Solar Water Heater

Overview

The solar water heater is an active, pumped evacuated-tube system that supplies domestic hot water from sunlight, with electric backup for cloudy spells. A roof-mounted glass-tube collector harvests solar heat and feeds a 300 L insulated stainless tank through a controlled circulation loop. Evacuated tubes outperform flat-plate collectors in cold and diffuse light because the vacuum gap suppresses convective heat loss.

The Evacuated-Tube Collector is an array of twenty double-wall borosilicate evacuated tubes. Each tube carries a selective absorber coating on its inner wall and a copper Copper Heat Pipe running up its centre. Sunlight heats the absorber, vaporising the working fluid in the heat pipe; the vapour rises and condenses in a dry pocket inside the insulated header manifold, giving up its heat to the circulating water before draining back to repeat the cycle.

How it works

Heated manifold water is moved to the Storage Tank Assembly by the Circulation Assembly assembly, a wet-rotor pump backed by an anti-thermosiphon check valve and a diaphragm expansion tank that absorbs pressure swings. The Controller Assembly compares collector and tank temperatures through two probes and runs the pump only when the collector is hotter than the store, maximising useful gain and preventing night-time heat loss.

The Storage Tank Assembly holds water in a welded stainless inner vessel inside a foam-insulated steel shell, with a magnesium sacrificial anode protecting the vessel from corrosion. When solar input falls short, the controller energises the Electric Backup Heating immersion element through its own thermostat to guarantee hot water on demand. A relief valve in the Piping & Fittings protects against overpressure, and the whole collector is carried on an adjustable roof Mounting Stand.