Strata Florida water treatment works hydroelectric scheme

Technical Overview
Power output:	140 kW
Turbine:	Canyon twin jet pelton
Generator:	Marelli induction generator
Control panel:	Dulas
Gross head & flow:	183m/195.5m, 100 l/s

Project overview

This innovative project involved the development and implementation of a 140kW hydroelectric plant embedded in Dŵr Cymru Welsh Water’s Strata Florida Water Treatment Works (WTW) in West Wales.

The treatment works takes raw reservoir water and processes it in a ‘dissolved air filtration’ (DAF) plant. Additionally, the works must pump clean water into the distribution network and so energy consumption is 250kW to 300kW typically.

The scope of work for this scheme involved connections into two high pressure raw water mains, constructing a new power house, specifying and installing the complete hydro plant, including its integration into the works and automatic operation, and the transfer of water from the power house into the DAF plant.

The hydro plant operation is completely independent of and does not affect the water treatment operation.

Implementation

Dulas has provided the customer with a complete service for development of the hydro plant at Strata Florida WTW from feasibility through consenting and detailed specification to construction, installation and commissioning.

Under contract, Dulas provides a three month reliability monitoring of the hydro plant with remote monitoring via the control panel HMI, ensuring the plant runs at the best possible efficiency and any potential issues are resolved quickly.

“Strata Florida is Dŵr Cymru Welsh Water’s largest embedded water treatment works hydro yet installed. Dulas bring a wealth of experience in the field of renewable energy engineering and delivered a solution to meet our complex needs.”

Mike Pedley – Head of Energy, Dŵr Cymru Welsh Water

Hydro ‘firsts’

Dulas in conjunction with Dŵr Cymru Welsh Water have achieved a number of ‘firsts’ on this project which include:

Concept, layout, construction and operation

The hydro scheme is truly embedded and integrated into the water treatment works (WTW) service operation, the first implementation of this kind for Dulas (although not for Dŵr Cymru Welsh Water).
The scheme features an elevated power house floor level – facilitated by casting a void between the floor slab and foundation slab.
The Canyon Pelton turbine is fitted with two jets fed from different water sources (Llyn Teifi and Llyn Egnant raw water reservoirs).
The turbine sump is connected directly to the WTW DAF inlet blend tank facilitated by an above ground stainless steel gravity feed pipe mounted on concrete supports.
Water continues to pass through the turbine casing even when the hydro generating plant is off-line.
The capacity factor for the plant is expected to be 85% to 95% – a truly “continuous duty” application.
The hydro control valves are used by the Works as the “flow control valves” (FCV) for the DAF plant operation
During commissioning of the hydro FCVs, the precision of the flow control at the Works was demonstrably improved.
The scheme was installed and commissioned largely with the treatment works in service operation with planned works shutdowns for work related to branch connection pipeline installation and “wet” commissioning of the hydro plant. Operation of the water treatment works was unaffected other than for planned shutdowns.

Engineering and procurement

The high head (20bar) raw water mains necessitated a customised equipment package to be developed. The turbine casing has been specially reinforced, based on FE analysis, to provide suitable stiffness for the hydraulic installation. Vibration sensors have been fitted for ‘foot printing’ wear and balance of the rotating plant during service.
The bespoke Dulas control panel is fitted with Siemens components (PLC, HMI, soft-start module, main contactor, multi-function meter). Connection to the PLC is via PROFIBUS communication link.
Smooth plant operation is guaranteed by an exacting turbine rotating balance specification (equivalent to that applied to gas turbines).

Powerhouse features

Constructed as a GRP kiosk.
Access is via external fabricated steps / landing.
32dBA noise level attenuation mineral wool lining in the wall structure, validated by sound level tests.
Fire safety / security level meets the requirements of LPCB level 3.

Contract Management

Dulas provided professional services for obtaining planning permission on behalf of the client and worked exclusively to Dŵr Cymru Welsh Water and other water industry standards such as WIMES and WRAS.