Eng Storage 1

Question 1

Merits of Pumped Hydro ES

Answer 1

mature technology, low running cost, reasonable round trip efficiency, good volume and power, can store for long periods, long life

Question 2

Cons of pumped hydro ES

Answer 2

geographic restriction, large land use is needed, low energy density, high capex, evaporation losses, environmental concerns

Question 3

3 types of hydro turbine based on flow

Answer 3

Axial, Radial, Mixed

Question 4

2 types of hydro turbine based on pressure change

Answer 4

Impulse (no change, ex pelton), Reaction (yes change, ex francis and kaplan)

Question 5

Friction factor is a function of

Answer 5

Reynolds # and pipe roughness/diameter

Question 6

Gas turbine power plants are cheaper or more expensive than vapor power plants

Answer 6

cheaper

Question 7

In air-standard analysis, air behaves…

Answer 7

as an ideal gas

Question 8

In cold air standard analysis, what is assumed constant

Answer 8

cp wrt temperature

Question 9

Isentropic processes are also…

Answer 9

adiabatic, but not the other way around

Question 10

In the brayton cycle, the expansion and compression are treated as

Answer 10

adiabatic

Question 11

In an ideal brayton cycle, the flow through the energy exchangers is _______ and the flow through compressor/turbine is _____

Answer 11

isobaric; isentropic

Question 12

Brayton Cycle is for ___; Rankine Cycle is for ____

Answer 12

air(+gas) ; steam

Question 13

The PV diagram shows _____; the T-s diagram shows _____

Answer 13

Work interactions (int:Vdp); Heat interactions (int:Tds)

Question 14

Increasing the pressure ratio increases the Brayton cycle ____ and ____ and ____

Answer 14

efficiency, back work ratio, turbine inlet temperature

Question 15

The biggest source of irreversibility (entropy production) in a gas turbine cycle is

Answer 15

combustion

Question 16

Name 3 ways of modifying gas cycles

Answer 16

regeneration, multi-stage compression, multi-stage expansion

Question 17

A regenerator increases ____ by preheating ____

Answer 17

thermal efficiency, air entering the combustor (using the exhaust heat from the turbine)

Question 18

For a regenerator, the temperature entering the cold side must be ____ than the temperature entering the hot side (exhaust)

Answer 18

less than

Question 19

SSS’s are … (combined cycle)

Answer 19

synchro self shifting (clutch)

Question 20

Thrust in a jet engine comes from

Answer 20

Increase in nozzle exit velocity relative to diffuser inlet velocity

Question 21

Pr in A-22 is

Answer 21

relative pressure

Question 22

Ideal gas model assumes u and h vary solely with

Answer 22

temperature

Question 23

dh = cp or cv * dT?

Answer 23

cp

Question 24

h =

Answer 24

u + pv

Question 25

Cp =

Answer 25

R+Cv

Question 26

3 main types of compressed air energy storage

Answer 26

Diabatic, advanced adiabatic, isothermal

Question 27

k for air =

Answer 27

1.4

Question 28

Isothermal expansion can deliver electrical energy without...

Answer 28

natural gas combustion for preheating

Question 29

High efficiency of flywheels is restricted by

Answer 29

storage time - only feasible in short periods

Question 30

Flywheels can be useful for supplying high ____ specialty needs

Answer 30

instantaneous power

Question 31

For a flywheel, doubling the mass doubles the force, but doubling the speed...

Answer 31

quadruples the force

Question 32

Depth of Dischage for a FW is

Answer 32

differnce between max KE (operating at highest speed) and minimum KE (operating at lowest speed)

Question 33

Liquid Air Energy Storage is also sometimes called

Answer 33

Cryogenic energy storage

Question 34

Nitrogen liquifies at about...

Answer 34

-196C

Question 35

For liquid air energy storage, the liquid is stored at ___ pressure

Answer 35

low

Question 36

The Linde-Hampson cycle is used to

Answer 36

liquify air

Question 37

The gas in a Linde-Hampson cycle is coolest when it leaves...

Answer 37

the expansion valve

Question 38

LAES generation scheme without _____ is considered too inefficient to be practical

Answer 38

additional energy input (slide 27)

Question 39

R134a is an example of an

Answer 39

Organic refrigerant

Question 40

For generation with LAES, __ and ___ cycles are 2 that could be added to boost net work

Answer 40

Cryogenic Organic Rankine and Cold Brayton

Question 41

The working fluid in an Organic Rankine cycle has a____

Answer 41

low boiling point

Question 42

Some advantages to LAES

Answer 42

Low upfront and lifetime costs, long lifetime, can be scales up, uses mature technologies, can be integrated with other industrial processes, not geographically restricted

Question 43

Disadvantages of LAES

Answer 43

Low round trip efficiency, safety risks, needs large scale to be efficient and cost effective

Question 44

Electricity, energy transfer, gasoline, etc are examples of

Answer 44

Secondary forms of energy

Question 45

Working Fluid for pumped thermal ES is often

Answer 45

Air or Argon

Question 46

Desrues and Howe are examples of

Answer 46

Cycles for Pumped Thermal energy storage

Question 47

A transcritical rankine cycle uses what as the working fluid

Answer 47

CO2

Question 48

In a transcritical power cycle, the working fluid is kept as a ___ during compression and as a ___ or as supercritical during expansion

Answer 48

liquid; vapor

Question 49

At the critical point on the phase diagram, the substance..

Answer 49

is indistinguishable from a liquid and a gas

Question 50

A saturation state is a state where...

Answer 50

a phase change begins or ends

Question 51

Curves bordering the vapor dome on a pvt chart are called

Answer 51

saturated vapor lines

Question 52

saturation temperature designates

Answer 52

the temp at which a phase change occurs at a specified pressure