This is a live view of what is happening now.LiveView Change Log
Looking from right to left, water arriving from upriver is impounded by the weir and enters the turbine through the screen.
It travels through the leat (concrete channel) until it reaches the penstock.
When the turbine starts, the penstock opens to allow water into the forebay (another concrete channel) and then into the top of the Archimedes screw.
The weight of the water entering at the top of the screw turns the screw as it falls to the river downstream of the weir. This lowering of the water enables the screw to absorb the water’s gravitational potential energy .
The rotation of the screw turns the gearbox input shaft where is it speeded up 62 times and exits at its output shaft.
This faster-turning shaft is then used to turn the generator which in turn generates electricity.
The amount of power the turbine can generate is dependent on the amount of water coming downstream towards the weir.
Water reaching the weir causes the level at the weir (Upper Level) to rise. When this rises above the ↑ Open level the control system opens the penstock slightly (see our hydraulics page) and starts the screw rotating at its minimum speed.
The water then passes through the screw generating electricity.
If the amount of water passing through the screw exactly matches the amount of water coming downstream the Upper Level will remain static.
However, if the amount of water arriving at the weir increases (e.g. due to more rain) the Upper Level will rise. The control system will detect this and instruct the penstock to open a little more to allow more water to enter the turbine.
Conversely, if the Upper Level falls below the ↓ Close level the control system will close the penstock slightly, which will reduce the flow slightly, thus attempting to balance the water arriving at the weir with the water passing through the turbine.
When the amount of water passing into the turbine goes above about 1 m3/s there will be more water available than can be passed through the turbine when rotating a minimum speed. This will cause the Forebay Level to go above the Setpoint level. This will cause the control system to instruct the screw to turn faster until the Forebay Level falls back to the Setpoint level.
When the amount of water passing into the turbine reaches 4 m3/s the screw will be turning at its maximum speed and be generating the maximum amount of electricity possible.
Rivers flows above 4 m3/s will cause the Upper Level to rise (because the turbine can’t take more than 4 m3/s) and the surplus water will fall over the top of the weir.
Notes/Glossary
| Brake | Used to lock the screw, gearbox and generator when shut down. |
| Efficiency: River | The overall efficiency from upper river to lower river (includes leat losses) |
| Efficiency: Turbine | The internal efficiency of the screw from forebay to lower river |
| Flow | The flow of water passing through the turbine. The mass flow rate is roughly equal to the volumetric flow (1000 l s-1 = 1 m3 s-1 ≈ 1 Te s-1). The generated power is proportional to flow. |
| Gauge Board | A board screwed to concrete in the upper river to show the current river level, augmented by a red/green panel to show the go/no level for the turbine to run |
| Generated Power | The amount of electrical power being generated in kW. Power (kW) = Head (m) x Flow (Te s-1) x g (m s-1 s-1) x efficiency. (g = gravitational acceleration , efficiency 70%-80%) |
| Generator | A conventional electric motor run backwards as a generator to convert rotational energy into electrical energy. |
| HMI | The control system’s display panel (Human/Machine Interface) |
| Head | The difference in height between the Forebay Level and the Lower Level. The generated power is proportional to head |
| Hydraulics | The electro/mechanical system which opens and closes the penstock (more info) |
| maod | metres above ordnance datum (levels used in Whitby are 3m lower). |
| Setpoint | A desired level in the control system. If the actual level differs from this the control system will take action to correct the level (See PID control) |
| Speed | The generator speed (the screw turns 62 times slower). |
| Three large circles | Magnified views of the water levels in the upper river, lower river and forebay |
| VSD | The device which changes the electrical frequency of the electricity connected to the generator to slow it down (Variable Speed Drive) |
| Alarms ► | Specific events the control system wants to show |
| Info ► | Information deduced from the current running conditions |
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