Solar water heating system
Topology of the hot-water circulation system (click on the image to
expand in a new window).
The lower array is a set
of 16 photovoltaic (PV) panels giving a peak output of 4.56
kW. This energy is fed into the mains electrical system via an
inverter, which is capable of exporting electricity in the event that
our own consumption should fall below the solar yield.
The upper array consists
of 6 Navitron SFB305818-AL evacuated tube solar collectors.
These 30-tube panels each have a maximum output of 1.85 kW,
giving a total of 11.1 kW for the whole system. Note that the area
efficiency is vastly superior to that of the PV system. The downside of
evacuated tube collectors is that the upper manifold will attain a
temperature of around 220°C in the event that the water
circulation should fail, producing a serious hazard for anyone working
on the system, and the likelihood of damage to the components. Note
therefore the presence of a 100 W PV panel in the gap at the middle of
the array. This is used to charge a 12 V 110 Ah lead-acid leisure
battery, which can be used to run an inverter to power the circulation
pump. The inverter is automatically activated, and the output of the
panels is switched to the heat dump, in the event of a mains power
failure during daylight hours.
Heat dump (10.5 kW), with filling point, pressure gauge, air
valve, and magnetic