scioly state: wp

Where is the airfoil the thickest?

at the root

What is the relationship between wind speed and power generated?

direct cubed

What are ideal locations for wind towers?

coastal regions and hills

In early publications, the efficiency curves of this design, and the American Multiblade design were switched inadvertently, making it appear as though the following design was less favorable to study. 

savonius rotor

At the tip of a rotor blade, describe the direction of airflow

Lower side of airfoil profile to upper side 

State the directionality of the lift force on a turbine blade relative to the direction of wind flow. 

perpendicular

what is the name of the opposing force on a turbine blade

drag

in what type of design can turbine blades have no twist?

VAWT

which of the following is not true of the darrius turbine?

A) it is known as the “eggbeater” turbine  B) relatively efficient  C) they produce cyclic stress on the tower D) they are a subtype of horizontal wind turbines  E) most require some external power source

D

Live storage of coal in a power plant means:

storage of coal sufficient to meet 24 hour demand of the planet

Cost of operation of which plant is least? 

Hydroelectric plant

An air filter is used in

diesel engine power plants

In which of the follwoing power plants is the availability of power least reliable

wind energy

reflecting mirrors used for exploiting solar energy are called

heliostats

Which country overtook the US with the leading installed wind energy capacity

china

Wind energy actually relies on what other force of nature

solar

how were the first windmills that appeared in europe in the middle ages different from those earlier turbines?

they turned on a horizontal axis

The mean wind speed at point A on a wind farm is 7% higher than at site B. What would be the expected increase in electricity production at site A compared to site B?

15.5%

Turbine blades designed for three bladed turbines with the same tip-speed ration have the same shape

true

The typical capacity of a wind farm is

20-40%

The smith power coefficient modifies the standard power coefficient as it relates ot the idealized derivation of the betz’s equation by accounting for the change in wind direction upon contact with the blade

false (The Smith power coefficient doesn't account for wind direction changes on blades, it accounts for the wind shear (variation in wind speed with height) and how it affects turbine performance, and the change in wind direction, if any, due to the turbine's shape, is accounted for by the turbine design and aerodynamics, not the Smith coefficient. )

the generator is a stationary electromagnetic component where mechanical energy from the turning rotor is transformed into electrical energy

false (While a generator does convert mechanical energy into electrical energy, it's the rotating rotor that's the source of mechanical energy, and the stator (not the rotor) is the stationary component with the magnetic field, not the electromagnetic component itself. )

how does the electricity generated by a turbine on a wind farm get transmitted to the grid?

Step up transformers are used to increase the voltage for transmission to substation and then to the grid

Assuming a wind turbine generates 630 KW, where voltage is 690 V, what is the approximate current that should be produced?

910

Voltage is increased to 30,000 V (AC) using a step up transformer.  How do the number of windings on the primary coil and secondary coil compare? 

The secondary coil should have more turns of wire 

American power distribution systems in rural or residential areas typically have a ____________ topology. 

radial because it is cheaper to build

The first all steel windmill and tower was designed by

thomas perry

What was the fate of the Smith-Putnam Machine? 

One of the blades broke off due to excessive loads

The world’s largest wind turbine generator has a rotor blade with diameter 126 meters.  The area swept is equal to:

12463 m²

The power generated by a turbine is 18,000 Watts.  If the wind speed, which is initially 30 m/s decreases by 25%, what must the lift force be in order to generate the same amount of power?

800 N

potential difference or electric potential is

voltage

kirchhoff's law

According to Kirchhoff's Current Law, The total current entering a junction or a node is equal to the charge leaving the node as no charge is lost

What orientation does the rotor shaft of a wind turbine need to be in in order to operate?

the orientation depends on the design of the turbine

What is the effect of a rotor with high solidity ( > 0.80)?

low speed high torque

Some experimental wind turbines have incorporated an added structural design feature, called a/an _________, intended to increase the amount of wind passing through the blades.

augmentor

Give at least two reasons why energy, once it’s produced, might need to be stored instead of used.

energy demand does not always coincide with energy production – both time of day and location are factors.

Explain how pumping water can be used as a power storage mechanism.

during peak generating hours, energy from wind is used to pump water to a higher elevation. During off-peak generating hours which may coincide with peak usage hours, water is released from the higher elevation to allow gravity make it flow past turbines

mechanical energy storage

Pumped Storage, Hydroelectric dams, Compressed Air, Flywheel Energy Storage, Gravitational potential energy storage, Thermal storage

Where (in general climate regions) is the use of heat storage to store wind energy most suitable?

Northern climates

If you ran a 60-watt bulb for 20 days and electricity costs are 12¢ per kWh, how much would it cost to run the bulb during that time?

60 x 20 x 24 / 1000 x 0.12 = $3.456

A 40 km long electrical power line supplies 700 MW on a 400 KV line. The line has a resistance of 0.2 ohms per km. What is the voltage drop between the ends of the line?

Answer: 700 MW / 400 KV = 1,750 A 1,750 A x 40 x 0.2 = 14kV

In the above situation, how much power is lost in the line?

Answer: 1,750 A x 14kV = 24MW

Windmills were first showcased at the Chicago World Fair in what year?

1893.

In the late 1990’s what percentage of California’s energy was generated by wind?

nearly 2%

What orientation did the first windmills have, and what two main purposes were they used for?

vertical axis orientation, used for grinding grain and pumping water

What and where was the first windmills used in the U.S. to provide electricity to the local utility company?

Vermont’s Smith-Putnam machine in 1941

Where were the first utility-scale wind energy conversion systems set up?

The development of bulk-power, utility-scale wind energy conversion systems was first undertaken in Russia in 1931 with the 100kW Balaclava wind generator. This machine operated for about two years on the shore of the Caspian Sea.

What type of windmill is shown in the picture to the right?

Tower mill

The first windmills were built to

pump water and grind grain

The first windmills were created in

Persia, and were vertical

What is the name of the type of power generating system shown in the picture to the right

concentrated solar power (CSP)

What type of energy source would most likely use a pressurized water reactor (PWR)?

Nuclear

Which of the following energy source would not use combustion to power a generator? Select all that apply

Nuclear, wind, hydro

Which energy source is reliant on gravity to create the conditions necessary for energy generation?

hydro

Gas turbine engines are most suitable for which of the following types of power generation?

natural gas

Which of the following statements is true with regards to lithium ion batteries?

Have a longer lifespan than alkaline batteries

Are not as toxic as alkaline batteries

Perform better at colder temperatures compared to alkaline batteries.

1 and 3

A simple battery consists of an anode and a cathode separated by an electrolyte solution. Which of the descriptions below best describes what is happening when a battery is being discharged?

Electrons flow out of the anode due to an oxidation reaction and into the cathode due to a reduction reaction

What form of energy storage uses large caverns left behind by mining?

compressed air

Which of the following is an advantage of VAWTs?

automatically faces the wind, heavy machinery can be located close to the ground, lightweight

Majority of transmission lines in the US transmit this

AC

More efficient form to transmit electricity over long distances

AC

The preferred transmission form of Nikola Tesla

AC

Has no transmission loss along power lines

Not AC or DC

A wind turbine is found to be generating 12.5 kW of power at the same time the wind speed was measured at 3.2 m/s. Two hours later the wind speed is found to have increased to 12.8 m/s. What quantity of power listed below would be closest to the expected output of this turbine at this wind speed?

800

A GE 1.5 MW wind turbine has three blades that each 116 feet long. If this turbine is spinning at 15 rpm’s at what speed in m/s are the tips of the blades moving?

formula: v=rw (v is linear speed, r is radius, w is angular speed in radians/second)

A wind farm supplies 25 MW of power to a town that is located 45 miles away. This power is sent over a 100 kV line with a resistance of 0.13 ohms/mile. What is the current flowing in the line?

250 amps (I=P/V)

How much power is lost during transmission?

P=I²*R (0.37 MW, 370 kW)

What percent of power is lost?

0.37/25=1.5%

Most utility companies around the world charge for energy by SI unit of energy the Joule. For some reason, utility companies in the US charge by the kwh. How many Joules are in a kwh?

3.6 MJ

How much power can we expect from a wind turbine located at sea level if the wind speed is currently measured to be 25 mph and the air temperature is 15C? 142 ft turbine blade.

½ density*cross sectional area*velocity*turbine efficiency (1343.2 kW)

Who built the first large size wind turbine for electricity generation in cleveland, ohio in 1888

Charles Brush

what is the difference between a wind mill and a wind turbine

What does NIMBY stand for? How does it apply to wind energy?

Not In My Back Yard. Indicates the preference of individuals to place wind turbines in areas not close to their homes (due to various reasons) even if they support the idea of wind energy

Define pumped storage and its connection to wind energy?

Pumped storage hydropower (PSH) is a renewable energy storage technology that uses surplus electricity to pump water uphill to a higher reservoir, storing potential energy, which is then released to generate electricity when needed, acting as a "green battery" for wind and solar energy

‍Open-loop: with either an upper or lower reservoir that is continuously connected to a naturally flowing water source such as a river. ‍

Closed-loop: an ‘off-river’ site that produces power from water pumped to an upper reservoir without a significant natural inflow.

Powerwall is a battery system being manufactured by what company

Tesla

What is being shown in the diagram to the right?

Flywheel

What is the benefit of increasing the elevation of the wind turbine?

wind can flow more freely, with less friction from obstacles on the earth's surface such as trees and other vegetation, buildings, and mountains.

What is corona loss (aka corona discharge?)

What form of current is impacted most by the skin effect? what impact does this have on transmission?

AC, leads to decreased efficiency in transferring current across transmission lines

DC vs AC

In direct current (DC), electricity flows continuously in one direction, while in alternating current (AC), the flow of electricity periodically reverses direction, creating a wave-like pattern

In DC, the electrons flow steadily in a single direction, while electrons keep switching directions, going forward and then backwards in AC.

What is the name of the wind turbine design shown to the right?

vortex