Weirs, Streams, Locks, Rivers and Wastewater outfalls
Starting from 1.5 m /s
1.0 - 4.0 m
As power is a function of head & flow, generating significant power from low head locations requires large volumes of water. Conventional technologies have one downside in common: Due to low available head pressures, they require large volumes of water which produce low rotational speeds requiring gearboxes to efficiently drive generators. This results in very large, heavy, expensive equipment and civil infrastructure.
VETT address this issue by using the venturi principles to achieve a pressure amplification for the turbine so that smaller, faster, no gearbox turbines can be deployed in low head hydro settings.
ACHIEVING PRESSURE AMPLIFICATION
The underlying principle is that when water is forced through a constriction (a venturi) the water speeds up and the pressure in the venturi will drop.
A duct (secondary flow pipe) is then located so that it ends in the low pressure area of the venturi.
If a turbine is then connected to that duct (as if it would be a turbine draft tube) the pressure (head) across that turbine is amplified.
With a VETT, a net 2.5 m water head across a weir can then be amplified to 7.5 m.
In a conventional VETT 80% of the water is used to create the low pressure in the venturi whilst 20% of the flow is used to drive the turbine at an amplified head.
This ratio can be amended for each site depending on whether more or less amplification is desirable.
VETT captures and converts this abundant source of natural energy in an efficient, environmentally benign and cost effective way.
VETT's structural, operational and installation specifications can accommodate for sensitive environmental parameters due to its design and configuration flexibility. As a result, VETT is able to achieve minimal environmental impact whilst maintaining its purpose as an economically viable solution to generate renewable hydropower.
80% of the flow travels through the venturi part of a VETT unit which has no moving parts which allows fish to migrate through the device. As fish will experience a sudden pressure drop extensive testing with live fish in an operating VETT was undertaken by expert parties Vis Advies and Fishtek. This third party verified test data has classified VETT as “outstanding” for fish survivability with 100% of sensitive juvenile fish passing through the primary flow path safely.
Only the 20% of the flow which drives the turbine needs to be screened as per conventional guidance.
These tests were done in constant communication with the Environment Agency and in 2017 the Environment Agency gave green light for VETTs to be installed .
VETT can easily be integrated into the existing water-course infrastructure. The unit can be located in the bank next to a weir or under the existing water level in a mill pond or lock structure.
The generator that is driven by the turbine is dry-encased and sits behind the turbine, also under water, negating the need for an above ground turbine house.
The control equipment of the VETT fits in a conventional road side kiosk which can be located near the hydro scheme in a location that doesn't disturb the landscape.
VETT scheme at Eaton Socon; Turbine located under seating area of pub
Conventional river management techniques such as by-pass for flooding or for fish transit can be incorporated into the design.
VETT design for Dalston Hydro; Left: VETT intake with debris screen, VETT unit buried in embankment; Right: Existing fish pass
The fundamental advantage of VETT is the low cost of renewable energy production, driven by its low capital cost. In comparison to other low head (1 – 3 m) hydropower technologies, VETT’s benefits are:
Small, high speed turbine
No gearbox required
Minimal fish screening - only 20% of flow passes through turbine
Small civil works
Very low visual impact
No impact on fish & aquatic ecosystems