Solar Hot Water Systems and Challenges - PPT by Eric Hawkins at the SHW Workshop Feb 2018

1. SOLAR HOT WATER SYSTEMS
By Eric Hawkins

2. HOW DO SOLAR SYSTEMS WORK
New - For housing developments

3. TYPES OF SOLAR HOT WATER SYSTEMS
Active pumped split system Passive Thermo Siphon Thermal System

4. TYPES OF SOLAR HOT WATER SYSTEMS
Passive mains pressure system Active pumped open vented system

5. TYPES OF SOLAR HOT WATER SYSTEMS
Direct System

6. TYPES OF SOLAR HOT WATER SYSTEMS
Indirect Common Western Systems
Antifreeze Drain Back

7. ADVANTAGES AND DISADVANTAGES OF DIFFERENT
SOLAR HOT WATER SYSTEMS

8. CHALLENGES AFFECTING HOT WATER
SYSTEMS AROUND THE WORLD

9. EXAMPLES FROM CHINA
• Pictures taken in 2011 at the Government funded
Haining Test Centre, China
• Performance of 30 solar collectors were being
tested to gain certification

10. EXAMPLES FROM CHINA
In some cases, like the tank standing
outside in the rain on the left, nobody
knew how to connect it up.
In this specific case, this tank is not for
outside applications compared to the
right hand picture
Availability of nice looking products at
popular annual exhibitions in China
that attract overseas buyers, as well
as website images are common

11. MAIN AREAS OF FAILURE
Insulation tube was low quality rubber
NBR insulation (maximum 80c allowed)
No UV protection over the insulation tube
Where flexible stainless steel pipe was
used, it was rusting due to wrong quality
The use of galvanized steel pipe and
fittings must also be banned.
Many pipes were of the wrong diameter
which would have affected the flow rates
of water, causing over heating and
internal corrosion.

12. PERFORMANCE ISSUES
Every pipe fitting exposed to outside air
without insulation will affect the
performance of the delivery of hot water
to the end user, who was sold the
benefits of solar water heating.
If insulation tube is not UV protected, this
will begin to break down within a year
due to the heat of the sun.
Very few installers provide a visual
service once a year to check the system
still works as from day one.
It’s a cost to the buyer in higher energy
bills, not the installer.

13. PLUMBING STANDARDS RESPONSIBILITY
Plumbing standards for solar water
heating systems and the choice of the
pipe, fittings and insulation should not be
left to the installer to buy from general
local merchants, who stock many
materials for many different applications.
The responsibility for the correct
plumbing system for the choice of system
MUST always be from the selling
company for the system to be 100%
guaranteed..

14. SOLAR COLLECTORS – BEST PRACTICE
The performance of every solar collector
sold and installed in the world is only as
good as the plumbing system.
Its up to the seller of the system to make
sure the best materials are outsourced by
the seller and not by the contractor.
Installers who are left to complete an
installation at a set price will tend to focus
on low price for plumbing material parts
and compromise quality

15. SOME INSTALLATION FAILS
A Chinese collector installed in
Jordon with galvanized pipe and
no insulation but did not work
A Tsinghai mains pressure heat
pipe system in Spain, failed after
5 months, as did 20 others
Unless the plumbing components used in solar water heating installations are
suited to very high temperatures and compatible to each other, pipes sized
correctly, the system will fail over the short and long term.

16. PEX AL PEX PIPE – WHAT TO LOOK OUT FOR
Examples of the use of the Pex Al Pex
pipe
Low quality and short life insulation is an
identified problem
The installations had to all be replaced
after just 4 yrs.
A cost to the home owner

17. A TYPICAL CYPRUS THERMO SIPHON FLAT PLATE SYSTEM
This type of system, will start to become
less and less efficient due to the build up
of lime scale in the copper pipe
serpentine inside the collector.
The same water in the hot water tank, is
the same in the solar collectors with the
cold water storage tank above.
The closed loop system, with a white
expansion vessel, is the correct type

18. GALVANIZED FITTINGS OUTCOME
If galvanised fittings are used in any solar
water heating system installation, the
continued heating of cold water to hot
water will affect the flow of water through
the system to the hot water outlet.
The picture below is a steel/Pex al Pex
pipe fitting that has been cut to fit a brass
TEE and lever valve to connect to my
stainless steel flexible pipe to replace all
the failed parts of the system

19. INSTALLATIONS IN KENYA
• Looking closely at this
installed system, there is a
mix of different pipes, and
some are not insulated
• There is no UV protection
and the stainless steel pipe
not insulated
• Also placing evacuated
tubes at this low angle
reduces the performance
affect of the heat pipes

20. INSTALLATIONS IN KENYA
• The initial installation was
hot glycol line with PPR
• After a day the pipes had
burst and all the heating
fluid poured out.
• The stainless steel
insulated pipe for the
whole hot fluid system was
installed
• It is important to be aware
of the dangers in both the
short and long term
•

21. UNVENTED HOT WATER TANKS
• The use of PPR when hot
water tanks are unvented
and heated by heat pipes
in a closed loop system is
dangerous
• A closed loop system can
heat up as high as 200c.
• The red expansion vessel is
also the wrong type for
solarThe black insulated pipe is the cooler
water to the collector
The returning hotter water from
solar is without insulation. The
temperature drop before
hot water arrives.

22. INSTALLATIONS TIPS
• Solar water heating installations installed with insulated UV
protected pipe need to be done away with.
• If these systems are of a mains water pressure type, PPR
should also be avoided, as is not designed for use in solar
water heating.

23. QUALITY INSULATION
Even in the UK the sun and very
high temperatures from closed
loop pressurized systems can
destroy low quality insulation from
the inside and the outside.
It is important for both the owner,
the seller and the installer to
deliver value all round and use
quality materials.

24. HIGH PLUMBING STANDARDS
Outside a domestic solar water system installation in Jordan that
depicts high standards of plumbing

25. HIGH PLUMBING STANDARDS
The show house of a manufacturer of electric water heaters -
visited in China, depicting impressive plumbing installation

26. SOLAR HOT WATER – THE KENYAN CONTEXT
Discussion Groups:
• What SHW systems have you installed and how did you size
it? What would be best practice?
• What type of plumbing( valves/pipes /controllers/pumps )
have you put in place and is the system working well?
• How are you handling the water crisis in the country with
regards to your SHW system?
• What are the major challenges facing SHW systems in
Kenya?
• What do customers complain most about with regards to
SHW sytems and why?