Inlet screen for a hydropower plant

1. An inlet screen adapted to be arranged at the water inlet ( 8 ) of a hydropower plant ( 2 ), comprising a plurality of elongated bars ( 20 ), said bars ( 20 ) being separated by a distance holding means ( 22 ), each elongated bar ( 20 ) having in its elongation a proximal portion ( 26 a ) and a distal portion ( 26 b ), and in a cross-section an upstream region ( 35 a ) and a downstream region ( 35 b ), at least one of said bars ( 20 ) defining a first space ( 36 ; 36 a ) extending along at least a portion of an extension of said bar in a direction of elongation of said bar ( 20 ), said first space ( 36 ; 36 a ) being defined in either of the upstream region ( 35 a ) and the downstream region ( 35 b ), said elongated bar having an intermediate portion ( 38 a ), said intermediate portion ( 38 a ) being elongated and extending along the direction of elongation of the bar ( 20 ) from the proximal portion ( 26 a ) of said bar ( 20 ) to the distal portion ( 26 b ) of said bar ( 20 ) between the upstream region ( 35 a ) and the downstream region ( 35 b ), said bar ( 20 ) being provided with an electric heating means ( 31 ), said electric heating means ( 31 ) comprising at least one electric heating member ( 37 ) being introduced into said first space ( 36 ; 36 a ) wherein the cross-section of at least one of said bars has a substantially aerodynamic profile.

2. An inlet screen according to claim 1 , wherein said bar defines a further space ( 36 b ) extending along at least a portion of the extension of said bar in the direction of elongation of said bar ( 20 ), said first space ( 36 a ) and said further space ( 36 b ) being spaced from one another, said space ( 36 a ) being defined in the upstream region ( 35 a ) and said further space ( 36 b ) being defined in said downstream region ( 35 b ), said intermediate portion ( 38 a ) extending along the direction of elongation of the bar between said first space ( 36 a ) and said further space ( 36 b ), said electric heating means ( 31 ) comprising at least one electric heating member ( 37 ) being introduced into any one of said first space ( 36 a ) and said further space ( 36 b ).

3. An inlet member according to claim 2 , wherein said first space ( 36 a ) and said further space ( 36 b ) extend from the proximal portion ( 26 a ) of said bar ( 20 ) to the distal portion ( 26 b ) of said bar ( 20 ), said bars ( 20 ) being supported by an elongated support means ( 28 ) arranged across the direction of elongation of said bars ( 20 ) at their distal portion ( 26 b ), the distal portion ( 26 b ) of said bars ( 20 ) being welded to said elongated support means ( 28 ) in such a way that the first space ( 36 a ) and the further space ( 36 b ) at the distal portion ( 26 b ) of said elongated bar ( 20 ) are closed, said at least one electric heating member ( 37 ) being provided with electric conductors ( 46 a , 46 b ), both of which being introduced into any one of or both or said first space ( 36 a ) and said further space ( 36 b ) of said bar ( 20 ), wherein the proximal portion ( 26 a ) of said bars ( 20 ) is provided with a top cover ( 32 a , 32 b , 32 c )

for housing said electric conductors ( 46 a , 46 b ).

4. An inlet screen according to claim 3 , wherein one of said first space and said further spaces ( 36 a , 36 b ) is provided with said at least one electric heating member ( 37 ), wherein the other one of said first and further spaces ( 36 a - 36 f ) is provided with a sensing means ( 40 ), the at least one electric heating member ( 37 ) being operated in response to said sensing means ( 40 ).

5. An inlet screen according to claim 1 , wherein said distance holding means ( 22 ) comprises at least one distance holding member ( 24 ) for keeping the bars ( 20 ) in a substantially parallel relationship, said distance holding member ( 24 ) being non-detachably or non-detachably connected to a pair of neighbouring bars ( 20 ) at said intermediate portion ( 38 a ).

6. An inlet screen according to claim 5 , wherein said distance holding means ( 22 ) comprises a rod ( 23 ), wherein a plurality of neighbouring bars ( 20 ) are provided with at least one bore ( 38 b ) across the intermediate portion ( 38 a ) of said neighbouring bars ( 20 ), said bore ( 38 b ) being positioned in said plurality of neighbouring bars such that the rod ( 23 ) is allowed to be introduced through the bore ( 38 b ) of the plurality of neighbouring bars.

7. An inlet screen according to claim 6 , wherein said distance holding member ( 24 ) is hollow and is positioned between neighbouring bars ( 20 ) and in front of the bore ( 38 b ) of the neighbouring bars in such a way that said rod ( 23 ) is allowed to be introduced inside the hollow distance holding member ( 24 ), and in such a way that the distance holding member is supported toward said intermediate portion of neighbouring bars.

8. An inlet member according to claim 1 , wherein said first space ( 36 ) extends from the proximal portion ( 26 a ) of said bar ( 20 ) to the distal portion ( 26 b ) of said bar ( 20 ), said bars ( 20 ) being supported by an elongated support means ( 28 ) arranged across the direction of elongation of said bars ( 20 ) at their distal portion ( 26 b ), the distal portion ( 26 b ) of said bars ( 20 ) being welded to said elongated support means ( 28 ) in such a way that the first space ( 36 ) at the distal portion ( 26 b ) of said elongated bar ( 20 ) is closed, said at least one electric heating member ( 37 ) being provided with electric conductors ( 46 a , 46 b ), both of which being introduced into said first space ( 36 ) of said bar ( 20 ), wherein the proximal portion ( 26 a ) of said bars ( 20 ) is provided with a top cover ( 32 a , 32 b , 32 c ) for housing said electric conductors ( 46 a , 46 b ).

9. An inlet screen according to claim 8 , wherein the exterior of said bar ( 20 ) is provided with a sensing means ( 40 ), the at least one electric heating member ( 37 ) being operated in response to said sensing means ( 40 ).

10. An inlet screen according to claim 9 , wherein said sensing means ( 40 ) comprises at least one sensing member ( 47 a , 47 b ), said sensing member ( 47 a , 47 b ) comprising at least one of a conductive sensor and a temperature sensor, or a combination thereof.

11. An inlet screen according to claim 9 , wherein said sensing means ( 40 ) is arranged substantially at the upstream portion ( 35 ) of said bar ( 20 ), said sensing member ( 47 a , 47 b ) comprising a conductive sensor.

12. An inlet screen according to claim 9 , wherein said sensing means ( 40 ) is arranged substantially at the downstream region ( 35 ) of said bar ( 20 ), said sensing member ( 47 a , 47 b ) comprising a conductive sensor.

13. An inlet screen according to claim 1 , wherein said bar ( 20 ) is made of an extruded polymer or a metal, wherein said extruded metal comprises a light metal or steel.

14. An inlet screen according to claim 1 , wherein the lateral dimension of said space ( 36 , 36 a - 36 f ) is larger than the lateral dimension of the electric heating member ( 37 ), creating at least one gap ( 39 ) between the space ( 36 ; 36 a - 36 f ) and the electric heating member ( 37 ) for receiving a substance, said substance being one of a granular material and a liquid, or a combination thereof.

15. An inlet screen according to claim 1 , wherein said granular material includes sand or iron fillings.

16. An inlet screen according to claim 1 , wherein said liquid is at least one or more of an anti-freezing agent and water.

17. A hydropower plant comprising an inlet screen according to claim 1 in front of the water inlet ( 8 ) of a turbine, wherein the bars ( 20 ) are arranged in such way that the distal portion ( 26 b ) of the bars is underneath the water surface ( 49 ), said proximal portion ( 26 a ) being arranged at, above or underneath the water surface ( 49 ).

18. A hydropower plant according to claim 17 , wherein the electric heating member ( 37 ) is arranged underneath the proximal portion ( 26 a ).

19. An inlet screen according to claim 1 , wherein said space ( 36 ; 36 a ) is closed, wherein the lateral dimension of said space ( 36 , 36 a - 36 f ) is larger than the lateral dimension of the electric heating member ( 37 ), creating at least one gap ( 39 ) between the interior surface of the space ( 36 ; 36 a - 36 f ) and the electric heating member ( 37 ) for receiving a substance, said substance being a liquid, wherein the liquid is received in said gap.

20. An inlet screen according to claim 1 , wherein the distal portion ( 26 b ) of each bar ( 20 ) is supported by a support means ( 28 ) in the form of an elongated profiled element ( 30 ), wherein the spaces ( 36 a , 36 b ) are covered by the profiled element 30 , such that the spaces are closed.

21. An inlet screen according to claim 1 , wherein a top cover ( 32 a , 32 b , 32 c ) is provided at the proximal portion of said bars ( 20 ), or the proximal portion ( 26 a ) of the bar 20 is closed by a removable lid or a stopper.