tailieunhanh - Sustainable Growth and Applications in Renewable Energy Sources Part 9

Parameterisation of the Four Half-Day Daylight Situations 151 120 Bratislava, clear days, 1 min data 8 April 2006 Gv Dv 20 July 2006 Gv th th 26 December 2006 Gv Dv th 100 Illuminance in klx 80 nd Dv 22 September 2007 Gv Dv 60 40 20 0 4 6 8 Clock time 10 12 Fig. 1. Illuminance courses during clear morning situations 1 Gv / Ev 0 10 20 30 40 50 60 70 Bratislava, clear mornings, 1-minute data 26 December 2006 th 20 July 2006 th 8 April 2006 nd 22 September 2007 th Solar altitude in deg Fig. 2. Gv / Ev courses under situation 1 after 1-minute measurements 152 . | Parameterisation of the Four Half-Day Daylight Situations 151 Clock time Fig. 1. Illuminance courses during clear morning situations 1 Fig. 2. Gv Ev courses under situation 1 after 1-minute measurements 152 Sustainable Growth and Applications in Renewable Energy Sources Fig. 3. Gv Ev courses under situation 1 after measured hourly averages Fig. 4. Tv courses under situation 1 after 1-minute measurements Fig. 5. Tv courses under situation 1 after measured hourly averages Parameterisation of the Four Half-Day Daylight Situations 153 It has to be noted that during sunrise and early morning hours the prevailing daylight is caused by skylight and therefore also on clear days the early Gv Ev values are equal or quite close to Dv Ev while under higher solar altitude the Pv Ev component is rising while Dv Ev value fluently decreases after Fig. 6 from roughly to . The average hourly decrease is slightly distorting this range showing approximately to respectively Fig. 7 . Fig. 6. Dv Ev courses under situation 1 after 1-minute measurements Solar altitude in deg Fig. 7. Dv Ev courses under situation 1 after measured hourly averages If simultaneous measurements of the zenith luminance is recorded under clear sky conditions the classifying parameters Lvz Dv can identify the momentary sky type with the fluent rising tendency dependent on the solar altitude. In Fig. 8 this tendency is shown using 1-minute data while in Fig. 9 the same is documented after hourly mean values. Due to rather constant and fluent trends during situation 1 besides the momentary one-minute recordings also hourly averages and appropriate parameters are quite satisfactorily reflecting clear half-days which might reduce the number of data considerably Darula. Kittler 2005a