|Heat Pipe Technology|
The main component of a Seido collector is the aluminum absorber mounted in an evacuated glass tube. The absorber, coated with a special aluminum nitride layer, converts incoming solar radiation to heat. The special coating absorbs more than 92% of the arriving radiation, but radiates less than 8% back to the environment.
Heat transfer from the absorber to the fluid circuit is performed by the "heat pipe". A heat pipe is a closed system, carefully evacuated and charged with a small amount of water before it is sealed. The absorber imparts heat to this water, causing it to evaporate. The steam rises to the upper end of the heat pipe where it transfers heat to the fluid circuit via conduction.
As a result of transferring heat, the water cools, condenses and returns to the bottom of the heat pipe in liquid form. This continuous cycle of evaporation and condensation imparts large amounts of heat to the fluid flowing around each heat pipe in the header. To encourage the convective process and allow the steam to rise, the heat pipe requires a minimum tilt of 15 degrees. Minimum tilt for Seido 1 collector is 15 degrees. Minimum tilt for Seido 5 Collector is 30 degrees. Seido 2 collector is not a heat pipe design and has no minimum tilt.
Being a 'dry' connection, the heat transfer fluid (water or water/glycol mix) moving through the header does not flow through the evacuated tube nor does it mix with the small amount of fluid in the heat pipe itself.
The absorber and heat pipe are mounted within a sealed evacuated glass tube, cutting heat losses via conduction and convection. The stable vacuum assures that the collector performs exceptionally well at low outside temperatures and protects the absorber against the environment.
R & D work for the Seido line of evacuated tubes using heat pipe technology was carried out by the Daimler-Benz Aerospace Group based on experience gained in the temperature control of satellite electronics.