Samenvatting - Introduction to Energy Analysis

• 1 Thermodynamics : The basis of energy analysis

• Describe the first law of thermodynamics?

  Energy can neither be created nor destroyed, but can only be converted from one form to the other (or from several forms combined to one or more other forms)
• what is energy analysis?

  Energy analysis is the study of energy use, energy production and energy conversion in society.
• Describe a number of energy number stages ? 

  Extraction    -> Conversion-> Transport->          End-Use              -> End-Use
                                                     Storage                 Conversion
                                                     Distribution
  
  Coal mining      refineries          Oil storage            Boilers                     Heating
  Wind turbines   power plants   electricity grids     combined heat       cooking
  natural gas                                 natural gas            and power               lighting
     production                                    transport            plants
• Energy exists in many forms. give some examples

  Kinetic energy
  potential energy
  chemical energy
  nuclear energy
  electromagnetic radiation
  electricity 
  heat 
• The energy content can be determined for a given substance. Give some examples 

  -an amount of coal
  -a certain volume of hot water
• The energy content is dependent on conditions like.. (give some examples)

  -pressure and temperature, and is always determined in comparison to a reference state.
• the energy content is then the amount of energy it takes to bring the substance from the reference state to the actual state. 
• in energy analysis, we generally use an environmental reference system, with the reference state for each chemical element the most stable naturally-occurring compound of that element. give some examples 

  carbon = CO2
  water = H20
• In practice, two slightly different concepts of energy content are used. which ones ?

  -(internal) energy 
  -enthalphy
• the change in internal energy of a substance is measured by ......

  adding (or removing) energy under constant volume
• the change in enthalphy is measured by.......

  adding (or removing) energy under constant pressure
• In practice enthalphy is usually used rather than the internal energy. Especially for solids and liquids, it is much easier to measure enthalphy, as measuring under constant pressure is easier than measuring under constant volume.
• The relation between internal energy E and enthalphy H is as follows:
  (geef de formule)

  H= E + p x V
  
  H=enthalphy
  E=internal energy (also often indicated with the letter U)
  p=pressure
  V=Volume
  
  for solids and liquids, the difference between H and E is very small, but for gases the difference cannot generally be neglected
• Describe the second law of thermodynamics?

  In simple words: "heat cannot be fully converted into work"
• describe the entropy concept (geef de formule)

  delta S = delta Q / T
  
  delta S = entropy change
  delta Q= heat extraction 
  T = Temperature
• calculate the amount of work that can be extracted from a thermal energy reservoir with constant temperature. (geef formule)

  W= Qh - Ql
  W=the amount of work delivered
  Qh=the heat extracted from the high temperature reservoir
  Ql= the heat added to the low temperature reservoir
  
  So the total entropy change of the process will be:
  
  delta S = Qh/T - Ql /Tref
  
  the second law says that the total of entropy changes in such a closed system is larger than or equal to zero. Now, let us first assume that we have an ideal process, where the entropy does not increase: delta S = 0.
  For ideal processes the following formula can be used:
  
  W= (1-Tref/T) x Qh
  
  we can conclude that for this ideal process, the maximum amount of work produced is always smaller than the heat extracted from the reservoir, which brings us back to our first formulation of the second law of thermodynamics.