Renewable Energy Systems

Question 1

which wind turbine axle is more efficient?

Answer 1

horizontal

Question 2

Which wind turbine axle is least efficient?

Answer 2

Vertical

Question 3

Which control system does horizontal axle turbine have?

Answer 3

YAW control system

Question 4

What is the power generated formula for wind turbines?

Answer 4

P=1/2(pxAxv^3)

Question 5

If p drops by 20% and V increases by 20% what happens to total power?

Answer 5

it increases and that depends on the values but in class question was something like 38-44%

Question 6

What type of motor is the most similar to the doubly fed induction generator?

Answer 6

Wound rotor motor

Question 7

Explain blade feathering

Answer 7

its when the blade goes flat to stop damage from high winds to avoid physical and mechanical damage

Question 8

Explain Furling

Answer 8

Turning the blades away from the wind direction to avoid physical and mechanical damage

Question 9

What components inside the turbine?

Answer 9

Blade, Hub, Low speed shaft, gearbox, generator, brakes, YAW system

Question 10

Explain rotor brake

Answer 10

Spring applied, hydraulically released

Question 11

Explain YAW brake

Answer 11

Hydraulically applied, and spring released

Question 12

What is the efficiency formula?

Answer 12

Pout/Pin=EFF
Wind input+Aux power input(if any)
Power out

Question 13

Explain Dry Steam plants

Answer 13

-best for high temperature geothermal fields with dry steam
-stem extracted from underground reservoirs to drive a turbine

Question 14

Explain Flash steam power plants

Answer 14

-Best for geothermal sources with both steam and water
-Extract high pressure hot water typically above 180 C from deep underground reservoirs, when it comes to surface it drops in pressure turning it into steam

Question 15

Binary cycle power plant

Answer 15

-Best for moderate to low temperature geo thermal fields
-lower temp geothermal resoruce typically 85-180 C
-heat from geothermal resource transferred to secondary liquid with lower boiling point
-most versatile

Question 16

Define Sensible Heat

Answer 16

The amount of heat added to or released from a substance to change its temperature

Question 17

Define Latent Heat

Answer 17

amount of heat required for the substance to change state of matter

Question 18

What is a condensor?

Answer 18

releases heat to surrounding environment

Question 19

What is an evaporator?

Answer 19

abosorbs the heat from the surrounding environment

Question 20

4 components for geothermal heat

Answer 20

-Evaporator
-Condensor
-Compressor
-Expansion Valve

Question 21

What is used for cooling mode?
What is used for heating mode?

Answer 21

-Cooling mode condensor is underground
-Heating mode evaporator is underground

Question 22

Explain the characteristics of the horizontal closed loop system?

Answer 22

-cost less to install
-reuires large amount of land or property
-10-15 ft deep

Question 23

Explain the characterisitics of the vertical closed loop system?

Answer 23

-requires less land
-more expensive to drill vertical bore holes
-100-200 ft deep

Question 24

Stand alone PV system requirements?

Answer 24

-large battery sized accordingly to run the system for 3-5 days

Question 25

What is utility interface?

Answer 25

-solar stored in energy bank -provides some or all building electrical needs -when battery is low transfer to utility power -PV arrays charge battery in the meantime

Question 26

What is utility interactive?

Answer 26

-no battery storage -excessive energy fed back to grid

Question 27

What is islanding?

Answer 27

When the PV systems keeps supplying power back to the grid when there is a power outage

Question 28

What are ani-islanding inverters?

Answer 28

All grid ocnnected system require this so they dont feed power to grid during power outage

Question 29

What happens when current is max and when voltage is max?

Answer 29

Current max= short circuit voltage max= open circuit

Question 30

What does the increase in temperature cause?

Answer 30

-Increases current slightly -reduces power output -reduces voltage quite a bit

Question 31

What does MPPT stand for and what does it do?

Answer 31

Maximum power point tracker is a high efficiency DC to DC converter

Question 32

Advantages of hydrogen fuel cells?

Answer 32

-high efficiency concerts chemical energy into electrical energy with low power losses -quite operation, minimal noise -environmentally friendly, only water and heat as emmissions -quick refueling unlike battery systems replenishes instantly -long life span, continuous operation without degradation unlike batteries

Question 33

Polymer exchange membrane fuel cell(PEM) characteristics?

Answer 33

-60-80 C -most common

Question 34

Direct methanol fuel cell(DM) characteristics?

Answer 34

-50-130 C

Question 35

Alkaline Fuel Cell

Answer 35

-used for long time -water that comes out is drinkable -60-80 C -used in space craft

Question 36

Solid oxide fuel cell(SOFC) characteristics?

Answer 36

800-100 C high temps

Question 37

Molten carbonate fuel cell(MCFC) characteristics?

Answer 37

600 C

Question 38

Phosphoric Acid fuel cells(PAFC) characterisitcs?

Answer 38

150-200 C

Question 39

What are some types of portable fuel cells?

Answer 39

PEM, DM, Alkaline fuel cell

Question 40

What are some types of stationary fuel cells?

Answer 40

SOFC, MCFC, PAFC