Question

Part II

HAWT DESIGN QUESTIONS

Hint: questions 1-3 are answered in terms of the definition of Cp.

1. Doubling power output requires what % increase in diameter? _______ Why? ___________________

2. Doubling wind speed provides what % increase in power? _______ Why? __________________________

3. Reducing air density by 10% changes power by what percentage? Increase or decrease in power?

________________________________________________________________________________

4. Doubling wind speed requires what change in rpm (to provide same efficiency)? (Hint: Dynamic similarity requires same tip speed ratio (TSR) _________________

Hint: Questions 5-8 are answered by running HAWTDES for the conditions stated.

5. What is the effect of doubling the airfoil drag coefficient? ___________________________________

6. What is the effect of doubling design lift coefficient? ________________________________________

7. What is the effect of doubling the number of blades for a given design power? ___________________

HYDRO-POWER QUESTIONS:

Hint: Hydraulic Head * g   = potential energy of dammed water / kg

8. A hydro power plant used for electricity generation and for storage has a turbine generating system with the following characteristics:

                Rated electrical output power = 200 MW         Hydraulic Head = 136 meters

                Mass flow = 166,000 liters/s = 166,000 kg/s at rated power

                Calculate input power = ____________; Watts = _________ MW

Hint: Typical hydro-turbines achieve 80 -90% efficiency.

                Annual electrical energy produced = 175,000 MWh

Calculate: a) Efficiency of the system ______________________

                    b) Capacity Factor of the system _________________

                    c) Explain why (a) and (b) are different. ____________________________________

Answer 1