Case Study: Cross flow turbine installation in Scotland

Technology: Cross Flow turbine installation

Year: 2015

Output: 32 KW

Renewables First Role: Feasibility, Consenting & Design, Installation

 

 

Curlew Cottage, Inchlaggan is located adjacent to Loch Garry approximately 30km north of Fort William. The property is supplied by the Garbh Allt burn that flows alongside. The burn provides water supply for the hamlet of Inchlaggan as well as being the site for a cross flow turbine installation for the Curlew Cottage hydro scheme.

This cross flow turbine installation makes use of an annual mean flow on the site of 0.280m3/s and a drop in water levels of approximately 29 metres. The Garbh Allt burn draws water from a catchment area of 5.35km2.

This hydro scheme has several features of interest. Constructing the intake in the run of the river involved excavating the edge of the stream to divert flow to one side. This along with the use of sandbags, temporary pipework and a pump, enabled the creation of a water free area in which to construct the intake structure. Following minor excavation of the river bed, the base slab was cast directly onto the bedrock, upon which the rest of the intake structure was built. The images below show the intake structure at various stages of its development. It is at this point in the scheme that the water for the Cross flow turbine is screened and diverted through the penstock.

 

 

 

 

 

The 450mm diameter, 210 metre long penstock snakes its way from the intake structure to the turbine house, via the banks of the Garbh Allt burn, alongside the access track to Curlew Cottage and through an ecologically sensitive Tree Protection Area. Installing the penstock required much consideration. Given the diversity of terrain of which it traverses, some sections are buried beneath the ground, whereas others navigate the surface. The pipe eventually terminates at the turbine house. The images below show the penstock from various points on the hydro scheme.

 

 

 

 

 

 

The turbine house is located at the edge of the tree protection zone.  In order to eliminate any impact on tree roots, all of the holes for the turbine house foundation were hand dug and the concrete ring beam the Cross flow turbine sits on is supported by posts. The turbine house structure is a lightweight, timber build with a mono-pitch roof. The images below show the turbine house at different phases of the project.

It is estimated that the hydro scheme will generate 149,000 kWh/year, enough to power an average of 34 UK homes. From an environmental perspective, the scheme will also generate a saving of 81,000 kg CO2/year.