Fresnel Lens Concentration Ratio

In summary, the conversation discusses using a Fresnel lens from an overhead projector to concentrate sunlight onto a glass window for a solar oven project. The person asking for help is trying to calculate the concentration ratio of the lens, and has attempted a method using the lens and window area. However, their professor has stated that this is not the correct way to calculate the concentration ratio and they are seeking assistance in finding the correct method.
  • #1
TJ_Laser
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Homework Statement


Hey guys, I am part of a group building a solar oven. It will consist of insulated sides and a glass window on the top. Rather than using reflectors we want to salvage a Fresnel lens from an overhead projector to concentrate sunlight onto the glass window. Part of the assignment is to calculate the steady-state temperature inside the box.

Homework Equations


How do I calculate the concentration ratio for a Fresnel lens?

The Attempt at a Solution


To keep the initial calculation simple I assumed an area of 1 m^2 for the lens (I know this is too big) and 0.25 m^2 for the window. I divided the lens area by the window area to get a concentration ratio of 4. My professor says this is not how you calculate the concentration ratio, and that I should research the correct method.
 
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  • #2
I'm stumped. Can someone help me figure out the correct way to calculate the concentration ratio of a Fresnel lens?
 

FAQ: Fresnel Lens Concentration Ratio

1. What is a Fresnel Lens Concentration Ratio?

A Fresnel Lens Concentration Ratio is a measure of the amount of light that is focused by a Fresnel lens. It is the ratio of the area of the incoming light to the area of the focused light. A higher concentration ratio means that more light is focused, resulting in a more intense beam.

2. How is the Fresnel Lens Concentration Ratio calculated?

The Fresnel Lens Concentration Ratio is calculated by dividing the diameter of the lens by the focal length. This ratio is commonly denoted as "C" and can range from 1 (no concentration) to 1000 or more (high concentration).

3. What factors affect the Fresnel Lens Concentration Ratio?

The concentration ratio of a Fresnel lens is affected by several factors, including the shape and curvature of the lens, the material it is made of, and the angle of incidence of the incoming light. Higher quality lenses with smoother surfaces and higher refractive indices will generally have higher concentration ratios.

4. How is the Fresnel Lens Concentration Ratio used in solar energy applications?

The Fresnel Lens Concentration Ratio is an important factor in the design of solar concentrators, which use lenses to concentrate sunlight onto a small area. By increasing the concentration ratio, more light can be focused onto the solar cells, resulting in higher energy output. However, there are trade-offs to consider, such as the cost and efficiency of the lens.

5. Are there any limitations to the Fresnel Lens Concentration Ratio?

While a higher concentration ratio can result in a more intense beam of light, there are limitations to consider. The lens must be able to withstand the intensity of the focused light without melting or deforming. Additionally, any imperfections or dirt on the lens can reduce the concentration ratio and affect the overall performance.

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