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    Solar Data - Roanoke, VA


    Average Climate Conditions
    Solar Radiation Data
    Altitude and Azimuth of the Sun


    Average Climate Conditions
        Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
    Element Units                          
    Average Temperature °F 34.5 37.3 46.8 55.4 64.1 71.5 75.6 74.6 67.7 56.5 47.5 38.3 55.8
    Daily Minimum °F 25 27.2 35.7 43.8 52.5 60.2 64.8 63.8 56.8 44.8 37 28.9 45
    Daily Maximum °F 43.8 47.3 57.8 67.3 75.7 82.9 86.4 85.3 78.5 68.1 58 47.6 66.6
    Record High °F 78 80 87 95 96 100 104 105 101 93 83 76 105
    Record Low °F -11 1 10 20 31 39 47 42 34 22 9 -4 -11
    Heating Degree Days note a 946 776 564 289 105 5 0 0 39 283 525 828 4360
    Cooling Degree Days note a 0 0 0 7 78 200 329 298 120 20 0 0 1052
    Average Humidity Ratio note b 0.27% 0.30% 0.41% 0.56% 0.87% 1.17% 1.34% 1.32% 1.09% 0.70% 0.48% 0.34% 0.74%
    Average Wind Speed mph 9.5 9.1 9.7 9.6 7.7 6.9 6.5 6.1 6 6.8 7.8 8.4 7.8
    Clearness note c 48% 50% 51% 52% 52% 53% 52% 52% 51% 52% 48% 46% 51%


    Note:
    1. Heating and cooling degree days calculated from 65 degree (F) base.
    2. expressed as pounds moisture per pound of air.
    3. Average atmospheric clarity to solar transmission, expressed as a percentage.

    Source:
  • National Renewable Energy Laboratory, Solar Radiation Data Manual for Buildings.


  • Averange Incident Solar Radiation (Btu/sq.ft./day)
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
    Horizontal
    Global 770 1030 1380 1730 1900 2000 1920 1740 1470 1190 860 700 1390
    Std Deviation 62 93 111 125 103 120 129 128 116 96 82 58 38
    Minimum 640 800 1150 1530 1620 1790 1640 1380 1220 1020 650 520 1280
    Maximum 890 1200 1600 2020 2080 2250 2140 1920 1690 1390 960 830 1450
    Diffuse 340 440 570 720 870 940 950 860 690 490 360 310 630
    North
    Global 220 290 370 460 570 640 600 510 410 320 240 200 400
    Diffuse 220 290 370 450 520 560 540 490 410 320 240 200 380
    East
    Global 500 650 820 1000 1040 1080 1040 950 840 720 550 460 810
    Diffuse 270 350 450 550 620 660 650 600 500 390 290 250 470
    South
    Global 1130 1190 1140 980 800 730 750 870 1030 1220 1190 1100 1010
    Diffuse 370 430 500 550 580 580 590 590 550 480 400 350 500
    West
    Global 510 650 830 990 1030 1070 1010 950 850 740 560 470 800
    Diffuse 270 350 450 560 630 670 660 610 510 400 300 250 470


    Average Clear Day Incident Solar Radiation (Btu/sq.ft./day)
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
    Horizontal Global 1080 1410 1860 2280 2520 2600 2520 2290 1920 1480 1110 950 1840
    North Global 210 260 340 430 580 680 620 490 380 300 220 190 390
    East Global 770 960 1170 1340 1410 1410 1370 1290 1160 960 770 690 1110
    South Global 1980 1970 1720 1280 950 800 850 1110 1490 1790 1880 1910 1470
    West Global 770 960 1170 1340 1410 1410 1370 1290 1160 960 770 690 1110


    Average Transmitted Solar Radiation (Btu/sq.ft./day)
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
    Horizontal
    Unshaded 510 710 980 1250 1380 1460 1390 1250 1050 840 580 460 990
    North
    Unshaded 150 200 250 310 370 410 400 340 280 220 170 140 270
    Shaded 140 180 230 290 340 380 360 310 260 200 150 130 250
    East
    Unshaded 350 460 580 710 740 760 740 680 590 510 380 320 570
    Shaded 320 420 530 640 660 680 650 600 530 460 350 290 510
    South
    Unshaded 850 860 780 620 490 450 460 550 690 870 880 830 690
    Shaded 830 810 640 450 370 370 370 400 530 780 860 810 600
    West
    Unshaded 350 460 590 700 730 750 720 670 600 520 390 320 570
    Shaded 320 420 530 630 650 670 640 600 540 470 360 300 510


    Shading Geometry in Dimensionless Units
    Window

    1

    Horizontal Overhang (h):

    0.423

    Vertical Gap (v):

    0.295



    Note:
    • Incident and transmitted radiation values are based on 30-year (1961-1990) averages for each month.
    • For explanation of shading geometry, see solar_shading.asp

    Source:
  • National Renewable Energy Laboratory, Solar Radiation Data Manual for Buildings.


  • Altitude of the Sun
      15-Jan 15-Feb 15-Mar 15-Apr 15-May 15-Jun 15-Jul 15-Aug 15-Sep 15-Oct 15-Nov 15-Dec
    Time of Day
    4:00           -10.4            
    5:00       -9.5 -2.8 -0.6 -2.8 -7.5        
    6:00     -7.0 2.3 8.3 10.2 8.1 3.9 -1.2 -6.3 -11.9  
    7:00 -6.8 -2.6 5.1 13.9 19.9 21.5 19.4 15.5 10.8 5.6 -0.6 -5.5
    8:00 4.1 8.9 16.7 25.8 31.7 33.2 31.2 27.4 22.5 16.7 10.0 5.0
    9:00 13.7 19.3 27.8 37.4 43.6 45.1 43.1 39.2 33.7 26.9 19.3 14.1
    10:00 21.9 28.4 37.7 48.3 55.1 56.9 54.8 50.4 43.8 35.5 27.0 21.7
    11:00 28.0 35.5 45.6 57.2 65.2 67.8 65.6 60.1 51.6 41.6 32.2 26.9
    12:00 31.3 39.5 50.2 62.2 71.3 75.4 73.2 66.1 55.5 44.1 34.2 29.4
    13:00 31.2 39.8 50.1 61.2 69.3 73.7 72.5 65.3 54.1 42.4 32.7 28.5
    14:00 27.9 36.3 45.4 54.5 60.9 64.5 64.2 58.4 48.0 36.8 27.9 24.6
    15:00 21.8 29.6 37.4 44.8 49.9 53.2 53.2 48.3 38.9 28.6 20.6 18.1
    16:00 13.5 20.7 27.4 33.6 38.2 41.3 41.4 36.9 28.2 18.6 11.4 9.7
    17:00 3.9 10.4 16.3 21.9 26.3 29.4 29.5 25.1 16.6 7.6 1.3 0.3
    18:00 -7.0 -0.9 4.7 10.0 14.5 17.8 17.8 13.2 4.8 -4.2 -10.3 -11.0
    19:00     -7.4 -1.8 3.3 6.7 6.5 1.8 -7.2      
    20:00         -7.6 -3.9 -4.3 -9.7        


    Azimuth of the Sun
      15-Jan 15-Feb 15-Mar 15-Apr 15-May 15-Jun 15-Jul 15-Aug 15-Sep 15-Oct 15-Nov 15-Dec
    Time of Day
    4:00           49.8            
    5:00       69.9 63.6 59.6 60.1 65.9        
    6:00     87.3 79.2 72.5 68.3 69.0 75.2 85.3 96.0 104.3  
    7:00 111.4 104.0 96.4 88.1 80.9 76.4 77.3 83.9 94.5 105.1 113.0 115.2
    8:00 120.4 113.3 106.0 97.5 89.5 84.5 85.5 93.0 104.2 115.0 122.6 124.2
    9:00 130.5 123.8 116.8 108.2 99.4 93.4 94.7 103.2 115.5 126.6 133.6 134.6
    10:00 142.4 136.3 130.2 122.0 112.3 104.9 106.3 116.3 129.8 140.7 146.7 146.7
    11:00 156.3 151.5 147.3 141.6 132.6 123.4 124.4 135.6 148.9 158.1 161.9 160.7
    12:00 172.0 169.2 168.8 169.5 168.0 161.2 158.7 165.3 173.4 178.1 178.7 176.0
    13:00 188.4 188.3 192.2 200.9 210.6 214.2 207.5 201.2 199.4 198.3 195.7 191.8
    14:00 204.0 206.3 213.5 225.9 238.2 243.9 238.7 228.7 221.3 216.2 211.2 206.5
    15:00 217.9 221.9 230.5 243.2 254.3 259.3 255.5 246.4 237.8 230.9 224.5 219.6
    16:00 229.7 234.7 243.7 255.8 265.5 269.6 266.6 258.8 250.3 242.9 235.8 230.7
    17:00 239.9 245.5 254.6 265.9 274.6 278.2 275.6 268.7 260.7 253.0 245.6 240.4
    18:00 248.9 255.0 264.1 275.0 283.1 286.2 283.8 277.6 270.0 262.2 254.4 249.0
    19:00     273.2 284.0 291.6 294.4 292.1 286.4 279.1      
    20:00         301.0 303.4 301.1 295.8      


    Get the data in CSV format


    Note:
  • Altitude are listed in degrees above the horizon. Azimuth values are listed in degrees, referenced to East of North.
  • Negative values indicate the sun is below the horizon
  • For further information, see solar_alt-az.asp

  • Source:
  • U.S.Naval Observatory.




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