The good project for daylight application should be made in an early phase of the project so to get a good level of integration [6]. It is important to know the characteristics of lighting that the room required, the activity that is supposed to be performed inside, the right position of the standing people and so on. Only when all these variables are well known it is possible to determine the sizes and the shapes of the transparent components, giving the quantity of natural light and their distribution in the wall [7].

At the end the whole lighting project should be checked by using of tables, plots abacus and codes [8].

The standard gives the formula to calculate the Daylight Factor:

DFm = Af x Ti x e x у / [( 1-pim) x Atot]

Af glass surface of the windows [m2]

Ti glass transparency

e window factor (ratio between the

window lighting and the sky radiance) у window factor reduction coefficient

(dependent on the protrusion of the wall respect the window) pim indoor surface average reflection

value

The transparency is the value of the optical transmittance for the PV component as it has been measured, depending on the optical transmittance of the transparent part and on the cell density.

In our case a project for the refurbishing of an health centre for mental disease to an university campus, with parts of the buildings available even to the inhabitants of the town.

In particular that building will be partially destroyed and then rebuilt, but keeping the original look by keeping the pristine outside walls, see figure 4.

In one block two PV plants will be installed in the facade acting as a sun screen by using the glass/glass technology and the spacing of the cells.

In the first case the PV modules will develop around the length of the building and should provide a good lighting on the working planes; in order to avoid the glaring and at the same

time to allow a good vision of the outside environment, the modules are designed on the purpose, as it can be possible to see in figure 5.

CONCLUSIONS

The sun light can be efficiently used fro daylighting with many advantages; a saving on the energy bill can be gained and the increasing of the comfort from optical, thermal points of views. The diffusion of the building integrated photovoltaics in form of fagade and sun screen and the new concept for projecting the PV module according its multifunction aspect making available semitransparent or translucent module created a good potential for that application. In that case some optical characterization could prove to be important and that work presented a methodology ENEA undertook in order to investigate the optical

transmittance. That value combined with the density of the cells are parameters that are

needed for the daylight factor determination to be used in the lighting project

The paper showed as an example that replacing a traditional glass fagade with Photovoltaic

resulted on the reduction of the day light factor so giving an improvement for the comfort of

the room. By using the density of the cells the glaring effect can largely reduced if not

avoided.