Primary and secondary energy with 10% environmental flow

Primary energy comes from the minimum usable flow; secondary energy from the usable flow above it, up to the design discharge. An environmental flow must first be subtracted from the river flow.

Environmental flow

Minimum river flow = 100 m³/s (January).

$$Q_{env} = 0.10 \times 100 = 10\ \text{m}^3/\text{s}\ \text{(released every month)}$$

Usable flow = Q − 10, limited to the design discharge 950 m³/s.

Power per unit discharge

$$P = 9.81 \times Q \times 150 \times 0.85 = 1250.78\,Q\ \text{kW}$$

Installed capacity $= 1250.78 \times 950 = 1{,}188{,}236$ kW ≈ 1188.2 MW.

Primary energy

Minimum usable flow = 100 − 10 = 90 m³/s.

$$\begin{aligned} P_f &= 1250.78 \times 90 = 112{,}570\ \text{kW} \\ E_p &= 112{,}570 \times 8760 = 986.11\ \text{GWh} \end{aligned}$$

Total energy (730 h per month)

$$\begin{aligned} E_{total} &= 1250.78 \times 6780 \times 730 = 6190.59\ \text{GWh} \\ E_s &= 6190.59 - 986.11 = 5204.47\ \text{GWh} \end{aligned}$$

Answer: Primary energy ≈ 986.1 GWh/yr; secondary energy ≈ 5204.5 GWh/yr (installed capacity ≈ 1188 MW).