Material, Energy, Exergy

Question 1

Formula and definition for Turnover time (tau0):

Answer 1

• tau0 = M/S
  M: mass in reservoir [kg]
  S: sink flux(es) [kg/s]
• Time to empty the reservoir (without filling it)
  (a system that is not in stady state has a constantly changing turnover time)

Question 2

Age of matter in reservoir:

Answer 2

• How long has a single particle been in the reservoir (until now)
• Avarage Age: tau_a

Question 3

Residence time in reservoir:

Answer 3

• The time a particle stayed in the reservoir T(ut) - T(in)
• Avarage residence time: tau_r
  (- in steady state: turnover time = residence time)

Question 4

Response time:

Answer 4

• The time for a system to adjust to a new equilibrium after a disturbance.
• tau_cycle
  (- usually untill you have something similar to equilibrium, different values are often given)

Question 5

Definition and value of revelle factor:

Answer 5

• The revellfactor is the factor betwwen the change of carbon amount in ocean surface and atmosphere.
• ~ 10% (9). (If ocean increase 1% atm. increase 10%)
  And it increase when carbon concentration in ocean increase.

Question 6

Definition and formula of energy quality:

Answer 6

• q: The posibility of an energy form to convert to another form. How much disequilibria is there?
• q = exergy/energy

Question 7

Definition exergy:

Answer 7

• (B) Maximal potential work from energy

Question 8

Definition Entropy:

Answer 8

• (S) Energy that goes to waste, natural breakdown.

When you reach equilibrium (Smax) There is no more Exergy left.

Question 9

1:st law of Thermodynamics:

Answer 9

• Energy is concerved and never broken down, only converted between different forms.

Question 10

2:nd law of Thermodynamics:

Answer 10

• The entropy S of a closed system can never decrease. (In real systems there are always irreversibal processes. Entropy will increase)

Question 11

How we use energy sources:

Answer 11

• Create chains of thermodynamic disequilibria
• Along the chain entropy is produced and exergy is destroyed, due to irreversibilities in non-ideal systems.
• Wherever there is disequilibria there is exergy.

Question 12

Formula for Exergy, max Work:

Answer 12

• W = Ein-Eout = (1-T0/Tin)*Ein Carnot factor!
  T0: temp of environment/sorounding
  Tout >= T0 (thermodynamic)

Question 13

Coefficient of performance (COP):

Answer 13

• (Verkningsgrad) benefit/cost
• Energy COP (etaE) = Eu/Ei
• Exergy COP (etaB) = Bu/Bi =
  = (Euqu)/(Eiqi) = etaE*(qu/qi)
• 0 < COP < 1