When we talk about a solar boiler we refer to a solar thermal system consisting of a storage tank (boiler) and a system to heat the water. The system can be given by one or more manifolds or by a simple copper plate or by a selective panel. From this it is clear that there are different types of solar boiler.
The solar boiler simpler but also less efficient, is that a "Natural circulation". In this case the water, heating up, by convection, rises in the boiler. In this case, the storage tank must be placed higher than the panel. From boiler the water will then be distributed to domestic taps.
In some cases the boiler it must be installed inside the house, with the solar thermal system a "Forced circulation", a coil is placed directly inside the boiler. The coil is connected to the panel. The collected heat is transferred to the so-called "circulator" pump which will transfer it in turn to the coil placed inside the boiler. In this case the circuit is very complex: a "expansion vessel ", the need to control the temperature and an electrical expenditure dictated by the pump and the control unit.
With the solar thermal system at "emptying", the system is similar to the one just described, the only difference lies in the boiler. In the emptying system, the accumulator is filled and then used only when possible: when the system does not reach the desired temperature it will not be possible to use it. Another difference is dictated by the need to have a certain minimum slope between the collector and the boiler collection.
The solar thermal system with "concentration with solar tracker ". In this case, the "panel" will consist of a particular parabolic shape thanks to which the sun's rays can be concentrated in correspondence with the heat conducting fluid.
A type of solar boiler in the experimental phase it is given by a municipality boiler electric modified to be powered and controlled directly by the direct current produced by the photovoltaic panels and, in the absence of this energy, by the alternating current network. A detailed study can be viewed at this link.