Introduction: Something From Nothing - DIY Solar Heater From Scrap Bottles

Picture of Something From Nothing - DIY Solar Heater From Scrap Bottles

One day, while walking I stumbled upon illegal dumping ground in the outskirts of the village - a familiar scene in Bulgaria: green meadows, blue sky and... piles of garbage dumped by fellow villagers. "One's trash is another's treasure", I said to myself and started collecting empty plastic bottles. This is to be my experimental environmentally friendly solar heater.

Step 1: Here's My Treasure

Picture of Here's My Treasure

About 100 empty bottles are required. The more - the better.

Step 2: This Is the Wood Drill Bit

Picture of This Is the Wood Drill Bit

This is the wood drill bit I used to drill the bottles. You can buy it from any hardware store. This particular one is 18mm.

Step 3: Drilling the Holes

Picture of Drilling the Holes

I drill a hole at the bottom of the bottle and in the cap

Step 4: Passing the Hose

Picture of Passing the Hose

For heating the water I used old garden hose. The bottles are strung together like this.

The bottle creates a greenhouse effect - the heat from the sun is trapped inside the bottle and is warming up the water that runs through the hose.

Step 5: The Pump

Picture of The Pump

For circulating the water I used a 12V DC Hot Water Brushless Circulation Pump. Got it from Ebay for about $14 with free shipping. It consumes just half an amper, so it can be connected to a 10W solar panel and make the solar heater self-running.

Step 6: The Heater

Picture of The Heater

Here's the finished heater. An old barrel was used to keep the water. The pump circulates the water from the bottom, through the black hose to the top of the barrel.

On a sunny day it makes hot water. It would be more efficient, I presume, if the barrel is insulated to keep the heat in.


Degga_D (author)2015-04-25

Glad you could use up the rubbish. Wish people had more care for our environment.
I think from looking on here, painting the bottles black would increase efficiency. :-)

dollarseed (author)Degga_D2015-05-10

Yes, painting anything flat black will cause it to absorb more heat. This is why most new cars come in shiny colors like white or silver.

ronniewhamond (author)Degga_D2015-04-28

I was about to suggest in order to increase efficiency white / transparent bottles should be used ....with a black hose inside.....

rmcguire (author)ronniewhamond2015-04-29

Makes sense. Then there would be less losses to the air because of cooling. Basically the bottles are acting as insulation. Think it would work even better if matt black hose was inside a vacuum but the bottles would just collapse if you tried to make a vacuum in them.

rmac704 (author)2015-04-26

Recycling empty plastic bottles as you have is absolutely amazing. What many of us don't know is it takes about 1 cup of oil to make 1 plastic bottle, especially the clear water bottles. And it takes many lifetimes for a plastic bottle to disintegrate. Thanks for your Instructable and putting trash to good use. Last note, quit buying bottled water. Nothing wrong with drinking water from the tap and help save more resources.

enchiladeeda (author)2015-04-29

Looks like it will work! The black hose will heat up by itself but never thought of using bottles to keep heat in. I am going to have to try this since I am off the grid and a Redneck Hillbilly forever! Always looking for ways to make things work better.

NewAge-2014 (author)enchiladeeda2015-04-29

Lucky you!

enchiladeeda (author)NewAge-20142015-07-09

Lucky and blessed!!! It isn't easy but it is definitely worth it! I wouldn't change it for a million dollars. (Wish I had a million dollars tho'! :) )

NewAge-2014 (author)2015-05-23

Check my new utilisation of plastic bottles ;-)

lisa.dukes.391 (author)2015-05-15

I have also seen some excellent plans online (probably even here) that use plastic bottles to build a greenhouse. A wooden wall frame is constructed and filled in by stacking plastic bottles on their sides (or vertically depending on the bottle size). A 2 x 2 x 2m greenhouse will use up to 1,000 bottles. And it actually makes a good looking and efficient structure. Here are some examples:

dollarseed (author)2015-05-10

Another thing to consider when playing in passive solar heating is this. You can make a box, use asphalt shingle material as a backer, and lay in thin walled copper tubing. Put any window glass over the front, so the sun's energy gets magnified, and run water through the system using a small pump. We built one of these years ago, to heat a huge swimming pool, and it was an awesome project with great returns on investment. The trick is to make the sun warm it up, and air tight the whole thing, so it keeps the warmth.

kimberley.vaughan.7 (author)2015-05-09

That is really awesome. I love it when people think differently. Very inventive. Congratulations.

ooohlaa (author)2015-04-28

Not sure if this is old news but here in North Central FL country folk fill gal milk jugs with water and put them around orange trees and other plants when we have a deep freeze period ... it can get down to 17 for several nites, but during day it will be in 50's during cold winters. Anyway I put about 8 of them in my small greenhouse and it seemed to have worked to keep fm freeze. Theory is that as water goes into freeze mode it gives off heat? Could this be true? I put some other jugs around delicate plants outside and it seemed to have helped. Unsightly though. I saved all the jugs in 2 huge trash bags for next season. I swear it saved my peach tree which is an early bloomer and then I lose all my blossoms to a late freeze.

pallc (author)ooohlaa2015-04-28

Good info still ooohlaa. I was thinking painting "flat" black since that is the best absorber of heat from my experience. Technically, flat black is the best absorber of light in the specific wavelength range that transfers to heat.

Like Gordyh noted, heat tries to obtain thermal equilibrium (balance). Therefore, to clarify, there is no such thing as energy known as "hot" or "cold." "Hot" or "cold" is a range of sensory perception based on our internal environment touch sensory inputs of our nervous system based on our created/evolved standard temperature and pressure environment in relation to an input of more or less heat than the body temperature or heat unit since our living being can only survive between a certain range of temperature without aid of external environment devices.

Basically, hot goes to cold to balance the heat. Some materials have heat capacities that absorb more heat than others, as well as thermal conductivities that transfer the heat at different rates. Water absorbs more heat than air due to its heat capacity being more and transfers the heat slower due to its thermal conductivity being less.

OK, tmi... anyhow... I went on a tangent and wanted to note that I grew up using flat black spray painted milk jugs for the most part throughout the outside garden and green house. We'd make hoop houses with clear or black plastic depending on what we were growing and place the milk jugs in those also for the outside garden. Sometimes, we'd just leave the jugs out next to tomatoes though I don't recall using outside of plastic too much.

We'd also cut the bottoms of some of the milk jugs and use the milk jugs as "mini" greenhouses. Some were flat black and some were left opaque.

tempt1 (author)pallc2015-05-09

Just like to add to your excellent notes, the sensory perception is often dependent on the speed of transfer. That's why when and water and air or metal of the same temperature is touched our reaction can be quite different. The water is very efficiency transfer medium (makes good molecular contact) so we "feel" the water as colder as the energy loss is much faster. Our body interprets the speed of energy transfer as a bigger heat differential (the bigger the difference the faster the transfer). Where with drier air, the air acts as an insulator, so the immediate point of contact warms quickly to equilibrium, so it doesn't feel as cold. To make the air feel like water we have to make the air move around more, so that thin layer touching the skin gets moved away.

pallc (author)tempt12015-05-09

Right temp1, I have to look at the units... though I want to say what you are referring to is the materials property of "thermal effusivity."

tempt1 (author)ooohlaa2015-05-08

the water to ice and vice versa is known as "phase change", and like any system of change it requires and/or releases energy. It actually takes/releases quite a lot of energy to make it happen, so what happens is the water continues to lose energy to the air until it can't do it any more, then the packing shape of the water starts to shift into something more convenient at a low temperature, like people huddling together in the cold. When enough of the water molecules have achieved that state, if a little more energy is _added_, the whole lot starts to compact together in the new "ice" form. As each molecule slips into it's new more efficient form, it releases a gasp of energy, triggering the molecules next to it, until all the molecules are locked into the new "ice" pattern. If you do the cooling -real- slow, and be very very careful not to bump the water, it can get well down into the negative Celcius temperatures...and a slight tap and the whole thing starts to turn to ice instantly in front of your eyes! Amazing to watch.

Some ice packs use similar processes. the chemical reaction sucks in energy, but the new chemical from the reaction is might also suck more energy in depending on it's melting point!

If you throw a bit of sand in those water containers, you should find they hold their heat a little longer

mworrall (author)ooohlaa2015-05-01

That stirreda memory from school days - latent heat of fusion of water?

yrralguthrie (author)ooohlaa2015-04-28

Yes, Ice at 32 degrees has less energy than water at 32 degrees. Also in the act of cooling water has to give up heat.

Perhaps more effective is a water misting system. Mist the trees with water and before the trees can freeze the water has to be evaporated. Trees can't freeze with any significant water on them.

Gordyh (author)ooohlaa2015-04-28

Generally it's called thermal mass, And can be rock's, concrete, soil, or water in containers, water has the highest heat storage capacity. As the temp rises the mass absorbs heat, and as the surrounding air temp drops the mass starts giving up it's stored heat. It has nothing to do with a "Freeze Mode" heat by it's nature wants to move from it's source to the cold area.

Sounds like the plain jugs are working for you, but if you want more heat, Search You Tube for "solar greenhouse heaters", many Northern folk's use black 55 gallon drums or other colored drums painted black. Some hardware stores carry spray paint that is safe to use on plastic without the risk of melting the plastic from the chemicals in regular spray paint. Set a black and clear water filled jugs out in the sun, at the end of the day measure the temp of both jugs to see the difference it can make. is a wheat of info if your interested.

philo36 (author)Gordyh2015-04-28

I bet if you used one black hose with all black bottles and one black hose with clear bottles and compare the two setups with all other factors being equal, the clear bottle set up will produce more heat, especially on windy days. How many solar water panels (other than the single wall rubber mat type) do you see that are all black? They almost all have black pipe inside reflective boxes and clear glass in front.

yrralguthrie (author)2015-04-28

I wonder if this setup produces enough addition heat over just the black hose laying on the ground to offset the energy used by the pump? Similar pumps that I checked use from 60 to 300 watts. Interesting use of scrap, but perhaps not energy efficient. On a hot day what is the temperature rise of the water? You probably said, but how big is the barrel?

philo36 (author)yrralguthrie2015-04-28

Any wind would cause a cooling effect on the hose, while using all clear bottles would allow the sunlight to fully hit the hose and help prevent any heat loss to the air or ground.

yrralguthrie (author)philo362015-04-28

I see that someone flagged my last post. Not sure why, since it's only a question.

That person will likely flag this though.

philo36 that is BS. Are you trying to say that the wind will affect a hose lying tight to the ground more than 4 in. diameter bottles? just thought that up and decided to counter with it.

And to whomever flagged my first post, without constructive critism these posted ideas are just flotsam like most of what is found on the internet. If an idea can't stand by itself and be questioned it not much of an idea.

tempt1 (author)yrralguthrie2015-05-09

the loss to moving air (by radiation and convection) is quite noticeable.

But utilising the bottles, the pipe is stored in a cavity, so the moving air can only go so far and the small cavity will rapidly rise in air temperature with the warm air trapped in place. This will reduce the thermal gradient between the pipe and the air, slowing the energy transfer (loss).
The trapped air, then must pass it's energy across to a very smooth surface (vs a rugged/spiky one). The smooth surface is a poor conductor, and ok reflector. The plastic has better heat characteristics that metal or moisture. Then the smooth external surface of the bottle will radiate poorly into the external atmosphere. This external radiation is much poorer energy transfer than warm fluid air intermixing directly with cold fluid air. This means the bottle will raise it's temperature over that of the atmosphere.

Factors such as making sure the bottles are out of the breeze, improving the transparency of the bottle, reducing cavity size, filling the cavity with Argon (as the plastic won't handle vacuum), using a more conductive pipe, making sure the plastic bottles are dry and not touching ground or metal, painting the bottom side of the bottles silver or white, using a second layer of clear plastic, and working out a thermal storage (eg mass) in relation to water flow and optimum time to heat are other factors.

But yes the bottles are quite effective, especially given their source.
test it and see.

philo36 (author)yrralguthrie2015-04-29

Any wind circulating over the hose will cause a cooling effect on it and since it is lying on the ground there will be also heat loss to the ground through conduction. Years ago, I took a class that during which you learned about and made your own solar panels. Those same panels sat on my roof for 17 years. I now have a different system which sits right next to my 10kW solar electric system also on my roof. Why do you think that most box style solar panels are have glass covering the front? Its there to help contain the irradiated heat around the piping.

dollarseed (author)2015-04-28

Something else to consider. If you paint this drum flat black, it will keep the water a lot hotter without the need to insulate. However, I played around a lot in passive solar heating, and found that a black bucket filled with sand and topped with water was the best storage container to disperse heat all night long. Maybe you could remove the top of the barrel, insert a can of sand in the middle to do the same?

Unfortunately, plastic bottle trash is a worldwide problem. Here where I live, you pay a nickel to get one, and get the nickel back when you recycle it. Much more environmentally friendly, as most people are scraping the bottom, and looking for free money.

Raphango (author)dollarseed2015-04-29

But why would we like to disperse the heat we've been building up the whole day? Does it mean we would have a cold shower at early morning? =)

NewAge-2014 (author)Raphango2015-04-29

Oh, I do not plan to use it in the morning. It is enough to take a warm shower at the end of the day.

tempt1 (author)NewAge-20142015-05-08

why not do both...there's plenty of rubbish to go around.

tempt1 (author)Raphango2015-05-08

It acts as space heating (or better "Thermal memory") for general heating in the house at night when temperature is dropping.
Also can be used for a heat transfer medium, put the incoming house cold water in one set of pipes before they reach the hotwater cylinder, use another set of pipes connected outside to the heating system to warm the thermal storage medium. The water increases the efficiency of transfer hugely, and the sand is more dense so can hold more energy (iron, with an oil would be better, a chemical with a phase change stage at the right temperature range is best-est). The bonus of this ssystem is it takes time for the cold water pipes to heat through, so you can have 100s of meters of thin pipe that heats fast or a 10meters of sand pipe that takes longer.

A collegue I spoke to, runs >100m pipe (20mm) in his ceiling cavity, just under the roofing surface. It passively lifts the incoming cold water by quite a few degrees. No moving parts, not the fastest heating, but it shaves real $$ off his power bill. Connect it to other things such as the sand-water box, you can have very cheap heatin and hotwater... or even better you only need a few kW more (say from a few PV panel) to be completely self-energised.

Rodeodog (author)Raphango2015-05-01

I would think that as the heated water enters the hose in the matt bkack painted barrel filied with sand, some of the heat warms up the sand. When the sun goes down and no more heated water enters the barrel, the sand disperses some of its stored heat back to the water, giving you a morning shower that may not be as warm as last night's shower, but is still warm enough not to be "cold". Nice 'ible, BTW.

dollarseed (author)Raphango2015-04-29

Park the barrel and shower head in it's own little greenhouse, then you could take a warm shower and both be out of the elements :-)

NewAge-2014 (author)dollarseed2015-04-28

during the 45 years of communist regime in Bulgaria, all drinks and foods was sold in
gass jars and bottles, including youghurt. There were special recycling centres, where you could
bring back all the glass packings and get paid. This way everything was recycled.
Then suddenly, after the fall of communist regime,
we carelessly adopted the western style buy-use-trash. And the market
was overflown with plastic bottles. The result was tragic!!! There was
no recycling centers for plastic, no recycling bins. People in villages across the
country were simply dumping the plastic into the rivers, just like what you see on the photo. My heart bleeds every time I see plastic bottles thrown all over the place in the most virgin and pristine places in Bulgaria.

Raphango (author)NewAge-20142015-04-29

It's really very sad.. =(

But God bless you for your initiative! =)

dollarseed (author)NewAge-20142015-04-28

Yes, that is sad. Many people do not realize that it will take more than a century for those plastic bottles to break down. There are many instructables coming out now that will show different methods of recycling those bottles to be reused, but they all require things that are not so easy to have at hand. On the other hand, people are starting to wake up and realize that we can not continue poisoning the planet, if we want to coexist with the trash.

dsandds2003 (author)2015-05-04

Great idea..Have some thoughts to think on...Like plastic becomes moldable around 140 degrees. Their are a couple articles where people remelt the plastic into blocks make things out of. you could also make castings for parts with the plastic.

It is GREAT to see people recycling and repurposing what is out their and see what ideas other people come up with.

Keep up the great ideas!!

Sivanendharan (author)2015-05-03

Concept of wealth from waste is excellent..........

clewis21 (author)2015-05-02

Thank you for sharing your awesome idea!

Ottoclav (author)2015-04-29

I really like this instructable, great job!!

Raphango (author)2015-04-29

Awesome idea!! Congratulations for your brilliant project! =D

Steelsmith1 (author)Raphango2015-04-29

Many people think it is new to not pollute. I am 67 and I was trained by my parents not to pollute. I have NEVER thrown one bottle in a bad place. i was taught to put any piece of paper or gum wrapper in my pocket and do so to this day. As the Crosby, Stills and Nash song says: "teach your children well" ; good advice.

aalonso motta (author)2015-04-29

those are the really fine ideas. Simply. All hands capable. Useful for other uses. Construction and technics can give ideas for many different projects. Million thanks man.

pinchebob (author)2015-04-29

Provided you find one that doesn't leak, a broken water heater tank makes an excellent insulated storage tank.

Smithhound (author)2015-04-28

Great idea and nice DIY, the pix speak for themselves. Hopefully this doesn't stay on the ground, maybe on the roof of the building to the left?

NewAge-2014 (author)Smithhound2015-04-28

Yes, it is intended to go on the roof with ceramic tiles. But first I decided to test it.

NewAge-2014 (author)2015-04-28

Here is another use of bottles I published yesterday: how to keep the paint always fresh:

kakashibatosi (author)2015-04-27

Do you have a thermometer attached to the water barrel? I'm interested in how much of a temperature rise you've seen on a good day. Cool 'ible, it made me think :)

Not yet. In this village I am living now they have no hardware store and I can't get thermometer.

Arno_NL (author)2015-04-28

I am wondering how much effect these plastic bottles actually have on the system. Look at commercial solar heaters based on the same principle of heating up water. They have a black surface with high radiation absorption. These are stored inside a clear container in a vacuum. Solar radiation is captured but losses through convection and conduction are very small because of the vacuum.

However in your case the bottles contain air. Hence losses through conduction and convection are still possible, especially because the layer of air surrounding the hose inside the bottles is quite large. Convection is however limited because direct gusts of wind are blocked.

I must say that I love this project . Especially the innovative recycling you have dreamed up. As an engineer I would love to see some measurements and more numbers. Also what are you using the heated water for?

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