The term “heliostat” is not a word you hear that often. And when you do, it’s usually in the context of a solar power plant.

They actually look like something out of a science fiction movie. But they are very real, and they are an important part of solar power plants.

So, what the hell are they?

What Is A Heliostat?

A heliostat is a mirror that revolves so as to reflect sunlight to a certain target, regardless of the Sun’s position in the sky.

Heliostats are commonly used in concentrated solar power plants, where they direct sunlight onto a central receiver.

They can also be used for daylighting, to keep a reflector pointed at an arbitrary point by tracking the Sun’s position in the sky, and for solar cooking, as well as other applications.

Related: Solar Advantages And Disadvantages

What is a heliostat made of?

A conventional heliostat, often known as a glass/metal heliostat, is used in this arrangement.

The items are:

  • A steel structural support
  • An adhesive layer
  • A protective copper layer
  • A layer of reflective silver
  • And a top protective layer of thick glass

A steel structural support

The support structure of a heliostat consists of support arms, a revolving shaft, and a pedestal.

There are three alternatives for lowering the cost of a heliostat’s support structure. The use of pre-stressed concrete is one option, as is utilizing guyed masts, and the third is to use lattice tower construction.

An adhesive layer

The water-repellent glue is strong enough to support the mirror while also having sufficient shear tolerance to allow for the two surfaces’ relative movements.

A protective copper layer

The copper layer protects the silver from tarnishing.

A layer of reflective silver

The surface of a heliostat’s mirror is typically covered with a thin layer of aluminum, which has good reflectivity in the visible spectrum but poor durability.

Silver, on the other hand, has both good reflectivity and durability. However, it is expensive, so it is usually used only on the most critical surfaces, such as those of primary mirrors in astronomical telescopes.

A top protective layer of thick glass

The final and topmost layer is a sheet of glass. This protects the silver from corrosion and keeps the surface clean for optimal reflectivity.

How Do Heliostats Work?

Most heliostats have a single axis of rotation, to keep the mirror pointing at the target as the Sun moves across the sky.

This axis is usually horizontal but can be tilted if necessary. The mirror is kept pointing at the target by a control system that uses sensors to track the Sun’s position.

The mirror is usually a flat plate, but can be curved or parabolic if necessary. The size of the mirror varies depending on the application but is typically around 4 to 5 meters square.

Related: Solar Panel Statistics

Heliostat Field

One of the most promising concentrated solar power systems available in the market is a Heliostat Field or Solar Tower Collector.

The heliostat field collector’s high operating temperature allows it to be used in a wide range of applications, including solar power generation and industrial commodity production.

What Are The Benefits Of Heliostats?

There are many benefits to using heliostats.

First, they can be used to concentrate sunlight onto a small area, which increases the amount of solar energy that can be collected.

Second, they can be used to track the Sun’s position, so that the reflector is always pointing at the Sun, regardless of its position in the sky.

Third, they are relatively inexpensive to build and operate, making them a very attractive option for solar power plants.

What Are The Drawbacks Of Heliostats?

There are a few drawbacks to using heliostats.

First, they require a large amount of land to be effective.

Second, they can only be used in areas with clear skies and good weather.

Third, they require regular maintenance and calibration to ensure that they are pointing at the Sun correctly.

How Do Heliostats Compared To Solar Panels?

Solar panels are the most common type of solar energy collector. They are simple to build and operate and can be used in a wide variety of locations.

However, they have a few drawbacks. First, they are only effective when the Sun is directly overhead, which limits their usefulness in many parts of the world.

Second, they are not very efficient at collecting solar energy, so a large number of panels are needed to collect a significant amount of energy.

Heliostats, on the other hand, are much more efficient at collecting solar energy and can be used in a wide variety of locations. However, they have a few drawbacks of their own.

First, they require a large amount of land to be effective. Second, they can only be used in areas with clear skies and good weather.

So, which is better? Solar panels or heliostats? The answer depends on the specific application. In general, solar panels are better for small-scale applications, while heliostats are better for large-scale applications.

Heliostat Size

Rather than concentrating solar power via a large collection of heliostats (as in a solar power tower plant), as is done at many advanced plants, a single heliostat about 1 or 2 square meters in the area reflects non-concentrated sunlight through a window or skylight.

The core technology of a heliostat is the same as that of a solar panel: it is a device that absorbs sunlight and converts it into electricity.

Related: The Advantages and Disadvantages of Solar Cells


Where are heliostats found?

The three HFS configurations are heliostats surrounding the central receiver from all angles, heliostats positioned on the north side of the tower with an enclosed heat transfer surface, and a central receiver with a north-facing heat transfer surface, and heliostats mounted on it.

Are heliostats efficient?

Yes, heliostats are very efficient. A single 1-m2 heliostat array has an efficiency of only about 12%. To improve their light-redirecting capabilities, these heliostats must be split and canted to increase their efficiency.

How do heliostats move?

A small heliostat, placed on the ground or on a building structure like a roof, shifts up and down and to the left and right in order to compensate for the sun’s continual movement. As a result, the reflected light is kept fixed on its target (e.g. window).

In Summary

Now you know a little bit more about heliostats and how they work.

They look totally amazing and serve an important purpose in solar power plants.

They have a few drawbacks, but overall they are a very efficient way to collect solar energy.

If you’re interested in learning more about solar energy, be sure to check out our other articles on the topic!

About the Author

Passionate about helping households transition to sustainable energy with helpful information and resources.

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