Case Studies

Business Problem Statement

The case study refers to a small 3 storey apartment block in the Johannesburg area, used for social housing. The present boiler is outdated and needs to be replaced. At the same time, energy savings need to be implemented.


Technical Situation
Building

  Storeys
  3
  Apartments
  25
  Persons
  75
Analysis of Energy Requirements

Water Heating

Note that costs are illustrative, based on simple principles. When designing heat pumps, we use simulation models. These show appreciably greater savings than we have presented here.
  No of Persons
  75

  Hot Water Per Person Per Day
  50
  litres
  Hot Water Temperature
  55
  deg C
  Avg Inlet Temperature Winter
  8
  deg C
  Avg Inlet Temperature Summer
  20
  deg C
  Boiler Efficiency
  0.8

  kCal to kWh Conversion
  1.16E-003

  Operational Hours per Day
  15


Winter
Summer

Boiler
Heat Pump
Boiler
Heat Pump
  Litres Demand / Day
  3500

  3500

  kCal Demand / Day
  164500

  122500

  kWh per day required
  153
  69
  113
  46.02
  kW Rating
  10.2
  4.6
  10.2
  4.6

    (Usage in Summer is approx 2 / 3)
  Avg kWh saved daily
  75.49



  Annual kWh saved)
  27572.17



Solution

Any form of direct heating, whether Gas, Oil or Electric has a similar cost structure, and because electricity in South Africa is predominantly coal fired, all have a detrimental effect on the environment. Solar heating is not an option in this case, because of lack of area (3 storeys to support). Heat pumps operate on the principle of moving energy from hot molecules in the air to cold molecules in the water being heated this is a very much more efficient process than trying to speed up molecules in the water using a heating element.



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