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    Solar Data - Sterling, 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 30.6 33.6 43.2 52.7 62.2 71.0 75.6 74.2 67.1 55.1 45.4 35.4 53.8
    Daily Minimum °F 21 23.3 31.8 40.3 50 59.2 64.1 62.8 55.4 42.4 34.2 25.8 42.5
    Daily Maximum °F 40.1 43.8 54.6 65.1 74.3 82.8 87 85.5 78.9 67.7 56.7 45 65.1
    Record High °F 75 79 89 92 97 100 104 104 99 90 84 78 104
    Record Low °F -18 -14 6 17 28 36 41 38 30 15 9 -4 -18
    Heating Degree Days note a 1066 879 676 369 140 7 0 0 44 319 588 918 5006
    Cooling Degree Days note a 0 0 0 0 53 187 329 285 107 12 0 0 973
    Average Humidity Ratio note b 0.26% 0.28% 0.39% 0.54% 0.86% 1.18% 1.36% 1.32% 1.07% 0.69% 0.47% 0.32% 0.73%
    Average Wind Speed mph 8.3 8.6 9.2 8.8 7.5 6.8 6.2 5.9 6.1 6.6 7.7 7.9 7.5
    Clearness note c 47% 49% 50% 51% 52% 54% 53% 52% 51% 50% 46% 44% 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.


  • Average Incident Solar Radiation (Btu/sq.ft./day)
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
    Horizontal
    Global 670 930 1250 1590 1820 1990 1910 1710 1410 1070 720 580 1310
    Std Deviation 65 86 99 158 117 120 134 95 103 94 68 43 50
    Minimum 530 730 1060 1330 1630 1740 1600 1550 1260 900 580 490 1180
    Maximum 780 1070 1420 1940 2040 2200 2130 1880 1610 1260 850 650 1400
    Diffuse 330 430 570 720 860 950 940 850 660 460 340 290 620
    North
    Global 200 270 350 450 550 630 590 500 390 300 220 180 390
    Diffuse 200 270 350 440 510 560 540 480 390 300 220 180 370
    East
    Global 440 590 760 930 1020 1080 1040 960 830 670 480 390 760
    Diffuse 250 330 430 530 610 670 650 600 490 370 270 220 450
    South
    Global 1040 1130 1100 970 830 790 810 930 1060 1170 1040 950 990
    Diffuse 360 430 500 550 580 610 610 600 540 460 370 320 490
    West
    Global 450 590 770 910 990 1050 1010 940 820 670 470 390 760
    Diffuse 250 330 430 540 620 670 660 600 490 370 270 220 460


    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 950 1290 1760 2220 2510 2600 2520 2250 1840 1370 980 820 1760
    North Global 190 250 330 430 580 680 620 480 370 280 200 170 380
    East Global 710 910 1140 1330 1420 1430 1390 1300 1140 920 720 630 1090
    South Global 1940 1980 1780 1390 1050 910 960 1210 1560 1800 1850 1850 1520
    West Global 710 910 1140 1330 1420 1430 1390 1300 1140 920 720 630 1090


    Average Transmitted Solar Radiation (Btu/sq.ft./day)
      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
    Horizontal
    Unshaded 440 630 890 1140 1320 1440 1390 1240 1010 740 480 370 930
    North
    Unshaded 140 190 240 300 370 410 390 340 270 210 150 130 260
    Shaded 130 170 220 270 330 370 350 300 240 190 130 110 230
    East
    Unshaded 300 420 540 660 720 770 730 680 590 470 330 260 540
    Shaded 270 370 470 570 620 660 630 580 520 410 300 240 470
    South
    Unshaded 780 830 760 630 520 490 500 600 720 840 780 720 680
    Shaded 760 770 610 420 360 370 370 400 530 740 750 700 560
    West
    Unshaded 310 420 540 650 700 740 720 670 580 470 320 270 530
    Shaded 280 370 480 560 600 640 610 570 500 420 290 240 470


    Shading Geometry in Dimensionless Units
    Window

    1

    Horizontal Overhang (h):

    0.504

    Verical Gap (v):

    0.315



    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 -7.7 -9.9          
    5:00       -7.1 0.2 2.2 0.3 -5.0 -10.6      
    6:00     -5.0 4.4 10.7 12.6 10.5 6.2 1.3 -4.5 -10.5  
    7:00 -5.6 -1.1 6.8 15.9 22.1 23.8 21.7 17.6 12.6 7.0 0.9 -4.5
    8:00 4.9 10.0 18.1 27.5 33.7 35.3 33.3 29.2 24.0 17.7 10.7 5.6
    9:00 14.1 19.9 28.7 38.7 45.2 47.0 44.9 40.7 34.7 27.4 19.5 14.3
    10:00 21.7 28.5 38.1 48.9 56.2 58.3 56.2 51.3 44.1 35.4 26.6 21.3
    11:00 27.2 34.9 45.2 57.0 65.4 68.4 66.1 60.1 51.0 40.7 31.1 25.9
    12:00 29.8 38.2 48.8 60.8 59.9 74.2 72.2 64.8 53.9 42.4 32.4 27.7
    13:00 29.2 37.8 47.9 58.8 66.8 71.1 70.1 63.0 51.8 40.1 30.4 26.4
    14:00 25.5 33.8 42.9 51.9 58.3 61.9 61.6 55.8 45.4 34.3 25.4 22.2
    15:00 19.2 27.0 34.8 42.2 47.6 50.9 50.9 45.8 36.3 26.0 17.9 15.5
    16:00 10.9 18.1 24.9 31.3 36.1 39.3 39.3 34.6 25.7 16.1 8.8 7.1
    17:00 1.5 7.9 13.9 19.8 24.5 27.7 27.7 23.0 14.4 5.2 -1.6 -2.8
    18:00 -9.5 -3.3 2.7 8.2 13.0 16.4 16.3 11.5 2.9 -6.4    
    19:00     -9.2 -3.3 2.2 5.6 5.4 0.5 -8.9      
    20:00         -8.4 -4.6 -5.1 -10.7        


    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         55.1 51.4 51.6          
    5:00       71.3 65.1 61.2 61.7 67.4 77.3      
    6:00     88.7 80.9 74.2 70.0 70.7 76.8 86.9 97.3 105.4  
    7:00 112.7 105.5 98.2 90.1 83.0 78.5 79.3 86.0 96.4 106.9 114.5 116.5
    8:00 122.1 115.2 108.2 100.0 92.2 87.1 88.1 95.5 106.7 117.3 124.6 126.0
    9:00 132.8 126.3 119.7 111.6 103.0 96.9 98.1 106.6 118.7 129.5 136.1 136.8
    10:00 145.1 139.3 133.8 126.5 117.3 110.0 111.2 120.9 133.9 144.2 149.5 149.3
    11:00 159.2 154.8 151.5 147.2 139.9 131.3 131.8 141.7 153.7 161.8 164.9 163.4
    12:00 174.8 172.6 172.9 175.1 175.8 171.4 168.0 171.9 177.9 181.5 181.6 178.7
    13:00 190.9 191.2 195.5 204.5 214.1 217.7 211.6 205.1 202.6 201.0 198.1 194.1
    14:00 206.1 208.6 215.7 227.6 239.0 244.1 239.4 230.2 223.2 218.2 213.1 208.5
    15:00 219.6 223.6 232.0 244.2 254.6 259.2 255.6 247.1 239.0 232.4 226.2 221.2
    16:00 231.3 236.2 245.0 256.6 265.9 269.8 266.8 259.4 251.4 244.2 237.3 232.3
    17:00 241.4 247.0 255.8 266.9 275.3 278.7 276.1 269.5 261.9 254.5 247.1 242.0
    18:00 250.6 256.6 265.6 276.3 284.1 287.1 284.7 278.7 271.4 263.9    
    19:00     275.1 285.7 293.1 295.7 293.5 287.9 281.0      
    20:00         302.9 305.2 302.9 297.8        

    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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