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Building & Testing 4 DIY Solar Water Heaters: Cheap Pipe vs Copper

Greenhill Forge

85,574 views

This video covers solar water heaters. I'll go over some of the science that makes heating water very different from heating air to help , then I'll build four different DIY solar water heaters to test and compare so we can see what design makes the most sense to build as a cheap, effective DIY water heater. This video will focus on really simple designs and I’ll do a follow up video with more complex diy water heating designs so we can compare the results to figure out the balance between design complexity and actual heating results.

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20 Comments

@chriscmoor 2 months ago

Interesting build. I constructed something similar using hdpe in a tight spiral and used the panels from a double glazed sliding glass door as the cover. This is strictly for heating laundry water, so it doesn't have to be strictly potable. I used a tight spiral for the pipe which allowed me to get a lot of feet into the collectors. It works like a charm and the only issue I have here in south Florida is that the water gets too hot. It recirculates through a repurposed 50 gal electric water heater so there is some ballast in the system to absorb the excess heat. I did add a temperature controlled mixing valve on the hot water side so the incoming water can be reduced to a more typical residential temperature of around 110F. Adding the tank to store the heated water was the game changer for the system.

@mattb54 2 months ago

Would be interested in seeing a standard household and/or vehicle radiator painted black and compare it to your custom set ups to see if the fully DIY version can perform better than a half DIY solution

@ArizonaRegime 2 months ago

I absolutely love your channel and what you do. I know that the level at which you speak at, technically, mathematically, scientifically, etc. will not resonate with the vast majority of users of YouTube. That being said, it’s a breath of fresh air that someone with expertise and knowledge shares it even if the majority of homesteaders/off-griders won’t understand these concepts to the degree that you do.

@jamesdim 2 months ago

The projects you're working on are the same projects i'm working on. And your testing is extremely helpful and saves me a lot of trouble. So thank you very much for sharing!

@bcftr 2 months ago

one of the best channels out there

@christopherlenahan3906 2 months ago (edited)

Great video as always, I really want to say, at this point you are up with Project Farm on my list of top youtuber's. Doing things people have been doing for years, but adding the scientific method to it. Grassroots backyard resourcefulness, done scientifically... LOVE IT!

@VikingExploration60 2 months ago

You should have used a bending spring or pipe benders for the copper.

@venusrise 2 months ago

I love this guy. So succinct, clear and organized. No wasted time. Really appreciate the knowledge and instruction

@simon_daytona 2 months ago

I love your channel, every project is so well planned and tested, you are one of the best engineers I have watched, and your testing methods and data logging is fantastic and adds real world data to these projects.
You are also a great educator too. I would go so far as to say the best channel on YouTube and also one of the most inspirational. Thank you for sharing it all with us.

@robinanderson2798 2 months ago

I used corrugated iron collector and laid thin poly tube in the vertical troughs . With T joiners top n bottom into common top and bottom receivers, A 12v thermostat control pump circulated water into tank. Worked very well. Cheers from New Zealand

@shrimpixel 2 months ago

I love this channel so much because it ranges from topics I did my thesis on (performance characteristics and comparison of axial vs radial flux permanent magnet arrays for low speed wind turbines) to things I was only theoretically aware of due to growing up in the south (solar water heating instead of solar electric generating) to things I'd literally never even heard of before but make total sense in hindsight (solar air heating). And every one of these videos feels like a masterclass on how to do it the right way rather than randomly trial-and-erroring your way toward a better result. Real data, real science, and most of all, a real kindness in the way it's presented. I've only been watching these videos for about 9 months now but never have I seen one that presents itself as an authority to an idiot viewer, nor as a "callout/correction" on any other specific youtuber; it's always just, "here's some information, I've documented and tested a wide range of situations, and I think it'll be useful to someone." Paired with the logical explanation of how these things work, as well as the thought process and reasoning behind each design decision, and this is genuinely one of the best channels on all of youtube, even if most of the homesteading stuff is not particularly relevant to me.

I was a little hesitant when I saw "two white guys are starting yet another podcast" but with how incredible your gift for information-seeking and sharing is, I have a feeling this may be one of the few podcasts I actually listen to regularly. Looking forward to where that ends up, and an immense thank-you for all your hard work with this channel.

@GoatZilla 1 month ago

Great data.

Couple of notes.

1. I'm kind of a fan of (5 gallon) buckets with lids. I sometimes double-bucket to kind of provide a little insulation at least on the sides/bottom, and stick push-connect fittings on the lid. Would have also shaded them underneath the panels themselves since the shade is already there.

2. UV exposure is apparently bad for PEX.

3. I wonder if a low-emissivity, high absorption paint will improve performance.

@MrStrizver 2 months ago

I definitely would like to see the difference between parallel vertical paths would make, as well as different tube sizes for the parallel paths.

@Zatto-d2h 2 months ago

I like how you reuse fit for purpose waste products most people would toss in the bin.

Those litter buckets have been extremely useful to me for storage and mixing liquids.

It's amazing how much engineering and resources go into one time use packaging.

@alexgreenwood3868 2 months ago

18:50 you could use a plumber's pipe bender to prevent copper pipe from crimping at the bend

@blimm2341 2 months ago

Great vid!
Variables worth testing, I think:
-glass faced box (tempered?)
-black painted copper (vanta black or other max absorbing black)
-polished aluminum backing
-copper tubing smashed square onto the backing for more surface contact
-thicker aluminum backing
-water behind the aluminum backing
-maybe a mirror for backing

@christophernelson3197 2 months ago

Brother you are among the giants upon whose shoulders the rest of us stand! Thank you for the good work and SO MUCH INFORMATION!!!!!

@scottwilling_OG 1 month ago

14:58 "It's a pretty simple system" (opens box full of rainbow spaghetti). 😂

I was tempted to make some crack about wire management but it's not as though this was a production prototype. Kudos for having the knowledge and making the effort to build and code your own datalogger, from this crusty old off-grid technologist / electrician.

Aside from smart relays, the last programming I did was in assembler on an HC11.

But my cable bundles were laced! 🤪

@GunterYang 2 months ago

Love your content, man. Also love all the stone walls in the background of your videos!

@garysmith5025 1 month ago

There are low cost solar heaters intended for temporary swimming pools. Typically they're made of black HDPE and you lay them out on the lawn, but if you enclose them in an insulated and glazed box like you've done in this video they are hugely more effective. The ones I use are 3 metres by 0.8metres, cost about £100, and with two of these we can cover 80% of the year round heating for a small swimming pool (8m x 2m) in the north of Scotland. They could easily be used to provide hot water up to maybe 60c and we've also never had any problems with freezing, they seem able to cope with -15c overnight temperature whilst filled with water with no antifreeze without bursting. Even on an overcast day they will produce a useful output, in summer you need to be careful that they're not exposed to the sun whilst empty or they can get hot enough to melt.