Linear Parabolic Solar Reflectors: A Practical Experiment for Students

www.liacoseduc....
In this practical activity/experiment, students will learn about parabolas, make a parabolic solar reflector, and then investigate its ability to focus sunlight.
Check out the student activity sheets at www.liacoseduc...
Liacos Educational Media is the creator of the famous Shedding Light series of videos. If you are a teacher and your school has ClickView, Learn360, Films on Demand, or Safari Montage be sure to check them all out at www.liacoseduc....

[@juantamad5784]

... explanation is as clear as the bright Sun... great job and thank you for sharing.

[@ayubasghar1345]

THE BEST VIDEO OF PARABOLIC MIRROR CONSTRUCTION ON THE NET, as far as I have searched, THANKS A LOT, GOD BLESS YOU!!!!!!!

[@LiacosEM]

Thanks, Ayub. It's more an exercise for Maths and Science education than a practical device like most of the other videos on KZbin, but I appreciate your comment.

[@1islam1]

​@@LiacosEM🔴 What Is Islam? 🔴 Islam is not just another religion. 🔵 It is the same message preached by Moses, Jesus and Abraham. 🔴 Islam literally means ‘submission to God’ and it teaches us to have a direct relationship with God. 🔵 It reminds us that since God created us, no one should be worshipped except God alone. 🔴 It also teaches that God is nothing like a human being or like anything that we can imagine. 🌍 The concept of God is summarized in the Quran as: 📖 { “Say, He is God, the One. God, the Absolute. He does not give birth, nor was He born, and there is nothing like Him.”} (Quran 112:1-4) 📚 🔴 Becoming a Muslim is not turning your back to Jesus. 🔵 Rather it’s going back to the original teachings of Jesus and obeying him.

[@Andymac1701A]

Best explanation I have seen, having the maths explained makes all this far easier to understand.

[@LiacosEM]

Thanks Andy.

[@DenBlackburn]

I made a Linear Parabolic reflector way back when I was in school so I could use it as a directional beam antenna for my CB, I pointed it in the direction of my friends CB antenna, it worked fantastic, (no good if you wanted a group chat) as I only wanted to talk to him, it did the job, that was about 40 years ago, eek!

[@XoshBitt]

I'm horrible at math but i'm interested to make my own parabola. Thank you so much for teaching this in a way that is simple an practical. I love now knowing how I can adjust the focal point. Thanks a lot for this video. Looking at your website too.. very interesting stuff.

[@OnHoldAt50]

Yup, good one. I'll be back when I'm ready for this stage of my solar project. Materials will increase in quality and ability, but the principles you outlined are exactly what this DIYer needed. Thanks.

[@LiacosEM]

Thank you. Hope the project goes well.

[@civismesecret]

You are a very good teacher.. I hated school but if I could have a teacher that explain with baby-steps like you did, I would love it. Thx !!

[@LiacosEM]

Thanks, Civisme. It's a shame you hated school. Feel free to visit the LEM website to read more about science.

[@rafaelvieira7897]

I did the math with different numbers and it worked perfectly. Thank you for the video it was really helpfull to me!!!

[@vinothini3366]

Is the paper burnt

[@pauloinventostube7533]

Great information 🤜🔔🤛 success there family

[@kennethd.9436]

Amazing video! Great job filming, editing, and recording this project.

[@TheSumpek]

Thankyou so much. I've been lookong for an answer of focus point in concave (from circle) mirror . And this video showed me that focus point only exist in Parabolic.

[@LiacosEM]

No problem!

[@poligraph841]

An absolute focus point only exists in parabolic, that's true. But practically for a solar concentration it is not a problem to use spherical one, because the reflectors usually are not very deep ( curved ) and the solar light will be concentrated practically in the same size area as for a parabolic mirror. Parabolic mirrors are important for telescopes only.

[@calopsitamalucabird9434]

@@poligraph841 spherical mirrors can be used in telescopes too. But below f10 they will start presenting spherical aberration.

[@Kube_Dog]

Very nice. Brought back some schoolin' from long ago. Well explained and demonstrated. And kept simple at the same time.

[@LiacosEM]

Glad you liked it, Kube!

[@lajoskekesi4274]

Nagyon részletes jól érthető volt.Köszönöm. Megpróbálom megvalósítani és használni

[@iandale]

Brilliant thanks, I’d just ordered some mirror card and wondered how to set up the parabolic frame to hold it in place.

[@buzzwerd8093]

A half ellipse containing 1 vertex will focus straight light coming in onto that vertex. A lot of car headlight reflectors are elliptical, check a car parts store or junkyard. When you make a trough reflector, run a pipe along the axis and heat water in that.

[@abo7sain1]

Thanks for the illustration, you solve the y-axis point. But still the focal point on the z-axis need to be calculated to set it outside the 3D parabolic receiver!

[@oktogen1476]

Definitely best, most useful video on topic.

[@LifesVoyager]

If you take a reflector such as this one, and point it straight up at the cloudless night sky, will it focus the absorption effect of the black body absorber that is space?

[@ElysianDreams]

I have always used the formula "depth = radius^2/(4*fp)", where fp is your desired focal point distance. Radius squared (x dimension squared) divided by 4 times desired focal point distance. Remember to use the same units for x and y Example: fp = 72 r = 30 = 900/288 = 3.125 depth

[@brandnewayurveda1835]

Hey Good Afternoon, As You seems to have knowledge in this kind of Stuff. I am a reaserch person (in medical science) and I want to evaporate water from a circular dish of radius appx 1.5feet. the depth of Dish is appx 10cm. I put that dish with some active material inside it to evaporate the whole mixture. At last i get solidified mass at bottom of that dish. What I am asking is i want to fasten the evaporation of the contains with help of solar energy. Any idea how to do that. I tried this parabola but it's hard to focus the point on ground as dish is heavy and I can't keep it in middle of air hanging. Can we focus this parabola on ground , how so? Is there any other method by which is can increase the evaporation of that dish contains without fuel ?

[@zucchina24]

@@brandnewayurveda1835 you need a larger dish! Large surface area of the dish larger amounts of sun energy can focused…

[@ananddharwar2198]

If you want to keep the dish to be heated on the ground, use a magnifying glass

[@LabradorLeader]

The parabolic trough you made has many (an infinite number !) of focal points along a line, instead you only placed the paper stick touching a small part of that line which you called the focal point. If you place another paper stick at right angles to the existing one at its tip (to form a letter 'T') , you will trace out the focal line with the top of the T.

[@crow578]

That can definitely needed to be positioned closer to the reflector.

[@gustavososa725]

wonderful awesome job congratulations. Thank You so muchq 👏👏👏 🇦🇷

[@PhG1961]

Excellent !! Very well explained !!

[@LiacosEM]

Thanks, Phillip.

[@sunshine7453]

This is the best video. It was so well done and explained. Thank you for making great effort.

[@arnaudwald3479]

thank you , merci I loved your demo, simple and clear .

[@LiacosEM]

De rien.

[@baranjan4172]

Cool explanation, thanks.

[@mia8139]

This is really helpful and great content THANK YOU

[@WTF_BBQ]

I like this. Makes it easy to understand....

[@sassysisplays9465]

Sir can you tell me the materials involved in it? Means the materials you used especially which cup you have used?

[@sassysisplays9465]

Oh i mean the controlcan

[@LiacosEM]

Both cans were small steel cans that we use as overflow cans. You can use any small cans!

[@jsudhakar9187]

Well explained about parabola calculation

[@tmahmood4]

Will you please tell me the focal length of an hyperbolic mirror.

[@ervinmontemayorsoe9789]

Good Video but I am planning to put a servo motor in a single axis direction to track the sun. Hope my project goes well.

[@bhanusingh8654]

Good information sir.

[@ajmalmaad4497]

Sir! You solved my problem. Although I made a water heater but it's shape was circular. Now I will use this parabolic formula. Thank you for sharing.

[@LiacosEM]

You're welcome. I hope it works out for you.

[@kumardigvijaymishra5945]

Thanks for giving working numbers. I shall get back to finding some supplies and much needed material. I suppose both mugs were made of anodized metal with black paint for maximum absorption?

[@mtiris1]

very good and teaching video.appreciated!

[@giovannig.624]

Is it possible to build a telescope with two linear parabolic mirrors? Instead of one "3d" parabolic mirror + one plane mirror...

[@thagrit]

Your struts are called gussets. great work sir! you just gained a subscriber.

[@LiacosEM]

Thanks, thagrit. I didn't know that. I've always called those kinds of things struts (or ties if they're made of wire).

[@Dendritic]

Great! How about Mylar (from emergency blanket) instead of aluminum foil?

[@addestensfors8425]

Since it's flat it is not really focusing in a point but a line, still very useful...

[@miguelorbe3000]

wow, your video is really helpful,l is exactly the information I was looking for, thank you.

[@LiacosEM]

You're welcome.

[@رابحعزيل-ب1ط]

Danke, Professor, für die Erklärung, wie man einen Solarkocher baut Damit die ganze Welt davon profitiert

[@LiacosEM]

You're welcome.

[@volt8399]

Thank you for showing such a practical example!

[@fernandoasprilla9733]

exelente comentario muy educativo saludos desde colombia

[@akashzend7097]

I am see no. of Video of how to make parabolic solar concentrater but you are the excellent 👌👌 because you explaine very perfect good job sir👍👍👍

[@LiacosEM]

Thanks Akash.

[@ycjeon765]

This video is so useful. Thanks for sharing!

[@abbasamro6645]

Good job dear , i would like to know what the equation that help me to know the concentrated resultant heat temperature ?.

[@LiacosEM]

Thanks, Abbas. Apparently, the heat we receive from the Sun averages out to about 1000 Watts per square meter on the Earth's surface. If this heat radiation is concentrated into a small area, there is significant heating. The surface area of my little experimental reflector is quite small, but my students have still managed to heat water to about 60 degrees Celsius.

[@fostnepal5534]

Very useful for the solar cooking promoters like us.

[@9035]

Great video and easy to understand.

[@LiacosEM]

Thanks, Peter.

[@ohno4988]

absolutely brilliant explanation ☺ thank you

[@LiacosEM]

Thanks, oh no.

[@corax2012]

Even I could understand this. :) Needed a good explanation of parabolic math formula.

[@3fulggg]

Very helpful video

[@shsw1273]

Thanks for giving the method of calculating the focal length .

[@LiacosEM]

No problem. Thanks for watching.

[@senensoberano847]

Thank you very much. Your illustration would be very useful to those who want to design efficient parabolic reflectors for solar cookers. Some are just constructing their parabolic reflectors based on random dimensions.

[@LiacosEM]

Yes, that's probably true. However, my linear parabolic reflector is not ideal for use as a solar cooker either; it's really a science experiment for students.

[@moonnight3847]

LiacosEM your linear parabolic project was great but let me tell you sir that you are wrong in onething, and that is that you are actually able to cook with that linear desing if the linear parabola is made biger and with better reflected material. thanks by the way understanding this will help any one desing their own parabolic cookers i learned alot thanks againg.

[@LiacosEM]

Thanks Moon Night. With my simple design, my students have managed to heat up a small amount of water to about 60 degrees Celsius. Real solar cookers I've seen are usually 3D paraboloids, like satellite dishes. However, parabolas are at the heart of both, and I hope that my students learn that maths plays a big part in the design process of so many things in our lives!

[@SurjitSingh-xl2jh]

Nice work Sir. U r a good teacher.

[@brandnewayurveda1835]

Hey Good Afternoon, As You seems to have knowledge in this kind of Stuff. I am a reaserch person (in medical science) and I want to evaporate water from a circular dish of radius appx 1.5feet. the depth of Dish is appx 10cm. I put that dish with some active material inside it to evaporate the whole mixture. At last i get solidified mass at bottom of that dish. What I am asking is i want to fasten the evaporation of the contains with help of solar energy. Any idea how to do that. I tried this parabola but it's hard to focus the point on ground as dish is heavy and I can't keep it in middle of air hanging. Can we focus this parabola on ground , how so? Is there any other method by which is can increase the evaporation of that dish contains without fuel ?

[@LiacosEM]

Good question. You can try just using flat mirrors or aluminium sheets. But the sun moves across the sky so they have to be movable. Good luck.

[@kusumahari89]

Indonesia watching. So good

[@LiacosEM]

Thanks Kusuma.

[@makewhatyoulike119]

terrific explanation of the math for plotting the curve and finding the focal point. Thank you. Subscribed

[@LiacosEM]

Thanks, Mark.

[@santoshk63]

Very exact information with simple language.

[@havehalkow]

Outstandingly good explanation, thousands of "thanks" ! :)

[@LiacosEM]

You are welcome, Have!

[@agoradacerto]

I liked your teaching approach!

[@sols1011]

Great. very lucid explanation.

[@stevenmcgarva574]

Great video and very well explained

[@canusakommando9692]

Simple. Thanks. I enjoy quadratic equations but this is very practical.

[@electricsaversavesit]

Thank you for sharing this experiment, hope you'll allow me to use this information to my research.. thanks..

[@LiacosEM]

Of course!

[@sarahb.6549]

It´s possible to draw parabolas with free CAD or SketchUp too. In Sketchup the Extension is named "curve maker"

[@WhatDadIsUpTo]

A much easier method to focus a large area of sunlight to a single point would be to make something on the order of a pie dish with the reflective surface being the slanted edge of the dish. If the dish slant is 45°, parallel light waves incoming will be focused to the center in a circle and eventually to a single point. Soooo much easier to construct. If you are dead set on building a parabolic curve, an easy method is to use a piece of plywood with an x and y axis, the axis running close to the bottom of the sheet. Just drive a nail on the y-axis where you want the focus to be and using a carpenter square, put the corner of the Carpenters square along the x line and the other leg of the square on the nail and draw a line from the corner out. Do this at several places along the x line on each side of the y line and the resulting mishmash of lines very closely approximates a parabolic curve. Now, you can cut that out with a bandsaw and you're on your way.

[@jabujavi]

Soooo god mix of math and physhics for a science experiment with teens...

[@laurencerilling5873]

Im surprised you didnt show easier ways to trace the shape

[@LiacosEM]

My aim was to show students how Math, Science and Engineering are all interrelated. All the tech that we use is refined and improved with mathematical techniques.

[@LaElahElaAllah01]

thanks

[@mrmshifan]

Great video, really well explained. Thank you. I like to make something similar to dry food. The information I got from the video is really valuable. Thank you :)

[@TymexComputing]

Nice :) haha - LEM is a classic Sci-Fi polish author :) Stanisław Lem :)

[@jobbingactor]

meanwhile, just bend a reflective surface and use a thermometer till it’s what you want.

[@pradeep-ez3dr]

Thank you so much

[@LiacosEM]

Glad you liked it.

[@ayubasghar1345]

please iron the aluminum foil with a piece of cotton or wool cloth above it, to make a more smooth mirror.

[@topannurhakim]

ini yg aku cari, penjelasan yg sangat gamblang,

[@VietNguyen-vi7xt]

Good illumination.

[@jolyzacharie8189]

thx a lot you are a good teacher

[@LiacosEM]

Thanks, Joly!

[@SWARAJSINGH2008]

thankyou

[@joesphhuffman4020]

How do you enunciate parabola

[@paulanthonybridge5741]

No calculus needed, the paraboloid can be drawn directly by using a ruler, and 90 degree angle.

[@spherevsgravity]

thank you thank you thank you thank you

[@LiacosEM]

You're welcome x 4. I'm guessing you found it useful!!

[@spherevsgravity]

@@LiacosEM yes to build a satellite reflector

[@HattiYounes]

Thank you! :)

[@corriedebeer799]

God the way you pronounced parabola was just about the most ridiculously Australian thing I have ever heard.

[@charliedevine6869]

You can also use 2 nails and a string.

[@RangerCaptain11A]

two nails and a string would create an ellipse, which has two focal points.

[@racketman2u]

Two nails and a string would be a straight line.

[@lylestavast7652]

drive a nail where you want the focus to be. Tie one end of the string around that nail. Extend the dangling string downward toward you on your surface with a loose loop where you want the base of the parabola to be, and run the rest of the string vertical up the surface past the nail but attach it to the side of a 90 degree triangle square just touching the nail... Put your pen at the loop directly down toward you from the focus nail - that'll be the start of one side of your parabola... now slide the square straight to the right side and keep the pen tight against the string - as you continue to move the square, the string will slide upward and you'll trace a parabola shape... reverse it the other direction or trace the 1/2 you already did... Bob's your uncle. (since the teacher sounded ozzish (well, at least commonwealth something...)). Cheers.

[@alvaro.sacris1930]

But, you make the parabola in one direction, but in the z axis there no curvature, it's flat. How is it that reflects light to the point

[@LiacosEM]

You are completely correct in your thinking. The reflector doesn't reflect light to a point (like a satellite dish would) and so it's called a "linear" parabolic reflector. My aim was teach my students about the importance of mathematics and to do a practical science activity that involves a lot of maths. However, a lot of people who actually want to design solar cookers (and related things) have found the video useful in the design process that they go through. I must admit I was surprised initially! However, the use of mathematics makes everything better!

[@alvaro.sacris1930]

@@LiacosEM thanks for your kick response. I was thinking about make a 3d model of a barabolic, I'll have to figure it out. Also how to manage to put this reflective metal paper on the surface without breaking it nor wrinkle it... Impossible to do it perfectly, isnt it? Heating it up would work? Thanks

[@jeromegorriz5452]

Thanks a lot !

[@ashtwenty12]

thanks for the information. no more templates online when making water heaters :D

[@LiacosEM]

No problem, ashtwenty12. I'd love to see your finished products.

[@romanzavodin6461]

Отличное видео, благодарю! Лайк!

[@madhavishrivant2480]

Sir what if We take an A4 size graph paper and takes X co ordinates form -12 to 12 ? Will it have The same focal length of 10 cm ?

[@LiacosEM]

Yes. If you look at the 5:30 mark of the video, you will see that the incident light will hit the parabola above the level of the focal point but it will then deflect downwards towards the focal point. For my specifications, all the incident light reflects back upwards towards the focal point except for the light that hits at -10 and at +10. These light beams reflect horizontally (with respect to the plane of the reflector). Every parabola has one focal point, regardless of how wide it is.

[@sivansantana]

perfect. its always better when apply mathematics.

[@LiacosEM]

It sure is. I think students understand Science topics better if a little Maths is applied.

[@harinik2890]

Super

[@arioacasius4027]

En Español por favor 🙏

[@deathray3004]

*coordinates

[@attilarivera]

👏👏👏👏👏👏👏👏👏

[@bren.r]

Or you can just use parabolic mirrors and make the effect exponentially better than your aluminum foil and linear approach.

[@LiacosEM]

It's really a science experiment to teach students the mathematics of parabolas and how they're used to focus light. However, linear parabolic reflectors are used to heat oil in a pipe that runs along the focal line. See commons.wikimedia.org/wiki/File:Parabolic_trough_solar_thermal_electric_power_plant_1.jpg. My school has a parabolic mirror and my students are really impressed when I use it to ignite paper. But teaching is not really about showing kids stuff, it's about getting kids to learn by doing stuff!!

[@carmenj2549]

interesante🙂👍

[@faustominuzzo9263]

Grazie, Fausto (Italia)

[@LiacosEM]

Prego, Fausto.

[@genesioapretto5077]

Nice

[@MrSolpoente]

interessante engenharia

[@BajicZivkoTesla8888]

Браво