Annual firm and secondary energy (900 m³/s, Nov 650)

Firm energy comes from the minimum flow, which is available throughout the year. Secondary energy is the extra energy from flows above the minimum, up to the design discharge (900 m³/s).

Power per unit discharge

$$P = 9.81 \times Q \times 100 \times 0.90 = 882.9\,Q\ \text{kW}$$

Installed capacity $= 882.9 \times 900 = 794{,}610$ kW ≈ 794.6 MW.

Firm energy

Minimum flow = 90 m³/s (March).

$$\begin{aligned} P_f &= 882.9 \times 90 = 79{,}461\ \text{kW} \\ E_f &= 79{,}461 \times 8760 = 696.08\ \text{GWh} \end{aligned}$$

Total energy (flow used = smaller of Q and 900; 730 h per month)

$$\begin{aligned} E_{total} &= 882.9 \times 6460 \times 730 = 4163.58\ \text{GWh} \\ E_s &= 4163.58 - 696.08 = 3467.50\ \text{GWh} \end{aligned}$$

Answer: Annual firm energy ≈ 696.1 GWh; annual secondary energy ≈ 3467.5 GWh (total ≈ 4163.6 GWh).