2 Flashcards
2.0 First law of thermodynamics
Energy can neither be created nor destroyed, only converted.
2.1 Energy systems
Extraction and treatment, primary energy carriers,
conversion, secondary energy,
distribution, final energy,
end-use technology, useful energy,
energy services.
Energy supply system and energy demand system.
2.2 Units of energy
One joule = 1 kg m2 s-2, the energy needed to accelerate 1 kg from 0 to 1 meter per second.
Exajoule 10^18, PJ Petajoule 10^15, TJ
terajoule 10^12, GJ Gigajoule 10^9
2.3 Power, load factor, load duration curve
Watt. Energy = Power * time.
Load factor - annual output divided by max output.
Load duration curve.
2.4 Energy carriers
Substance that is predominently used as source of energy. Coal yes, potatoes no.
2.5 Energy content of energy carriers, a piece of coal, reference
For a piece of coal the chemical energy content is dominant, and kinetic, gravitational, and thermal components can be safely ignored.
Always determined in comparison with a reference state - the energy content is the amount of energy obtained by bringing from actual to reference state.
2.5a Energy content, reference states. 3
For chemical energy reference is the most stable naturally occurring compound, CO2, H2O.
For fuels, the energy of combustion reference 25 C and 1 atm.
For water and steam reference is 0.01 C.
2.5.b Energy content - from coal combustion
Coal, combustion, start with coal and oxygen from air, then combustion products brought back to reference conditions.
2.5.c Energy and enthalpy
Energy, under constant volume,, enthalpy under constant pressure.
H = U+ p*V.
Important for gasses.
2.6 Higher and lower heating value of fuels
Water vapour in the combustion can condense, giving up heat.
2.7 Energy use and energy consumption
In thermodynamics energy is not consumed. But the energy left after it no longer has economic value can be considered consumed.
2.8 Final energy use - how to calculate - subscripts
Final energy use = purchased energy - sold energy + own extraction + extraction from stock - input to conversion process + output from conversion process.
Joule subscripts.
2.9 Calculating primary energy use from final energy use
Substantial losses in conversion.
2.10 Energy balances and energy statistics. Abbreviations used.
Energy statistics - in original units, energy balances in J.
TPES total primary energy supplies.
TFC total final consumption.
TFC = TPES - input to conversion + output from conversion.
Non-energic use - vaxes, chemical industry.
IEA and GEA conventions
