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Aside from cost and greenhouse gas emissions
savings, the beauty of a solar hot water
panel system is its relative simplicity and
durability!
There are two types of collectors used in a
solar hot water service:
flat plate collectors (suitable where tank
roof mounting is required)
evacuated tubes (great for frost prone
areas)
Flat plate solar collectors
Flat plate collectors work on copper pipes
running through a glass covered collector,
often connected to a water storage tank on
the roof. The hot water can then
thermo-siphon itself in and out of the tank,
thus heating the water.
Evacuated tube solar collectors
Evacuated tubes use a glass tube with a
vacuum inside it and copper pipes running
through the centre. The copper pipes are all
connected to a common manifold which is then
connected to a slow flow circulation pump
which pumps water to a storage tank below,
thus heating the hot water during the day.
The hot water can be used at night or the
next day due to the insulation of the tank.
The evacuation tube system are superior as
they can extract the heat out of the air on
a humid day and don't need direct sunlight.
Due to the vacuum inside the glass tube, the
total efficiency in all areas is higher and
there's better performance when the sun is
not at an optimum angle - such as when it's
early in the morning or in the late
afternoon.
The water tank and thermal mixing
As heat rises, the hot water delivered to
the tank from the solar collector is drawn
from the top for use in the house. As the
temperature of the water may exceed 60
degrees Celsius/140 degrees Fahrenheit (a
requirement to kill bacteria), in order to
ensure a safe temperature at the taps, a
tempering valve will reduce the temperature
to around 45 degrees Celsius/113 degrees
Fahrenheit.
Electricity and gas boosters
While the sun can provide sufficient energy
to provide you with plenty of hot water for
most of the year, there may be extended
periods of cloudy, cold days where your
system will need a helping hand. This is
provided with an electricity boosted or gas
booster system.
Boosting using a tankless gas water heater
is the most efficient boosting method as
boosting only occurs when hot water is used.
With an electric system, the tank is heated
as soon as the internal temperature drops.
Retrofitting for solar hot water
If your current hot water system has plenty
of serviceable life left or you've recently
purchases a gas/electric hot water system,
you can still go solar with a retrofit kit!
Hot water and household energy usage
Electric and gas hot water systems
accounting for approximately 20% of a
household's greenhouse gas emissions. By
installing a solar water system you will
reduce these emissions and also save up to
75% of your water heating costs!
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