Evacuated tube technology was first developed in Australia at the University of Sydney — some 40 years ago.

More recent developments have improved their technical efficiency and they are now rapidly invading the solar hot water market worldwide as Chinese manufacturers have managed to bring down the manufacturing costs to very competitive levels.

So now, at long last, we have a state-of-the-art solar hot water system that is very affordable. They have also stood the test of time, systems installed 40 years ago are still going without maintenance.

Each tube is double walled, with a vacuum between for insulation. The sun’s heat is conducted to the top of each tube and used to warm water pumped up from a ground level tank. The result is a very efficient freeze-proof solar heater without a large tank on the roof.

The glass tubes are open at one end (like a vacuum flask) the glass tube itself being comprised of two layers of glass with a vacuum in between, giving very effective insulation from cool exterior air.

The glass tubes are nothing more than a very effective insulator, enabling the copper heat tube (inside) to reach temperatures of up to 170 degrees. Without the insulation of the glass tube they would not get much hotter than ambient air temperature.

Through this method, the collector is able to gain heat even on quite cold sunny days, and even during light cloudy weather. They are therefore most suitable in cool temperate climes such as ours.

The copper heat tubes are totally sealed, a small amount of volatile liquid inside them assisting with transfer of heat. This makes them vastly more efficient than a solid copper rod.

Hot water supply only goes through the insulated manifold which receives heat via metal-to-metal contact from the collector.

When your HW cylinder gets up to 80°C the pump simply shuts down and the 250ml of water in the manifold turns to steam. This prevents hot water tap temperatures from becoming scalding. When water is draw out of cylinder, the steam condenses back to water and the system reverts to normal operation.

Solar hot water systems are in widespread use in much less favourable climatic conditions — such as Northern Europe and Alaska.

The development of the evacuated tube solar technology has enabled solar hot water to become even far more financially attractive in cooler climates such as ours.

The Apricus system will boost the cylinder temperature to 80°C, so a fully charged hot water cylinder will give you ample heat capacity for a typical home.