Rainbow on Photo Voltaic.

Thanks for help!

You're welcome. Interesting idea; hope you get good results.

Usbport that is a very nice reply to repnitskiya. Greg

Thanks!

I really like this idea. I think the main challenge is that you've created a very complex system of solar cells. Each one is a current limiter, and the spectrum is going to change throughout the day. That can be overcome or accepted. The enemy in concentrated solar cells is heat. I don't know what the materials are that would make this prism and mirror work, but I applaud your creativity, and you should look at how to make the heat do work to gain more efficiency.

Sorry, I forgot to tell that the mirror will be moved during the day by two-axis tracking system following the sun, like a sunflower does. Now they already use photovoltaic on medium and even high concentrated systems; lower concentration sometimes does not require coolant, but high-concentrated systems, like Zenith (http://www.zenithsolar.com/), need water or some other coolant. Photovoltaic can be hot (up to some point) and still work well. The small mirror would be made of metal (maybe bronze or copper covered with nickel or chrome) with coolant (water or, better oil for higher temperature, depending on needs) inside, so it will not make red-hot.

Thank you for your comment!

You may want to consider the effect of heat on PV efficiency. Google "The Impact of Ambient Temperature on the Efficiency of Photovoltaic Cells". Seems to be a paper with some quick data.

Yes, I was thinking about something like dichroic mirror when looking at DVD on light; it also creates 'rainbow'. This mirror is covered with special optical solution that deviate spectrum colors and if properly polarized, might be used on this system (this is probably something from micro or nano-technologies; I am completely illiterate in it).That is why I rather considered putting many small prisms on a big mirror (sheet of thin glass with many cut in prisms in it covered with mirror coating from inside). The idea you describe was my first choice and it seamed to work much better, but I quit it because I found out that light and heat are very friends; not only infra-red rays produce heat, but also all others. Let's look what the Wiki says:

" Infrared light from the Sun only accounts for 49%^[11] of the heating of the Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths." (Wikipedia, http://en.wikipedia.org/wiki/Infrared).

It confused me a little bit, but if you read the sentence above carefully (not like I did), visible light will produce heat only after it is "re-radiated at longer waves." So, before it is "re-radiated", it might give us some electricity exhausting all of its energy on PV?

Yes, I think you right!

Thank you very much!

Dichroic optics, such as the thin film anti-reflection coating on a camera lens, can be "tuned" to pass certain wavelength bands, while reflecting others. One thing you should look at before you dive way off the deep end on the optics, though is the economics of the overall device per kWH produced. Adding a whole wide array of various types of PV may only serve to drive up cost without delivering any extra punch. Consider using a silicon type with the lowest heat coefficient for loss of output that simultaneously has the widest response to the spectrum that will be incident, and you will come up a winner.

I like your project. Concentrators are being used more and more in solar. Your prism thought is already being used. A number of start up and pre-start up companies are trying this approach. On of the main advantages of splitting the light is you don't need a solar tracker. A number of companies are doing this with film technology to increase the output of traditional panels. You're probably going to have heat issues with your concentrator. Be careful or you might fry your cell during testing until you get the cooling right.

You might want to check these guys out. http://www.prismsolar.com/ Good luck on your project!

You would almost have to use Automobile hoses that have already cleared for hot oil.

There would be gasket issues.Why use oil when we are at a time when oil is

getting hard to come by.It might be wiser to use some waste product that is similar

to it and more affordable. The questions you need answered are easy to locate in

Wikipedia.com under any word you have used.Soliel Power Plants have built a similar

type of energy producing plant in the CA. Desert using hot steam (water)in copper

tubing and large mirror panels that get turned manually by the plant operator.ds

How about combining a hot water system with the PV. Tubes behind the PV panel soak up heat from the panel, and keep its temperature down, hopefully improving performance.

This is being said without trying to discourage you. Most in the solar-thermal field use antireflective coating on the tube to couple the energy to the absorbing medium. I totally get the idea of splitting the incident radiation, and allowing the un-reflected light to reach the absorbing media. There is a problem in concentrated PV that when the PV material heats up, efficiency is majorly lost. You could see some improvement by efficiently de-coupling the infrared (still a major component of incident radiation), from the visible and ultraviolet. I am not an expert on which materials to use for UV, and which for visible, but if you used a dichroic mirror as mirror 2, where the mirror was set up to have high reflectivity below 700nm, and high transmissivity above that wavelength, I think you would have something indeed. Good luck. Perhaps just use "run of the mill" PV material below the prism, or no prism at all, rather a lens to spread the light back to the size of the PV, so you don't "cook" it. (For example a concave cylindrical lens, but you have to choose material carefully to not cut-off the UV.)

You are expressing creative ideas. In a large field like solar power, with many thousands of people working in it, you can expect to find that most of the ideas you create have already been looked at by others. This is normal and should not discourage you. My comments are about how you analyze your ideas. You have created an interesting idea set. Your intention is "improving efficiency of current solar-power systems." It sounds to me that you are intending to "create new solar power system(s) of higher efficiency than current systems." This may seem to be quibbling over minor details, but it is very important to identify exactly what is the goal of your work. This is because I am suggesting that you need to quantify the elements of your design. That is, you should have at least an estimate of how much the efficiency changes as a result of what you do, and where the effective changes occur. As an example, you collect heat from the mirrored tube because the "steel mirror-like bumper on my van" gets very hot. Well, how hot? Or more importantly, how much energy does it absorb? The reason it gets hot (rises in temperature) is that even though it is reflecting most of the the incident radiation, what the mirror-like finish is best at doing is NOT radiating at the IR frequencies, and since in general more heat is lost from ordinary objects from radiation than from conduction, the internal temperature of the bumper rises to "very hot." Yet just how much energy are you actually going to collect from adding this element of hot oil thermal collector? As has been stated above in another post, the efficiency of present-day solar collectors falls as the temperature rises (the transitions between energy levels in the molecular structure changes), so that you will not get twice the electric power for twice the incident energy. Your "efficiency" seems to be aimed at the amount of energy in the solar radiation, which at present is not in short supply. How about "energy collected per dollar of investment, or of running cost?" Please do not be discouraged by what I say. If you are ready to add this design approach to your work, you will be ahead of the game. Just do not let it squelch the creativity you clearly have within you.

Well said.

Thanks for your warning and comments! No, you are not discouraging me, and neither does James Steward (#12). I understand that you are here not to discourage someone, but to help, and I greatly appreciate this! I am glad that our discussion is very fruitful (I got new vision on this problem, thanks to all of you) and understand that you worn me to prevent from possible mistakes. Thank you all!

You touched several great questions like efficiency and cost per Watt.

Let me explain what I expect.

First, I am not so naive to expect 2kW of energy from the area that receives only 1kW from the Sun. What I think is that mirror is much cheaper than PV; that is the reason why people try to use concentrated light even on PV. They also build thermal solar-power plants; they do it for a reason: cheaper to build even though the system is much more complicated to build and maintain than PV facility.

The idea to split lights came to me about a year ago when I read somewhere about thermal solar-power plant. I posted it on this forum (http://cr4.globalspec.com/thread/46219#newcomments); my purpose was maybe just like yours: to make our life a little bit better, to breath with fresher air... it's not about money. Solar plants are good especially because they replace fossil-fuel plants; they considered to be 'green' and 'clean'. However, they are not completely 'green' because the area they take is not as green as it used to be before; grass or trees are much greener! In a long run these plants might become another disaster (maybe not like fossil-fuel facilities, but still...) that we will suffer from. That is why efficiency is important for us; I try to find the way how we could utilize all spectrum of the sunlight, not just some part of it. The system with two mirrors was my second choice because it involves very high precision: because the mirrors are faraway one from another, it is easy to reflect the light on the wrong point of the small mirror; if the ray is not pointed exactly to the center-point, it will not come through the prism but will go back to the sky. That was my biggest concern. The reason why I chose this system was because I read that visible light also produces heat (just like you, I concerned about efficiency of hot PV), but thanks to "TopCT", #5 of our discussion, I read it again and think that it is not as big problem as I thought; now I want to turn back to my first choice.

The cost per Watt shell drop down due to using less of PV; I mention much less. Their area will be tens of times smaller than the area of mirror! If IR will be concentrated on a thin heat-collector, the PV-strips will not be much wider, but they will be made of different materials that will work on different colors. One of the problem of PV is that it is 'picky' on spectrum: they might work on some bandwidth while other colors remain useless. With splitting light and using different materials for PV this problem might be gone for a good! The concentrated visible and UV light should not heat PV saving its efficiency.

Yesterday I read Fredski's reply (#9) and went through the Web site he provided. Thank you, Fredski. Something like that HPC Film can be used on my big reflector instead of prism-set. That film deviates light too hard, and we need much smaller deviation; hopefully, it is possible with another similar material.

You know, Fredski, I am glad it is possible to collect light 'from all directions', not only from direct sun; it is just great because these panels can be used on buildings and other structures like above the roads and parking lots. About a year ago I posted another thread on this forum (http://cr4.globalspec.com/thread/46222#newcomments). I think the panels that 'Prism Solar' came up with would be a good solution!

Thank you, gentlemen, one more time for your help and the great discussion we have.

God bless you all!

Andrey.

To be more specific in commenting, several aspects of your ideas have already been looked at by others, and found to be not useful to their own work. This includes splitting the frequencies and using customized PV materials for different bandwidths and collecting the energy for PV with mirrors. I would like to emphasize the importance of quantifying - using actual numbers (or ranges of numbers, or symbols to represent numbers, etc) - the characteristics of your concepts. So when you consider a mirror, ask yourself how big a mirror? How accurate does the surface need to be? Can this be purchased from someone else, or do I have to manufacture it myself? How much energy (or power) does the mirror actually absorb? If the secondary mirror is absorbing enough power to justify the cost of a heat collection system, how much energy am I losing in the primary mirror? In general, anything you do to the energy flow will lose you something. So ask yourself, what is it I am losing? The point of using a cost analysis of your ideas is not so you can make lots of money, but so that you can identify whether or not the project is feasible. Good luck. PS - there is much more that can be addressed to the details of your ideas.