Results of the Simulation

The simulation measurements have been made in the days of the equinoxies and solstices, between the hours 6 AM and 6 PM. We used the following hypotheses for the simulation: the roof oriented South, у = 0; the inclination angle of the roof is equal with the latitude of the place, 5 = Ф = 45 deg; the sky is clear; the contribution of the diffuse radiation to the photovoltaic effect is inessential; the input aperture radius is R= 50 mm; the photovoltaic cell radius is r = 20 mm; the parabola’s parameter is p = 20 mm; the distance between the peak of the parabola and the cell is H0 =10 mm; the geometric concentration factor is Cgeom = 6.25; the paraboloid’s height is h = 62.5 mm.

We have obtained the following results :

– The incidence angles of the radiation on the input aperture vis a vis to the rotation axis of the paraboloid are presented in the Fig.3. The analysis of the Fig.3 evidentiates the following aspects relative to the angles of incidence: at noon, it varies between 1.5 degrees (autumn equinox) and 24.2 degrees (winter solstice).

– The orar variation of the direct solar radiation intensity is presented in Fig. 4. The solar radiation is minimum during the winter solstice, for all the hours and has the highest values at all the hours in the summer solstice.

– The density of the solar flow on the input aperture is presented in the Fig.5. The highest values are : 799.5 W/m2 for spring equinox, 792.5 W/m2 for autumn equinox, respectively 808 W/m2 for summer solstice and 495 W/m2 for winter solstice.

– The density of the concentrated solar flow, depending on the hour, on the solar energy receptor, is presented in the Fig.6. The highest values are : 2837.5 W/m2 for the spring equinox, 2830 W/m2 for the autumn equinox, respectively 1219 W/m2 for the summer solstice and 708 W/m2 for the winter solstice.

– The average optical concentration factor, < Coptic > x102, and average optical efficiency < Ioptic > x 102, depending on the month, is presented in Fig.7. The lowest values of the average

optical concentration factor and the average optical efficiency are in December and June and the highest values are in March, respectively in September.

The radiation’s concentration is efficient for incidence angles at which the proportion between flow density on the receptor and the flow density on the input aperture is higher than 1, Brec /Bconc > 1. In the morning and in the evening the incidence angle is high and the optical concentration factor is smaller than 1. If the incrementation step of the time is small, in the value table it is determined the angle at which the concentration factor is equal with the unity. It has been established that the maximum value of the incidence angle is 6max = ± 30.06 deg. For the given case, the environment that fills the concentrator is the air, n = 1, the maximum concentration is Cmax = 1/(sin 6max )2 = 3.98. In the Fig.8 is shown the variation of the efficiency depending on the month. The highest efficiencies are obtained in March (25.30%) and September (26.10%).

Updated: July 15, 2015 — 12:35 pm