Many factors affect the positioning of the solar system’s intercepting surfaces. Among them, the most important is the study of the place and users’ requirements; actually, it is important to examine carefully the consumptions trend during the year. Another factor that has a strong impact on the positioning of the intercepting surfaces is the shading phenomenon at the installation site. To determine accu­rately the shades which can appear on a certain surface, we can use the solar tra­jectories diagram or the Sun’s position diagram (par. 10), which provides precise information on the Sun’s position in the celestial vault during the day and the year at a certain place.

It is clear that the best orientation for an intercepting surface is the one that is orthogonal to the solar rays. The fixed intercepting surfaces (i. e. the ones that do not have automatic Sun chasing devices) meet that orthogonality condition once a day. Hose surfaces are normally installed southward to maximize the energy received during the day. However, this is not a strict norm, especially where the roof is not north-south oriented. Panels which are eastward or south-eastward ori­ented favour the morning running while the westward or south-westward oriented panels favour the afternoon running.

Choosing the best inclination is not easy and immediate; generally, it is chosen such that it is equal to the latitude L decreased by about 10° to maximize the energy collected during the year (e. g. in Rome since the latitude is 42°, the best inclination will be 30°).

If users require the system to work especially in winter months, this value will not be satisfactory. During winter, the apparent trajectory of the Sun in the celestial vault is on average low so that the average inclination of solar radiation reaches the minimum yearly values. A panel inclination higher than the mentioned 30° (e. g. 60° for a hotel located in a skiing resort) will be necessary to favour the intercept­ing surfaces’ exposure to direct radiation.

On the contrary, in summer (e. g. for an open air swimming pool) users can maximize the service with an inclination of about 10°.

The last factor which contributes to the correct positioning of surfaces is the economic result of the investment: the right dimensions and the correct realization of the system minimize the need for the active surface and therefore the number of collectors to be bought and the overall cost of the operation. Eventually, it is necessary to point out that small positioning variations compared to the best panel positioning can lead to negligible loss of energy received [2, 5].

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