Case Studies

Client Profile

Landlord of large building in the Inner City of Johannesburg.

The Landlord renovated his building which was previously a hotel in which no water meters, and all pipes, and hot and cold ring mains supplying individual flats were concealed in inaccessible blind ducts.


Business Problem Statement

With the conversion to individualised rented units it became necessary to measure both hot and cold water consumption for each flat.

Technical Situation
Building
Stuttafords
  Storeys
  12
  Apartments
  324
  Persons
  972
Analysis of Energy Requirements

Water Heating
  No of Persons
  972

  Hot Water Per Person Per Day
   50
  litres
  Hot Water Temperature
  60
  deg C
  Avg Inlet Temperature Winter
  5
  deg C
  Temperature Rise Requirement
  55
  deg C
  Energy Requirement
  2 673 000
  kCal
  kCal to kWh Conversion
  1.16E-003

  Operational Hours per Day
  15

  Heat Pump Requirement
  79.7
  Kw

Winter
Summer

Boiler
Heat Pump
Boiler
Heat Pump
  Litres Demand / Day
  50000

  50000

  kCal Demand / Day




  kWh per day required
  3901
  993.6
  3601
  993.6
  kW Rating

  9.2

  9.2





  Annual Rand Saving
  R 506,825.28



  Two Year Rand Saving (12% Incr)
  R1 074,469.59



  Five Year Rand Saving (12% Incr)
  R3 219,783.64



  Annual kWh saved
  974664



Solution

Gas, Oil, Coal and other forms of direct heating all have comparable costs to direct heating by electricity the alternative that we are comparing against.

Solar heating was not considered because it is not feasible for high-rise apartments and in urban areas where there is insufficient area to provide adequate heat collection.

Heat pumps work by moving heat, in this case from hot molecules in the atmosphere to cold molecules inside the hot water supply using the same principles as a refrigerator. Moving heat is very much more efficient than generating it in the first place and savings of 50 to 60% are routinely achieved compared to direct heating by electricity.



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