed of the rotor constant. However, W02011095240 does not provide any system to control the flow upstream of the turbine in order to prevent flooding or system breakdowns. Summary of the invention

[0008] It is therefore a feature of the present invention to provide a system that allows to suitably regulate the speed of the water flow passing through a hydroelectric turbine, constantly guaranteeing its optimum efficiency.

[0009] It is also a feature of the present invention to provide such a system that guarantees the safety of the turbine and of the operators involved, even in the case of maximum flow rate of the water flow. [00010] It is also a feature of the present invention to provide such a system that reduces noise pollution and the environmental aesthetic impact produced by the system.

[00011] These and other objects are achieved by a system for the regulation of a water flow passing through a hydroelectric turbine, according to claims from 1 to 14.

Brief description of the drawings

[00012] The invention will be now shown with the following description of some embodiments, exemplifying but not limitative, with reference to the attached drawings in which:

Fig. 1 shows a possible embodiment of the system for the regulation of the water flow applied to a vertical axis turbine;

Fig. 2 shows the embodiment of Fig. 1 in the flow acceleration configuration;

Fig. 3 shows a possible embodiment of the system for the regulation of the water flow applied to a horizontal axis turbine; - Fig. 4 shows the embodiment of Fig. 3 in the flow acceleration configuration;

Figs. 5A and 5B show a possible embodiment of the release mechanism.

Description of some preferred embodiments [ 00013] With reference to Figs. 1 and 2, in a first embodiment of the invention, the system 100 comprises a working canal 110 arranged in a water flow having a main sliding direction d, a speed v _u upstream of the turbine 200 and upstream of the system 100, a speed v _t at the turbine 200, a speed downstream of the turbine 200 and a height h _u of the free surface upstream of the system 100. The working canal 110 comprises two containing walls 115 and houses inside the hydroelectric turbine 200 itself.

[ 00014 ] The system 100 then comprises two movable walls 120a,120b located upstream of the hydroelectric turbine 200, each of which defines a planar surface S arranged to form an angle a with respect to the main sliding direction d. Furthermore, each movable wall 120a,120b is arranged to rotate about a rotation axis y changing the angle a to switch between a neutral configuration (Fig. 1), wherein a = 0 and v _t = v _u , and a flow acceleration configuration (Fig. 2), wherein a > 0 and v _t > v _u .

[00015] Advantageously, the system 100 comprises at least one sensor configured to measure at least one fluid dynamic parameter of the water flow. In particular, this sensor can be a speed sensor for measuring the value v _u of the speed upstream of the system 100 or a sensor configured to measure one or more parameters p of the flow from which such value v _u can be indirectly derived, such as the flowrate of the water flow. Furthermore, there is at least one sensor, or the same previous sensor, configured to measure the height h _u of the free surface upstream of the system 100. The measurements carried out are sent to the control unit that operates the movable walls 120a,120b for suitably adjusting the speed v _u and the height h _u of the water flow upstream of the system 100.

[00016] The present invention therefore allows to receive information regarding the hydrodynamic conditions of the water flow upstream of the system 100 and to modify the inclination of the movable walls 120a, 120b to intervene in the event that the water flow presents an excessive height and/or speed which could be dangerous for the system 100 or for the operators involved.

[00017] For example, in case that the height h _u is higher than a predetermined threshold height h _u ^* , the control unit is arranged to operate the movable walls 120a,120b, even individually, to arrange them in the neutral configuration, reducing the resistance opposed to the flow and avoiding unwanted increases in the water flow. [00018] In addition, the control unit can operate the movable walls 120a,120b to increase the intensity of the flow at the turbine 200, in the event that the flow rate is not sufficient to produce the desired efficiency.

[00019] For example, in case that value v _u is less than a predetermined threshold value v^, the control unit is adapted to operate the movable walls 120a,120b to increase the angle a by arranging them in the flow acceleration configuration .

[00020] This way, when the speed v _u upstream of the turbine 200 is too low to make the turbine work at a sufficient speed, the system 100 allows the flow to be conveyed in a sort of converging duct, generating an increase in speed. On the other hand, when the speed v _u is sufficient, the system works in the neutral configuration and the movable walls 120a, 120b are substantially transparent to the water flow, not accelerating it in correspondence with the turbine.

[00021] In particular, the control unit is adapted to control the movable walls 120a, 120b to vary the angle a in an inversely proportional manner to the speed value v _u . The lower the speed value v _{u r} the greater the flow convergence angle a will be.

[00022] In this way, the control unit can adjust the value of the angle a as a function of the speed v _u to keep the speed v _t of the flow inside the turbine substantially constant, guaranteeing, within certain limits, a constant working speed and improving the efficiency of the turbine.

[00023] With reference even to Figs. 3 and 4, in a possible embodiment of the invention, the system 100 also comprises two auxiliary movable walls 130a,130b located downstream of the hydroelectric turbine 200 and also configured to switch between a neutral configuration, wherein v _t = v _d , and at least one flow deceleration configuration, wherein v _t .

For graphic simplicity, the auxiliary movable walls 130 are arranged in the neutral configuration in both Figs. 3 and 4.

[00024] In a completely analogous manner to the movable walls 120a,120b, each auxiliary movable wall 130a,130b form an angle a' with respect to the main sliding direction d and is adapted to rotate about a rotation axis y' changing the angle a ' to switch between the neutral configuration, wherein a' = 0, and at least one flow deceleration configuration, wherein a' > 0. These geometric parameters are not shown in the figure for graphic simplicity, but are, mutatis mutandis, completely similar to those shown in Fig.

2.

[00025] The presence of the auxiliary movable walls 130a,130b reduces the turbulence downstream of the turbine, increasing the efficiency of the turbine's electricity generation process.

[00026] In particular, in a possible variant embodiment, the system 100 also comprises a release mechanism arranged to arrange the auxiliary movable walls 130a,130b between a constrained configuration, wherein they are constrained to keep the angle a ' constant, and a released configuration, in which they are free to rotate about its rotation axis y' orienting themselves according to the hydrodynamic forces expressed by the water flow. [00027] The release mechanism allows to release the movable wall or the movable walls downstream of the turbine in case of excessive flow rate, so as to allow the movable wall to orient itself according to the hydrodynamic forces expressed by the water flow, guaranteeing the safety of the system. [00028] Furthermore, alternatively or in addition to the release mechanism of the auxiliary movable walls 130a, 130b, the system 100 can provide a further release mechanism adapted to arrange the movable walls 120a,120b between a constrained configuration, in which they are constrained to keep the angle a constant, and a released configuration, in which the movable walls 120a, 120b are arranged in the neutral configuration, reducing the resistance to the water flow.

[ 00029] Both release mechanisms can be operated, for example, in the event that there is a fault in the system 100 and the control unit is unable to control the movable walls 120a,120b and/or the auxiliary movable walls 130a,130b. In this case, the release mechanisms make it possible to reduce the resistance of the walls to the water flow, avoiding dangerous increases in the height and/or speed of the flow itself.

[ 00030 ] In the figures 5A and 5B a possible embodiment is shown of a release mechanism 150 that can be used in the present invention. In particular, the mechanism comprises a housing 151, a sliding element 153', a wedge 152 and two pins 153. The pins 153 can translate vertically, integrally to the sliding element 153', bringing two springs 154 into compression or expansion. In Fig. 5A, the wedge 152 is not pulled by external forces and remains steadily in its housing. When the wedge 152 is subjected to a pulling action, the pins 153 slide upwards compressing the springs 154. When the pulling action exceeds a predetermined threshold, the wedge is released from the sliding element

153', disengaging from the housing 151, as shown in Fig. 5B. [ 00031 ] The release mechanism 150 of Figs. 5A and 5B can be applied both to the movable walls 120a,120b and to the auxiliary movable walls 130a,130b. In this case, when these walls undergo a flow force greater than a certain threshold, in the relative release mechanisms 150 the wedges 151 are released from their respective housings 151, disconnecting the movable walls from the relative actuation systems and leading them to follow the direction of the flow or, alternatively, in the neutral configuration which minimizes the resistance to the flow.

[ 00032 ] Furthermore, the system 100 may comprise an emergency extraction device. This way, in case that the height h _u reaches a predetermined threshold height h _u ^* , the emergency extraction device allows removing the hydroelectric turbine 200 by the water flow. Such device is an emergency measure and can be activated, for example, in the event that the variation of the angle of the movable walls is insufficient to keep the flow rate of the water flow below a predetermined threshold and that this could jeopardize the structural integrity of the turbine 200 and/or the safety of the operators involved.

[ 00033] The embodiments shown in Figs. 1 to 4 comprise two movable walls 120a,120b and, optionally, two auxiliary movable walls 130a,130b so as to be able to share the resistance opposed to the water flow, reducing the structural load of each movable wall. However, the present invention also intends to protect embodiments which comprise a single movable wall and/or a single auxiliary movable wall. These solutions may be necessary in case of small dimensions or particular geometry of the canals in which the system 100 is installed. In case of use of a single movable wall and/or a single auxiliary movable wall, the working channel must be placed laterally with respect to the main canal using a side wall of the main canal as a containment wall for the working canal.

[00034] With reference to Figs. 1 to 4, the system also provides a lifting device 140 arranged to vary the height of the hydroelectric turbine 200.

[00035] The lifting device 140 allows adjust the height of the turbine 200 according to the level of the water flow, keeping it in the optimal position, i.e. completely immersed but close to the surface of the water.

[00036] In particular, the sensor configured to measure the height h _u can allow the control unit to command the lifting device to vary the height of the turbine 200 according to the height of the detected water flow.

[00037] The fact that the turbine 200 always remains completely immersed in the flow makes it possible to avoid the onset of noise due to the flapping of the blades on the free surface of the water and not to alter the view of the natural state of the canal. At the same time, keeping the turbine 200 at the point as far away as possible from the riverbed ensures to work where the flow velocity is greater, producing greater efficiency. [00038] In addition, the lifting device 140 can allow the extraction of the turbine in the event that the upstream flow is too high, in order to put the turbine in safety and avoid any flooding of the canal.

[00039] With reference to Figs. 3 and 4, in one embodiment, the system 100 also provides a lower movable wall 125 arranged on the bottom at said working canal 110.

[00040] In particular, the lower movable wall 125 may have an inclined geometry upwards at the turbine entrance and downwards at the turbine exit, to increase the convergent- divergent duct effect.

[00041] Furthermore, the lower movable wall 125 can incline allowing to further increase the speed of the flow entering the turbine 200.

[00042] In particular, at least one electrical energy accumulator is provided which is suitable for activating the movable walls and/or the auxiliary movable walls in the event of a power failure on the system network.

[00043] The foregoing description embodiments of the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.