Small hydropower plants at drops on multi-use water courses

Abstract

In arid regions of various countries in the world, multi-use water courses take off from storage reservoirs or diversion head works. The canals, running at very mild slopes to maintain maximum command negotiate steeper slopes of the terrain through drops at suitable intervals. The energy of flows at these falls, otherwise dissipated causing thermal pollution of the environment, can be utilized to generate hydropower by mini/micro hydro turbine generator. Canal drops are standardized, thus offering an excellent opportunity to standardize the small hydropower units, resulting in economy. The canals carry regulated and predictable flows free from debris. The flow-duration curves can be easily obtained with precision. The greatest advantage for hydropower generation at the canal drops is operation at maximum efficiency under constant head and discharge for a unit. A battery of hydro units can be installed to be successively started or stopped as the discharge and hence the water level in the upstream reach of the canal rises or falls. Bulb turbines with fixed guide vanes and runner blades in siphons placed directly over suitably modified drop walls present the simplest and most economical solution as all civil works and complicated controls are avoided. Grid connected systems with induction generators will simplify controls. Prompted by the canal water level sensed, the control unit starts vacuum pump to prime a siphon and start a unit or de-prime the siphon by opening to the atmosphere a vent on the siphon hood and thus stop the unit. A number of units on various falls on a canal can remotely be controlled. The bulb units with hermitically sealed generators can be replaced through manholes for maintenance at a central workshop. A small traveling crane over the units and a cabinet for controls are all that are required as auxiliaries. The design case study of such a mini-micro hydropower station on a two meter drop on a canal is presented to exemplify.