Development stages and PRoR working principle

Stages of hydropower development

1. Reconnaissance study
2. Pre-feasibility study
3. Feasibility study
4. Detailed engineering design and tender
5. Construction and commissioning
6. Operation and maintenance

Working principle of a peaking run-of-river (PRoR) plant

A PRoR plant has a weir plus a small reservoir (pond) at the headworks that can store the river flow for several hours. In the dry season the river flow is small. During the off-peak hours the turbines run at low load or stop, and the water is stored in the pond. In peak hours (usually 4-6 hours in the morning and evening) the stored water plus the inflow runs the turbines at full load. In the wet season, when flow is large, it behaves as an ordinary RoR plant. So the installed capacity is larger than for a pure RoR plant, and the energy has a higher value because it is supplied at peak time. Examples are Kaligandaki A and Upper Tamakoshi.

General arrangement of components

 River --> Weir + Undersluice --> Intake --> Gravel trap
                  |                              |
              Pond (daily)                    Desander
                                                 |
                                       Headrace tunnel
                                                 |
                                            Surge tank
                                                 |
                                             Penstock
                                                 |
                         Powerhouse --> Tailrace --> River

 Section
 FSL ~~~~~|weir          intake====tunnel====(ST)
 MDDL ~~~~|pond                                 \ penstock
                                                  \__PH

Fluctuating pond level between FSL and MDDL gives the daily storage.