question re Fresnel lenses

The Original Ralph
The Original Ralph Solar Expert Posts: 50 ✭✭✭✭
off, this is my first post, and i've got a long climb up the learning curve or re-learning curve on solar power. I had gotten close to pulling the trigger and got side tracked a few years back.

about 3-4 years ago, the tv show Mythbusters did a segment on a fresnel lense that multiplied the current output of solar panels considerably (my memory is bad, but iirc, by a factor of 8-10X). Basically the lenses was a curved glass tunnel with ridges on the undersurface that captured ambient light and redirected it down toward the lense. (think in terms of a hotel canopy leading out to the sidewalk's edge, but glass not canvas).

did anything become of that or anyone introduce any to the market?

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: question re Fresnel lenses

    Welcome to the forum.

    Did anyone ever develop Fresnel lenses for solar panels? Probably not. If you concentrate the sun's rays on a panel you concentrate the heat that builds up as well. So, more power but shorter panel life. Conceivably instantaneously shorter life. We've actually had a few discussions here about reflecting light on to panels for increased output. Based on the experiences of those of us who live in snow half the year, it does work (especially with snow as the cold temps also help panel output). But as a practical application it has its drawbacks.

    I believe there is a company making (or did at one point) panels with lenticular lenses to grab the sun from the rising and setting angles and angle it to the panel. This results in a more consistent output during daylight (not unlike the "right amount of cloud" effect) but reduces peak output at midday due to its diffusing effect.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: question re Fresnel lenses
    Welcome to the forum.

    Did anyone ever develop Fresnel lenses for solar panels? Probably not.
    They have (http://www.greenrhinoenergy.com/solar/technologies/pv_concentration.php), but they are generally not for conventional flat modules.
  • The Original Ralph
    The Original Ralph Solar Expert Posts: 50 ✭✭✭✭
    Re: question re Fresnel lenses
    Welcome to the forum.

    Did anyone ever develop Fresnel lenses for solar panels? Probably not. If you concentrate the sun's rays on a panel you concentrate the heat that builds up as well. So, more power but shorter panel life. Conceivably instantaneously shorter life. We've actually had a few discussions here about reflecting light on to panels for increased output. Based on the experiences of those of us who live in snow half the year, it does work (especially with snow as the cold temps also help panel output). But as a practical application it has its drawbacks.

    I believe there is a company making (or did at one point) panels with lenticular lenses to grab the sun from the rising and setting angles and angle it to the panel. This results in a more consistent output during daylight (not unlike the "right amount of cloud" effect) but reduces peak output at midday due to its diffusing effect.

    now that you mention it, i'm recalling the demonstrator indicating in other than the northern climates, the PVs would require cooling
    ggunn wrote:
    They have (http://www.greenrhinoenergy.com/sola...centration.php), but they are generally not for conventional flat modules.

    TKS for the link -

    it would seem that for the average user, some 2' wide white panels on either side of each panel would boost efficiency some, without creating too much heat,
    angled like in ConcentratingPV-03.jpg
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: question re Fresnel lenses
    now that you mention it, i'm recalling the demonstrator indicating in other than the northern climates, the PVs would require cooling
    Generally, the PV designed for using with solar concentrators (mirrors or lenses) is engineered to function at much higher temperatures than conventional PV.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: question re Fresnel lenses

    concentrators need track the sun as well. failing to track the sun would eventually show it to shadow as its collection window would be smaller.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: question re Fresnel lenses
    niel wrote: »
    concentrators need track the sun as well. failing to track the sun would eventually show it to shadow as its collection window would be smaller.
    True. Actually, with the high magnification concentrators, the tracking has to be very precise because being even a few degrees off would place the PV completely in shadow.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: question re Fresnel lenses

    Adding reflectors fresnel lens etc. is NOT the solution to increasing power from standard solar panels..
    (1) the increased heat will REDUCE the power, after about half an hour in direct sun.
    (2) the increased heat will reduce the lifespan of the panel to as little as one year
    (3) You will need a very accurate tracker for the panels or you will get less output than with no reflector or lens assistance
    (4) even highly specialised cencentrator panels made by Emcore are only good for about 15 yrs and they cost about $100 per watt.
    (5) your warranty will be a bit less than Zero if you use fresnel lens on them as its easy to see as the cells go a golden brown colour.
    (6,7,8,9,10) DONT DO IT.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: question re Fresnel lenses

    i agree with you john, but the pic does not show a lens and the reflective panels are white and should be acceptable for any pv warranty as pvs can get diffused reflections.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: question re Fresnel lenses

    Niel Those reflectors are going to put a lot of heat onto those panels, it will be more than they are designed for and the cells will turn brown and the manufacturers wont replace theM
    Reflective panels really do work.. have a look at many solar ovens their performance is improved dramatically with the use of reflectors , they also stop airflow over the panels as the reflectors hold in the heat just above the glass..

    Please dont go giving the wrong ideas to others that it mabe ok to do that .. its NOT. It will definately shorten the life of the panels... You wont get good person points from NAWS if people that have bought them from them and damage them and say they were told on here that its ok to use reflectors .
    Panels normally get very little reflected light on them. except in places where it snows..
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: question re Fresnel lenses

    calm down john as i'm not including the likes of mirrored reflectors or lenses as i totally disagree with doing that. in day to day life we can expect to encounter reflections of some sorts like white-washed walls and large bodies of water. these can concentrate the same as what those white reflectors can. for the record, i do not feel i'd ever do it and i won't advise people to do it. if it is no more than they can expect to find normally around them like the examples i stated, then i believe it should be ok. it matters not if it is a white wall in back and a lake in front or a small white colored reflector. the white will diffuse the light so as not to concentrate it very well.

    just to be certain, do not do such a thing as outlined in the pic without consulting the manufacturer first to see if it meets their criteria for their warranty. i will not advocate doing this even with the manufacturer's permission and any who do so are on their own.

    any pv should be allowed to breath and dissipate their heat and i still see people mounting them like 1in above their roof. mine has lots of room in back and the heat still drags the output down some so i can imagine what 1in clearance in a hot climate is doing to their pvs. you are correct here john that heat is detrimental and if it unnaturally increases the heat on a pv then it should not be done.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: question re Fresnel lenses

    ":Please dont go giving the wrong ideas to others that it mabe ok to do that .. its NOT. "

    By that logic every place is snows and nature puts down a nice layer of snow (white reflector) the warranty will be voided.

    It is ok to use white reflectors, but on a practical level, probably not worth the hassel!
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: question re Fresnel lenses

    Niel im not getting up you about it.. sorry if it looks that way.. but you are all missing something. have a look at panels mounted on a roof and tell me how much reflection is getting on them?? it aint much. same goes if panels mounted on a in a field ,you dont get much reflection from grass. Now to say you are getting reflection from snow so that will by defination void the warranty. is not good thinking.. If there is snow the air is more likely to be cold rather than hot.. well that is how it was when I was in snow Now obviously the panels will be cold so it can under those conditions make the panels give greater output. this is a totally different situation to putting reflectors around the panels on a hot roof in a hot climate and depriving the panels of natural airflow over them..

    And I cant see how a white wall behind the panels will reflect on to the panels or how a lake in front will reflect on to panels facing at a fairly steep angle upwards. And I have never seen solar panels mounted in front of a white wall. mabe you have ,but not me All the ones I see are on roofs and in clear view of the sky and nothing that can really reflect on to them.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: question re Fresnel lenses

    :confused: Didn't I mention this already in post #2? :confused:

    :p
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    And another thing...

    In order to have any benefit at all, your Fresnels would need to be considerably larger than your array. For a single module you might be able to do it, but for a packed array it just would not be buildable, all the heat issues aside. A Fresnel lens the same size as a module won't buy you a Watt.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: question re Fresnel lenses

    GGUNN I dont think you have played around with fresnel lens much.. using one the size of a panel at just he right height to give a spot say 4in round will burn that cell in minutes , but before it does you will get higher output . but you will only get the chance to see it happen with that panel once..
    A 24in sq fresnel lens wil burn a hole through 1/2 plywood in less than 2 minutes. if held so it makes a spot on the ply about 2in dia..
    it will also cook scrambled eggs in a frypan in about 30 seconds..:cool:
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: question re Fresnel lenses

    BTW the info ggunn linked to lists three levels of concentrated PV. At the top level they note the need for two axis tracking and active cooling. This pretty much confirms what john_p and niel have both been saying.

    Short form, there's no simple piece of plastic you can lay over your panel and increase its efficiency.
    Or "do not try this at home".

    I can tell you from experience that reflected light off snowpack works. But as has been mentioned, it's well below freezing and that keeps the panels cool. Remember that much of the panel's heat is generated inside by the process of converting light into electricity. Accelerate the process and you accelerate the heat, which ironically reduces the efficiency of the process.*

    Or "there's no free lunch".

    *Layman's explanation; not exact science. Engineers do not "jump" on me.
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: question re Fresnel lenses
    john p wrote: »
    GGUNN I dont think you have played around with fresnel lens much.. using one the size of a panel at just he right height to give a spot say 4in round will burn that cell in minutes , but before it does you will get higher output...
    From that cell, maybe, but not from the module as a whole because to produce that spot of light on one cell you have taken it from the rest of the module. In order for you to get more output, you must either raise the efficiency of the module or increase the collection area. No free lunch.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: question re Fresnel lenses
    john p wrote: »
    Niel im not getting up you about it.. sorry if it looks that way.. but you are all missing something. have a look at panels mounted on a roof and tell me how much reflection is getting on them?? it aint much. same goes if panels mounted on a in a field ,you dont get much reflection from grass. Now to say you are getting reflection from snow so that will by defination void the warranty. is not good thinking.. If there is snow the air is more likely to be cold rather than hot.. well that is how it was when I was in snow Now obviously the panels will be cold so it can under those conditions make the panels give greater output. this is a totally different situation to putting reflectors around the panels on a hot roof in a hot climate and depriving the panels of natural airflow over them..

    And I cant see how a white wall behind the panels will reflect on to the panels or how a lake in front will reflect on to panels facing at a fairly steep angle upwards. And I have never seen solar panels mounted in front of a white wall. mabe you have ,but not me All the ones I see are on roofs and in clear view of the sky and nothing that can really reflect on to them.

    i think you are just a bit.

    it matters not if the reflections are generating electricity or not as the reflections are allowing the pv to heat up even if from the back and i can visual how a wall that is white that is behind the pvs, but with height, can add some to the electric generation as can reflections off of large bodies of water. the pvs don't have to be aimed directly at the reflections to get an increase in power and infrared heat. how about neighboring windows during december in northern lats (aka low solar angles)? it can happen from buildings that are higher up like skyscrapers and even homes that are in highly terrain like mine. high intensity reflections do happen more often than you think john.

    now i can visualize many scenarios that cause increases that can occur naturally that you are picking me apart for. snow does exist at times even when it reaches 60 degrees or so, but it won't last long depending on the depth of the snowpack and that could still be around long enough to reflect light under warmer conditions.

    with this i can conclude that for the most part i was agreeing with you john when it came to purposely implementing these reflections as indicated by the pic's example and i totally disagree with anyone putting fresnel lens to their pvs at any time and with that this should be dropped.
  • The Original Ralph
    The Original Ralph Solar Expert Posts: 50 ✭✭✭✭
    Re: question re Fresnel lenses

    okay - you guys convinced, vis-a-vis the heat element but to make sure you understood the lens i was referring to, they showed a large canopy lense, iirc about 3-4' in height, 5' wide and 6-8' long (canopy similiar to the canopies you see at hotel entrances). The under side surface of the canopy had ridges running lengthwise, not circular as in the ones pictured in that earlier link.

    there was no focus'd spot of light on the panel - the canopy's purpose, as i understood them to explain it, was to capture ambient light and redirect it all downward, in an unfocused pattern, toward the panel.

    Obviously, a focus'd light beam that can heat metal till it glows would burn out individual cells, and i can see where reflective panels would block air movement over the panels as well.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: question re Fresnel lenses
    okay - you guys convinced, vis-a-vis the heat element but to make sure you understood the lens i was referring to, they showed a large canopy lense, iirc about 3-4' in height, 5' wide and 6-8' long (canopy similiar to the canopies you see at hotel entrances). The under side surface of the canopy had ridges running lengthwise, not circular as in the ones pictured in that earlier link.

    there was no focus'd spot of light on the panel - the canopy's purpose, as i understood them to explain it, was to capture ambient light and redirect it all downward, in an unfocused pattern, toward the panel.

    Obviously, a focus'd light beam that can heat metal till it glows would burn out individual cells, and i can see where reflective panels would block air movement over the panels as well.

    This doesn't actually matter.
    What does matter is that if you increase the amount of light falling on the panel by any means you increase the amount of energy falling on the panel (or else there is no point). This results in increase electrical generation, and that means more current and that means more heat. If that heat can not be dissipated (and PV panels don't radiate heat well) it builds up internally. That will shorten the lifespan, no two ways about it. How much shorter depends on how much light is concentrated and how poorly the resulting heat is dissipated. The focus beam is an extreme example of the net effect.

    Energy entropy; it always comes down to heat, no matter what it starts out as. And heat is the enemy of electronic components.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: question re Fresnel lenses

    A great engineering rule of thumb... For every 10C (18F) increase in operating temperature, life of the component/system is cut by 1/2... Increase by 30C life is cut by"
    • 1/2 * 1/2 * 1/2 = 1/8th the original life.
    And on the cooling side, a 10C drop will 2x life.

    Note--Much of the failures in electronics, disk drives, (and even jet turbines) appear to be the result of thermal cycling instead... If you can keep everything at a stable temperature (whether cool or warm), you will have fewer failures too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: question re Fresnel lenses
    BB. wrote: »
    Note--Much of the failures in electronics, disk drives, (and even jet turbines) appear to be the result of thermal cycling instead... If you can keep everything at a stable temperature (whether cool or warm), you will have fewer failures too.

    -Bill

    I am a firm believer in this, my computers sit in idle mode use, I never set the Disk drive to spin down. With Multiple Mac Mini's it has been 3 years since we had a disk failure (knock on wood). They may draw a few watts (not very much BTW) but it is cheap insurance in my book.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    Re: question re Fresnel lenses

    I think Solar Dave, BB,and Cariboocoot fully understand what im talkng about.
    As for everyone else do what ever you like. their your solar panels not mine.. If you think you can improve their output go for it,, if you reduce their lifespan to one year do not go complaining .
    My message was simple and true if you do ANYTHING that increases the panels temperature above the manufacturers rated figure you will decrease its life..
    I have nothing more to say..
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: question re Fresnel lenses

    :D I will have you know my panels do get hot! Damn hot, I measured the back of one on a 110F afternoon and the back was about 150F using one of those infrared guns. I am not cranking any more into mine other than what nature provides! :D
  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    Re: question re Fresnel lenses

    If you are the thrift-store shopper, and want to experiment with large fresnel lenses, look for broken overhead projectors at Salvation Army, Goodwill, etc. Each has a 1 foot square plastic fresnel lens under the glass plate, and I've seen one flash-fry a sheet of plastic acetate when the projector mirror was accidentally left at that perfect reflection angle. An 8000 Lumen lamp rebounded back onto itself and incinerated the acetate in seconds, nothing left but the smell.


    broken overhead projectors are your cheap source for fresnel fun. Even if the glass plate is broken, the plastic fresnels are high impact, usually not affected by minor scratches.
    john p wrote: »
    GGUNN I dont think you have played around with fresnel lens much.. using one the size of a panel at just he right height to give a spot say 4in round will burn that cell in minutes , but before it does you will get higher output . but you will only get the chance to see it happen with that panel once..
    A 24in sq fresnel lens wil burn a hole through 1/2 plywood in less than 2 minutes. if held so it makes a spot on the ply about 2in dia..
    it will also cook scrambled eggs in a frypan in about 30 seconds..:cool:
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: question re Fresnel lenses
    BB. wrote: »
    A great engineering rule of thumb... For every 10C (18F) increase in operating temperature, life of the component/system is cut by 1/2... Increase by 30C life is cut by"
    • 1/2 * 1/2 * 1/2 = 1/8th the original life.
    And on the cooling side, a 10C drop will 2x life.

    Note--Much of the failures in electronics, disk drives, (and even jet turbines) appear to be the result of thermal cycling instead... If you can keep everything at a stable temperature (whether cool or warm), you will have fewer failures too.

    -Bill
    I have friend who is an IT guy. They keep a freezer in their lab, and when a non-backed up hard drive bites it, they put it in a ziplock bag in the freezer overnight, and then try to spin it up for a one-shot attempt to retrieve the data the next morning. He tells me that it only works about half the time, but that's half of the data that would have otherwise gone off to byte heaven.
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: question re Fresnel lenses
    ggunn wrote: »
    I have friend who is an IT guy. They keep a freezer in their lab, and when a non-backed up hard drive bites it, they put it in a ziplock bag in the freezer overnight, and then try to spin it up for a one-shot attempt to retrieve the data the next morning. He tells me that it only works about half the time, but that's half of the data that would have otherwise gone off to byte heaven.

    Yeah that work as does hitting with some freeze in a can prior to power up, I like that method better as it minimizes condensation. If it is a bearing failure mostly the thing is trashed.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: question re Fresnel lenses
    ggunn wrote: »
    I have friend who is an IT guy. They keep a freezer in their lab, and when a non-backed up hard drive bites it, they put it in a ziplock bag in the freezer overnight, and then try to spin it up for a one-shot attempt to retrieve the data the next morning. He tells me that it only works about half the time, but that's half of the data that would have otherwise gone off to byte heaven.

    hah, i thought you were going to end it as saying, .....gone off to byte the dust.:p
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: question re Fresnel lenses
    niel wrote: »
    hah, i thought you were going to end it as saying, .....gone off to byte the dust.:p
    I could also have said "gone off to byte the tera", but that's a bit of a reach. Bit, heh heh...

    Practice safe sectors
    A hard disk has no conscience

    and

    Establishing solid connectivity between network components ensures that when you throw the computer out the window, the printer goes with it.

    Have a great weekend!