Tracking motions in current heliostats are usually performed in discrete steps, even though the motion of the sun is continuous. Aiming errors due to the discrete steps are often about 1 mrad or more. A significant reduction of tracking error by smooth continuous tracking is presented. The implementation uses an electronic speed control unit to modify the rotational speed of the two AC motors on an existing heliostat. The continuous tracking system was implemented and successfully operated at the Weizmann Institute heliostat field. Measurements of heliostat motion show that aiming error due to tracking intervals was practically eliminated. A comparison of heliostat motions and flux on the target in step-tracking and continuous tracking modes is reported.

Issue Section:
Technical Papers
Keywords:
solar energy concentrators, solar energy conversion, tracking, motion measurement, measurement errors
Topics:
Errors, Motors
1.
Vant-Hull, L. L., Izygon, M., and Imhof, A., 1999, “Optimization of Central Receiver Fields to Interface with Applications Requiring High Flux Density Receivers,” 9 Intl. Symp. Solar Thermal Concentrating Technologies, Journal de Physique IV, Flamant, G., Ferriere, A. and Pharabod, F., Eds., Font-Romeu, France, pp. 65–70.
2.
Buck, R., Bra¨uning, T., Denk, T., Pfa¨nder, M., Schwarzbo¨zl, P., and Tellez, F., 2001, “Solar Hybrid Gas Turbine Based Power Tower Systems (REFOS),” Solar Engineering 2001, Washington, D.C.
3.
Karni
,
J.
,
Kribus
,
A.
,
Rubin
,
R.
,
Sagie
,
D.
,
Doron
,
P.
, and
Fiterman
,
A.
,
1997
, “
The DIAPR: A High-pressure, High-temperature Solar Receiver
,”
J. Sol. Energy Eng.
,
119
, pp.
74
–
78
.
4.
Levy, I., and Epstein, M., 1998, “Design and Operation of a High-power Secondary Concentrator,” 9th International Symposium on Solar Thermal Concentrating Technologies, Flamant, G., Ferriere, A. and Pharabod, F., Eds., Odeillo, EDP Sciences, pp. 575–580.
5.
Monterreal, G., Garcia, G., Romero, M., and Barrera, G., 1997, “Development and Testing of a 100 m2 Glass-metal Heliostat with a New Local Control System,” Solar Engineering 1997, Washington D.C., pp. 251–259.
6.
Stone, K. W., and Lopez, C. W., 1995, “Evaluation of the Solar One Track Alignment Methodology,” Solar Engineering 1995, Lahaina (Hawaii), 1, pp. 521–526.
7.
Stone, K. W., and Sutherland, J. P., 1997, “Solar Two Heliostat Tracking Performance,” Solar Engineering 1997, Washington, D.C., ASME, pp. 237–242.
8.
Kribus, A., Vishnevetsky, I., and Yogev, A., 2002, “Closed Loop Control of Heliostat Fields,” 11th International Symp. Concentrating Solar Power and Chemical Energy Technologies, Zurich.
9.
Schubnell, M., and Ries, H., 1990, “Velocity Controlled Tracking of the Sun,” Solar Energy Materials 21, pp. 207–212.
10.
Duffie, J. A., and Beckman, W. A., 1991, “Solar Engineering of Thermal Processes,” Wiley, New York.
11.
Ries
,
H.
,
Kribus
,
A.
, and
Karni
,
J.
,
1995
, “
Non-isothermal Receivers
,”
J. Sol. Energy Eng.
,
117
, pp.
259
–
261
.
12.
Kribus, A., Doron, P., Karni, J., Rubin, R., Reuven, R., Taragan, E., and Duchan, S., 2000, “A Multistage Solar Receiver: The Route to High Temperature,” Solar Energy 67, pp. 3–11.
13.
Kribus, A., Huleihil, M., Timinger, A., and Ben-Mair, R., 2000, “Performance of a Rectangular Secondary Concentrator with an Asymmetric Heliostat Field,” Solar Energy 69, pp. 139–151.
14.
Mancini, T., 2000, “Catalog of Solar Heliostats,” IEA SolarPACES Report III-1/00.
Copyright © 2004
 by ASME
You do not currently have access to this content.