Sustainable and Renewable Energy Development Authority (SREDA)- 2026

Solution: Wind power density is the power available in the wind per unit swept area normal to the wind (W/m²): WPD = ½ρV³.

$$\rho =\frac{p}{RT}=\frac{100,410}{287\times 298.15}=1.173{\text{kg/m}}^3$$

$$WPD=\frac{1}{2}\rho V^3=0.5\times 1.173\times 7^3=201.2{\text{W/m}}^2$$

∴ Wind power density = 201.2 W/m² (Answer)

Solution: P ∝ V³ (same ρ, A and C_p):

$$P_2=200\times {\left(\frac{10}{7}\right)}^3=200\times 2.915=583.1\text{kW}$$

∴ Power output = 583.1 kW (Answer)

Solution: $$Q_{in}=500\times 14=7000\text{MJ/h}\left(=1944.4\text{kW}\right),P=\frac{0.25\times 7000\times 10^3}{3600}=486.1\text{kW}$$

∴ (a) 7000 MJ/h; (b) 486.1 kW (Answer)

Solution:

Solution: REEs are a group of 17 metallic elements — the 15 lanthanides plus scandium and yttrium — with similar chemical properties, found together in ores. They are “rare” because economically mineable deposits are rare. They are used in permanent magnets of wind turbines and EV motors, batteries, catalysts and electronics.

Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Scandium (Sc) and Yttrium (Y).

Solution:

Solution: Rotor blades, hub, pitch system, nacelle, low-speed (main) shaft, main bearing, gearbox, high-speed shaft, mechanical brake, generator, power converter and controller, yaw drive and yaw bearing, anemometer and wind vane, cooling system, tower and transformer.

Solution:

• High initial investment and limited access to low-cost finance
• Scarcity of land in a densely populated country
• Low wind speed in most inland areas
• Weak grid, lack of energy storage and intermittency of solar and wind
• Inconsistent policy implementation, slow approvals and unclear tariffs
• Dependence on imported technology; little local manufacturing
• Shortage of skilled manpower and research facilities
• Dominance of and subsidies for fossil fuels
• Low public awareness; climate risks (cyclone, flood, salinity) in coastal areas

Solution: The energy mix is the combination of primary energy sources (gas, oil, coal, hydro, solar, wind, biomass, nuclear, imported electricity) used to meet the energy or electricity demand of a country, expressed as percentage shares.

In Bangladesh, electricity generation depends mainly on natural gas (domestic and imported LNG), followed by coal, liquid fuel (furnace oil, diesel) and imported electricity from India; renewables (Kaptai hydro, solar home systems, rooftop and utility solar, small wind and biomass) contribute only a few per cent. As domestic gas reserves decline and fuel imports strain foreign exchange, the plan is to diversify the mix by increasing renewable energy (target about 20% by 2030), importing regional hydropower, using efficient gas and coal plants and adding nuclear power (Rooppur).