Solar Collectors

in Solar Energy

THE DOUBLE-PARABOLIC SOLAR COLLECTORS

They consist of a curved mirror that has curvature in a curved mirror parabolic two axles. The form of the solar collectors is similar to satellite dishes to track spacecraft.

The double-parabolic solar collectors can get extremely high temperatures, but have the problem of requiring a very precise monitoring of the Sun and also in two directions: from east to west and from bottom to top. This requires a complex tracking mechanism with two motors, one to perform the horizontal movement and one for vertical movement.

Heliostat

The heliostats are flat mirrors which are part of a collector of large concentration.
The heliostat field is similar to one collector. Each heliostat consists of several flat mirrors subject to a support.

The heliostats are oriented to the sun by a movement in two directions, so that sunlight reflected by the heliostat affect a receiver.

Because the heliostats are located in various positions of the field, the angle at which should be directed is different for each. Notwithstanding this, as each heliostat occupies a fixed position by means of a computer ¬ I can easily control the correct positioning of all the heliostats, based on geometrical considerations. Thus, all heliostats directed its rays into a small area due to the amount of radiation will give a very high concentration factor.

COLLECTORS SPECIAL CONCENTRATION

There is a variety of special concentrating collectors, which have some interesting properties. Here we will discuss two of them: the cylindrical collector and collector Winston.

The collector consists of a cylindrical arc of cylinder (usually half-cylinder) with the mirror on the inside. The advantage over the parabolic trough is its lower cost of manufacture: it is easier to make a cylindrical shape that a dish.

A beam of parallel rays is reflected in a cylindrical surface does not lead to a single focus, but the so-called paraxial focus, which is located approximately 0.5 times the radius. Among the paraxial focus and the mirror surface is the focus area of the sun. In the vicinity of the mirror surface is an area where sunlight affect that have undergone several reflections.

The receiver usually consists of a rectangular tube located in this area of concentration of solar rays.

Given the characteristics of these collectors, direction need not be very accurate, then, for a wide range of angles of incidence, the solar radiation reflected in the mirror always have an impact on the receiver.

The Winston collector is a collector consisting of two parabolic trough mirrors and a flat surface, which is the receiver. The two mirrors are arranged symmetrically about the axis of symmetry, and give such a very closed manifold

The geometric characteristics of the collector make any radiation coming through the cone aperture and is absorbed into the receiver, which means that does not require tracking the sun while it is within the cone of opening. This way some scattered radiation can be captured.

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