Page 256 - Design of Solar Thermal Power Plants

4.2 PRINCIPLES FOR CONCENTRATION FIELD LAYOUT 239

solar beam concentration calculation for a concentrator with errors
extremely difficult; also, precision is low, so experimental values may be
comparatively more precise. Due to the different temperature strains of
the concentrator support frame under different temperatures, a good
equation must consider the influence of temperature on optical concen-
tration precision or give separate calculation equations for winter and
summer in estimating concentrator output energy during winter and
summer:

4.2.5 General Principle for Heliostat Field Layout

According to Figs. 4.11e4.14, there are a few typical heliostat fields for
solar thermal tower power plants.
1. For the heliostat field in a solar tower power plant, for the case
where the receiver’s shape (cylinder or cavity), location, and
aperture have been determined, the heliostats shall be arranged
following the basic principle of achieving optimal annual efficiency
of the heliostat field. In this case, tower height, the distances
between heliostats and the tower, and solar shading and blocking
between various rows of heliostats shall be considered in
determining heliostat locations.
In cases where the receiver’s aperture and location have not been
determined, four factorsdthe receiver’s geographic location,
position, and aperture, as well as the solar concentrating fielddshall
be comprehensively considered while striving for solar-
concentrating field design optimization. From the 1970s through the
1990s, a variety of heliostat field design software was developed,

FIGURE 4.11 North sector field of heliostats at the Beijing Dahan power plant (1 MW,
Beijing, China).