Energy

Solar systems

Passive solar systems 
Passive solar systems are those where the solar energy is used directly. For example, greenhouses are glass structures which allow the sunrays to get in, but do not let the heat go out. Thus their inner temperature might be higher than outdoors. Another example is provided by solar stills, in which, in an indoor environment covered by transparent panels exposed to the sun, seawater evaporates, later condensing as salt-free water, which can be used for other purposes. 
Attive solar systems 
On the other hand, active solar systems collect solar energy and transform it into thermal or electric energy before using it. They include: thermal solar panels; concentration collectors, used to produce thermal energy; photovoltaic solar panels, used to produce electric energy. 
The best technologies make the co-generation of different types of energy possible. It is possible to accumulate thermal energy in several ways and for different aims.