Photovoltaic Operated System
The photovoltaic system differ from other direct pumped systems in that the energy to power the pump is provided by a photovoltaic (PV) panel. The panel converts sunlight into electricity, which then drives a DC pump thus eliminating the need for an AC inverter (which converts solar DC into AC). Therefore water is only circulated through the system when there in sunlight.
Proper matching of the PV panel and the DC pump is paramount in order to ensure proper performance. The pump starts when there is sufficient solar radiation available to heat the solar collector. It turns off later in the day when the available solar energy diminishes. Timers may also be incorporated to control the system operation. The timers must incorporate battery backup in the event of power failure. The timer is set to operate during a day when solar radiation is available to heat the portable water.
In order to avoid loss of energy from the tank during overcast days, the collector feed and return lines are both connected at the bottom of the storage tank with a special valve. During operation, natural stratification allows the warmer water to rise to the top of the tank.