Easy Heat from DIY Solar Thermal Panels

In this video I decided to make a solar heating panel with design features that will be compatible with sky cooling later on. Solar heating is a very efficient method of using solar energy, with the ability to absorb 900-1000w/m2 of heat from sunlight, compared to only 200-300w/m2 of electricity that could be generated from a similarly sized standard solar panel.

Here are a few links to solar fan kits that can be used to complete this project (these are affiliate links):

Here are a few links to the videos referenced in this project:

Thank you so much to those of you who support this channel on Patreon! Your support really helps give me confidence to spend my time researching projects that are of value for more than just video views. Shoutout to my top patrons: Eugene Pakhomov, Peter Gordon, Evan Hughes, Teague Lasser, Matthias S., Michel Pastor, PabloXIII, Parker Jones, Simone Chiesi, Steve C, Yanko Yankulov

Thanks everyone for watching!

[Nighthawkinlight]

Best ideas to improve these panels so far: @bobkins20 suggested tablecloth clips to hold the panel together. This is a great idea! They are inexpensive and durable stainless steel. Multiple people suggested that pink foam board does not last long in high heat and may offgas unhealthy fumes. Aluminum coated yellow foam board would probably hold up better to heat, and the aluminized surface should prevent offgasing into the circulating air. An extra precaution against this could be using an extra layer of cellophane to cover the foam board behind the metal.

[RageKroc]

Every time I check in on your channel you're either teaching people how to commit neat science or you're inventing something awesome. May you continue to thrive for mankind's sake Mr NightHawk.

[OceanBagel]

I'd love to see an update video of this panel being used in cold weather, to see how much heat is conducted away into the cold outside air and thus reducing the amount of usable heat.

[noobslayer]

The high tech coatings series has been one of my favorite arcs of this channel. Such interesting stuff

[HGS]

Your fabrication here is slick with today’s materials. Only as a point of interest, about 50 years ago, I built a similar wooden box to yours using regular tin cans spaced apart inside, all painted black. I used plexiglass for the top of the box. The box, with one end open, was propped on outside wall at a 45 degree angle and secured under the open window sash all insulated against cold air intake. Worked fine! Some home made stuff becomes classic!
Keep on goin’!

[maglev_]

i love how many of your projects are basically purpose made to be as simple, doable, and open source as possible. all your videos are entertaining and relatable for the common man just as much as for the science nerd. keep doing what you’re doing its great stuff!

[buffalojones]

You’re one of the best parts of the internet. You create inventions that could be used for patented gain, but you instead share them for free for the world to see. Thank you!

[AnonymosAnthropos]

You could build a changing surface for the outer facade of a house with a simple already known techinque: trilons (like for billboards). A trilon surface in black (for winter time) a trilon surface in white (for summer time), and one colored in your favourite color, if you plan to invite guests, when the sky is cloudy. The airflow could be managed within the trilons. At the same time it would be a good insulator.

[ElectroBOOM]

Great project! A question, wouldn't painting the other side of the metal panel black also help radiate heat better to the air passing over, as in dark body radiation? Or maybe it makes the thermal conductivity worse...

[kvg]

The heat transfer rate difference between turbulent and laminar flow conditions is due to turbulent flow’s larger Reynolds number. This isn’t always the case though. I was lucky enough to have Ephraim Sparrow as a professor in college. He’s better known for his pioneering work in radiant heat transfer (I have so many stories and on his teaching that), but he also did some work on laminar reynolds numbers. He was able to get laminar flows (water) to have reynolds numbers greater than 32, 000.

A story relevant to your cooling paint: Eph was working for the US government in the 1940s or 1950s where they needed to put sensitive electronics in metal boxes on the top of telephone poles in the Nevada desert. The electronics kept failing due to the high temperatures and the requirement that the boxes had to be completely sealed. I’m guessing that these were sensors for the nuclear tests done at Los Alamos, but he specifically said that he couldn’t talk about the specifics because it required a security clearance. Well anyway, His boss said, “polish the box exteriors to a mirror finish” and Eph replied, “no that won’t work, paint them white.” When asked why, Eph responded with “it’s intuitive.” Well, that didn’t go over well and while he didn’t go into the specifics, he was fired and his boss told him his idea didn’t make any sense. Fast forward 10 or so years and he ran into his former boss at a convention or a presentation and his boss apologized and said that Eph was right about the white paint. But that’s why Eph is basically the father of radiant heat transfer theory.

[drewcress]

XPS foam board is great for the cold and wet but has some limitations when it comes to heat. It stats to melt at 70c and is combustible - probably not desired in a solar heating panel. Polyiso performs better in this temapture range, often comes with an aluminized facing as an added radiant / vapor barrier, and at roughly the same cost. The alu layer pointing inwards will likely act as a heat sink/spreader (given the limited air space within) and increase performance as well.

If the expected lifespan of the film is just a year then shipping tape should be able to handle that while being replaceable in the same time frame. This would make the screen frame largely optional (but sooo much easier to work with for prototyping)

[marklefler]

Great video. One thing, the shiny back of the painted panel reflects is making it act like a radiant barrier, meaning it only emits a fraction of IR. If it was painted black also, it would radiate much more IR, heating both the air that touches the panel (via conduction and convection) as well as radiate to heat air molecules which are not directly touching the panel. Also as you mention the polyethylene passes IR, so so a lot of the heat on the black painted panel will radiate out through the film. Glass or an IR opaque film would work better in heating season. I suggest two films, IR transparent for the "cooling" side and IR opaque for the heating side.

[aje]

A possible clip alternative could be 1" sections of a large diameter pvc pipe with either a slit or section removed to allow it to open and apply adequate clamping pressure.

[debbiejansen]

I just found your channel and I can’t stop watching… you’re a wonderful teacher and keep your audience captivated- thank you for teaching us and inspiring future scientists.

[scott]

They sell pre-made support strips for the corrugated metal panels. You could add them behind the metal panel to use as both supports and walls to force the air to take a longer path

[marcelihryniow]

This one will become a classic (for me at least). One of the most useful, interesting, easy and thought provoking videos I watched in a while. Thank you for all your work

[SteveEh]

Just did a bit of research on plastic types to use for the covering. My first thought was clear "shrink plastic", for draft protecting and winter insulating windows. Turns out, the type of plastic, from what I can find, Is IR blocking. Polycarbonate would be a good option, but expensive. Greenhouse plastic (Polyethylene Film) has all the right properties, UV resistant, high IR pass-through, fairly inexpensive. Good luck to anyone building these panels!

[cimachu]

Awesome video Ben, I love how you walk through your design process without dragging it out or making it boring. This video sort of reminds me of some of your older ones because its something that anyone can make, and that I can imagine a lot of people would want to make, but maybe that's just me. Cheers!

[Bigman]

The increase in temperature difference in the second setup is partly due to the decreased air flow. To het a better picture you should also measure the airflow...

[gregcarlson]

You are a cool dude. You are one of those videos you get straight to the point without the 45 minutes of blah blah before sharing what you want to say. Keep up the good information for us viewers. Your cool