An approach to the design of active window shades is developed to control the direct solar gain through a window. Using simple actuation hardware and sensors, a control strategy is presented that automatically adjusts window shades to save HVAC energy by controlling direct solar radiation passing through a window. The control algorithm is based on a simple approach that admits direct light in the winter and blocks the direct light in the summer, while providing shade adjustment that affords maximum visibility through the window. Cloudy skies or indirect sun result in horizontal placement of the shades, and the shades close at night. The implementation uses two thinfilm photovoltaic cells as sensors and a control algorithm that is independent of the window orientation, latitude, or solar time, so that it operates properly in any installation location. Preliminary analytic and test results show significant energy savings when the automatic window shades are compared with a window without shades, and with a window outfitted with fixed horizontal shades.

1.
Bilgen
E.
,
1994
, “
Experimental Study of Thermal Performance of Automated Venetian Blind Window Systems
,”
Solar Energy
, Vol.
52
, No.
1
, pp.
3
7
.
2.
Duffie, J. A., and Beckman, W. A., 1991, Solar Engineering of Thermal Processes, John Wiley and Sons, New York.
3.
DiLaura
D. L.
,
1984
, “
Recommended Practice For the Calculation of Daylight Availability
,”
Journal of the Illuminating Engineering Society
, Vol.
13
, No.
4
, July, pp.
381
392
.
4.
Kinney, L. F., and Reynolds, D. R., 1983, “Daylighting and Shuttering: Reflective Insulating Blind System Mechanical Design and Preliminary Performance Data,” Alternative Energy Sources IV, Proceedings of the Sixth Miami Conference on Alternative Energy Sources, Dec., 1983, pp. 159–173.
5.
Mills
L. R.
, and
McCluney
W. R.
,
1993
, “
The Benefits of Using Window Shades
,”
ASHRAE Journal
, Vol.
35
, No.
11
, pp.
20
27
.
6.
Rubin, A. I., et al., 1978, “Window Blinds as a Potential Energy Saver, A Case Study,” NBS Building Science Series, #112, U.S. Department of Commerce, National Bureau of Standards.
7.
Selkowitz, S., 1984, “Influence of Windows on Building Energy Use,” presented at “Windows in Building Design and Maintenance Conference,” June 13–15, Gothenburg, Sweden.
8.
Skerrett
P. J.
,
1993
, “
Window Technology; Part Two. Through the Glass Darkly
.”
Popular Science
, Vol.
243
, No.
1
, pp.
80
85
.
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