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The Vacuum Tube. The
tubes are 'twin-glass' construction similar to that of a thermos flask but made
out of exceptionally strong borosillicate glass aka Pyrex. Unlike the silvered
surface of a thermos flask, the inside of the tube is covered in an advanced
'selected coating' which is able to absorb 93% of the light energy while re
emitting only 7% in radiant heat. The presence of a vacuum eliminates convection
and greatly reduces conduction losses enabling the tube to harvest useful energy
even on cold, windy days. Even with cloud cover the tubes can pick up the
scattered radiation from the sun (typically of the order of 30% of all available
energy). The system is far superior to the older style flat plate collectors at
the time when the demand is highest and the insolation is lowest, meaning that
is feasible to use the The vacuum tube has been around for over 20 years proving its stability and long life. The tubes used have been sourced from the highest quality glass manufacturing plant which has obtained a wide range of quality management and control certificates, including the internationally recognized ISO9002 standard. The tubes have also PASSED BS EN 12975 accreditation from an independent Swiss testing body (SPF) and it is from these preliminary tests that the absorption (93%) and emission (7%) efficiency values have been verified. Due to the cylindrical design of the collector surface (all models of vacuum tubes supplied) the amount of solar energy that falls on the collector surface is maximized due to passive solar tracking. This functionality (known as Incidence Angle Modifier or more simply Exposure) increases exposure to sunlight by as much as 15% when compared to an equivalent area of flat plate collectors – further widening the efficiency gap between the two.
In the Vacuum Tube range we offer 3 different types of collectors to cater for individual needs and situations.
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collectors as a year round hot water source – not just a
pre heat device. Also in the colder, mountainous regions, the tubes will start
absorbing energy as soon as the sunlight hits their surface, without the long
start up time associated with flat plates. The sheer mass of the older style
system means that on some days the available solar energy will be unable to
raise the temperature of the frame, insulation, trapped air, collector panel and
glass to a usable level.
