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ECEN Renewable Energy > Midterm > Flashcards

Midterm Flashcards

1
Q

How much of the energy in burning coal reaches the consumer as electricity?

A

33%
Roughly the efficiency
causes: waste heat, transmission, Rankine cycle - thermodynamics, machine losses, generation losses/

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2
Q

Are losses higher in transmission or distribution systems?

A

Distribution
P_loss=i^2r
the transmission we use very high voltage which means a low current - preventing loss. Distribution lines have to use a lower voltage creating a higher current, thus higher loss.

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3
Q

Which state consumes the most energy?

A

Texas

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4
Q

What state produces the most coal?

A

Wyoming

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5
Q

What country produces the most coal?

A

China

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6
Q

What country generates the most electricity from nuclear power?

A

United States

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7
Q

What country generates the greatest share of its electricity from wind power

A

Denmark

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8
Q

Most of the energy we use originally came from?

A

The sun

- everything comes back to nuclear other than nuclear which relies on gravitational pull

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9
Q

primary energy

A

gross energy - before transmission into more useful forms like electricity

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10
Q

% of total energy utilized to produce electricity

A

38.1%

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11
Q

overall efficiency of electric power generation

A

37%

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12
Q

power units

A

watts (W) or kilowatts (kW - W/1000) or joules/second or ampere*volt

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13
Q

voltage

A

electrical potential - the energy (E) required to move a unit charge through an element

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14
Q

Electrical Energy (E)

A

the power multiplied by the time the power is used - usually measure in kWh.

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15
Q

AC

A

both current and voltage are sinusoidal waveforms

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16
Q

decarbonize the grid

A

electricity huge demand for energy, tech for other services.

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17
Q

green house gases

A

carbon (CO2)
Methane (CH4)
Nitrous oxide (N20)
Fluorinated gas (F-gas)

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18
Q

July 2021

A 
1.67F above 20th-century average - the last 7 July's have been the highest temperatures in history.  
Sea ice concentration
species extension 
increase temperatures
water supply
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19
Q

Top 3 CO2 emitting countires

what share of global co2 do they emit

A

China, US, EU

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20
Q

what percent of GHG emissions worldwide are from electricity and heat generation
what percent of US CO2 emissions are from the power sector?

A

global - 25%

US electricity 27%

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21
Q

US generation mix

A 
ng 40%
renewables 21%
coal 19%
nuclear 20%
other <1%
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22
Q

US electricity generation

A

renewable 17% (wind - 7.3%, hygro-6.6%, solar-1.8%, biomass 1.4%, geothermal 0.4%)
nuclear 20%
coal 23%
ng 38%

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23
Q

Electricity flow conversion losses

A

25.22

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24
Q

if the load is purely resistive

A

current and voltage are in phase and the product of voltage and current is positive or zero

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25
Q

if load is purely reactive

A

current and voltage at 90 degrees out of phase and for 2 quarter of each cycle, the product voltage and current is positive for the other 2 quarters

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26
Q

electricity loads can be

A

resistive (heaters)
inductive (motors)
capacitative (capacitors)

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27
Q

Active Power

A

The power that is dissipated in the resistance of the load

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28
Q

Reactive Power

A

Power that is exchanged between reactive components. Capacitors generate reactive power and inductors consume it.

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29
Q

Apparent power

A

Taken into account when designing and operating power systems, because although the current associated with reactive power does not work at the load, it still must be supplied by the power and source.

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30
Q

Frequency Control

A

Active Power Balance (System Wide)

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31
Q

Voltage control

A

reactive power balance (local)

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32
Q

Energy

A

Integration of power over time - what people want from a power system

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33
Q

Energy Units

A 
Joulse = 1 watt-second (J)
kWh = kilowatthour (3,6 x 10^6 J)
BTU = 1055 J or 1 MBTU = 0.292 MWh
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34
Q

US annual electric energy consumption is about

A

4000 TWh

1TWh = 10^12Wh=10^Mwh=10^3 GWh

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35
Q

Power in power systems

A

kW, MW - installed capacity
Capital investments to build power plants
plan and design

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36
Q

Energy in Power Systems

A

kWh, MW does the actual work

Recover investments by selling energy

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37
Q

Energy in Power Systems

A

kWh, MW does the actual work
Recover investments by selling energy
power capacity = peak demand

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38
Q

Conventional Power System

A
  1. Generation (source)
  2. Transmission Substaion
  3. Transmission System
  4. Distribution Substation
  5. Distribution System
  6. Customer (Loads)
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39
Q

3 synchronous grids

A

east, west, texas

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40
Q

3 largest power plants in the US

A

Grand Coulee - Washington - hydro - 6.8MW - 35.26%
Palo Verde - Arizona - nuclear - 3.9mw - 90.05%
West county - Flordia - NG-3.7MW - 60.40

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41
Q

PEAKER PLANT

A

LOWER CAPACITY FACTOR

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42
Q

NUCLEAR
CONTROL ROD
PLANTS

A 
FISSION
ABSORBS NEUTRONS-CONTROL THE REACTION
OVER 400 PLANTS OPERATING IN 30 COUNTRIES
URANIUM 235
Nuclear waste is a problem
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43
Q

NUCLEAR and Grid Intergration

A

extremely long start-up times and shut-down times (a week or more)
very little ramping
ultra-high minimum generation levels
large capacity plant - 90% of cap.

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44
Q

Nuclear in the US

A

61 plant and generate 20% of the nation’s electricity

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45
Q

Coal grid intergration

A

plants tend to have long start-up and shutdown times
-24 hours or more
slow ramping up and down
long min run times
high minimum generation levels
400 coal plants in US and generate 30% of nations electricity

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46
Q

Natural Gas: Steam

A

efficiency 32-35%

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47
Q

Nature Gas Turbine

A 
compressor - combustion system - turbine
historically peaker plants
start up and shut down faster
20-35% conversion effieicnt 
fuel flexiable
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48
Q

increase ng turbines

A

utilize waste heat - cogeneration plant (turbine +steam plant) combined cycle plant
run all the time

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49
Q

ng combined cycle plants

A

increase efficiency to 50-60%
startup time -2-4 hours
mid-range units

50
Q

gas power plants

A

open cycle gas turbines
combined cycle gas turbines - most effieicnt
internal combustion engines and steam turbines
high ramp rates
thermal efficiencies 20-60%

51
Q

gas in US

A

1793 plants-34% of nations electricity

52
Q

oil

A

similar to gas plants
peaker plants
most polluating
diesel in isalnds and remote

53
Q

conventional systems

A 
nuclear
natural gas
gas
oil
coal
54
Q

what is renewable energy

A

renewable energy is energy from sources that are naturally occurring replenishing but flow-limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time.

55
Q

hydropower turbines

A

francis - larger

pelton

56
Q

Hydropower

A

80-95%

6-10% US generation

57
Q

Geothermal

A

the heat from the earth’s core is used to heat water or another working fluid to turn an electricity generator turbine

baseload power - similar to nuclear and coal

58
Q

Geothermal Power Plants

A

Dry steam - simple -oldest - most efficient - 150 C or greater

Flash steam - most common - fluid temp 180 C

Binary Cycle - most recent development - temp as low as 57

secondary fluid with a much lower boiling point than water flash vaporizes

59
Q

Biomass

A

is organic material that comes from plants and animals, and it is a renewable source of energy.

Contains stored energy from the sun. Plants absorb the sun’s energy in a process called photosynthesis when biomass is burned. the chemical energy in biomass is released as heat. can be burned directly or converted to liquid biofuels or biogas that can be burned as fuel.

60
Q

Biomass types

A

wood and wood processing waste:
burned to heat buildings, to produce process heat in industry, and to generate electricity.

agricultural crops and waste materials:
burned as a fuel or converted to liquid biofuels

food, yard, and wood waste in the garbage:
burned to generate electricity in power plants or converted to biogas in landfills

animal manure and human sewage-converted to biogas which can be burned to fuel

61
Q

Biomass Power Generation

A

similar to fossil fuel power plants, fuel sources can be stored and used for electricity generation when needed.

Energy density of biomass is limited, mostly needs to be consumed locally. small plants.

usually combined heat and power (CHP) plants

power plant types - steam turbine, gas turbine, internal combustion engine

62
Q

Offshore wind pros and cons

A

pros: generally higher capacity factor
less visual impact
often closer to load centers
better correlation with load in some locations

cons: higher installation cost
maintenance issues

63
Q

Power in the wind equation

A

P = K0.5densityAV^3

V = wind speed
A = Swept Area
Density = Air density
K = Efficiency constant
0.45 efficiency for modern machines
64
Q

Wind axis types

A

the vertical and horizontal axis

65
Q

Wind Turbine Types

A

4 Types

66
Q

GHI

A

Global Horizontal Irradiance (GHI)

67
Q

Direct Normal Irradiance

A

(DNI)

68
Q

Solar Energy Technologies

A

Photovoltaic (light -> electricity)
Concentrated Solar Power (heat -> electricity)
Solar Heating (heat -> heat)
Solar Lighting (light -> light)

69
Q

Energy

A

ability to do work

70
Q

toe

A

ton of oil equivalent

71
Q

Exergy

A

energy content of an energy carrier is the max. amount of work that can be extracted from it

72
Q

heat rate

A

measures the amount of heat input in BTU’s per hour for each kilowatt-hour of electricity produced
mmBTU/MWh = BTU/kwh

the efficiency is 1/(BTU/KWH))

73
Q

Manufacturers typically provide the following operational data on PV panels:

A

the shortcircuit current, the open circuit voltage, the maximum power point current and voltage, the
temperature coefficients of short-circuit current and open circuit voltage, and the efficiency

74
Q

PV module in Series

A 
In a series PV module, the voltage drop across each individual solar cell adds up to the total
module voltage, whereas the current flow through each solar cell is the same and is equal to
the total module current:
75
Q

PV module in Parallel

A 
In a parallel PV module, the voltage drop across the cells remains constant and equal to the
total module voltage, whereas the current flowing through each individual solar cell, adds up
to the total module current
76
Q

run of river vs humped hydro

A

In the case of a hydroelectric dam, the potential energy of water is converted into
mechanical energy during the water fall, which is then converted into electric energy, while
in the case of a run-of-river plant, the kinetic energy of water flow is converted into
mechanical energy, which is then converted into electric energy. The energy that is
converted into mechanical energy is different for these two hydropower plants, and
consequently, the types of hydro turbines employed needs to be adequate and differs for
these two hydropower plant types.

77
Q

the typical capacity factor for hydro

A

30-40%

78
Q

typical efficiency for hydro

A

80-95% effiency

79
Q

wind blade materials

A

strong and light - fiberglass for max amount of energy + hold up in high wind speeds

80
Q

the vertical and horizontal axis

A

the horizontal axis has a higher efficiency, reach higher and more consistent wind speeds, typically 3 blades.

vertical axis needs more support

81
Q

parts of a horizontal axis

A

Tower, nacelle + gear box, rotor blade.

82
Q

how does a wind turbine produce eletricity

A

kinetic energy (wind) is captured by the blades which turn due to their profile (lift) which creates thrust through the sweep of the blades which turns a shaft into kinetic energy to a generator to electricity

83
Q

Pitch in wind turbine

A

a wind turbine can move in 2 directions: deals with the blades can also be called feathering, shifts the angle to capture more or less energy. why capture less? to high wind speed

84
Q

Yaw in wind turbine

A

a wind turbine can move in 2 directions: the gear box turning generally to capture the most wind. Yaw drive rotates the gearbox.

85
Q

changes in wind turbine design

A

higher hub height
larger rotor diameter
higher capacity factor averaging around 40 or above

86
Q

type 1 and 2 wind turbines

A

limited operating - they want to operate at a fixed speed. Bad power quality and low capacity factor.

does not provide reactive power to grid pf = 1

87
Q

1st law of thermo

A

energy cannot be created or destroyed but can only convert from one form to another

88
Q

746 W

A

1 hp

89
Q

m2 to ft2

A

m2 * 10.7 = ft2

90
Q

what are power electronics

A

semi-conductor devices used for power conversion

91
Q

dioide

A

controls the flow of current in one direction

92
Q

transistor operations

A

control and switch speeds

93
Q

4 basic topologies for power electronics

bridge the gap

A 
rectifier = AC to DC
Inverter = DC to AC
Converter = DC to DC
Cycloconverter = AC to AC
94
Q

is it adequate for an inverter to just create a steady sinusoidal waveform (60hz) in order to interface with the power system?

A

No, relative phase, between the interfacing device and point of interconnection, dictates power export.

power equiv, sin(phase angle)

95
Q

3-phase grid-following power electronic converter

A

changes the ouput for the phase angle difference
adjust the sinusoidal voltage at the connection point
it maps the generation output (solar/wind) to the grid signal
this is historically created by a synchronous convertor.

96
Q

maintaining ____ is one of the fundamental drivers of power system reaila

A

system frequency.
frequncy is global-transmisson
voltage 0local - distribtuin

97
Q

unit commitment

A

which generation sources will be on

98
Q

synchronous machine convertors (generators)

A

large mass electromagetically coupled to AC system - embeds interia in power system

protection system - such as protection against overcurrent

99
Q

are inverters the only type (4 basic types) of power electronics devices used for integrating renewables?

A

rectifiers may be used in type 3 and 4 turbines

dc/dc converters -charge controllers (manage output voltage)

100
Q

resistive loads

A 
PF = 1
requires only real power
incandaescent light bulbs
kettles
irons
electric water heater
101
Q

partially reactive loads

A

the wave offsets require the supply of reactive power
washing machine
refrigerator
freezers

102
Q

importance of reactive power

A

provides voltage control to ensure proper operations.
voltage control is important for preventing damage to generators and motors. reducing line voltage.
Preventing voltage collapse (more load than voltage can support) local

103
Q

Reactive power sinks

A

transformers - reactive losses
shunt reactors
overhead AC lines
Load

104
Q

Reactive power sources

A

shunt capacitors
underground AC lines (high capacitance)
overhead AC lines (light loading)
capacitance exceeds reactive due to impedajce

105
Q

vertical integrated

A

control transmission, generation, distribution

106
Q

Reactive power sources

A

shunt capacitors
underground AC lines (high capacitance)
overhead AC lines (light loading)
capacitance exceeds reactive due to impedance

107
Q

Investor-owned utilities (IOUs)

A

privately owned and publicly traded stocks. can be vertically integrated or participate in electricity markets

108
Q

Federally owned utilities

A

produced power at facilities run by federal entities

109
Q

Public owned utilities

A

state and local government agencies which may generate power but are mostly distribution utilities

110
Q

Rural electric cooperatives

A

owned by groups of residents

111
Q

Independent Power Producers and merchant Power pants

A

privately owned entities that generate power
do not operate transmission or distribution networks
IPPS- have prenegotiated contracts with customers. Specified by a power purchase agreement (PPAs).

Merchants do not have predined customers and sell power in wholesale electricity markets

about 40% of electricity in the US is generated by IPPs and merchant power plants.

112
Q

RTO

A

RUNS TRANSMISSION GRID IN AREA MAY OVERLAP WITH ISO WITH OPERATES A MARKET/
SUPPLY MEETS DEMAND

113
Q

m to ft

A

m*3.28 = ft

114
Q

gallon to m3

A

gall*0.0037=m3

115
Q

gallon to m3

A

gall/264=m3

116
Q

transformer

A

v_s/v_p = N_s/N_p

117
Q

cells in series

A

voltage is summed

current same throughout the module

118
Q

cells in par

A

voltdrop is same

current is summed

119
Q

ISO VS RTO

A

Both provide transmission and reliabilty however and RTO does not have a market.

BA’s are the smallest.

120
Q

btu to kwh

A

btu/3412 = kwh

ECEN Renewable Energy (2 decks)

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