Design and Function Of Evacuated Tube Collectors
Historical roots – the invention of the thermos flaskIn 1893, Scottish physicist James Dewar invented a double-walled vessel with a vacuum-insulated gap - the thermos flask.Based on the principle of the thermos flask, already in 1909 Emmet developed evacuated tubes in order to make solar power usable. Even today, his patents from that time are the basis for modern evacuated tube technology. However, the efficiency of this old and well-known technology of the thermos flask could be brought to the highest level only with the help of modern coating technologies and highly selective layers. The technology - today The Heating Solutions evacuated tube collector consists of 3 main components which are completely pre-assembled: evacuated tubes, CPC mirrors, and collecting box with heat transfer unit.
Historical roots – the invention of the thermos flaskIn 1893, Scottish physicist James Dewar invented a double-walled vessel with a vacuum-insulated gap - the thermos flask.Based on the principle of the thermos flask, already in 1909 Emmet developed evacuated tubes in order to make solar power usable. Even today, his patents from that time are the basis for modern evacuated tube technology. However, the efficiency of this old and well-known technology of the thermos flask could be brought to the highest level only with the help of modern coating technologies and highly selective layers. The technology - today The Heating Solutions evacuated tube collector consists of 3 main components which are completely pre-assembled: evacuated tubes, CPC mirrors, and collecting box with heat transfer unit.
The evacuated tube.
The evacuated tube is a product that is optimized in geometry and performance.The tubes are composed of two concentric glass tubes which in each case are half spherically closed on one side and fused together on the other side. The gap between the tubes is evacuated and afterwards hermetically plugged (vacuum insulation). In order to make solar power usable, the internal glass tube is provided on its external surface with an environmentally friendly, highly selective layer and thus designed as an absorber. This coating is thus protected within the vacuum gap. It is an aluminum nitrite sputter layer which is characterized by very low emission and very good absorption.
The CPC mirror (not evident in other evacuated tube suppliers so watch for this)
In order to increase the efficiency of the evacuated tubes, a highly reflecting, weather-proof CPC mirror (Compound Parabolic Concentrator) is placed behind the evacuated tubes. The special mirror geometry ensures that even at unfavorable irradiation angles direct and diffuse sunlight falls onto the absorber. This substantially improves the energy yield of a solar collector. Unfavorable irradiation angles are given at diagonally incoming light (azimuth angle) (no south adjustment of the mounting area, sun progress from east to west, diffuse irradiation).
Collecting box and heat transfer unit
The insulated collecting and distribution pipes are located inside the collecting box.The advance or return connection can take place alternatively on the left of or on the right.In each evacuated tube there is a U pipe with direct flow-through that is connected in such a way to the collecting or distribution pipe that each individual evacuated tube exhibits the same hydraulic resistance. This U pipe is pressed to the inside of the evacuated tube with the heat guide plate.
To give you an idea of how efficient our Evacuated tubes are let me give you a working Irish example. We powered one up 4 weeks ago in the middle of September. In 8 hours the evacuated Tubes (cloudless day) raised the temperature of the water in the 300 Litre cylinder from 22 degrees to 73 degress.
Heating Solutions Ltd
Solar Panels – Underfloor Heating – Heat Pumps
29 Suil na Habhann, Mill Rd, Limerick, Ireland
Tel: 086 3823062;
Fax: 061 346011
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