Hello Dr.N.P.Singh.

What size of lance are you looking for? Can you please specify exact size?

What if a glass tube is ballooned in hollow lance shape and filled with water? I guess it should work although coefficient of refraction may be different,

I am associated with scientific and laboratory equipments and know some of glass grinding facility here producing lances but I doubt that they will produce large enough for your requirements,

Anyway just reply with the size and other details,

Regards

Thanks dear for the reply,

Yes I should have been more specific to mention the size of lens.

For the ease of deployment in field or on roof top, lens with 1 to 1.25 meter diameter should be OK.

And in my openion each lens with dia 1.25 m will have an area of approx 1 sq.m.

-N P Singh

Dear Dr. Singh, what purpose you will use the lens for? If it is for cooking purpose, then I would suggest an alternative of conical reflective cookers.

I have procured conical reflective solar cooker that works fine for a family and cooks in about 1.5 hours. I have distributed few in rural families on experimental basis to see how the families in villages react to the concept.The cost of the cooker is only Rs. 1600 and weight is hardly 3kg.

Thanx Rajesh for the reply,

I would like to know the size of conical reflective solar cookers, their effency and the range of temperature that are available in the cooker design that you are producing. Any further scope of tracking the sun for effeciency ?

Dr N P Singh

Honored sir,

Company that produce parabolic mirors gave this

Specifications: Dish size 1meter dia
Weight Less than 2.5kg
(depends on the
reflectors used)
Temperature 350oC+
(In tropical zone)
Tracking Devise: The basic model tracking is done manually every 20 min.
There are mechanical,electrical and electronics tracking which can be supplied separately as we we get this from sub contracting.

As their tecnologicall advisor and worldvide representative, I invite You to send Your requirements to get quotations.........

Regards,

Marijan Pollak

oberon@globalnet.hr

Dear Marijan Pollak,

The specs given sound quite close to the requirement.

Size of Dish : 1meter dia (Amounting to 0.78 sq.m area)

Weight of the dish : Less than 2.5kg

Temperature Approx: 350oC+

Dear What I wish to know is the cost of one parabolic mirror dish ?

One more clarification that the weight 2.5 kgs as mentioned in specs hereabove, does that includes the frame that will hold the mirrors together to make give the mirrors the shape of a parabolic dish.

Regards- NPSingh

Honored sir,

At best of my knowledge it is weight of complete Solar oven, withut dishes for baking.

Price goes from 200$ with manuall Sun tracking system to 600$ for owen with automatic Sun tracking system.

But since You are from India and those factories are also, perhaps I could negotiate better prices, provided You need bigger quantities supplied.

Also, they produce much bigger parabolic mirrors that is used for powering steam

owens......

This is one Solar owen with mirror of requested size.........

Here You could see three mirror steam ovens system... Sory that place is not more representative, but it was donation to some ashram by factory owner........

I am sending this as ilustration that larger parabolic mirrors could be produced.

Factories have capacity of 5500 pieces for Solar owens per month, and all production for next two years is allready sold, but I am sure that if there would be serious order and also from government, few hundred more could be produced, and if necesary capacities extended............

Regards,

Marijan Pollak

Dr. Singh,

Grinding disc will have to be customized to your requirements, please answer few questions as follows-------

Are you willing to spent the cost of development?

What is the qty you can lift in one go?

What is the focus distance you want?

And what is the max area of focused light you can accept?

Regards,

Thanx Dear for your reply.

The idea is infact is great, if instead of a glass tube, 2 transparent poly carbonate sheets UV stablized (1mX1m = 1 sq.m ) or a glass sheet of the same dimensions can be moulded and joined from all the sides to act as a hollow lens and be filled with water to be used as a lens for concentrating solar radiation on a small area.

It will be great to have the adress/ contact no or e-mail of glass grinding companies/Firms and find out if any of them is interested to take up this type of work.

Pl do give me contact adress of glass grinding firms.

Thanx once again,

N P Singh

Mr. Singh,

Glass lenses and even water filled ones are weighting too much for practicall use without strong support, and glass lenses are costly unless You have them made of poured glass, and stronger is support, more costly it is and unvieldy for tracking Sun!

If You dont like parabolic mirrors I offered that are allready produced in India, then Fresnell Lenses are better solution, and they could also be made out of poured glass, but for same weight You get much stronger lenses.......

They could also be made from transparent polycarbonate plates, and need not be precise as You dont need 100% clear picture without distorsions, just ability to concentrate sunlight, right?

On the other hand, glass made Fresnell Lenses could use recycled glass so they would be cheaper than policarbonte plates and need not use imported materiall that would be more costly, even if weight is much greater.........

But You still need cheap and good Sun tracking system, and this is also produced in same Indian company according to Europeian technology, and if You take them for suplier, in long run You would save lot of money for transportation, customs fees, taxes and so on...........

As I am their representative and technicall advisor, You could contact me with requirements, and I shall send You informations on quantities per month and production time.....

I am sure they could produce also other elements of Your system, whatever it is supposed to be, so You could get complete product for marketing..........

Regards,

Marijan Pollak, IT SA/SE 1st. Class, Instructor and Team Leader

oberon@globalnet.hr

you wrote***...'On the other hand, glass made Fresnell Lenses could use recycled glass so they would be cheaper than policarbonte plates and need not use imported materiall that would be more costly, even if weight is much greater.........'...***

can you provide links to quotes or examples of large glass lenses made from recycled glass with pricing less expensive than similar polycarbonate or arcylic, ??? even before considering any(surely substancial) cost differences for the associated packaging, shipping and handeling charges.

forgive me if my comments seem rude....i am a natural skeptic,and i do not intend any personal affront, and will be very appreciative if you prove my suspicions incorrect (and teach me something new).

i have serious doubts about the cost advantage possible by sourcing lenses manufactured from recycled glass.

utilization of recycled glass is common, but even if it wasn't the cocts for the raw materials are not that large.

the energy and time designing/planning, tooling, producing and finishing (which are the same whether recycled or not) are sure to dominate cost... (until the whole packaging, handeling, shipping project arrives)

also, is there really no polycarbonate in India?

On different note...... i might take some flack for this.. but...... Dr. Singhe.... how can you spend enough time in Acedemia to earn a PHD in addition to working 23 years professionally in this field, and have so little knowledge of the manufacturers of lenses and reflectors in your country??????

for fairness and full disclosure, this is Benbenben (aka Benbenbanned)

'here comes the sun, little darlin', here comes the sun, i will say, it's all right.....'

Honored sceptic Guest,

Main difference is in quality of workmanship and tolerances involved. Acrylate lenses of Fresnel type are usually made with high precision optic standards, so picture would not be distorted or blurred.

Since this does not matter for use as Sunlight focusing device, specially if (if I remember it correctly) required focus can be 10 centimeters wide, then surely they could be made in any glass factory by pouring.

What I would do is to make glass molds and then send them to nearest glass factory together with order, so transport should not be so expensive from there to usage location. Packaging and handling need not be more expensive than it is for windows glass from glass factory to windows factory, and production price would be much less than for windows glass, because for windows glass have to be perfectly transparent without blemishes, and for just concentration of Sunlight quality does not matter so much, I would say.

Even construction need not be much sturdier to support weight difference, for this relatively small size.

Only thing that votes against poured glass versus acrylate plastic (which has to be UV stabilized, and therefore more expensive still) is hail stones. If hail is falling relatively often in installation area, then perhaps it would break glass, if big enough to be weighty.

In regard to shipment, container space is paid according to volume used, not weight, i I remember correctly what they told me some 4-5 years ago :-))

But there is another thing to consider, if my Indian wife has told me the truth, and this is that no glass window can remain whole long time, so perhaps there is no window glass factories in India and all window glass is imported, or there is many of them to constantly replace broken windows :-((

So if same fate of stoning awaits Your Light concentrators, then use polycarbonate plates, by all means! It would surely stand much more of such kind treatment :-))

In regard to prices, why don't You just inquiry in nearest glass factory or manufacture, as this could even be produced by hand pouring, I imagine, just because quality of glass and small thickness differences would not matter in usage like this, because active elements would work same for so rough focus as is necessary.

In regard to mould planing and preparation, maybe it would take same time or maybe not, but surely production from recycled glass is faster as it has to be just melted, and I would say that even glass with occasional speckles or slight impurities would work the same for this purpose, but best is to ask glass manufacturers, and that is not ME. I am also on the other side of Globe, four time zones distant from India, so don't ask me for price quotes, please?

In regard to finding lens manufacturers, I have found them trough WEB search engines, and so can anybody else. I was too polite to ask Dr. Singh why he ask for address of manufacturers, when he could have browsed Yellow pages and find it fast.

We say in Croatia: >>It is not hard to pray to God, but it is easier to be silent<< :-))

So, You were banned from CR4? There is another saying in Croatia:

>>Sharp tongue sooner or later cut throat of its owner<<......

So, abstain of asking such questions, as nobody forced you to give answer at all, and if nobody answered, then Dr. Singh would have to do some search himself :-)

I greatly appreciate your response. Thank you.

I cannot promise to abstain from incendiary nor cutting lines of questioning. Else, I may miss insiting a response as knowledgable ancd worthy as your own.

Concordia cum veritate!

bENBENBEN

You must be Diplomat or Politician, since you answer without answering.......

Do You agree that Fresnel Lenses made of recycled glass can be cheap enough to be cheaper than acrylic ones?

Since I have read suggestions to use front side of used TV cathode tubes as lenses, which idea may work but still would not be practical as it is hard to find so many of same used TV sets, and would take more work to cut it properly and prepare for use, and which would require much sturdier frame to hold and use on heliostat device, I would say that my idea with using recycled glass is much more practical and almost equally cheap if not cheaper.

In regard to Dr. Singh, what surprised me in first place was his requirement that asked for mirrors or lenses, because of totally different use in practice. Since mirrors (and here I assume parabolic, not flat ones) have focus in direction of Sun, putting some obstacle of ten square centimeters would cast at least that big shadow, or much bigger since there has to be some frame and supports for whatever is put in focus, while Fresnel's lenses have focus on opposite side, therefore they can focus all light coming from direction of Sun.

If for nothing else, like much more expensive production of parabolic mirrors, then because of this practical reasons and 100% transparency versus reflection coefficient of mirrors which is never so good, I would never think of using mirrors........

But if people think using TV cathode tube front is good solution, or plastic bags filled with water, where obviously Dr. Singh have big serial production in mind, then I abstain from commenting, even if I could say many things against such ideas that are fit for >>Do it Yourself at Home<< projects, but not for serious electricity production.

Also, requested size show that quantity of electricity produced would be small, specially if Photo Voltage elements are to be used. On the other hand, some breakthroughs have been achieved using Nanotechnology, and Dr. Singh are not revealing what would this mirrors or lenses be used for after all........

Anyhow, comments on this thread are becoming far and wide spaced, and mostly no comment is forthcoming from Dr. Singh himself, so I would most likely stop responding to this thread........

Dr.Singh.

Sorry for not replying your post.

Please send a direct message to my inbox.

Thanks and regards

Rakesh Semwal.

Singhji

Why don't you register on CR4?

1. You can create your own water lens by stretching polythene plastic sheet on a metal ring and filling the water in it. But, this can be only used in horizontal position. With horizontal position, the focus goes on shifting.

Instead if you make metal rod grid and stretch polythene on it , fill the water in each rectangular sector from top, you will form many number of small rectangular/ parabolic lenses. In this case, though the focassed rays go on shifting, the collector will get one or the other of the focussed rays.

2. You may try fresnel lens, which are normally available in big size and cheap compared to the size.

3. Instead of making big mirror, better you stick the small mirrors on a dish antenna. It will work nice. Or make the reflective dish antenna. Making big mirror (in convensional sense is too costly.

I hope you concider compound parabolic dishes as well as parabolic. Depending on your use, compound parabolic do not have to be aimed as accurately as parabolic dishes and can still give good results. This can make tracking much cheaper. Brian

Hello Guest,

being a 'Professional', as you say, it would be nice to join and help other?

Have you tried to do a web search for Indian Companies making these types of lenses and mirrors?

I would have thought, as you were in that type of business anyway you would have a head start on most of us?

Good luck anyway...........and No offence intended OK?

Yes dear,

I have tried the web search to find out which Indian companies are making the required type of lenses or mirror, but unfortunately all the companies are making very small size lenses to be used in microscopes etc. for imaging. Non of the company is producing large size lens or mirrors for focussing Solar energy where the basic requirement is focussing not imaging. In our case the area is important as the requirement of energy can only be met with large area.

Yes dear as far as your suggestion for joining and helping others is concerned, I am willing to share with others, what ever little I have read or learnt during my Ph.D. in Solar Energy applications.

Regards -

NPSingh

http://www.lenseloptics.com/ here You have one company that produce Fresnell Lenses for Solarpower use.......

Regards, Marijan Pollak

Dear All,

I once made a solar concentrator (bad optical quality but good for lighting or cooking) from 1x1m aluminum sheet, a. quadratic, b. octagonal, c. circular.

These were clamped at the rim and formed by hydraulic (water from the tap) pressure to give an acceptable curvature.

If you start with reflecting grade Al you will get a pretty good mirror at minimum cost.

Version a. is considerably distorted, but b. and c. are nearly ideal.

RHABE

Did you see this: apparently old back projection TVs had a Fresnel lens as part of the screen, and, you can pick them up for almost nothing.

http://www.instructables.com/id/Giant-Fresnel-Lens-Deathray-An-Experiment-in-Opti/

Watch out for his warning to ensure you wear suitable protective (dark) glasses.

Also:-

http://www.google.co.in/search?hl=en&q=fresnel+lens&btnG=Search&meta=cr%3DcountryIN

Dear Friends

To me, the question posed by Dr.Singh is extremely simple one but so far nobody has given a direct answer to that. I am sure, Dr.Singh is not looking for lenses as big as those used by the Japanese during the World War 2, to burn enemy ships.

The question & therefore requirement. is extremely interesting with great potential, but personally I donot know anybody in India or abroad who makes such lenses & I feel, these will have to be designed & manufactured specifically with somebody manufacturing industrial lenses. I donot know of anybody in this field either.

Ashok Toshniwal, Bangalore, India

Dr.Singh, Can I know where are you posted now?

Hello,

I recommend Fresnel lenses as already mentioned in one comment above. They can be made from acrylic plates. Using NC machines it would be easy to manufacture them.

regards

Claus

Fresnel is ok, but not at all simple.

To make these masters are cut in brass or bronze or aluminum sometimes coated by NiP before final cut.

Cutting tool has to be mono-crystalline diamond.

V-grooves at varying angles of flanks with varying pitch are cut, slopes have to be accurate (in orientation of angle) to allowed defocus/(focal length).

So any groove has to have 2 different angle settings of the tool.

Radial and axial and tilt runout of main-spindle has to be so good that only airbearing spindles are used for this purpose.

So you come up with a machine that will cost around 300K$ to 1.2M$.

Ask Moore or Precitech or LTUltra (all aerostatic spindles, maybe hydrostatic slides) or Hembrug (hydrostatic spindles and slides).

Machining time very often is not only hours but days.

This will yield a stamping tool to be replicated in PMMA or COC many 1000 times.

So in total a mirror of medium quality is likely to be cheaper.

RHABE

Now we are in the age of Flat panel TV. The older TV one can pick up free or even if you are in US they will pay to take them out. In India there are glass cutting shop they can puncture and then cut the curve portion.

Dip the sheet in hydrocluric acid (0.1N) to remove all aluminumand phosphour and then dip in 4% sulpheric and 4% hydrofloric acid for about 30 minutes. This will give you lense which may meet your need.

Masyood

Dear Masyood

Your language speaks about the extent of knowledge you have not only about the subject under discussion, but also about the current state of affairs in India. It is not unusual for people to buy TVs costing US$8,000.00., off the shelf and the stores have at least few of them in READY STOCK.

Requirement of Dr.Singh is HIGHLY technical in nature and NOT AS SIMPLE as you have thought & THEREFORE explained in a public forum like this. Though I am an Indian but this mail, I am NOT WRITING as an INDIAN but as a person with some technical knowledge & ability.

Ashok Toshniwal, Bangalore, India

When I wrote the email I did after having a Ph.D. in Glass from Alfred University and used TV to create lens for one of early part of one of the experiment before working with glass industry to copy the same as of one we created out of old TV set.

If Dr. Singh needs my help I will be in India visiting Banglore and will be more happy to make sure provide one during my visit if time permits to do so.

If needs are well defined then one can this happen. Best invention is to collect junk and make some thing out of the junk. Best business practice is one which does not generate garbage for disposal and after long working experience in electronic I have implimented in few area and realized in other. Buying is not always solution for all problem. Creats the basic from available resources and will be okay.

Masyood

Hello Maysood,

Just want to know.

Are you sure a TV Screen is convex on both side or atLeast flat at one side and convex at other side?

Its not going to work if it is concave inside and convex outside,

Hello ashoktoshniwal:

I disagree with pretty much all you say. No offence intended.

And I also think Mr Singh should look at what is already in use around the world, as looking in India only, in limiting.

Because large lenses are so expensive, a compound type or Fresnel lens which does not need to be anywhere near so accurate will work because, any slight aberrations in one part of the compound or Fresnel lens will be compensated for by other parts of the lens. It can also be adjustable to achieve a very good focus.

I note you criticize but no help?

The lens can also be made from several separate 'lens' made from highly polished metal, each of which can be focused to a fine degree. These are already in use for power stations. It really depends what the final use is and the amount of room available as some of these types of lens systems can be very large. But, they also produce huge energy.

Thats my say too.

Yes Dear,

Fresnel Lens is a good option but I have tried hard to find out if any company is making fresnel lens in India, but so far I have no idea/info. on the availablility of Large size Fresnel lens in India. So far only lens of dimensions 8X10 inch are available in India, which are too small for the purpose.

We can try making the, but no design details are available.

- N P Singh

Dear Ashok Toshniwal,

Thanks for taking interest in the topic and replying to the participants.

Fresnel lens is a very good option but so far I could not find info. about any Indian company making large size Fresnel lens, only small Fresnel lens of dimension 8X10 inch are available in India, they are too small for the purpose.

From the discussion I feel you have good knowledge about fresnel lenses, please do send the design details ( ie the number of groove per inch, depth of grooves, angle of each groove, in case we wish to make a fresnel lens of dia= 1m or dimension 1mX1m, with focal length to be of the order of 1m)

Regards,

Dr N P Singh

Dear Dr. Singh,

I have sent You data about parabolic mirrors from India. But I am also interested in Fresnell lenses for use in my projects, where I would need 4m x 4m size or even larger even if made in segments. Dont let size of Fresnell Lenses You find confuse You, who has technology to make small ones has technology to make big ones also, even if they dont realize this!

So, could You kindly supply Email address of this company?

If they have no email address, or web site, then name and address, telephone......?

Regards,

Marijan Pollak

oberon@globalnet.hr

Mr Marijan Pollak,

The company that make/sell small fresnel lens in India is Lensel Optics Pvt. Ltd and e-mail is: http://www.lenseloptics.com.

Regards-

Dr N P Singh

Honored sir, that is same Web address I gave You when You were writting that You cannot find any?

I am in contact with them in regard to my own project that requires lenses in size up to 65 m2 for 10 MW Solarpower 24/7 stations.........

Now, if You would like to contact me privately, You could do so at oberon@globalnet.hr to be able to organize some production for You......

Regards,

Marijan Pollak

Dear Mr. Masyood,

Your solution is interesting. My interest is in concentrating solar energy at low cost. I have experimented wirh conical and parabolic reflectors but never thought that old TV could be of use.

I agree that there are old TVs and nobody knows what to do with these. But I have questions.

1 - How to cut the glass shell, is it risky(any pressure or vacuum?)

2 - Also please let me know if the glass can be used as reflector or lens.

3 - How good is the concentration? Is it as good as a lens.

Any additional information would be interesting.

Thanks

Rajesh Salaskar

India

Dr. Singh,

I am not in India, however, may I reply to let you know that the mirror/lens concept for focusing solar energy oh PV cells is being used throughout the world. You would be limiting your supply availability to seek on Indian solar concentrators. Also, may I point out that yesterday, I read in ScienceDaily of the development of a Germanium solar cell that requires concentrated sunlight to achieve 40% efficiency.

Respectfully yours,

A good US company for such a large concentrator would be Advanced Glass (AGI)

They are located in Rochester NY. The specialize in large diameter optics and mirrors.

I do not recommend the suggestions or plastics or other fringe ideas. You need a material that will not degrade in harsh environment, and glass is the best suited.

Advanced Glass Industries
PO Box 60467
1335 Emerson Street
Rochester, NY 14606

Good luck,

Honored sir,

There is Your contrymen, Mr. Chandu Krishnamurti from Mysore, who allready produces Solar parabolic mirrors of requested size for steam ovens in his factories.

Mr. Krishnamurty has recommended that I handle Your request as Worldwide representative of his company (because it include India also) even if I tought You two could do it directly......

His factory could make it for You, and one mirror with supporting construction should not cost more than 200 US $, but You also need Sun tracking mechanism(s) if You intend to put this on the roof. All this is available and could be produced on order!

But, You dont say what would You produce with this Solar concentrators?

Mr. Krishnamurti is producing steam owen systems using parabolic mirrors, too!

So, if You dont mind, send all details of Your requirements to me first, and I shall take care that You get response from factory soonest.

Contact me on oberon@globalnet.hr directly........

Regards from Marijan Pollak

Dear Contributors,

Thanx for sparing ur time for rendering help regarding Large size lens/mirrors for solar energy focussing. The lenses/ mirrors that I have in mind to meet the requirements is approx 1 or 1.35 m diameter, with effective area of 0.8 t0 1.0 sq.m.

Focussing requirement not to be very pointed one, even if it can focus solar radiation on a area of 6 to 9 inch diameter that will serve the purpose very well.

Regards,

Dr N P Singh

Dear Dr. Singh,

We allready know You want to concentrate Solar energy, but question is what would You USE such concentrated energy FOR?

It seems to me You are not reading my posts?

I allready informed You that this size parabolic mirrors are produced in India.

They could supply 5500 pieces per month if You need, produced on Europeian standards for technology........

Company whose I am representative produce Solar steam owens too, if You need steam produced.......

Regards, Marijan Pollak

Fresnel lens is the way to go I would think there companies all over the world the make

them ebay something like 4 ft x 6 ft hits 2K or 3K degrees in there some where it is dangerous about $100 USA plus shipping there are 2 kinds one condenses to a spot

the other one draws it out to a line to be used to hit metal pipe full of water to steam

it requires no solar tracking as the cuts are on angle and they converge also if hit your

search engine for buy direct from manufactor in other countys you can buy wholesale

100 sheets for about .60 cents to .80 cents apiece

have a good day

KK

what size of frencial lens required to concentrate the solar light in a single point.

pls reply...........................