Types of Systems
Types Of Solar Thermal Systems
There are a two main/common types of thermal solar collectors available on the market today - Evacuated Tubes and Flat Plate/Bed panels .
Evacuated tubes are glass tubes - a vacuum is created within them except for thin strips of twisted metal which act as an absorber. The vacuum means conduction losses are reduced so heat transfer in evacuated tubes is very efficient. The evacuated tube system consists of a row of these tubes and is better in climates where there is not always direct sunlight i.e. when the radiation is high but not necessarily the temperature. The increased efficiency of evacuated tubes does not necessarily mean that they can produce more hot water just that the area can be reduced. Although evacuated tubes are slightly more efficient they are more fragile and replacing a broken tube can be very expensive.
By contrast, flat bed panels tend to lose more heat, especially when it's cold. Flat plate panels are a thin panel of metal that acts as an absorber positioned just below a sheet of glass. The metal panels absorb the sun's heat and this heat is then transferred to a liquid that is pumped through the system. These are robust, long lasting systems. Also flat panel systems are very robust - you can actually stand on them and they wouldn't break.