Reassessing the existing hydropower methods at Bonnington power station, New Lanark

The two 'run-of-river' hydro-electric schemes are situated on the Upper River Clyde at Bonnington and Stonebyres power stations. Dating back to 1926, the stations were an innovative adaptation of hydropower technology which eliminated the requirement for a reservoir and so preserved the appearance of the landscape (Fleetwood and McDowell, 2010). At Bonnington Power Station, a tunnel and two large penstocks divert water from above two waterfalls to the power station 57.6m below. A tilting weir upstream of the falls controls the river to maintain a constant net head (57.6 m) at the tunnel intakes (Scottish Power, 2011a). Water from the penstocks is passed through two vertical-shaft Francis turbines, each generating 5.5 MW of power at full load, before returning to the river through the tailrace (Scottish Power, 2011a). Each turbine’s flow consumption at full power load, which is also the maximum flow rate for turbine, is 12m3/s. The station regularly uses 24 m3/s for the two turbines, running at maximum capacity. The station has the capacity to generate a total of 11 MW, enough electricity to power 11,000 homes (Scottish Power, 2011a).
Scottish Power (2011b) recognise that hydropower is entirely renewable and sustainable. They have identified that the power station produces no direct CO2 emissions or other greenhouse gases. To ensure that the scheme’s operation has minimal impact on the surrounding environment, Scottish Power have continuous interaction with governing bodies, such as the Scottish Wildlife Trust and SEPA (Scottish Power, 2011b).
This research and design project was undertaken to reassess the existing hydropower methods at Bonnington hydro-electric power station , situated on the Upper River Clyde, near the Falls of Clyde, New Lanark. with emphasis placed on improving the hydraulic design of the existing machinery by reviewing its current operating characteristics. Given the increasing demand for energy generation and the need to revisit existing sites, this timely research presents outcomes relevant to the IWA conference’s themes of asset management, economics and technical innovation.

During this study siteThe hydrological conditions at the ‘run-of-the-river’ site were evaluated using the river flow data extracted from a SEPA gauging station situated 1km upstream of the station’s intake. The oOperating characteristics of the two existing 5.5MW vertical-shaft Francis turbines were assessed, in conjunction with the available river flow data, to determine if the hydraulic design and operation of the turbines could be improved.
It was concluded that the power output of the existing system could not be increased due to the 5.5MW output capacity limits of the two turbines. , hHowever, by optimising the turbine’s efficiency characteristics of the turbines, the amount of flow required to achieve the peak power output could be reduced. A 5.5MW power output is achieved normally at full flow (12m3/s) with a turbine efficiency of 81%. It was also found that if the flow passing through a turbine is limited reduced to 9.73m3/s, 100% efficiency is achieved along with the peak power output of 5.5MW. By reducing the flow, the turbine efficiency would be maintained for a longer period due to reduced wear-and-tear and less flow is required to be extracted from the River Clyde, hence, reducing environmental impacts.