How do vacuum
tube solar panels compare with flat plates?
On a hot, sunny day, flat plate panels will produce the same amount of
heat, more or less, as for vacuum tube panels of the same area. Under
ALL other conditions, the vacuum tube panel will outperform flat plate
panels - usually by a very significant margin. Flat plate panels perform
badly during windy weather, in cold conditions, in overcast conditions
etc. Some of the very best flat plate collectors can compensate for this
with more advanced design, but even then, they still do not perform as
well as vacuum tube panels.
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What
weight are the collectors?
The 20tube 47mm panel is 48kg, the others are more or less proportional
to this weight
Are The
Tubes Fragile? Are they tough enough to survive impact from falling
hailstones and animals?
The tubes are made from borosilicate glass,
which is very tough (also known as pyrex). The tubes are designed to
withstand hailstones up to 35mm - so they are unlikely to be
broken, unless dropped onto a solid floor prior to installation. Impact
from falling animals is not normally considered in the design of the
tubes(!)
What
size solar cylinder should I fit?
We recommend that the 20 tube panel is used with cylinders up to
175litres, and the 30tube panel is used with cylinders up to 260litres.
Larger cylinders can be heated with 2 or more panels, and it is possible
to add an extra panel to benefit from higher temperatures in the winter.
In fact, if you fit a smaller cylinder, you will have hotter water, but
of course less of it. We would recommend fitting a tank of 135litres if
you prefer a smaller amount of hotter water.
What is the
output of the panel in terms of kWh?
This varies according to the time of year - in summer we get almost
10times the amount of solar energy that we do in the winter. In the
summer, you can expect to get 14kWh of heat per day from a single 20tube
panel, whereas in December you can expect only 1.15kWh per day on
average. Even in the winter, it is possible to preheat the water to 40C
or more if the sun comes out. In fact, if you fit multiple panels, it is
possible to heat your hot water to 100C in January (we have seen this in
Cornwall).
How hot
will the water get?
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Where do
these need placing and at what angle?
Panels should be sited on a south facing wall or roof. In fact, anywhere
between South-West and South East will give good results. If you are
limited to an East-West facing system, then you will need two panels to
provide the same amount of hot water as a single south-facing roof
slope. The most frequent solution to this problem is normally to mount
one panel on the east slope and a second panel on the west slope. A
special controller is available for East/West facing installations.
The panels should be mounted at
the angle of your lattitude. For example, at our location in the UK,
this is 53˚. This is AVERAGE optimum angle. In fact, in winter the
optimum angle is 15˚ steeper, whereas in the summer it is 15˚
shallower. The panels will function anywhere between 15 and 90˚
angle of inclination. This is actually academic, a variation of 15˚
will make very little difference to the output, so most people simply
settle for whatever angle their roof slope is. The extra cost of trying
to stand panels off the roof to achieve better efficiency would probably
be better spent on purchasing a second panel!
Does the roof
need to be strengthened at all?
The solar panel in operation weighs around 50kg - this is really not
much weight for a roof, when you consider the weight of the tiles or
slates. Generally there is no requirement to strengthen a house roof
prior to mounting the solar panel, except if you are fitting a panel to
a very old roof, which has sagging and decaying timbers.
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Are
spares available?
Yes, spares are always available, should you need them. With no moving
parts, it is very unlikely that you will need to replace anything, but
occasionally customers break tubes during the installation process, in
which case you can purchase a modestly-priced replacement. However, it
is not possible to post a replacement tube, so you will need to collect
it. The tubes are made of borosillicate glass (aka 'pyrex') so they are
actually very tough.
Are the panels
guaranteed?
Yes, we offer a 12month guarantee, although, with no moving parts the
panels are extremely long-lived, probably in excess of 25years. In fact,
the manufacturers offer a much longer guarantee, but in the UK we do not
offer this extended period due to the legal requirements - if we were to
offer a 25year guarantee, we would need to take out an 'indemnity'
policy on the product. The insurance company bases its risk on an
assumption that if it priced the policy on the basis of replacing the
unit once within 25years, then they will ensure profitability regardless
of claims - thus they would cost this in at probably £300 or more per
item sold. The cost is out of line with our policy of keeping prices as
low as possible, and We decided that most customers probably would not
want to pay this additional fee!
Can I fit this
system DIY?
Yes you can! These systems are very easy to fit, and anyone with basic
plumbing and electric skills can carry out a DIY installation. Mounting
the panel on the roof is sometimes daunting, although it is actually
quite simple - but we can offer this service, if required.
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Will the system
need to be inspected by a plumber or be installed by a
plumber?
No, you can do this yourself. However, you can call in a
plumber to carry out the work if you feel you are not able to tackle the
plumbing yourself or give us a call.
We normally recommend that you fit a pressurised system. This is not
essential, but it allows you to place the solar panel on the roof
without worrying about whether it is possible to place the header tank
high enough to function correctly. With a pressurised system, the
plumbing is simpler, and by running the system at 1-2bar, it is
possible to increase the boiling point of the water to 120C or higher
- allowing greater safety margins, and lower chance of fluid loss.
What about
freezing in Cold Weather?
The solar panel is very well insulated - the manifold is surrounded by
2"of rockwool insulation. This is better than your outdoor water
pipes, so it is unlikely to freeze except in exceptionally cold
weather. However, it is recommended that you take precautions to
prevent the possibility of freezing, by either adding antifreeze to
the system (use a non-toxic solar antifreeze) or you can use a
DELTASOL B controller which has 'freeze protection' - this controller
monitors the temperature of the collector - and if it falls below 4C,
it will turn on the pump, allowing water to circulate and heat the
manifold. You should turn this function off if you use antifreeze.
Can I use Solar
Power with a Mains Pressure Hot Water Cylinder?
Yes. There are two ways to achieve this. You can either purchase a
mains pressure unvented water cylinder (these can be expensive).
Please note that you will have to have a pressure vessel certificate
to install these. Alternatively, you can fit a 'solar store' cylinder
(see below)
What is a
Thermal Store?
A thermal store is a tank which has an additional large surface area
high efficiency coil fitted. The mains cold water is fed into this
coil, thus heating the water on its way through. The mains water exits
the tank as hot as the hottest water in the tank, but without losing
any pressure - thus providing mains pressue hot water to the household
taps.
Can I get
a grant for these systems?
Yes Our Vacuum Tube Solar Panels have passed rigorous test and a small
Grant may be available
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Do I need
planning permission?
In most cases, no. Evacuated tube solar panels are considered
in the same way as roof windows. Unless you live in a listed building,
it is unlikely that it will require planning permission. Even if you
do live in a listed building, you can usually fit the panel to the
rear of the building, or at ground level without requiring planning
permission
How many
panels/tubes do I require to meet my household needs?
This is a difficult question to answer as it depends on your water
usage. For example, one person that contacted us lives in a motor
home,
and uses only 70litres of hot water over a two week period. A young
couple I spoke to estimated their hot water consumption to be at least
400litres per day!
First you should calculate how large a hot water cylinder you require
to meet your needs. Remember that solar cylinders are normally
designed to store water for use over 2 days, rather than one, thus
allowing you hot water even if the following day is cloudy. Once you
have calculated your cylinder size, you can estimate your panel size
on the basis of One Solar Tube per 6.5 - 8.5litres of hot water
cylinder (i.e. a 20 tube panel can supply hot water for a 120-170litre
cylinder, and a 30tube panel can supply 180 - 255litres). This assumes
you have an unshaded south-facing roof slope to mount the panel
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Can I heat my
house with evacuated solar tubes?
There is 10 times more sun energy in the summer than in the winter.
(this is the reason for the different seasons, after all). Therefore
you immediately have the problem that the bulk of the energy is at the
wrong time of year. The other problem with using solar to heat your
house is that it is not present at the times when it is really cold -
at night, on very overcast days, in winter evenings etc.
In practice you can provide a significant amount of supplementary heat
in the spring and autumn (and some people have implemented such
systems), but the contribution in the winter will be minimal,
restricted to sunny days, but you will need to fit many more panels,
as heating a house is a lot larger task than heating an insulated
cylinder of water. Solar water heating on the other hand, can be
effective even in the winter, as the amount of heat required is
considerably less than that required to heat a house.
How many panels
do I need to heat my pool?
It depends what area of pool you need to heat, how well insulated it
is, whether it has a pool cover, if it is above/below ground, how many
weeks of the year you need to use it etc. However, as a rule of thumb
we recommend that you start with solar panels equivalent to 25% of the
pool area, but you can increase this up to 35% if more heat is
required. As the panels are modular, it is easy to upgrade the panels
at a later date if required. We strongly recommend the use of a pool
cover when the pool is not in use, as it dramatically reduces heat
loss through evaporation.
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Contact
us Tel:01278429938 Mob:07858753462
