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solar powered melting machine

Jörg Polzin jungpionier

solar powered melting machine

04/03/2016 at 04:32

Hello Guys,

I am a German living in a Colombia. I am in a project with some friends to start a comunity in a jungle on the sea.

I am very concerned with all the plastic waste arriving to the beaches and thought make it an advantage using it as building material for houses like roofs and beams. Also use it to make artwork.

I would like to create a very simple solution using sun light to melt the plastic and to bring it to the form we need. Also no using electricity. I want it to be very simple and cheap to make it available to the poor people arround, so they can have a benefit from it, and thus clean up the sea from the plastic waste.

If you can give me any direction on my study, I would be more than greatful.

Thank you

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05/03/2016 at 18:27

Sounds like a great and doable plan! Haven’t tried solar heating though.. I guess the injection machine is best suited for this purpose.
Good luck and keep us updated

30/03/2016 at 20:24

I am also interested in this idea, but have not yet tried building a prototype. For injection molding, I imagine that you must turn the “barrel” to be horizontal or gently sloping downward. Compression molding might be easier, but will be very slow…I guess. Please let me know your thoughts. — John Busch

02/04/2016 at 14:52

look there is already something out there, but I believe it is too complicated, to much tecnology and electricity involved:


doing it with a fresnel lens seems also a solution:


this project seems to go into the right direction:

Researchers Create Solar Powered 3D Printer to Turn Plastics at Sea Into Furniture

these guys build house from recycled plastic, great, id we could do the same simply using sunlight to heat it up:


Would be great to know your thoughts on that.
What is your profession? Do you work in recycling?

08/05/2016 at 07:45

I would suggest building a “Solar Oven”, it’s a very old idea with lots of available designs that you could use for your project.

You could build a Solar Oven like this one https://www.youtube.com/watch?v=4qN27f7zO2M&ab_channel=comuntierra and then make a mold to melt your plastic in the oven in the form of “plastic bricks”.

You might just need to shred the plastic, put it in the “brick” mold, place it in the solar oven, and then just wait for the sun to do its thing.

The bricks could be melted in the form of giant Legos, or using these guys idea:

22/10/2017 at 13:58

you can create a heat collector using mirrors that can concentrate the energy of the sun to one point and the energy produced mostly heat can melt the plastic.

23/10/2017 at 02:36

Well first lets see how much energy solar energy you have hitting you in that region. Check map bellow
Colombia seems to be on par with where i am from in central California, United States.
From the chart you get about 5.25 KWh/m^2 of energy density hitting the floor in the Columbia region.
so lets say you have a 1 m^2 lens you will be able to focus 5.25 kWh of energy daily
So lets say you are melting HDPE
which has a specific heat of around 2400 J/(KG-K). and melting point of 112C
Lets say the average temperature in Colombia is 25C
SO Q=M(dot)Cp(deltaT)
Solving for M(dot)
lets say 6 hours of sun to work with
plugging in:
Q= 5.25(1000) = 5250 Watthours/6=875 watts, DeltaT = 112-25=87, Cp=2400
You can process .00419 Kg/Sec of plastic
.25 Kg/Min
15 Kg/Hour
90 Kg/Day (6 hour day)
so 90 Kg/Day of plastic
definitely productivity with a 1 m^2 lens
Note: This equation above is ideal case. And with no phase change equations used.
Im going to say it is definitely a good place to do melting of plastic by solar
Great energy density hitting the ground.

24/10/2017 at 07:36

Keep me updated interesting in seeing the design. what would be sweet is if you used solar steam engine design to power it. Did you know that steam engines are about 4 times as efficient as solar panels?
It would be super cool if you used the plastic melting to condense the vapor back into water. and used the steam turbine to drive the shredder.

24/10/2017 at 08:35

Use like a water tank that is heated with a 1m^2 into boiling to turn it into steam
Then have a turbo out of car expand the steam to generate rotation and torque.
That torque to turn the shredder
Then to change phase back into liquid suck away the heat by using it to melt the plastic.
Then maybe use another turbo as a turbine to turn a constant extruder.
this would be a pretty cool project

24/10/2017 at 09:01

this would be a pretty cool project

, sounds pretty cool indeed, are you going to try develop it?

24/10/2017 at 09:08

Maybe i could run some calcs off what he and I have (cali is very similar solar energy as Columbia) as far as parameters. And see what type of energy i could generate. calc for isentropic efficiency, HP, Torque, turbine efficiency, material process rate in both the shredder and extruder etc. and mabye a rough sketch of what it would look like. I might integrate that into my senior engineering project next year for off the grid recycling farm. Because for most productive circumstances solar panels are terrible.

24/10/2017 at 09:10

@thegreenengineers, good, keep us updated 🙂

28/10/2017 at 07:01

ok so maybe i will do the first calculation for a steam powered shredder and melting machine.
First we have to decide what our temperature high and temperature low we want
we can determine this by looking at the maximum efficiency that we want
maximum effeciency of a thermal cycle is know as a carnot cycle
a carnot cycle is a ideal 100% efficient use of the heat you have without any leakage
the equation is ((Th – TL)/Th)*100 output is a percentage which shows our maximum efficiency
Plugging in this into a graphing calculator we can plug in Th to find a temp we want
For Tl we are going to go with 25 Celsius (environment temp)
727 celcius is 70% efficiency lets go with that

A steam engine is also known as a Rankine Cycle
there are 4 steps to the cycle minimum
1st: water at room temperature is brought into water pump to increase pressure
2nd: water is sent to boiler to be heated at constant pressure into water vapor (phase change)
3nd: Water is expanded in a turbine (drop in temp and pressure aka energy loss)
4th: Water is condensed in a heat exchanger to change the phase from vapor back to liquid
Then cycle completes indefinitely

So maybe find a mechanical pump that is powered by the excess would be nice so now electric power is needed thi would be powered by the second stage
A 18 wheeler turbo would be used for a turbine and output shaft to drive shredder
A third stage turbo could be used to drive a continuous extruder or something

So to calculate the power generated and isentropic efficiency
You do so by calculating the pressure and temperature at each of those stages
then using those pressures and temperatures you use a saturated steam table
to look up the specific energy that the water contains known as enthalpy
by knowning the enthalpy at each point and the flow rate of water from the pump
you can solve for the hp and the efficiency

28/10/2017 at 09:06

Ok so lets talk about some pressures and temperatures at each point using more practical numbers
1) (Starting Point) Temp = room temp 25C Pressure= 1 atm (~ 15PSI, ~100Kpa)
2) need to solve for
3) need to solve for
4) 100c at 1 atm
Enthalpy for each step
1)419.098 KJ/KG
2)need to solve for
3)need to solve for
4)2675.76 KJ/KG
ok so we can get our hands on 1m^2 Fresnel lense and 875 watts of power
lets solve for how much steam mass flow rate we can make with that
solve for mdot
.875/(2675.76-419.098)= .0003877 KG/sec of steam
We want to have a output of about half a horsepower to run the shredder. so 372.85 watts which is about 40% effeciency
solve for h3
(Qdot/(mdot)) + h4
(.37285/(.0003877)) + 2675.76) =3637.5 KJ/KG
so at 50 psi we need a temperature of 423 celcius (increase of 300C)
to make half a hp.

ok so how much plastic can we melt from point 4 to 1
Q=Cp*mdot*(Tmelt – Tenviroment)
solve for mdot
Q/(CP*(Tglass-Tenviroment))= mdot
.37285/(2.4*(126-26)) = .001553 KG/Sec
.0932 KG/Min or 5.592 KG/Hour or 33.55 KG/6 Hour Work Day

So process 33.55 KG of plastic per day and Shred plastic with at 1/2 HP motor. Using a 1m^2 Fresnel lens, the sun, and a used car turbo.

04/11/2017 at 11:27

@thegreenengineers @davehakkens
As soon as I learned of the “container shop” I thought about it being solar-powered. It surely is something that for instance African countries have plenty of…
Looking forward to seeing this take shape.

19/11/2017 at 09:20

O you guys foreal want to see one? i mean if there is a market for it i can try building it.

06/12/2017 at 16:05

For sure there is a market for a thing like that!

Access to electricity is a real problem in unindustrialized countries where the waste problem is almost the greatest. I think it would be a bit of a sensation.
Are you serious you think it could work?

06/12/2017 at 21:32

Energy is known to be more clean when less steps are required to produce it.
You blew my mind with this idea. It needs some calculations and some heavy equipment. But the end result (zero energy bill, zero CO² emissions) is really worth it.

You should be making some tests using a Fresnel lens or a reflector, before setting some heliostats for more efficiency.

07/12/2017 at 18:58

alright i will look into it. I will see if i can do it for a university project. as we have alot of solar collectors sitting around. However the cheapest to do right now is use like aluminum foil and a curved piece of aluminum.

08/12/2017 at 00:44

check this out for a low focal length mirror (parabolic). This guy uses metal coated mylar film as a reflective surface.

23/02/2019 at 07:01

Hi. I am working in an extruder similar to Precious plastic extruder, but I try to put  a satellite dish (parabolic) in the barrel for concentrating light purpose, instead the heater band elements. Then, I will use a heliostat for redirect the sunlight to the parabolic dish. I build all this stuff from trahs, literally. If you interested send me a message, Im still work in this project. Greeting from México!

26/06/2019 at 03:01

This is a project I am also interested in. I have had some success melting certain forms of plastic using solar energy focused by a simple makeup mirror as you can see in these videos:

I am however seeking other like minded individuals that may be able to solve various problems and give suggestions as to improve this process and make it simple for anyone to melt plastic and mold it for various purposes.
Feel free to contact me here if you have any suggestions.

26/06/2019 at 11:57

here’s a very interesting article on the topic. evtl. the engineers here on board can make some predictions whether this could heat up an extrusion

05/07/2019 at 04:13

I thought this was an interesting concept for making less expensive solar collectors for melting plastic.
That cheap solar heater for high temperatures 200 ºC (HT solar collector-concentrator) Sergiy Yurko


Using thermal transfer oil and an insulated tank, make a plastic melting oven.

I am working on recycling used plastic mulch into pavers and roofing tiles using sand and heat.

I have a concept of using a heated drum roller to mix courser plastic particles into a homogeneous blend before adding sand.

21/09/2019 at 04:13

It’s a great idea to utilize solar energy for heating the plastic. I believe that you need some control system or at least measurement for the temperature? Since different kind of plastic have different melting point. Has anyone made this solar heating into realization? Or any more info about this?
I happen to live close to the equator, which gives me plenty of solar energy. So I’m very much interested.

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