CPC and Fresnel Lenses for Solar Cell Power

In summary: Compound Parabolic Concentrator (CPC) over the top of a high efficiency round solar cell. If a good design is achieved, the goal is to manufacture these for a potential small business. There are three main questions being considered: 1) Is it most efficient to use CPCs over highly-efficient round solar cells, or would adding a Fresnel lens or a "DTIRC" provide more efficiency? 2) Can a Fresnel lens be designed to filter out IR frequency and reduce heat for increased efficiency? 3) What are the most efficient solar cells, particularly round ones? Additional information and suggestions can be found through extensive literature research on the subject. It may also be beneficial to stack and align
  • #1
Yachtsman
13
0
I want to maximize solar cell efficiency regardless of the sun's angle and so I've been looking at placing Compound Parabolic Concentrator (CPC) over the top of a high efficiency round solar cell. If I come up with a good design then I would like to try and manufacture some of them to see if I could start a small business for myself. I have 3 questions that I am working on, I will appreciate any advice.

1. Will it be most efficient to use CPCs placed over the top of highly-efficient round solar cells? Or will it add efficiency to place a Fresnel lens over the top of each CPC? or perhaps using a "DTIRC" (Dielectric Total Internal Reflection Concentrator) rather than a CPC?

I could design the Fresnel lens to be a square that will refract all light into the round CPC directly below it so that I gain extra light, but I don't know if I will lose efficiency in other ways; e.g. it captures less sun angle than the CPC alone.

2. If I use a Fresnel lens can I design the prisms to filter out the IR frequency to reduce the heat of the solar cell? I've read that the cells become less efficient with heat.

3. What are the most efficient solar cells right now, especially the round shapped cells?


A fourth question is regarding books on this subject; can you tell me any recommended books that would help me with the mathematics of the CPC and Fresnel designs; and also to learn about high efficiency designs in general. Thanks for your help.
 
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  • #2
There is a lot of research in this area at the moment. There are a number of factors that need to be considered. For example, sending the light in at normal incidence to the solar cell may not be very efficient. This is because the path length of the transmitted light is small since it will pass in and out via the shortest distance. It is more desirable to trap the light as a traveling wave inside the cell so that the light wave travels large distances, allowing a long absorption. This is more easily obtained by sending the light in at an angle. Another problem is that the index of refraction of the solar cell is different from the air which causes some of the light to be reflected. Allowing an impedance transformer between the air/cell interface helps increase the transmission into the cell (at the same time it unfortunately helps facillitate the transmission out of the cell).

So an example of some of the ideas is to use a gathering lens in the front with a Bragg diffractor on the cell backing. The Bragg diffractor will scatter the light inside the cell at large angles so that when it reflects it does so in a traveling (or more a leaky) wave mode. Light gathering elements on the front of the cell can be far more sophisticated than a simple external lens. There are ideas of having a spherical lens on the surface and there are a lot of research in using nanoparticles as well. I would suggest doing an extensive literature research into what is currently being done on the subject.
 
  • #3
Born2bwire said:
There is a lot of research in this area at the moment. There are a number of factors that need to be considered. For example, sending the light in at normal incidence to the solar cell may not be very efficient. This is because the path length of the transmitted light is small since it will pass in and out via the shortest distance. It is more desirable to trap the light as a traveling wave inside the cell so that the light wave travels large distances, allowing a long absorption. This is more easily obtained by sending the light in at an angle. Another problem is that the index of refraction of the solar cell is different from the air which causes some of the light to be reflected. Allowing an impedance transformer between the air/cell interface helps increase the transmission into the cell (at the same time it unfortunately helps facillitate the transmission out of the cell).

So an example of some of the ideas is to use a gathering lens in the front with a Bragg diffractor on the cell backing. The Bragg diffractor will scatter the light inside the cell at large angles so that when it reflects it does so in a traveling (or more a leaky) wave mode. Light gathering elements on the front of the cell can be far more sophisticated than a simple external lens. There are ideas of having a spherical lens on the surface and there are a lot of research in using nanoparticles as well. I would suggest doing an extensive literature research into what is currently being done on the subject.


Given what you have said the first thing that comes to mind is to stack the solar cells at an angle, providing enough gap in between each cell to insert an impedence transformer to refract the light onto them at an optimal angle, or better yet, by stacking them vertically in sandwiched pairs with a shared aluminum backing, aligning them into parallel banks and providing an optimal light gap between each of the banks to facilitate the impedence transformer.

This kind of impedence transformer design allows light to bounce back and forth between the Left facing half of bank 1 with the Right facing half of Bank 2. Perhaps it may be possible to maximize absorption and minimize leakage by using the "Illumination Problem" proposed by Ernst Straus in the 1950's (see http://mathworld.wolfram.com/IlluminationProblem.html and http://numb3rs.wolfram.com/401/).

Here the impedance transformer now becomes a refraction chamber designed with either right triangles or ellipticals designed to maximize refraction and absorption, while minimizing leakage.

Please let me know if my comments spark any further ideas. Thanks.
 
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  • #4
Yachtsman said:
I want to maximize solar cell efficiency regardless of the sun's angle and so I've been looking at placing Compound Parabolic Concentrator (CPC) over the top of a high efficiency round solar cell. If I come up with a good design then I would like to try and manufacture some of them to see if I could start a small business for myself. I have 3 questions that I am working on, I will appreciate any advice.

1. Will it be most efficient to use CPCs placed over the top of highly-efficient round solar cells? Or will it add efficiency to place a Fresnel lens over the top of each CPC? or perhaps using a "DTIRC" (Dielectric Total Internal Reflection Concentrator) rather than a CPC?

I could design the Fresnel lens to be a square that will refract all light into the round CPC directly below it so that I gain extra light, but I don't know if I will lose efficiency in other ways; e.g. it captures less sun angle than the CPC alone.

2. If I use a Fresnel lens can I design the prisms to filter out the IR frequency to reduce the heat of the solar cell? I've read that the cells become less efficient with heat.

3. What are the most efficient solar cells right now, especially the round shapped cells?


A fourth question is regarding books on this subject; can you tell me any recommended books that would help me with the mathematics of the CPC and Fresnel designs; and also to learn about high efficiency designs in general. Thanks for your help.

Are you thinking of using something along the lines of what Solyndra manufactures, but with Fresnel lenses integrated into the system ? Just out of curiousity, are you familiar with electrowetting ?
 
  • #5
Isaacsname said:
Are you thinking of using something along the lines of what Solyndra manufactures, but with Fresnel lenses integrated into the system ? Just out of curiousity, are you familiar with electrowetting ?

Solyndra is very interesting, but I can't tell if how well they are truly bouncing light around in their glass tube to harvest all of the available light; they are very expensive--I'm hoping to provide a more reasonably priced solution.

I would rather use cheaper refraction material to focus a larger concentration of light onto the solar cells; and I'd like to use designs that maximize on harvesting the full spectrum of light.

I am also curious if work has been done to capture frequencies at ultra violet and greater. At what frequency does glass or other typical refraction materials stop refracting?

Thanks for asking about electrowetting; i will not rule it out, but I do think that concentrating large amounts of light is key. It's the cheapest way to turbo charge the solar cell I think.
 
  • #6
This material was studied and written up about forty years ago. It may applicable to your search:

Nonimaging optics (also called anidolic optics) is the branch of optics concerned with the optimal transfer of light radiation between a source and a target. Unlike traditional imaging optics, the techniques involved do not attempt to form an image of the source; instead an optimized optical system for optical radiative transfer from a source to a target is desired.

See: http://en.wikipedia.org/wiki/Nonimaging_optics

The use of a compound parabolic concentrator as field collector, in conjunction with a primary focusing concentrator for photovoltaic applications is studied.

See: http://www.archive.org/details/nasa_techdoc_19760005394
 

FAQ: CPC and Fresnel Lenses for Solar Cell Power

1. What is CPC and how is it used in solar cell power?

CPC stands for Compound Parabolic Concentrator. It is a type of optical device that is used to increase the amount of sunlight that can be captured by a solar cell. It works by directing and focusing the sunlight onto the solar cell, increasing its efficiency and therefore producing more power.

2. What are Fresnel lenses and how do they improve solar cell power?

Fresnel lenses are a type of lens that is made up of concentric rings, similar to a bullseye. They are often used in solar cell power systems to increase the amount of sunlight that is focused onto the solar cell. This results in a higher efficiency and more power production.

3. How do CPC and Fresnel lenses differ from each other?

CPCs are typically used for smaller solar cell systems, while Fresnel lenses are more commonly used for larger solar cell arrays. Additionally, CPCs are designed to collect and focus light from a specific angle, while Fresnel lenses can collect light from a wider range of angles.

4. Can CPC and Fresnel lenses be used together in a solar cell power system?

Yes, it is possible to use both CPC and Fresnel lenses in a solar cell power system. This can result in even higher efficiency and power production, as the lenses can work together to focus and capture more sunlight.

5. Are there any limitations to using CPC and Fresnel lenses in solar cell power systems?

While CPC and Fresnel lenses can greatly increase the efficiency and power production of solar cell systems, they do have some limitations. For example, they are most effective in areas with high levels of sunlight and may not be as effective in cloudy or shaded areas. Additionally, they can be more expensive and require careful installation and maintenance.

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