M&V Solar Water Heating Guideline - Eskom

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
2 Establish how , when and how much and for what
purpose water is heating by electricity.
3 Establish the power in [kW] of the water heating device
and evaluate the energy/demand used.
The electrical water heating used at a low-cost
household is based on average figures and often on the
assumption that the water is heated by
standard/conventional electric kettle with an typical
installed power of 2 kW and a typical volume of 1.8
litres. The cold water temperature may wary by the
season and is taken as Tcold = 16 o C . The water is
heated until boil i.e. Thot = 96 o C (it assumed that the
kettle switches off automatically at that temperature).
The heating process efficiency ( ) is taken as 90%
which takes into account losses if the water is heated
not by kettle but by hot plate for example. The thermal
energy for each boil ( Ehw) is calculated by:
)
The corresponding electrical energy needed to produce
this thermal energy is :
4 Obtain information for electricity and water bills for
the household for crosschecking the information
above.
30
the actual number of people living
at the house might vary.
Urban households would use more
electricity than the rural ones.
1.This might be misleading since
the households use predominantly
prepaid electricity and when the
balance is negative the inhabitants
might use alternative means for
heating water.
2. It might be useful to assume that
all the water heated electrically in
a household is done by an
”equivalent electric kettle “(2 kW)
as it is in the majority of urban
households. This would simplify
the process of base line
development. Note that, the water
heated by the kettle for bathing,
washing and cooking is always
mixed with cold water in order to
meet the volume and temperature
needed.
This might be grossly misleading
since in most of the cases
inhabitants do not provide
accurate answers due to one
reason or another.
Note: An example for a typical house base line determination using interviews is given in section
10 below.
6.4.3 Using Base Line Measurements by Dedicated SWH data Loggers after
the Retrofit
The dedicated data loggers supplied by EA are shown in Figure 18 and 19.