Photovoltaic Boiler heat sanitary water in an ecological way, saves money and produces other advantages.

The prototype described here has replaced the sanitary hot water production of a classic wall-hung boiler which is left with the sole function of heating the house during the winter months.

The plant has been in operation since August 2012 and meets the needs for hot water for sanitary uses of a family of four living in Italy. The solar photovoltaic boiler consists of a common electric boiler modified to be powered directly by the direct current produced by the photovoltaic panels and, in the absence or insufficiency of this current, by the national electricity grid in alternating current.

How is the photovoltaic boiler made?

It is a common 80 liter electric boiler to which the native electrical part has been replaced with another specifically designed to be powered directly by the photovoltaic panels and the AC mains.

How does the photovoltaic boiler work?

The photovoltaic panels switch is closed so it circulates
direct current in the electric resistance connected to them and water
  of the boiler heats up, if there is sun

The AC side switch is open, the temperature
water rises to the limit value of 75 degrees Celsius,
after this threshold the DC current switch opens
while the alternating current side was already open and remains open

When there is no sun or when a large quantity of water is taken in a short time, the water temperature is lowered below the adjustable threshold of 48 degrees centigrade so that the switch on the alternating current side is closed to allow the passage of current from the network to the resistance connected to it.


Due to the electric current drawn from the mains the temperature rises up to 50 degrees Celsius then the alternating current switch is opened, the photovoltaic panels switch is closed and remains closed. If the lack of sun persists or a lot of water is taken in a short time, the water temperature remains heated between 48 and 50 degrees Celsius, taking electricity from the mains.

When the sun returns and the water temperature rises above 50 degrees centigrade, the alternating current switch opens and only the continuous current side opens and remains closed, which was already closed and then everything starts again as said at the beginning.

The photovoltaic boiler is powered by three 240Watt 40 Volt photovoltaic panels each, connected in series.

Realization of the photovoltaic boiler, the red element is the hot water meter produced which allows to measure the efficiency of this solution.