Photovoltaic systems
To begin
Photovoltaic systems produce electrical energy by using direct conversion of solar energy. This conversion is possible since by enlightening some given materials, such as silicon based composites, an electrical current can be generated.
In order to maximize the production of electrical current, the collected solar energy should be maximized as well. A lot of techniques to accomplish this goal do exist. They can be divided in fabrication techniques of the raw materials and installation techniques of panels. The former is likely to be a duty of scientific research, while the latter is delegated to the designer who shall choose among several installation options. We show some of these techniques in the following.
In the first figure, we show a classic system for residential users. The roof is facing the SOUTH (i.e. the azimuth is 0). Together with the optimum tilt, this is the best orientation. Optimum tilt basically depends on the latitude (for instance in Italy is about 30o). This optimal couple (0o, 30o) is obtained in obstacle-free condition, otherwise it must be computed by taking into account the actual conditions of the site.
On the other hand, if there is a large amount of horizontal surface, it is possible to choose an all-planar installation. Actually, nowadays, there are commercial solutions of panels made by cylindrical modules (based on thin film composites). Such panels can 1) generate a higher amount of energy with respect to the flat panels thanks to the ability to collect the light coming from every direction, including the light reflected from the groundt and 2) can be installed very easily. An example of such panels is shown in the above figures (Solyndra type).
Last figure shows the array or rack mounting alternative to cylindrical modules. In this case, the panels are usually aligned in parallel rows. Rows are carefully separated by a minimum distance in order to avoid unacceptable self-shading phenomena. Usually, for mid latitudes this distance is roughly 2 meters. As a consequence, in this case to attain the same energy yield provided by the first case (single side roof), the overall available surface must be the double .