M&V Solar Water Heating Guideline - Eskom

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Corporate Services Division
Assurance and Forensic Department
Contracted the Tshwane University of Technology to execute this
project
Measurement and Verification Standard Guideline for
Low Pressure Solar Water Heating Systems
Project Name: Measurement and Verification Guideline
Project Number: N/A
Report Type: M&V Guideline document
Reporting Period: N/A
Report Issue Date: 06 th March 2011
Report number: PM/M&V/TUT/2011-03-01
Revision number: v1r1
1

Compiled by:
Authorized by:
Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
……………………………………………
Prof. O.D. Dintchev
M&V Team leader
Tshwane University of Technology
Mr. G.S. Donev
M&V Team Member
Tshwane University of Technology
…………… ……………
Prof. O.D. Dintchev (CEM, CMVP)
2
M&V Team leader
Tshwane University of Technology
Submitted to: Corporate Services Division
Assurance and Forensic Department
Eskom
Copyright in this report is reserved. No publication or dissemination of its contents is
allowed without written permission.
Date: 06-03-11
Date: 06-03-11

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
EXECUTIVE SUMMARY
This document presents a standard guideline for Measurement and Verification for Low
Pressure Solar Water Heating Systems, and the application thereof in the context of Eskom’s
energy efficiency and demand-side management programme (EEDSM).
The Guideline is based on the review of essential topics related to the technology and
associated Measurement and Verification (M&V).
This document overviews the main solar water heating programmes based on the Low
Pressure Solar Water Heating Systems. The basic features of the solar water heating
technologies are considered in order to allow better understanding of the physical process
and their relation to the performance of the technologies in typical designs for South African
Conditions. The climate conditions in South Africa and the solar energy potential of the
country are reviewed.
Performance tests done by the South African Bureau of Standards (SABS) are reviewed and
their reported results are linked to the M&V work. Examples are shown to illustrate how to
allocate the parameters that are needed for the M&V process.
The document reviews the Retrofit and Green Field projects and recommends that the Low
Pressure Solar Water Heating Systems Projects will be considered as Retrofit projects since
prior to the retrofit there is a presence of electrical water heating process (although, by not
through dedicated electric water heater) at the project site.
Baseline process is presented and associated metering and other alternative procedures
leading to the baseline development are given in the document. Results from prior research
at the energy related issues at low-cost housing are presented. Examples and data from
energy audits are included based on the experience of the developers in similar projects.
For the determination of the energy savings, Option A is proposed as a suitable M&V
solution. The procedure is developed and the possible options are given with typical
examples.
The document answers the main M&V question related to Low Pressure Solar Water
Heating Systems, namely: “What is the thermal output of the systems and how it is related
to the base line determined?” This is done by the development of a performance model
based on SABS test results, geographical location of installation and hot water consumption.
The model outputs are properly used to evaluate, quantify and report the energy savings at
M&V process.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
DB Distribution board
Nomenclature
EEDSM Energy efficiency and demand-side management
MW Megawatts
kW Kilowatts
LPSWH Low Pressure Solar water Heating Systems
kWh Kilowatt hours
M&V Measurement and Verification
MWh Megawatt hours
M&V Measurement and Verification
MD Maximum Demand
ADMD After diversity maximum demand
MVA Mega volt ampere
kW Kilowatts
TOU Time of Use
ESCO Energy Service Company
SWH Solar Water Heating
SABS South African Bureau of Standards
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Table of Contents
1 INTRODUCTION ................................................................................................................... 7
2 OVERVIEW OF SOLAR WATER HEATING PROGRAMMES ....................................................... 7
2.1 Background ...................................................................................................................... 7
2.1.1 National Solar Water Heating Programme Launch .................................................. 7
2.1.2 Low Pressure Solar Water Heater Roll-out ............................................................... 7
3 OVERVIEW OF RESIDENTIAL SOLAR WATER HEATING TECHNOLOGIES ................................ 8
3.1 General ............................................................................................................................ 8
3.2 Solar Collectors ................................................................................................................ 8
3.2.1 Main Types of Collectors Used in South Africa ........................................................ 8
3.2.2 Collector Orientation ................................................................................................ 9
3.3 Influence of the Local Climatic Conditions on the SWH System Performance ............. 12
3.3.1 Climatic Zones in South Africa ................................................................................ 12
3.3.2 Evaluation of LPSWHS in respect of Installation Site Location and Climatic
/Seasonal variations ......................................................................................................... 14
3.4 High Pressure and Low Pressure Solar Water Heaters ................................................. 14
3.4.1 High Pressure Solar Water Heaters ........................................................................ 14
3.4.2 Low Pressure Solar Water Heaters ......................................................................... 15
4 Low Pressure Solar Water Heating Systems as Retrofit projects or Greenfield Projects17
4.1 Retrofit projects ............................................................................................................ 17
4.2 Greenfield Projects ........................................................................................................ 17
4.3 Low Pressure Solar Water Heating Systems as Retrofit Projects ............................... 17
5 Testing of Low Pressure Solar Water Heating Systems. .................................................... 17
5.1 Tests by South African Bureau of Standards (SABS) .................................................... 18
5.2 Essential Information from SABS Test Reports Used to Determine the Performance of
the Low Pressure Solar Water Heating Systems ................................................................ 18
5.2.1 Examples based on extracts from a typical SABS Test Report Performed on
LPSWHSs ........................................................................................................................... 19
5.3 Accuracy and Errors of the Tests at SABS ..................................................................... 22
6 Baseline of low pressure solar water heating projects ........................................................ 22
6.1 Typical Site Description ................................................................................................. 22
6.2 Electricity Usage Patterns in Low-cost Housing Environment ....................................... 24
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
6.2.1 Installed Electrical Appliances at a Typical Low-cost House .................................. 24
6.2.2 Electricity Usage / Load Profiles at Low-cost Housing Environment ..................... 25
6.3 Installation of Dedicated M&V Equipment at Project Sites .......................................... 28
6.4 Base Line Methodology ................................................................................................. 29
6.4.1 Base Line Main M&V Question .............................................................................. 29
6.4.2 Interviews with the inhabitants .............................................................................. 29
6.4.3 Using Base Line Measurements by Dedicated SWH data Loggers after the
Retrofit .............................................................................................................................. 30
6.4.4 Measurements of the Electrical Energy Prior and after Retrofit at the Household
.......................................................................................................................................... 31
6.4.5 Recommendations for Baseline Procedure ............................................................ 32
7 Determination of the Savings .............................................................................................. 32
7.1 M&V RECOMMENDED OPTION ............................................................................................. 33
7.2 MAIN M&V QUESTION FOR DETERMINATION OF THE SAVINGS RESULTING FROM LOW PRESSURE
SOLAR WATER HEATING SYSTEMS ................................................................................................ 33
7.2.1 Scenario 1: Baseline energy in [kWh] is less or at least equal to the retrofit
(LPSWH system) energy output in [kWh] ......................................................................... 33
7.2.2 Scenario 2: Baseline energy in [kWh] is higher or at least equal to the retrofit
(LPSWH system) energy output in [kWh] ......................................................................... 34
7.2.3 Examples to illustrate the energy savings .............................................................. 34
8 Thermal Performance Model of Low Pressure Solar Water Heating Systems .................. 35
9 SUMMARY ............................................................................................................................ 36
10 A Worked Example for Development of the base Line AND DETERMINATION OF THE
ENERGY SAVINGS of a lpswh project ....................................................................................... 37
11 REFERENCES ....................................................................................................................... 44
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
The Measurement and Verification Standard Guideline for
Low Pressure Solar Water Heating Systems
1 INTRODUCTION
The purpose of this document is to facilitate M&V teams involved in ESKOM’s EEDSM
projects in quantifying and reporting of the energy savings resulting from ESKOM Low
Pressure Solar Water Heating Programme.
2 OVERVIEW OF SOLAR WATER HEATING PROGRAMMES
2.1 Background
2.1.1 National Solar Water Heating Programme Launch
The South African Government has set a target for renewable energy to contribute 10 000
GWh of total energy consumption by 2013. Solar water heating could contribute up to 23%
towards this target.[1]
The Government has the ambition of installing one-million solar water heaters across South
Africa by 2014, and is aiming at creating the best policy and legislative environment for this
to be achieved. [2]
To actively encourage and promote the widespread implementation of solar water heating,
Eskom has rolled out a large-scale solar water heating rebate programme.[1]
2.1.2 Low Pressure Solar Water Heater Roll-out
Eskom has partnered with government and local municipalities in certain areas of
South Africa to provide free Low Pressure Solar Water Heaters (LPSWH) to needy
households. Local authorities will determine which households will get priority, in most
instances priority will be given to:
• Low cost houses that are connected to the electricity network
• Low income households
• Permanent built brick structures
Solar water heaters can replace electric geysers and other inefficient methods of
heating water (electric stoves, kettles, and gas and paraffin burners). As water
heating accounts for most of the average household’s use electricity, this roll-out will really
help households to save on electricity costs. This programme forms part of Eskom’s overall
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
strategy of encouraging and assisting all sectors of South African society to reduce electricity
use and to relieve pressure on the electricity network. [1]
3 OVERVIEW OF RESIDENTIAL SOLAR WATER HEATING
TECHNOLOGIES
3.1 General
A conventional Solar Water Heating System operation is based on the physical
phenomenon known as natural convection or thermo siphon effect. This effect manifests in
circulating the water (or other designated heath transfer fluid) through the solar collector
and hot water storage tank. It is essential that the hot water storage tank is positioned
above the solar collector to use the natural flow of the water being heated. As water in the
collector heats, it becomes lighter and naturally rises into the tank above, thus creating a
circulation flow between collector and hot water storage tank.
To eliminate the dependence of the position of the storage tank and to increase the rate of
circulation /heat transfer a forced circulation may be employed, thus allowing the hot water
storage tank to be placed in a convenient place at the house.
3.2 Solar Collectors
3.2.1 Main Types of Collectors Used in South Africa
To obtain maximum utilisation of the solar irradiation various collectors are in use. The
collector performance characteristics are shown in Figure 1. and illustrate the efficiencies
of the main three types solar collectors use presently in South Africa, namely:
standard non selective-coated flat-plate collectors
selective coated flat-plate collectors
evacuated glass tube collectors.
From the graphs shown in Figure 1, it is evident that the different collectors should be used
for different purposes, namely:
The tested non-selective coated flat-plate glazed collectors perform poorly at high
operating temperatures. Their normal operational temperatures are in the limits of
30 – 80 o C, heat loss coefficient is above 5 W/m 2 .K, and optical efficiency of 0.8; thus
the applications for these collectors are limited for domestic hot water.
The tested selective coated flat-plate glazed collectors perform well at high
operating temperatures. Their normal operational temperatures are in the limits of
40 – 90 o C, heat loss coefficient is above 3 W/m 2 .K, and optical efficiency of 0.80.
Thus the applications of this collectors is extended for domestic and commercial hot
water large systems. The higher operational temperatures allow reducing the size
of the collector when compared with non-selective coated collectors.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
The tested evacuated tubes collectors have high operating temperatures, namely
between 90 – 130 o C, heat loss coefficient is above 2 W/m 2 .K, and optical efficiency
of 0.65. These collectors are ideal for space cooling and heating and for process
heat.
Figure 1:. Collector Output Efficiency Curves measured for several types of solar collectors
available in South Africa as a function of (Tm – Ta ) where: Tm - average collector
temperature and Ta - ambient temperature. Source [3]
Low Pressure Solar Water Heater Roll-out as supported by ESKOM and the South African
Government, initially will be based on mainly imported SWH systems [2]. According to the
Energy Minister Ms. Dipuo Peters on the opening of the one of the first roll-outs at
Winterveldt (Tshwane) , “the units installed there were imported, as would be the case with
the first 200 000 units installed through the programme, as the country gears up its
manufacturing capacity towards SWH” [2]. The SWH units installed at Winterfeldt were
based on evacuated tubes collectors and should perform as shown in Figure 1. One could
expect that the rest of systems installed initially will be similar.[5]
3.2.2 Collector Orientation
To achieve maximum performance of the SWH system the collector should be facing ideally
in the equator i.e. in the North direction in South Africa. Roofs and houses position toward
North does not always allow this rule to be observed. Deviations from North up to 45 0 will
reduce the solar harvesting insignificantly (less than 10%). This is illustrated on the chart
shown in Figure 2., where positioning of a house is shown. The size of the suns pointed at
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
the installation angle symbolizes the harvesting potential of the solar collector at different
angle of deviation from the North.
Figure 2: Orientation of the house’s roof for potential SWH system installation in respect to
the North direction
Prior to the installation of the collector, a study should be performed on the particular
household to determine the profile of the hot water usage. If the bulk of the hot water to be
used is between 10 a.m. and 2 p.m. the orientation of the collector should be North-East
(NE). If the hot water is to be used after 2 p.m. the collector should be orientated in North
West (NW) direction allowing longer harvesting of the solar energy during the afternoon
hours. The orientation of the collector(s) in the above conditions is shown in Figure 3 to
Figure 5.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 3: Collector (s) orientation toward North-preferable positioning
Figure 4: Collector (s) orientation toward North-East. Collector output is reduced slightly
(less than 10%). Applicable when roof does not allow North orientation of the collector.
Apply it when the bulk of the hot water is used before 2:00p.m.
Figure 5: Collector (s) orientation toward North-West Collector output is reduced slightly
(less than 10%). Applicable when roof does not allow North orientation of the collector.
Apply it when the bulk of the hot water is used after 2:00p.m.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
3.3 Influence of the Local Climatic Conditions on the SWH System
Performance
3.3.1 Climatic Zones in South Africa
The performance of any SWH system is influenced in a great deal by the geographic location
of the installation site and it is extremely seasonal. Thus, the actual installation site will be a
dominant factor in the system thermal performance and related energy savings from the
retrofit.
The average annual solar energy potential per day is shown in Figure 6 and 7. It is evident
that the South African solar potential could be simplified if the country is divided into six
regions according to the availability of solar incoming energy as presented in Figure 8.
Obviously, the same type of SWH system will perform differently if it is installed on different
climatic regions.
Figure 6: Southern Africa average annual solar energy potential per day in [ kWh/m 2 ]
Source [8]
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 7: Southern Africa average annual incoming solar power potential per day
in [ kW/m 2 ] Source [8]
Figure 8: South Africa’s solar energy radiation zones
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
3.3.2 Evaluation of LPSWHS in respect of Installation Site Location and
Climatic /Seasonal variations
In order to evaluate the LPSWHS performance and to report it for each month of the year, a
monthly assessment of the energy (hot water) output is necessary.
This Guideline employs a weather simulation software Meteonorm ®. The software
simulates the weather information for the different locations in South Africa and generates
the necessary hourly profiles for the incoming solar radiation, ambient temperature for each
day of the year. This information is incorporated into the Performance Model (PM) of the
LPSWHS and the its performance is evaluated and reported as per ESKOM EA’s
requirements.
3.4 High Pressure and Low Pressure Solar Water Heaters
Essentially, high and low-pressure solar water heating systems have a similar design and
work on the same principles. However, the differences between the two are the pressures
under which they operate in their normal cycle.
3.4.1 High Pressure Solar Water Heaters
High-pressure SWH are connected directly to the consumer’s water supply (mains) thus
developing a very high internal tank pressure (in the region of 600kpa). This pressure is the
main force that drives the water through the pipes resulting in high water pressure and
flow from the taps, thus providing the desired hot water service level. In South Africa, as a
rule the high-pressure SWH systems have an electric back-up element. A schematic basic
drawing illustrating the operation of a High-pressure indirect thermo siphon SWH system is
shown in Figure 9.
A high-pressure system is required to be equipped with a number of protection and safety
equipment in compliancy of the following standards SANS 60335-2-21 part2 (Electrical
requirements), SANS198 (Functional control and safety valves for pressurized hot & cold
water supply systems) & SANS 0254 The installation of fixed electric storage heating systems
and SANS0142 code of practice the wiring of premises. [5]
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 8: Principle of operation of a High-pressure indirect thermo siphon SWH system
3.4.2 Low Pressure Solar Water Heaters
Low-pressure solar water heating systems in contrast to the High-pressure SWHs cannot
tolerate the high pressures associated with their high-pressure counterparts and therefore
have to be connected indirectly to the water supply through an additional system such as
auxiliary (small) tanks that avoids the pressure rise in their main hot water storage tank.
Basically, only limited pressure builds up in the low-pressure SWHs systems. Low-pressure
solar water heating systems utilize the gravity to supply water through the piping system
resulting in lower water pressures and associated low flows from the hot water outlets
(taps). The principle of operation of a system employing an evacuate d tube solar collector
is shown in Figure 10 and Figure 11.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 10: Principle of operation of a LPSWS employing an evacuate d tube solar collector
Figure 11: LPSWS employing evacuated tubes solar collector
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Low pressure SWH systems can be equipped with an electric back-up element in a similar
manner as the High-pressure SWH systems. However, for the purposes of this Guideline
which serves ESKOM’s Low Pressure Solar Water Heater Roll-out Programme the Lowpressure
SWHs will be considered without any electrics back-element.
4 LOW PRESSURE SOLAR WATER HEATING SYSTEMS AS
RETROFIT PROJECTS OR AS GREENFIELD PROJECTS
4.1 Retrofit projects
These Projects are based on existing systems that are already in operation,
and are either replaced with more energy efficient ones or operated in an altered
fashion to deliver DSM impacts. The systems exist prior to the EEDSM intervention and
allow for baseline metering [9].
4.2 Greenfield Projects
Greenfield Projects (also referred to as new construction projects) deals with systems that
are not in operation at time of the EEDSM proposal [9].
The proposed energy conservation measures for the DSM programme are consequently
integrated into the design and construction of new systems. The systems do not exist to
allow for baseline metering. [9]
Thus, the fundamental difference between the M&V of Retrofit and Greenfield projects is
related to the system baseline that is used as a reference point from which project impacts
are determined.[9]
4.3 Low Pressure Solar Water Heating Systems as Retrofit Projects
Low Pressure Solar Water Heating EEDSM Projects could fall into the scope of the
Greenfield Projects since the LPSWHS (or similar dedicated water heating unit ) did not exist
before the retrofit . However, due to the M&V fundamental reporting methodology
applicable the EEDSM projects, the projects are to be classified as Retrofit Projects. The
main reason for this is the fact that prior the Retrofit, the projects had a base line
determined by taking into account ONLY the electrical energy used for heating of water at
the households prior the retrofit.
5 TESTING OF LOW PRESSURE SOLAR WATER HEATING
SYSTEMS.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
5.1 Tests by South African Bureau of Standards (SABS)
The Required Tests in Compliance with the relevant South African Standards for
Supplying and Installing Solar Water Heater Systems in ESKOM’s SWH Program are given
in Table 1.
Table 1: Compulsory Tests in Compliance with South African Standards for Supplying
and Installing Solar Water Heater Systems. Source ESKOM EA Package to M&V
Teams.
No SANS Number Description/ Title
1 SANS 1307:2008 (SABS 1307) Residential solar water heaters
2
SANS 6210:1992
(SABS SM 1210)
3 SANS 6211-1: (or part 2) 2003
4 SANS 60335-2-21: 2000
Residential solar water heaters - Mechanical qualification
tests
Residential solar water heaters Part 1: Thermal performance
using an outdoor test method (part 2 is an indoor test method)
Safety of household and similar electrical appliances - Safety
Part 1: General requirements
5 SANS 151: 2002 Fixed Electrical storage water heaters
6 SANS 10106: 2008
7 SANS 10252-1:2004 Water drainage for buildings
Note: SANS 60335 is compulsory under the building regulations at present
The installation, maintenance, repair and replacement of
domestic solar water heating systems
5.2 Essential Information from SABS Test Reports Used to Determine the
Performance of the Low Pressure Solar Water Heating Systems
The results from the tests according to SANS 6211-1: (or part 2) 2003 are essential for
evaluating of the thermal performance of the SWH systems.
This Guideline aims to develop a performance evaluation model which uses the main SWH
system parameters experimentally determined by the SABS tests as shown in Table 2.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Table 2: Essential parameters extracted from SABS Test Report
No
Parameter determined by Test
Report according to: SANS 6211-
1: (or part 2) 2003
19
Symbol
Coefficient 1 m 2
Units
1
2 Coefficient 2 MJ/K
3 Coefficient 3 MJ
4 Heat capacity of the tank Cs MJ/K
5 Heat loss coefficient Us W/K
6. Q-factor / value Q MJ
Value as
per SABS
Test Report
5.2.1 Examples based on extracts from a typical SABS Test Report Performed
on LPSWHSs
The following figures below show extracts from a SABS report and illustrate how to
identify and select the important parameters needed to evaluate the thermal performance
of the LPSWH systems. Note that, SABS is changing some of the conditions for the testing
(for example for Q-factor/value) and the reports may differ from system to system.

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Based on the above extracts from SABS test report, for this particular LPSWH system Table 2
can be completed as shown in Table 3.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Table 3: Example of Essential parameters extracted form SABS Test Report for a typical
LPSWHS
No
Parameter determined by Test
Report according to: SANS 6211-
1: (or part 2) 2003
22
Symbol
Units
Value as
per SABS
Test Report
Coefficient 1 m 2 0.625150588
1
2 Coefficient 2 MJ/K -0.034373641
3 Coefficient 3 MJ 2.114795133
4 Heat capacity of the tank Cs MJ/K 307798.3
5 Heat loss coefficient Us W/K 0.482
6. Q-factor/value Q MJ 11.773
5.3 Accuracy and Errors of the Tests at SABS
As evident from the extracts from the SABS test reports the standard error when
determining the LPSWH system coefficients is high (often more than the value of the
coefficient itself). However, the M&V process will consider that these tests are justifiable
since they are the corner stone for participation in ESKOM’s and Government SWH
Programmes [1] and [2].
6 BASELINE OF LOW PRESSURE SOLAR WATER HEATING
PROJECTS
6.1 Typical Site Description
The LPSWHSs typically fall out in the rollout Programmes launched to the
undeveloped communities. A typical such a site is shown in Figure 12.

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 12: Typical installation site foe LPSWH Systems
The living environment and the underdeveloped infrastructure make the installation and
more over the safety for the M&V equipment and personnel very difficult. Individuals should
therefore take the necessary care to avoid any incidences and/or damage to property.
Electrical connections in the low-cost houses might be very unconventional and unsafe as
evident from Figure 13.
Figure 13: Electrical Installations at RDP Houses pose hazards for the inhabitants of the
houses and M&V teams.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
6.2 Electricity Usage Patterns in Low-cost Housing Environment
6.2.1 Installed Electrical Appliances at a Typical Low-cost House
Some typical electrical devices used in low-cost houses are shown in Figure 14.
Figure 14. Typical low cost housing electrical appliances. Source [10]
An audit [11] conducted in low-cost housing environment showed the following appliances
and associated installed power as per Table 4.
Table 4. Installed Power in a Typical Low-cost House . Source [[11]
No
Appliance
Installed Power
1 Fridge 133
2 Kettle 1980
3 Hot Plate 850
4 TV 51
5 DVD player 22
6 Iron 1100
7 Fan 150
8 Space Heater 1500
W
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
9 Incandescent lamps 600
10 Total Installed Power 6386
6.2.2 Electricity Usage and Load Profiles at Low-cost Housing Environment
An end of winter, load profile in a low-cost housing environment (corresponding to Table 4
above) is shown in Figure 15.
Figure 15. Electrical Load Profile and Inside and Outside House Temperatures. Source [11].
As seen from Figure 15, the load profile shown there contents electric water heating
components in the morning, noon and evening.
The load profile of the same house is shown in Figure 16, after the house was supplied with
thermal ceiling insulation, solar water heating, solar cooker and LPG gas cooker.
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Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 16: Electrical Load Profile and Inside and Outside House Temperatures after the
house was a subject of a sustainable “ makeover” where all major electrical appliances
were replaced by sustainable alternatives. Source [11].
From Figure 16 is evident that the electrical energy consumption for this particular house
was reduced and the electricity is used for refrigeration, lighting and entertaining purposes
only.
Another study [10] investigated the Electrical energy consumption in a typical low-cost
house and the results are shown in Table 5.
Table 5. Installed Power and Electrical energy consumption in a typical low-cost house.
Source[10]
Appliance Qty
CFL lights
Incandescent
Lights
TV
Kettle
Rated
Power
Operating
Hours per
Day
26
kWh per
Day
Days
kWh per
Month
3 16 6 0.288 30 8.64
2 60 6 0.72 30 21.6
1 80 4 0.32 30 9.6
1 2000 1 2 30 60

Hotplate
Iron
Fridge
TOTAL
Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
1 850 2 1.7 30 51
1 1000 1 1 30 30
1 150 16 2.4 30 72
4156 36 8.428 252.84
From Table 5 is evident the eclectic energy used for water heating is about 2 kWh a day.
Several energy audits were made by the authors of this Guideline and the results of
auditing of 582 low-cost (RDP) houses are shown in Table 6 and Table 7.
Table 6. Audits of Electrical Water Heating usage (before retrofit) and Solar Water Heating
Usage (after retrofit) at 582 houses at Tshwane area.
Houses Solar Water
Heating Litres
582.00
83
53
154
179
113
Litres
Electric Water Heating up to the Boiling Point
Morning Noon Evening
Litres
27
Litres Litres
5 436.70 726.10 244.40 565.85
3 492.30 450.60 230.80 371.90
10 803.88 1 466.30 318.20 1 004.81
11 922.70 1 264.40 565.90 946.90
9 907.48 1 188.80 190.66 641.80
Totals
41 563.06 5 096.20 1 549.96 3 531.26
Total Litres Electrical Water
10 177.42
Heating at Boiling Point
Average Consumption per House in Litres
71.41 17.49
The results from Table 6 are used to determine the average electrical energy used to heat
the water at the houses and the findings are summarised in Table 7.

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Table 7. Average Hot water usage heated by electricity at an average low-costs household
Hot Water Usage by
Electricity Heating.
Total Houses
interviewed 582
Litres heated
at 96 o C
Energy
Used
l kWh
28
T C Thot Tcold Efficiency
of heating
o K kWh/kg.K
o C
o C %
17.49 1.81 80 0.001167 96 16 90
From the results and deliberations in sections 6.2.1 and 6.2.2. above, is evident that the
average daily usage of hot water heated by electricity up to the boiling point could be
summarised as follows:
Volume of hot water in litres……………………………………………………………..17.49 l
Electrical energy usage to boil this volume of water……………………………1.81 kWh
6.3 Installation of Dedicated M&V Equipment at Project Sites
Examples of data loggers installations are shown in Figures 17 and 18.
Figure 17: Installation of dedicated SWH Data Logger at a RDP House

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 18: Complete Installation of a dedicated SWH Data Logger at a RDP House
6.4 Base Line Methodology
As elaborated in Section 3.3. above the LPSWH systems will be treated as Retrofit Projects,
thus the system (electric water heating at the houses) physically exist and can consequently
be measured and monitored before it is altered by the EEDSM project (the installation of
the LPSWHs). Thus, the base line is determined on the basis of hot water usage heated by
ELECTRICITY ONLY i.e. what the grid would “see”.
6.4.1 Base Line Main M&V Question
The main M&V question when dealing with LPSWH projects is to identify the electricity
consumption and its time of use to heat water prior the retrofit. This may be achieved by
the following ways:
By interviews with the inhabitants
By dedicated SWH measurements after the retrofit
By measurements of the electricity prior and after retrofit.
6.4.2 Interviews with the inhabitants
This method provides information on the following activities as summarised in Table 8.
Table 8: Possible Information obtained by interviews by the occupants of the households.
No Information Obtained Remarks
1 Number of people living in the house (their profile:
gender, age, working , unemployed, culture etc.)
29
Often people are giving misleading
and inconsistent information. Also

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.

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 19: SWH Data Logger
The measurements obtained by the data loggers installed after the retrofit do not provide
correct information about base line hot water usage. The amount of hot water used after
and before the retrofit is not the same. However, they could be used to determine the
performance assessment evaluation.
6.4.4 Measurements of the Electrical Energy prior and after Retrofit at the
Household
The most appropriate way is to measure the savings and determine the base line is to
measure the electrical energy and determine the base line in combination with the
interview as described in Section 5.3.2. above.
Simple and inexpensive data loggers and CTs as shown in Figure 20 and Figure 21 could be
used to measure the current at the household and thus to determine the savings in a way
that the grid can “see” them. This will allow a precise measurements of time of use for
electrical water heating appliances.
Figure 20: A Current Transformer (CT) and its connection to a Data Logger is installed at a
DB in a Low-cost House to determine the base line and energy savings by the retrofit.
31

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 21: A Hobo Data Logger installed at a DB in a Low-cost House to determine the base
line and energy savings by the retrofit.
It should be noted that, the field measurements after the retrofit will be misleading when
taken after the installations of the LPSWHs. This is due to the fact that the households could
use the electricity for other applications such as : refrigeration, entertainment etc.(in the
same manner as in the CFL rollouts) and the fact that some hot water usages has been
replaced by the LPSWH. On the other hand people get used to utilize hot water for different
applications after the retrofit.
6.4.5 Recommendations for Baseline Procedure
The following methodology is recommended as a Standard Guideline for Baseline
development for Low Pressure Solar Water Heating Systems:
Perform interviews and fill the information as required in Fieldworker Form [6]. A
typical form is shown at the worked example shown in Section 10.
Identify representative houses in terms of number and profile of occupants and
install data loggers (if and where appropriate ) to measure the electricity
consumption prior the retrofit.
Determine electrical energy and find out the time of its use for water heating,
based on the information obtain above .
7 DETERMINATION OF THE SAVINGS
32

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
7.1 M&V RECOMMENDED OPTION
Option A [5] [6] is recommended as a Standard Guideline for determination of the savings
resulting from implementation Low Pressure Solar Water Heating Systems.
Option A recommends Retrofit Isolation: Key Parameter Measurement Savings are
determined by field measurement of the key performance parameter(s) which is the
current (power) and which define the energy use of the household under consideration.
Parameters not selected for field measurement are estimated. These are the inputs to all
the engineering calculations based on the interviews leading to determination the amount
of electrically heated hot water used by the household.
7.2 MAIN M&V QUESTION FOR DETERMINATION OF THE SAVINGS RESULTING FROM LOW
PRESSURE SOLAR WATER HEATING SYSTEMS
The Baseline is determined as: energy kWh and power W at its time of use, the amount of
hot water in terms of volume (litres) and temperature ( o C). It is more convenient to use as a
volume the amount of water mixed (heated water by electricity with cold water). This allow
to have a realistic figure for the amount of hot water usage. This is explained in details in the
worked example at Section 10 below.
The base line should be compared with the thermal output in [kWh] of the Low Pressure
Solar Water Heating Systems during the month of consideration. Thus the main M&V
question on which the M&V practitioner should report is : “ Can or cannot the LPSWH
system offset the energy in kWh which was determined as a baseline”?
There are two possible scenarios to report the savings.
7.2.1 Scenario 1: Baseline energy in [kWh] is less or at least equal to the
retrofit (LPSWH system) energy output in [kWh]
The maximum value of the energy savings that grid would “see” is the value of the baseline
as per equation (1) :
where:
the grid “sees”
when ...............(1)
- is the energy in [kWh] saved and produced by the LPSWH system and which
33

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
-is the energy in [kWh] prior the retrofit
-is the thermal energy in [kWh] produced by the retrofit (LPSWH system)
In this case there might be excess of energy which is not to be reported as energy savings
resulting from the retrofit , but should reported separately .
7.2.2 Scenario 2: Baseline energy in [kWh] is higher or at least equal to the
retrofit (LPSWH system) energy output in [kWh]
The value of the energy savings that grid would “see” is the value of the retrofit energy
output as per equation (2) :
when ...............(2)
7.2.3 Examples to illustrate the energy savings
Example: Consider a house which has an average monthly base line determined as
2.05 kWh per day. The months under consideration are February and July. The
house is supplied by a Low Pressure Solar Water Heating system which has average
monthly thermal outputs for these months of 4.13 kWh /day and 1.29 kWh/day
respectively. Determine the savings which the grid would “see” for these months.
Solution:
(a) Savings for the month of February
Use the Scenario 1 and apply the equation (1)
ESAVINGS = 2.05 kWh to be reported in the M&V reports. The project performs 100 % .
In addition there will excess of energy not to be reported Eexess = 4.13 – 2.05 = 2.07 kWh
(b) Savings for the month of July
Use the Scenario 2 and apply the equation (2)
ESAVINGS = 1.29 kWh to be reported in the M&V reports
The Project is underperforming by 0.76 kWh ( 0.76= 2.05 – 1.29)
34

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
8 THERMAL PERFORMANCE MODEL OF LOW PRESSURE SOLAR
WATER HEATING SYSTEMS
As seen in section 6.2. above to quantify the energy savings, the thermal performance of
the LPSWH system need to be determined. The model is based on the relevant standards
such as SANS 1307 and ISO 9459 [5 ] [7 ]. Note that the model thermal outputs will be
seasonal and dependant on the installation location and its accuracy is based on the
parameters determined by the SABS test.
The model inputs and outputs are shown in Figure 22.
Figure 22: Thermal Performance Model
An example from the model run for a particular LPSWH system is shown in Figure 23.
35

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 23. Example of the Thermal Model run for a typical LPSWH system
9 SUMMARY
From the deliberations above the following findings could be summarised as a Standard
Guideline for Low Pressure Solar Water Heating Systems.
The LPSWH system Project should be considered as Retrofit Projects not as Green
Field Projects
M&V Option: Option A is suggested which recommends Retrofit Isolation: Key
Parameter Measurement Savings are determined by field measurement of the key
performance parameter(s) which is the current (power) and which define the
energy use of the household (s) under consideration.
Base Line determination: the energy used for electrical water heating of a
household(s) is determined by : interviews, field measurements. Also the volume
and the temperature of the hot water usage is identified.
Energy saving determination is based on modelling of LPSWH system(s). The model
uses as inputs: the parameters determined by test report by SABS, the installation
location, the hot water usage and the day/ month under consideration. The model
outputs are: hourly, daily, monthly thermal output in [kWh] of the LPSWH system
and the temperature hot water produced.
It is possible that in addition to the energy savings reported to be an excess of
energy produced by the retrofit. This energy will be reported separately and will not
be part of the savings that grid would “see”.
36

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
10 A WORKED EXAMPLE FOR DEVELOPMENT OF THE BASE LINE
AND DETERMINATION OF THE ENERGY SAVINGS OF A LPSWH
PROJECT
The example below illustrates the process of quantifying of hot water usage when
determining a Baseline prior installation of a LPSWH system at a typical low-cost household
having four to five occupants. The LPSWH system and its specifications and SABS Reports
findings are shown in Table 3 in Section 5.2.1. above. A photo of a typical LPSWH used for
the example is shown in Figure 15.
Hot Water Consumption and associated energy determination
Table 9 below is populated from the results on the audits done for the particular house. The
audit is based on the field worker form filled by the M&V team. A sample form is shown at
the end of this example.
Table 9: Example for Baseline calculations
The process used in this example is based on the assumption that the hot water used by
this particular household is heated by an “equivalent kettle” of 2 kW and capacity of 1.8
litres. The water heated by the kettle for bathing, washing and cooking is mixed with cold
water in order to meet the volume needed. Also the water usage for tea, coffee or cooking
is ignored since it will be heated at the same rate by electricity after the installation of
LPSWHs.
Hot Water Usage by
Electricity
Litres Actual Energy T C Thot Tcold Efficiency
Litres Used
of heating
l l kWh o
K kWh/kg.K o
C
o
C %
MORNING 14.4 10.8 1.12 80 0.001167 96 16 90
Morning cooking
tea/coffee
Morning bath/sanitation
(average 4 persons X 1.8 l
each)
1.8 0 0.00 80
37
0.001167 96 16 90
7.2 7.2 0.75 80 0.001167 96 16 90
Morning washing (1 X 1.8 l) 1.8 1.8 0.19 80 0.001167 96 16 90
Cooking (just hot water) 1.8 0 0.00 80 0.001167 96 16 90
Others (babies, minor
washings etc.)
1.8 1.8 0.19 80 0.001167 96 16 90
LUNCH 3.6 1.8 0.19 80 0.001167 96 16 90
Lunch dishes washings 1.8 1.8 0.19 80 0.001167 96 16 90

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Lunch tea 1.8 0 0.00 80 0.001167 96 16 90
EVENING 9 7.2 0.75 80 0.001167 96 16 90
Evening cooking 1.8 0 0.00 80 0.001167 96 16 90
Evening bath /sanitation 3.6 3.6 0.37 80 0.001167 96 16 90
Evening dishes washing 1.8 1.8 0.19 80 0.001167 96 16 90
Others 1 x 1.8 l 1.8 1.8 0.19 80 0.001167 96 16 90
Total per day 27 19.8 2.05 Total Baseline energy is 2.05 kWh
Mixing of Hot Water
The hot water of each kettle is mixed with cold water in a ratio of say 1:4 in order to be
usable for bathing , washing etc. This process is illustrated in Figures 24 and 25.
}
1 Kettle
Hot Water
1.8 l at 96 o C
}
4 Kettles
Cold Water
4 x 1.8 =7.2 l
at 16 o C
Figure 24: Mixing of hot water boiled by a kettle with cold water in ration 1:4 for further
usage by the household.
38
}
1 Bucket
Mixed Water
5 x 1.8 = 9 l
at 33.78 o C

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
11 11 11
} 19.8
l
at 96 o C
Figure 25: Mixing of hot water boiled by all kettles with cold water in ration 1:4 for further
usage by the household. The Base Line or entire hot water consumption by the household
per day is determined as: 99 litres at 33.78 o C.
The calculation of the mixed hot water temperature is based on the equations from Table 8
(row 3).
The results are shown in Table 10.
}
79.2 l
at 16 o C
Running of the LPSWH Thermal Performance Model
To determine the performance of the LPSWH system against the Base Line the performance
model should be run.
The inputs are as shown in Figure 26. The month under consideration is February. This
month is chosen as a typical month for high performance of the SWH system. The model
outputs are reflected in Table 10.
39
99 l
At 33.78 o C

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 26: Thermal Performance Model for the month of February
To illustrate a low performance for the SWH system the month of July is used. The model
outputs for the month of July are shown in Figure 27, and then the results are reflected in
Table 10.
Figure 27: Thermal Performance Model for the month of July.
The Yearly Thermal Performance Model Report is shown in Figure 28 and then the results
are reflected in Table 10.
40

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Figure 28: Yearly Thermal Performance Model Report
Table 10. Hot Water Usage Profile and Thermal Performance Model Comparison
Hot Water (1 kettle) at 96 o C
Litres of Cold Water at 16 o C
( 4 kettles x 1.8 l) mixed with
1kettle x 1.8 l (hot water at 96 o C)
Litres per a
kettle
41
Litres total Used
a day
1.80 19.80
Kettles used
per day
11
7.20 79.20 44
Base Line
Mixed Water total litres Base
Line (used as an input to the
Thermal Performance Model)
99.00
Temperature of the mixed water
Base Line
Electrical Energy used Base Line
33.60
[kWh]
2.05
Performance
February July
Annually *
( per 365 Days)
Model output per month [ kWh] 115.60 40.10 1184.81

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
Model output per day [ kWh ] 4.13 1.29 3.246
Model output hot water [ o C ] 59.65 39.11 52.1682
Energy Balance as compared with
the Base Line [ kWh ]
2.07 -0.76 1.19
Status of Performance
over
performing underperforming
over
performing
Monthly Energy Savings [ kWh ]
Energy Savings
2.05 1.29 2.05
*Note: The annual performance is given for reference only. The savings are reported
on monthly basis.
Savings Determination
The savings are determined as comparison between the Base Line [kWh] and the
performance [kWh] as verified by the Model for the months of February and July and are
given in Table 5 above.
Field Worker Form (sample)
A typical such a form is shown below in Figure 29.
42

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
No Place:
1.
2.
3.
4.
5.
6.
7.
House Number
Solar Water Heating System Type
(tank Capacity Litres..................................................... )
Roof / SWH System Orientation
Estimate the angle of deviation of the collector axis from
the NORTH Direction
Number of people living in the house
Estimate the amount of hot water in litres per day which is
used at the household NOW after installation of the SWH
Systems
How the water was heated before the installation of the
SWH Systems?
How much is the monthly water bill of the household?
One Kettle = 1.8 Litres , One bucket = 20 Litres K-kettle S-stove
Figure 29. Typical Field Worker Form
43
N S E W
NE
NW
SE
Adults working M F
Adults Pensioners M F
Children older than
6 years M F
Children younger
than 6 years M F
For bathing (sanitation)
total household
For cooking
For washing
Electricity Litres:
Paraphine Litres:
Gas Litres:
Firewood Litres:
Other Litres:
Rand
Electrical Water Heating up to BOILING Point heated by Kettle (K) or Stove (S)
morning morning morning midday evening evening evening
Off peak standard peak standard peak standard Off peak
00:00-06:00 06:00-07:00 07:00-10:00 10:00-18:00 18:00-20:00 20:00-22:00 22:00-00:00
Litres Litres Litres Litres Litres Litres Litres
K S K S K S K S K S K S K S
SW

Measurement and Verification Standard Guideline for Low Pressure Solar Water Heating Systems v1r1
11 REFERENCES
[1]Eskom Solar Water Heating Programme
http://www.eskomidm.co.za/residential/residential-technologies/solar-water-heatingprogramme-overview
[2] Department of Energy http://www.energy.gov.za/files/swh_overview2.html
[3] Dintchev OD Report to SANERI: INVESTIGATING THE BENEFITS OF DEVELOPMENT OF
TECHNOLOGY FOR HIGH-PERFORMANCE SELECTIVE-COATED SOLAR WATER HEATING
COLLECTORS December 2009
[4] René Coetzee, Christo van der Merwe , LJ Grobler :THE MEASUREMENT AND
VERIFICATION GUIDELINE: SOLAR WATER HEATING , July, 2007
[5] SATS 50010:2010 Measurement and Verification of Energy Savings South African
Standard
[6] International Performance Measurement and Verification Protocol Concepts and
Options for Determining Energy and Water Savings Volume 1, September 2010 Prepared
by Efficiency Valuation Organization www.evo-world.org
[7] International Standard ISO 9459 Solar Water Heating-Domestic Water Heating
Systems-Part 3: Performance tests for solar plus supplementary systems.
[8] Solar Maps at http://www.solarfeedintariff.net/aficamap.html
[9] Measurement and Verification Guideline for Greenfield DSM Projects, Version 2, 26
March 2008
[10] M.F. Manganye ,Prof O.D. Dintchev THE IMPACT OF SOLAR WATER HEATING
TECHNOLOGY IN LOW COST HOUSING ENVIRONMENT AS ONE OF THE RENEWAL ENERGY
OPTION TO REDUCE THE LOAD ON THE NATIONAL GRID Presented and published at the
proceedings of the DUEE International Conference , 2009, Cape Town, South Africa.
[11] Ognyan Dintchev, Georgie Donev, Adisa Jimoh GREEN LOW-COST HOUSES
MAKEOVER AS A MAJOR PHASE TOWARDS SUSTAINABLE DEVELOPMENT IN SOUTH
AFRICA Presented and published at the proceedings of the NORTH CAROLINA A & T STATE
UNIVERSITY FIRST INTERNATIONAL CONFERENCE ON GREEN AND SUSTAINABLE
TECHNOLOGY 17-19 November 2010 at GREENSBORO, NORTH CAROLINA, USA.
44