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   Excess ventilation  evaluated  
Due to internal or external heat sources (passengers, lights, electrical equipment, sunshine through the windows) temperature inside coaches may rise beyond 20° C even for much lower outside temperatures. In this case the coach may be cooled by outside air through an excessive operation of ventilation. This saves energy for air-conditioning.
Technology field: Optimisation of comfort functions
close main section General information
  close sub-section Description
   

Without air-conditioning the inside temperature of passenger coaches would in many cases exceed outside temperature due to the following heat sources: human beings, lights and other electrical equipment, sunshine through the windows.

For an outside temperature of 12° C and a coach with 80 persons (~ 7 kW) and sun shining through the windows (~ 2 kW), 20° C inside temperature are reached without any additional heating.

If these heat sources cause overheating (> 20° C) of coach and outside temperature is still < 20° C, the coach may be cooled by outside air. For this purpose the air intake may even be increased to values beyond the necessary intake for ventilation. Such an excessive operation of ventilation may save energy air-conditioning. For comfort reasons there is however an upper limit for interior air flow and thus for maximum ventilation (UIC 553, EN 13129).

Excessive ventilation is usually an option for outside temperatures between 10 and 22° C depending on sunshine and occupancy.

close main section General criteria
  close sub-section Status of development: in use
    Excessive ventilation is currently being used in some trains at German DB AG and at Swiss SBB (double-decked IC2000).
  Time horizon for broad application: 2 - 5 years
    (no details available)
  Expected technological development: basically exploited
    There may be some improvement potential in the control algorithms of excessive ventilation.
    Motivation:
    Energy saving
  Benefits (other than environmental): none
    (no details available)
  Barriers: medium
   

Technological

A control algorithm for excessive ventilation is required. Ventilation equipment must allow for variable and excessive operation.

Passenger comfort

According to Swiss SBB there were initial problems with the system due to excessive air flow within the coach. This problem has been resolved in the meantime.

    Success factors:
    Combining this measure with other improvements of climatisation requiring an intelligent tool, e.g. a smoothened operation of coach climatisation (cf. IC 2000).
  Applicability for railway segments: high
    Type of traction:  electric - DC, electric - AC, diesel
    Type of transportation:  passenger - main lines, passenger - high speed, passenger - regional lines, passenger - suburban lines
    In principle, all passenger coaches may be equipped provided that technological conditions such as variable and excess operation of ventilation equipment are given.
    Grade of diffusion into railway markets:
  Diffusion into relevant segment of fleet: < 5%
  Share of newly purchased stock: < 20%
   

German DB AG: Excessive ventilation is a standard in all newly purchased passenger stock.

Swiss SBB: IC 2000.

  Market potential (railways): high
    Excessive ventilation is expected to become a standard in new stock in mid-term perspective.
    Example:
    Swiss IC 2000.
close main section Environmental criteria
  close sub-section Impacts on energy efficiency:
  Energy efficiency potential for single vehicle: < 2%
  Energy efficiency potential throughout fleet: < 1%
   

Energy savings result from the net effects of saved climatisation energy and higher energy demand of ventilation motors.

No quantitative data on energy savings realised is available.

The following calculation gives a rough estimate of the saving potential:

  • 20% of the total energy demand of a passenger train is due to comfort functions (mainly air-conditioning).
  • According to a rough estimate by a DB expert, cooling to make up for interior heat sources amounts to about one third of energy for air-conditioning.
  • Conditions for excessive ventilation (occupancy, sunlight, outside temperature) are only given in a certain time portion (presumably < 50%) of operation.
  • Excessive ventilation alone will in many cases not be sufficient to reach target temperature.

Taking these limitations into account, excessive ventilation will save < 2% of overall energy.

  Other environmental impacts: neutral
    (no details available)
close main section Economic criteria
  close sub-section Vehicle - fix costs: low
    (no details available)
  Vehicle - running costs: minor reduction
    (no details available)
  Infrastructure - fix costs: none
    (no details available)
  Infrastructure - running costs: unchanged
    (no details available)
  Scale effects: not applicable
    The programming of additional algorithms and implementation into air-conditioning will yield certain scale effects in large vehicle series.
  Amortisation: (no data)
    (no details available)
no data available Application outside railway sector (this technology is railway specific)
close main section Overall rating
  close sub-section Overall potential: promising
  Time horizon: short-term
    Cooling by excessive operation of coach ventilation is an effective means to reduce energy demand for air-conditioning. Barriers are medium for a retrofit and low for a dedicated solution in new stock. Energy efficiency is moderate. Economic details are not available, but profitability is expected to be promising.
References / Links:
Attachments:
Related projects:  Energy Management System of New Coaches
Contact persons:
 date created: 2002-10-09
 
© UIC - International Union of Railways 2003