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Correct answer is (c) FLAT Rating

To explain: More cost-effective design to a WIND mill to produce rated power at less than the maximum prevailing wind VELOCITY, using a smaller turbine and generator and to maintain a constant output at all wind speeds above rating. This is CALLED flat rating.

Correct answer is (a) Because of long drive shaft

To EXPLAIN I would say: Savonius rotor is not useful for very HIGH installation because of long drive shaft problems. Bracing of the TOPMOST bearing above the rotor of a very tall vertical axis machine is difficult REQUIRING very long guy wires.

Right option is (a) Feet per minute

Explanation: The anemometer measures in feet per minute, or FPM. The rotation is sensed by a MAGNETIC or OPTICAL SENSOR that converts the SIGNAL to FPM measurement. An ARROW on the vane head identifies the direction the airflow must travel through the vane to obtain proper measurements.

Right OPTION is (b) Smock mill

To explain I would SAY: The smock mill is a type of windmill that CONSISTS of a sloping, horizontally weather boarded or THATCHED tower, usually with six or eight sides. It is TOPPED with a roof or cap that rotates to bring the sails into the wind. It is similar to post mill. It is named so because of its appearance.

Correct answer is (a) 1.149 kg/m^3

To explain I WOULD SAY: For AIR, gas constant R = 287 J/kgK, 1ATM = 1.01325 X 10^5 Pa

Air DENSITY, ρ = P/RT = (1.01325 × 10^5)/(287(34+273.15)) = 1.149 kg/m^3.

Correct answer is (b) Savonius rotor

The BEST explanation: Savonius rotor is a simple WEC system which woks like a cup anemometer. This type was invented by S.J. Savonius in the year 1920. It requires relatively low velocity winds for OPERATION. It consists of two half cylinders facing opposite directions forming as S-shaped CROSS section.

Correct ANSWER is (c) Iran

Easy explanation: The earliest KNOWN wind mills were in Persia (Iran). These early wind mills looked LIKE large paddle wheels. Centuries later, the people of Holland improved the basic design of wind mill. Holland is famous for its wind mills.

Correct choice is (b) Weather vane

For explanation: A weather vane works similarly to WIND SOCK. Instead of a tubular sock, the weather vane is made by placing a horizontal POLE at the top of VERTICAL pole. The poles are JOINED together so that the horizontal pole has a flattened, vertical end that reacts to wind.

Right OPTION is (a) availability factor

Explanation: The overall LOAD factor, also called the PLANT operating factor and the plant capacity factor is the ratio of the TOTAL energy generated during a GIVEN period of time to the total rated generation capacity during the same period.

The correct option is (d) TRANSMISSION systems

The EXPLANATION is: The type of the supporting structure and its HEIGHT is related to cost and the transmission system incorporated. Horizontal axis wind TURBINES are mounted on towers so as to be above the level of turbulence and other ground related effects.

Correct answer is (b) 1.6 X 107 MW

Explanation: The energy available in the winds over the earth surface is estimated to be 1.6 X 107 MW which is ALMOST the same as the present DAY energy consumption. Wind energy can be UTILIZED to run wind MILL which in turn, is used to drive the generators.

The correct choice is (a) Wind socks

For explanation: Wind sock is a very basic device that measure wind DIRECTION and PROVIDE a rough idea of the wind’s INTENSITY. A wind sock is a tubular piece of fabric or THIN, flexible fabric attached to a pole. When there is no wind, the fabric hangs VERTICALLY from the attached pole.

Right option is (a) True

Explanation: The rotor BLADES are continuously flexed by unsteady aerodynamic gravitational and inertia loads, when the machine is in OPERATION. If the blades are made using metal, FLEXING reduces their fatigue LIFE.

Correct option is (d) Fan mill

For explanation: The fan type windmill is specifically made for INDIVIDUALS. It is much SMALLER and used primarily for pumping water. It consists of a fixed TOWER (mast), a wheel and TAIL assembly (fan), a HEAD assembly, and a pump.

The correct answer is (c) Their dependency on the wind SPEED

The explanation: An inherent WEAKNESS of all wind machines are the strong dependence of the power produced on WHEEL diameter and wind speed, being proportional to turbine wheel AREA, i.e. to the square of its diameter and to the cube of wind VELOCITY.

Correct choice is (b) Up wind location

The best I can explain: In the upwind location (i.e. the wind encounters the TURBINE before reaching the TOWER), the wake of the PASSING rotor blades causes repeated changes in the wind forces on the wind forces on the tower. Due to this the tower may vibrate and may eventually be damaged.

The correct choice is (a) Renewable energy

Explanation: Wind is called a renewable energy SOURCE because the wind will blow as long as the SHINES. Wind power, as an alternative to burning fossil FUELS, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas EMISSIONS during operation, consumes no water, and uses LITTLE land.

The correct option is (b) Sun

Best explanation: Wind is FREE and RENEWABLE form of energy, which throughout history has been used to grind grain, POWER ships, and pump WATER. Wind is created when the sun unevenly heat the earth SURFACE.

The correct CHOICE is (d) HORIZONTAL axis wind mill Dutch type

For EXPLANATION: Dutch type wind mill is one of the oldest wind mills in designs. The blade surfaces are made from an array of wooden slats which rotates at high wind speeds. These TYPES of wind mill are cheap to build since the wood is made use of to build.

Right answer is (a) POST mill

Best explanation: The post mill has blades MOUNTED on a central post. The horizontal shaft of the blade is connected to a LARGE break wheel. The break wheel interacts with a gear system, called the wallower, which rotates a central, VERTICAL shaft. This motion can then be used to POWER water pumping or grain grinding activities.

The correct OPTION is (a) 2

The best explanation: There are two types of forces operating on the blades of a PROPELLER type wind turbine. They are the circumferential forces in the direction of WHEEL rotation that PROVIDE the torque and the axial forces in the direction of the wind stream that provide an axial thrust that must be counteracted by proper mechanical design.

Right ANSWER is (a) True

For EXPLANATION I would say: During the day, the air above the land heats up more QUICKLY than the air over water. The warm air over the land expands and RAISES, and the heavier, cooler air rushes in to TAKE its place, creating winds.

The CORRECT ANSWER is (d) Magnus effect rotor

The best I can explain: Magnus effect rotor concept was first demonstrated by Magnus in 1912. It consists of spinning cylinders. When cylinders spun in wind stream, TRANSLATIONAL FORCES are produced perpendicular to the wind stream by the Magnus effect. Such a device can be used to PROPEL ships or land vehicles.

Right answer is (d) Anemometers

Easiest explanation: An anemometer is any DEVICE that measures wind direction and INTENSITY. It MAY be SIMPLE, such as the devices described above, or it may be a complex, computer-aided machine that measures and records wind patterns over time. More advanced anemometer machines are used to aid in professional weather reporting and air traffic control.

The correct CHOICE is (c) Vertical axis

The explanation is: A Savonius wind energy conversion system has a vertical axis and hence eliminates the expensive power transmission system from the ROTOR to the axis. Since it is a vertical axis MACHINE it does not matter MUCH about the wind direction.

The correct option is (b) Horizontal axis propeller type wind mill

The best explanation: Horizontal axis propeller type wind mill consists of a LONG blade mounted on a rigid hub, induction generator and GEAR box. If EXTREMELY long blades are mounted on rigid hub, large blade root bending moments occur DUE to tower shadow, GRAVITY and sudden shifts in wind directions.

The correct option is (a) Cut in velocity

Best explanation: Due to several loss in efficiency and POWER at low wind VELOCITIES, a wind turbine is designed to come into operation at a MINIMUM wind speed called the cut in velocity. Thus the wind turbine operates with variable LOAD over a narrow range between cut in.

Correct answer is (c) Control SYSTEMS

The best explanation: Control systems involves SENSORS and actuators. The modern large wind turbine generator requires a versatile and reliable control system. A control system is USED for i) changing the orientation of the ROTOR into the wind. ii) Start up and cut-in of the equipment. III) Power control of the rotor by varying the pitch of the blades.

Correct answer is (B) 2 KW

The best I can explain: These might be used on FARMS remote APPLICATIONS and other places requiring relatively low power. The GENERATING capacity is up to 2kW. Small scale WIND machines lower your electricity bills by 50% – 90%.

Right answer is (d) Medium size machines

The explanation: These wind turbines may be USED to supply less than 100 kW rated capacity, to several residences or local USE. These do not require much SPACE they can be installed on roof tops or on some HIGH elevated areas.

Right option is (c) Darrieus type rotor

Explanation: Darrieus type rotors are lift devices characterized by CURVED blades with air foil cross sections. They have relatively low solidity and low STARTING torques, but high tip to wind SPEEDS and therefore relatively high POWER OUTPUTS per given rotor weight and cost.

Right choice is (d) 6

Best EXPLANATION: Wind turbines have been built with upto six PROPELLERS type blades but two and THREE bladed propellers are most common. A one bladed rotor with a balancing counter weight has some advantages, including lower weight and cost and simpler CONTROLS, over the multi-bladed type.

Right OPTION is (a) Wind energy conversion system

To explain I would say: A wind energy conversion system (WECS), or wind energy harvester is a machine that, powered by the energy of the wind, generates MECHANICAL energy that can be used to directly power machinery or to power an electrical generator for MAKING electricity.

The correct choice is (a) Tail vane

For EXPLANATION I WOULD say: In small turbines, yaw ACTION is controlled by a tail vane while is larger MACHINES a servomechanism operated by a wind-direction sensor controls the yaw motor KEEPING the turbine properly oriented.

Right option is (d) Horizontal type windmills

Easy explanation: The horizontal axis MILLS generally have netter performance. They have been used for VARIOUS applications including ELECTRIC power generation, and pumping water. The latter INTRODUCES some complexity into the design as the mechanical energy has to be transmitted over a DISTANCE.

The CORRECT answer is (a) COEFFICIENT of performance

The BEST explanation: The coefficient of performance of an aero turbine is the fraction of power in the wind through the swept area which is converted into useful mechanical SHAFT power. Cp for horizontal axis wind machine has theoretical maximum VALUE = 0.593.

Right answer is (a) 2

To elaborate: There are two classes of windmill, horizontal AXIS and vertical axis. The vertical axis design was popular during the early DEVELOPMENT of the windmill. However, its inefficiency of operation let to the development of numerous horizontal axis DESIGNS.

Right answer is (a) 0.277 KW

To explain I would SAY: Total power P,

P = 0.245 X (πD^2/4)

= 0.245 X (π (120)^2/4)

= 0.277 KW.

Correct option is (C) 1990

For explanation I WOULD say: The development of wind power in India began in 1990s. PRESENTLY India is the world’s fourth largest wind power generator. The Indian energy sector has an installed capacity of 32.72 GW. Today India is a major player in the global wind energy market.

The correct option is (d) 30-35 mph

Easy explanation: WIND turbines are DESIGNED with cut-in wind speeds and cut-out speeds i.e. the wind speeds when the turbines start TURNING or shut off to prevent drive train damage. TYPICALLY, maximum electric generations occurs at speeds of 30-35mph.

Correct choice is (c) Convection currents

To explain: WIND ENERGY can be economically USED for the generation of electrical energy. Heating and cooling of the atmosphere generates convection currents. Heating is caused by the absorption of solar energy on the earth SURFACE.