The Rothbury Spiral design (registered design no. 001598483) has been designed to
optimise performance on less favourable sites and in northern latitudes where the
sun does not hit the panel with as much energy as you would like. The panel’s unique
spiral coils suffer less from poor orientation to the sun’s rays than more traditional
‘snake’ or ‘ladder’ thermal solar panels, giving an earlier start and later finish
to daily heated water production as well as the ability to produce worthwhile amounts
of heated water at each end of the summer season.
To get the best performance from the Rothbury Spiral it should be plumbed in to an
indirect pre-heat cylinder (essential in hard water areas) so that the annual recovery
of the energy collected by the panel is maximised. This also extends the time that
useful amounts of solar energy can be added to the household consumption equation
and reduces pay-back time. Experience in Germany and Scandinavia shows that when
used with a low-temperature heating system and a well-insulated building then this
design of installation can make a useful contribution to the annual household heating
energy input as well as hot water production.
Our records show that at a winter air ambient of 0°C, a Rothbury Spiral at 55°N can
recover energy on a sunny day at over 2kwh, bringing heated water into the house
envelope at about 40°C. This energy is then used either to pre-heat water, or by
dissipation to raise the house temperature. Typical readings between March and October
at latitude 55 degrees N show that there is the potential for energy to be recovered
at the rate of 3 kwh in partial sun to 5 kwh on sunny days and up to 8 kwh in good
conditions. The minimum heat recovered on start-up (at a 6 deg C temperature rise)
is 0.75 kwh which is comfortably in excess of the pumping power requirement of less
than 0.04 kwh.
In changeable conditions the spiral’s small tube diameter allows a fast reaction
to radiation changes and the 95m length gives a higher output than more traditional
panels. The spiral design avoids sharp bends in the heating tube, giving better flow
characteristics to the heating fluid with a consequent reduction in the energy requirement
for pumping and an improved thermal efficiency.
The Rothbury Spiral costs less per metre of heating pipe than any
other solar thermal panel, thus reducing pay-back time. The panels
are supplied complete ready to be installed and we offer free advise
to you or your builder or plumbing regarding installation. Every
aspect of the Rothbury Spiral has been designed to optimise the
output while keeping the cost down, and the construction of the
panel has been carefully examined to continue this design philosophy resulting in
a very cost-efficient panel.