Understanding Fresnel Lens Collector And Its Uses

Solar panels harness the sun rays falling on them. While some rays are absorbed, the others get reflected. 

Several technologies are used for solar energy concentration to maximise the benefit from sunlight. 

One such technology is the use of the Fresnel lens. It is an effective way to make full use of sunlight.

Let us learn more about Fresnel lens collector technology and its benefits. 

What is a Fresnel Lens? 

A Fresnel lens is a succession of concentric rings etched into the plastic. Each ring consists of an element of a simple lens. 

These lenses are arranged in a specific manner on a flat surface so that they provide a short focal length. 

They have a thin and lightweight construction. Fresnel lenses are available in small as well as large sizes, and their excellent light gathering ability makes them useful in various applications. 

In addition to solar panels, Fresnel lenses find application in magnifiers, image formation, and projection lenses in illuminating systems. 

How are Fresnel Lens Made?

You must know the manufacturing of Fresnel lenses to understand their applications. Initially, Fresnel lenses were fabricated by grinding and polishing glass manually. It was a tedious task. 

Later with the advent of optical-quality plastics and injection-moulding technology, Fresnel lenses were easily made and were practically implemented in various industrial and commercial applications. 

Today Fresnel lenses are made of acrylic or polycarbonate or vinyl based on the desired wavelength of operation. 

Fresnel lenses for solar applications are mostly made from acrylic as it has high transmittance in the visible and ultraviolet (UV) regions. Polycarbonate is also used because of its resistance to impact and high temperature in harsh environments. 

How does a Fresnel Lens Work?

If you happen to observe a magnifying glass, you must have noticed that it is thick in the middle and tapers at the edges. 

Similarly, a thin piece of plastic is used to make a Fresnel lens. It is ridged on one side and flat on the other. It is most suitable for applications where image quality is not necessary.

Large Fresnel lenses are used as ­solar concentrators. These lenses increase the amount of sun striking individual PV cells with a concentration ratio of 500:1. 

Thus, the active surface of the solar cell can be reduced in volume, and only a small volume of silicon solar cell materials will be needed.

What are the Different Applications of Fresnel Lens? 

Do you know the earliest application of the Fresnel lens? The use of these lenses in lighthouses is amongst the earliest and most popular applications. 

Since then, they have been utilised in various applications, including light collimation, magnification, and collection. 

1. Light Collimation

Fresnel lenses are capable of effectively collimating a point source. Place the lens exactly one focal length distant from the source, and it will collimate the light. 

The lens has two sides, a grooved side and a plain side. You must place the grooved side towards the longer conjugate in a finite-conjugate system to get the best performance.

2. Light Collection

One of the most common applications is the collection of solar light. The Fresnel lens collector collects the sunlight, which is nearly parallel. 

So, when you use a Fresnel lens collector, it efficiently concentrates light onto a photovoltaic cell. 

A Fresnel lens can also be used for home maintenance like heating a home or pool. Solar heaters and solar cooling systems also use Fresnel lens collectors. 

It is important to note that the overall surface area of the Fresnel lens determines the collected light amount. 

3. Magnification

Another implementation of the Fresnel lens is magnification. It is used as a projection lens or magnifier. But this application is the least popular because of the high level of distortion produced. 

The magnified image quality does not compare to that of a higher-precision system because of the amount of distortion.

What is the Use of Fresnel Lens Collector in Solar Power Systems?

Fresnel lens collector is popularly used as a solar concentrator since it offers high optical efficiency. It has minimal weight and low cost. 

It gathers sunlight and makes it available for solar panels. So, a Fresnel lens collector has the potential to maximise your benefit from a solar power system. 

Benefits of a Fresnel Lens Collector

The most striking advantage of a Fresnel lens collector is that it offers the highest solar-to-electric conversion efficiency. 

These lightweight lenses can elevate the density of solar energy. Thus, the Fresnel lens collector is perfect for economical photovoltaic power generation.

Its concentration ratio, size, and shape are the major design aspects for optimisation. 

Also, the use of a Fresnel lens collector allows reaching high temperatures up to 600°C at very short exposure times of about 1 minute. 

Moreover, they also make it possible to maintain high temperatures up to 1200°C for a long time (up to several hours).

Conclusion

Fresnel lenses are an asset to solar power systems. Photovoltaic cells are able to collect high amounts of sunlight and thus produce more solar power. 

While commonly found in solar applications, a Fresnel lens collector is ideal for various applications because it is inexpensive, thin, and lightweight.  

They are not a new technology and range back to the nineteenth century, but improvements in their manufacturing materials and technologies have increased their use. 

FAQs

Q. How do Fresnel lenses work?

Fresnel lenses create bright light beams using glass prisms in a metal frame. The prisms are mainly responsible for changing the direction the light is travelling in. 

Thus, all the light that exits the lens appears in the same direction. The prisms refract and reflect the light.

Q. What are the two types of Fresnel lens collectors?

The two types of Fresnel lens solar collectors are:

• Point focusing Fresnel lens collector: It is suitable for high-temperature applications like solar concentration systems.  
• Line focusing Fresnel lens collector: It is used for mid-temperature applications like solar cooling. 

Q. What is a Fresnel lens solar concentrator?

A solar concentrator using Fresnel lenses is called a Fresnel lens solar concentrator. It takes a large area of sunlight and directs it towards a spot by bending and focusing the light rays. 

The same principle is used in a magnifying lens to focus the sun’s rays and start fires.