SOLAR HOT WATER IN KENYA
Many countries are installing solar hot water systems
AUSTRALIA. NewSouthWales and
Queensland. Electric hot water cylinders cannot be used in new
houses. Solar hot water systems with gas backup if required.
India more solar hot water
Spain Solar
units everywhere
USA Tax credits up to 30% for solar equipment including labour .
ISRAEL Solar hot water
units on every rooftop.
UK All homeowners can
install solar electricity panels or solar hot water panels or
windmills without needing to get planning permission, as long as
there is clearly no impact on others.
GERMANY Germany added an extra 20.6 gigawatts of solar power and solar hot water enough to supply the needs for 5 million homes. 45,000 new jobs have been created in the solar sector. Good progress towards their target of 20 percent renewable by 2020.
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Solar hot water in Kenya
Kenya has regulations regarding solar hot water for all new houses using more than 100 litres of hot water per day.
There are two main types of solar collectors.
(A) Flat panel collectors. These are a flat panel of copper with a number of copper pipes brazed to the flat panel. Size is around one meter by two meters When faced to the sun the flat panel heats water in the copper pipes which then moves into a hot water insulated storage cylinder. These flat plate collectors have been used for years. They perform well but can develop leaks because every day there is expansion and contraction of the pipes and the collector panel The flat panel collector only heats water when the sun is shining. Scale from hard water can block the copper pipes.
(B) Solar glass tubes. These are glass tubes made from very tough
glass and have a vacuum inside. The tubes collect heat from the
sun and can heat water even on an overcast day and keep the water
hot for many hours. Tubes for houses are 1.8 meters long and 58
mm in diameter. The number of tubes usually starts from 10 tubes
up to 30 tubes but can be many more tubes for one installation if
more hot water is required. Solar glass tubes can be of several
types which may be full of water or have no water inside them.
These solar glass tubes are outstanding technology and used all
around the world.
There are two main types of glass tube solar hot water units available
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Integrated (all in one) or split unit. (panel + cylinder)
INTEGRATED
SOLAR UNIT
NUMBER ONE LOW COST
SOLAR HOT WATER UNIT
A low cost unit 
using THERMOSYPHON TUBES, not suitable for
connection to household hot water cylinder. Not suitable for
freezing areas. This basic no frills model is not very expensive
and used by the millions in every hot country. These units have
solar tubes full of water. They are made in huge numbers for hot
climates Africa, Middle east, Malasia, Indonesia, China to
collect hot water during the day and use at night.
Prices start at 50 US dollars for a unit with 100 litres of water
and 10 solar tubes with a stand ex China.
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SPLIT SYSTEM
Second main solar type is the Split system with separate hot water cylinder using HEAT PIPE tubes. Pumped system
There is no water in the heat pipe tubes. They collect heat and use a heat pipe to put heat into a manifiold which conducts heat into the hot water cylinder which is inside the house.
Ok for areas with frost.
This solar hot water
type is where the collector assembly is on the roof
(or on the ground ) and the hot water pumped to your hot water
cylinder
The split system using heat pipe tubes is a well developed solar
hot water installation used all over the world and is a simple
and reliable system to heat water with very few problems
The collector must be installed at an angle of between 25 degrees and 90 degrees to the horizontal to make the heat pipes work.
For roof fitting a
permit from your council may be required. Usually there is a fee
for roof mounting. On steep roof safety 
precautions should be taken. You
do not need to put a split system on your roof . You can use the
stand usually provided and mount the collector on the ground or
on posts. You need a pump and a controller and one or two
temperature sensors. Manufacturers say these tubes work down to
minus 20 degrees centigrade. The tubes are dry there is no water
in them and you can remove tubes to reduce Summer overheating.
The system still works with some tubes removed.
These systems need a pump to move the hot water from the solar
collector to the hot water cylinder. The pump can be run from
house electricity or a small solar panel.
It will work at mains water pressure or low pressure
Heat pipe tubes is used all around the world and are a very well
established solar hot water technology. It is a robust and simple
system that works very well.
Prices start at US $250
ex China which includes 12 tube solar collector with heat pipe
tubes and includes the 200 litre hot water cylinder which has
back up electric element in case there is not enough solar energy
to bring the hot water temperature up to 60 degrees centigrade
every day to avoid legionaires disease.
SOLAR HOT
WATER TUBES.
Glass tube diameters are usually 58mm diameter and 1.8meter long.
(A) THERMOSYPHON tubes ... Water inside the tube
(B) Heat
pipe tubes
................... No water in the tube
THERMOSYPHON WATER
FILLED TUBES
Water filled collector tubes are good and efficient at collecting
solar heat and are cheap
The tubes are cold to the touch
Being filled with water they can freeze.
If a tube breaks all the hot water in the cylinder pours out and
a new tube must be fitted. These tubes are not suitable for
freezing conditions.
DRY HEAT PIPE TUBES
Tubes are dry there is no water in the tubes.
Tubes do not leak. Tubes are cold on the outside. They are easy
to put tubes in or take them out. If a tube breaks the hot water
in the cylinder does not pour out
If a tube breaks there is no dangerous chemicals that leak out.
Manufacturers say they are ok down to minus 20 degrees centigrade
so good for area with frost
If a tube breaks very very unlikely unless caused by misuse the
solar unit continues to function no hot water spills out
You can remove tubes if the solar unit is overheating in a very
hot climate.
Dry HEAT PIPE tubes are
used all over the world. They are dry tubes they do not contain
hot water and almost nothing can go wrong with them.
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In addition to being very good to collect sunshine to make solar hot water these glass solar tubes are very good to cook food
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PROBLEMS
The stand stainless
steel bolts rust. Put some grease on them or replace
Painted steel stands rust. Treat the rusty parts with a rust
converter and paint.
Stainless steel stands rust. Not much but some.
Richard Williams
remp@ps.gen.nz