Let’s begin with some basic physics.

Heat energy gets from one place to another by one of three methods:

 

Conduction – where the energy moves through the material, for example a steel poker resting in a fire, conducts heat easily and the handle gets hot quickly.

 

Convection – where something is heated and then physically moves taking the heat energy to wherever it moves to. For example, air in a room next to a radiator gets hot and rises to circulate heat around the room; this is natural convection.  An example of forced convection is where water enters a boiler, gets heated by a gas flame, and is then pumped to a radiator.

 

Radiation – this is the direct transfer of heat energy by photons of light. For example, you can feel the radiant heat from the sun on your face on a sunny day.

 

And remember, that heat energy moves from hot to cold; you cannot make something hot by sitting it next to something cold.

 

Solar thermal systems comprise panels, usually situated on the roof of a building but they can sometimes be placed in a ground-mounted array.  These panels are generally referred to as “collectors” and are further defined as either “flat plate” or “evacuated tubes”.

 

To be useful, the solar collectors need to be hotter than the ambient temperature and therefore conduction and convection will both work against the process by taking heat from the collector to the outside world, which isn’t where we want it.  The only way to get higher temperatures transferred to where we do want it e.g., our water system, is by radiation. All solar collectors require radiation to get higher temperatures than the ambient temperature.

 

Flat panel collectors are generally less efficient than vacuum tube collectors because they suffer from both conduction and convection because, no matter how good the insulation, there is always a loss of heat energy that the vacuum collectors do not have. 

 

Conversely, the LaZer2 collector, which is an evacuated tube collector, suffers no such inefficiencies because in a vacuum tube there is no material in the vacuum to enable conduction or convection to happen.  The inner part of the tube has no physical contact with the ambient temperature; it could be 10c below zero, but the inner part of the tube can only see radiation; it cannot feel the outside temperature and so, if there is simply daylight, the LaZer2 tube will get hot.

 

The rest of the solar system is designed to get the heat from the solar collector to where it is needed, and it does that by the medium of a circulation fluid linked to a pump to move the heat from the panel to the hot water cylinder as required.

 

We use an inhibited antifreeze solution to transfer the heat from the collector to wherever it is needed e.g. the hot water cylinder.  The hot water cylinder used in solar thermal systems has a second coil that physically separates the domestic hot water from the inhibitor and transfers the heat.