All hydro power installations follow the principles of conservation of energy to extract power from a body of water. The potential energy of flowing water is converted to kinetic energy through a drop in height, which is then used to drive a turbine and generator to produce electricity. Typically, hydro installations abstract water from a river or reservoir and divert it through a series of pipes and channels to drive a turbine.

The typical components of a run of river hydro installation are:

Intake: The intake is a structure that abstracts water from the water course and diverts it into the hydro scheme. Filters and trash gates are employed to remove any unwanted debris from the water that may result in damaging the turbine.

Penstock: Once diverted and cleaned the water travels to the penstock, which is the pressurised pipeline leading directly to the turbine. It is within the penstock that the potential energy the water has at the intake is converted to kinetic energy through the drop in height.

Power house: The turbine, generator and switchgear are located in the power house. Power cables connect the switchgear to either a grid connection whereby the power can be distributed or to a source of local demand.

Tailrace: Upon exit from the turbine, the tailrace channels the water from the power house back to the water course.

We are specifically interested in run of river schemes as they have little or no capacity to store water in a reservoir and are highly dependent on the flow rate in the river. As a result, if sized incorrectly, a hydro installation may experience times of zero generation. Depending on the rainfall patterns of the site, dry periods may be wholly unavoidable. Our aim within the project was to initially investigate variable flow schemes without storage and identify areas that had potential for improved exploitation.

The Combined Pressure Header

Our case study in Glen Almond has topography typical to that of other areas of hydro potential in Scotland. Rainfall runs down the hillsides to corries and burns, which in turn feed the River Almond. It is notable that the areas where possible flow extraction points could be built are in geographical proximity to one another. It is therefore feasible that, instead of constructing a number of individual systems, (as shown in Figure 2) one could join up the systems into a single network, as shown in Figure 3.

An investigation strategy was devised to evaluate both individual and common pressure header systems, details of which can be found here.