Class 2: concepts and global picture Flashcards
(27 cards)
energy vs power
energy: ability to carry out work, measured in Joules
power: work done per unit of time, measured in Watts
Joules
1 Joule: energy needed to lift 100g by 1m
Watts
Joules per second
exergy vs anergy
exergy: energy that is actually usable
anergy: share of energy that cannot be transformed into work (i.e. gets lost as heat)
energy = exergy + anergy
different forms of energy
mechanical, chemical, thermal, nuclear, radiant (light), etc.
2 theorems of thermodynamics
1st: within a closed system, energy is not consumed, only transformed
2nd: within a closed system, over time entropy increases (energy is transformed into less usable/concentrated form of energy, e.g. thermal heat spreads until evenly distributed)
primary, secondary and tertiary energy
primary: fossil fuels, solar radiation, waves, wind, uranium, trees
secondary (primary but more processed): firewood, gasoline, electricity
tertiary (usable energy): light, heat, cold, mechanical energy
efficiency formula
ƞ = output/input = exergy/energy
Carnot efficien cy
ƞ Carnot = 1 - (T low / T high)
T is temperature in Kelvin, T low is usually environment’s room temperature
gives the highest theoretical possible efficiency
efficiency of different energy types
heat generation has very high efficiency because energy isn’t “lost” as heat (80-100%)
lightbulbs: 5%
fluorescent lights: 20%
diesel/gas engines: 25-50%
electric engines: 80-90%
what do kJ, CE, OE, and BTU stand for?
kilojoule, coal equivalent & oil equivalent (how much energy you get from 1kg of each), British thermal unit
10 to the power of 1, 2, 3, 6, 9, 12, 15 and 18
deca, hecto, kilo, mega, giga, tera, peta, exa
10 to the power of negative 1, 2, 3, 6, 9, 12, 15 and 18
deci, centi, milli, micro, nano, pico, femto, atto
globally most used energy sources yearly
oil, coal, natural gas (160 EJ each), bioenergy (wood, 60EJ), nuclear (30EJ), RES uncommon (15EJ all together)
what are different energy types used for?
oil for transport, mostly fossils for manufacturing, mix of RES and fossil fuels for heating/lighting
problem with “we use 50% renewables!”
input ratio could be 75/25 fossils/RES, whereas output is 50/50 (because RES are more efficient)
varies depending on what stage of energy flow you’re looking at
global energy efficiency
useful energy about 55 EJ, lost in conversion about 420 EJ
ƞ = 55/420 = 13%
Switzerland energy consumption, where electricity comes from
Still mostly fossil fuels overall (especially transport), but electricity very clean
electricity: 60% nuclear, 30% hydro, rest RES
when did different fossil fuels take off globally?
until industrialization: only biomass (wood)
industrialization after 1850: coal used for manufacturing
WW2: oil used for war transportation, lots of technologies developed
post WW2: oil for cars/trucks, international trade by planes/ships
when did nuclear and RES take off globally?
around 1970 started being used, but slow growth
which energy types’ shares of total consumption have declined/increased since 2000?
oil, coal and nuclear declining
natural gas and RES increasing
how does each region’s energy consumption look? (North/ South America, Europe, CIS, Asia Pacific, Middle East, Africa)
graph in word
North America: mostly oil and gas, some coal, 20% RES and nuclear
South America: most RES globally (about 1/3), lots of hydro
Europe: 70% fossils, most nuclear globally (10%)
CIS: almost 90% fossils, over 50% natural gas
Middle East: almost 100% fossils, about 50/50 oil & gas
Africa: 90% fossils, rest mostly hydro
Asia Pacific: most coal globally (50%), about 15% RES and nuclear
areas with highest/lowest energy use per person
highest: US, Canada, Saudi Arabia (then Russia, Australia)
lowest: Central African countries
where is coal/gas/oil production highest?
oil and gas: US, Middle East, Russia (then China, Brazil, Canada)
coal: China, then Russia, US, India, Australia
