The hydro power in a stream or river can be calculated as follows:
Hydro Power (kW) = Net Head (m) x Flow (m3/s) x 9.81*
(*9.81 is acceleration due to gravity which can be assumed to be constant).
Net head is the total head, less any losses which may occur. These result from friction or turbulence in the water. For an accurate estimate of net head, the head loss needs to be calculated depending on the site conditions and the hydropower system which is proposed.
To estimate the electrical power produced by a generator, the efficiency of the system must be taken into consideration. A turbine that has an efficiency of 70% will convert 70% of the hydraulic power into mechanical power (30% being lost). The system (or ‘water to wire’) efficiency is the combined efficiency of all the energy transfer stages.
Electrical Power (kW) = Hydro Power x System Efficiency
The Feasibility Study in 2009 estimated the Average River Flow to be 550 l/sec.
The existing Abstraction Licence allows water abstraction of:- 187 l/sec
From levels measured at the existing old installation we get:-
So working with the allowable flow of 185 litres per second we get a power output of:-
|Gross Head||Flow m3/sec||Gravity||Output Kw||Efficiency||Actual Output Kw|
The turbine selected for the Flow / Head conditions is a cross flow turbine. The water is channeled across and through the turbine cylinder as shown in the diagram above. The water powers the turbine both on the way in and out of the turbine.