The solar collector works very simply - it is in the sun, absorbs heat and transfers it where you need it. In order to do this effectively, solar collectors need to absorb every day - and retain - a lot of sunlight. There are two main techniques that have been time tested and achieved this goal, so the debate about which technology is considered "best" is almost endless. The two main technologies are flat panels and solar vacuum tubes.
Flat Plate Collectors
Flat panel collectors have been on the market and in use since the beginning of the 20th century and are one of the most time tested and well known techniques. They consist of an absorbing plate - usually painted metal, such as copper - connected to a copper tube where water or a heat transfer liquid goes through. It is wrapped in a metal frame surrounded by a thick insulating material that helps to retain the heat collected and is protected by a sheet of glass, which also provides an insulated air space.
Solar Vacuum Tube Collectors
The vacuum tube collector is a recently developed technology that was introduced to the market in the 1970s. There are many kinds of vacuum tubes, but the most common type is the use of heat pipes surrounded by glass tubes under vacuum. The glass tube is actually composed of two glass walls. Between the two walls, all the air is removed, creating a vacuum, just as a transparent thermos can work. This vacuum is the best insulating material that one can demand and gives the vacuum tube better insulation than air space.
The heat pipe is also pressurized, allowing the liquid (usually water) to boil very rapidly at very low temperatures (typically between 75 °F and 80 °F). When the water boils, it collects the collected heat to the top of the collector, then collects the heat through the water or working fluid that flows around the top of the heat pipe and then transfers it to a storage tank or elsewhere of system.
The flat plate collector is usually designed with an unsealed case. This may make them prone to condensation over time, which can lead to corrosion. However, this does not primarily affect the actual performance of the flat panel unless it is corrosive and is primarily a cosmetic downfall.
The flat plate collector - If it is damaged, it will continue to run and can sometimes be repaired. At other times, the entire flat panel must be replaced.
On the other hand, the vacuum tube is vacuum sealed. This gives them high insulation properties, however, without such a vacuum, the performance of the vacuum tube collector is very poor. If the tube loses its vacuum, it is usually easy to correct and can be easily done by replacing the tube.
Typically, the vacuum tube performs better in the colder or cloudier days than general weather. This is due to the vacuum in the glass tube, which allows the tube collector to maintain a high percentage of heat collected. They work well under freezing conditions where flat panel does not work.
However, in areas where heavy snow may be a problem, the vacuum tube collector does not leak too much heat from the collector, so it does not melt snow and heavy frost as quickly as a flat plate collector. Vacuum tube collectors in cold climates can be mounted at higher angles to better face the sun, and this together with the separation between the tubes allows the snow to slip more easily. On the other hand, the flat panel collects some heat from the sunlight reflected by snow and ice and rises above the freezing point, thus melting the snow or heavy frost more quickly, even though it may not produce any hot water in cold conditions.
For customers who need real hot water, such as laundry, car wash, manufacturing process, etc. Please note that the tablet collector cannot reliably perform 130-140F or more. The vacuum tube collector can produce up to 200F of hot water.
Due to the automatic tracking design of the vacuum tube collectors, they collect heat evenly throughout the day from sunrise. Flat plate collectors must collect almost all of the heat in the middle of the day.
Heat pipe solar collector has longer service life. The flat plate collector is best suited for users in the southern climate or northern seasonal families that are only used during the summer months. The vacuum tube collector is best suited for areas where the winter temperature drops frequently to 40F or less. Customers who require high temperature hot water in all climatic conditions should consider using a vacuum tube collector. In areas where the air is highly corrosive, such as by the sea, heat pipe collectors are recommended.