energy units

8/10/2019 Energy Units

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Energy has its own vocabula


2/16

Energy and Power are of

used interchangeably, but th

mean slightly different thing


3/16

Energy: quantity

Ability to do work


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Energy Has Many Units

Scientific Units:

!Fuels:

!BTU = British Thermal Units

!Quad = 1 quadrillion (BTU)

!Joules (J, kJ, MJ,)

!Calories

!Electricity:

!kWh = kiloWatt-hour

!MWh = MegaWatt-hour

!GWh = GigaWatt-hour

Proxy Units:

!Volume: assumes a particular

volumetric energy density

!barrels of energy (boe),

!barrels of oil equivalent (boee),

!cubic feet,

!Mass: assumes a particular

gravimetric energy density

! tons of energy,

! tonnes of oil equivalent (toe),

!kg of energy (kgoe)


6/16

Power is a Rate of Energy

Power: work performed over a period of time

!Or energy produced over a period of time

!Or energy consumed over a period of time

!Its a rate not a quantity


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Power is a Rate of Energy

Units:

!Watt (W, kW, MW, GW,)

!Horsepower

kiloWatts of energy is nonsensical

Power density: W/m2

!Heat flux density, irradiance,


8/16

Energy = Power !Time

A light bulb consumes energy at a rate of

Its instantaneous power consumption is

After 1 hour, it has consumed 100 Wh or 0

After 10 hours, it has consumed 1 kWh

!Note: power consumption at a house is roughly 14 kW

!Note: a humans nominal power consumption is 100 W

de.wikipedia, original upload 26 Jun 2004

by de:Benutzer:KMJ


9/16

Energy = Power !Time

Example: A nuclear plant has a power capacity of 1 GW

!After 1 hour, generates 1 GWh of electricity

!After 1 year, generates 8,760 GWh of electricity

! NOTE: 8,760 hours per year

Converting from GWh to kWh

!1 GWh = 1 million kWh

!Total U.S. electricity in 2011: 4,000 billion kWh


10/16

There is a Difference Between

Primary and Secondary Energy

Primary energy:original/unconverted fuel sources

!petroleum

!natural gas

!coal

!biomass

!water, wind, solar,

Secondary energy:converted/stored en

!electricity

!hydrogen

!pumped hydroelectric


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Energy Notation

Scientific Prefix Multiplier English Roman Numerals

m = milli 1/1,000 thousandth

c = centi 1/100 hundredth

d = deci 1/10 tenth

da = deka 10 ten X

h = hecto 100 hundred C

k = kilo 1,000 thousand M

M = mega 1 x 106 million

G = giga 1 x 109 billion

T = tera 1 x 1012 trillion

P = peta 1 x 1015 quadrillion

E = exa 1 x 1018 quintillion


12/16

Energy Notation

MW = megaWatts = 1 million watts

MMBTU = million BTU = thousand, thousand BTU

MMBBLS = million blue barrels = thousand, thousand barrels

MMBD = million barrels per day = thousand, thousand barrels

!also sometimes noted mbd

!BOE = barrel of energy or barrel of oil equivalent

!MMBDOE = million barrels per day of oil equivalent (an amount of energy)


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We Have Some Fortunate Conversion

Natural Gas

The energy content of 1,000 SCF ofnatural gas is approximately 1 million BTU

!SCF = standard cubic foot

!MCF = thousand cubic feet (also mcf or Mcf or mil)

!1,028 BTU per cubic foot

!1,000 SCF = 1 MCF = 1.028 MMBTU

Price is often given in MCF or MMBTU

!The energy content is the same within 3%


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TonsA ton is about a tonne

English system:!Ton = dry ton = short ton = 2000 lbs

Metric/SI system:!Tonne = metric ton = metric tonne = MT = 1,000 kg

1 kg = 2.2 lbs1 metric ton = 1000 kg = 2200 lbs = 1.1 tons

1 metric ton = 1 tonne = 1.1 tons!Only wrong by 10%


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Large Scale Energy Units

An Exajoule and Quad are about the same

Metric/SI system:

!1 Exajoule (EJ) = 1 quintillion Joules = 1 1018J

English system:

!1 Quad = 1 quadrillion BTU = 1 1015BTU

1 EJ = 0.948 Quad

100 Quads = 105 EJ

!Accurate within ~5%


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Data Sources

Energy is highly politicizedpay attention to sources

Guide for evaluating sources

Sample authoritative sources

!Governmental agencies

!Industry and trade associations

!NGOs and watchdog groups

energy units

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