Glencorse WTW Energy Recovery Scheme
Energy Recovery from Pressurised Water Systems
Scottish Water’s £130m flagship investment set just outside the Edinburgh ring road is a 21st century replacement for two now decommissioned WTW’s at Alnwickhill and Fairmilehead. Glencourse is fed by the Talla Aqueduct and the water comes from a variety of sources, primarily the Talla, Megget and Fruid reservoirs.
Employing DAF pre-treatment, tertiary sand filtration and final disinfection, the works is able to provide up to 175Ml/d of potable water to the Scottish capital. As with any physical or biological treatment system maintaining a steady flow though the works is paramount to its stable and efficient operation.
Due to the varying head and flow characteristics, Black and Veatch (Scottish Waters delivery partner) approached Gilkes for a solution to pressure management at the inlet to the works. Two possibilities were considered including pressure reducing valves (PRV’s) and also a hydro turbine to manage the pressure and provide a steady flow to the DAF cells.
The Gilkes Turgo
The Gilkes Turgo was selected as it is capable of continuously delivering pre-determined flows even in the event of a loss of grid situation. The Gilkes Turgo provides a proven and robust solution for pressure reduction and power generation in one box. Simply put the turbine is able to operate as a pressure reducing valve (PRV) whether it is functioning as a turbine or not. In a conventional reaction turbine, there is the risk that a grid trip would either require the turbine to shut down or for a complex by-pass arrangement to be in place. This Turgo turbine also avoids the possibility of pressure surge travelling back up the main.
The Energy Recovery turbine at Glencorse captures 30-35% of the energy needed to run the WTW. This helping to reduce the sites Carbon Footprint and dependence on external energy sources.
- Turbine 20" Twin Jet Turgo
- Net Head 53 m
- Flow 550 l/s
- Speed 600 rpm
- Power 735 kW
- Commissioned 2009
Pressure Reduction & Power Generation
Due to the Turgo’s unique design, Gilkes engineers were able to achieve pressure reduction and power generation from a single machine without the use of hydraulics or additional valves.
The Turbine is fitted with Deflectors that allow water to continue passing through the turbine while at the same time being deflected away from the Runner. This allows the machine to achieve a rapid shutdown, regardless of the Spear Valve (flow regulation) setting. This means that the flow through the turbine is not effected should the unit be required to shut down. The top and bottom Deflector plates are mounted on vertical shafts supported by flanged bushes inside the Turbine case. The Deflectors are independent of each other and each unit is operated by its own electrical actuator mounted on the Turbine case. Each Deflector actuator has an integrated position transducer which indicates the Deflector’s position for the full range of travel to the control system.
The Turgo turbine is able to operate continuously as a pressure reducing valve (PRV). This is true whether the machine is operating as a PRV or as a PRV and turbine combined.
Gilkes has considerable, worldwide experience of replacing the break pressure valve with a Turgo Impulse Turbine. The use of a Turgo Impulse turbine does not result in the plant using losing any flow control. The turbine may be set so that is primary purpose is to provide the correct value of water at the correct pressure. One of the great advantages of a Turgo Impulse turbine is that it generates within a wide variety of flows.