Easy Heat from DIY Solar Thermal Panels

hi everyone in this video we'll be taking a quick pause from my ongoing radiative cooling paint project to go off on a bit of a rabbit Trail if you've been following my channel recently you've seen that I've been working on high-tech Coatings that can actually absorb heat from their environment and radiate it directly into outer space with a sort of reverse greenhouse effect it sounds impossible but this paint can actually cool down a surface below Ambient Air Temperature making it potentially very useful for cooling buildings and perhaps whole cities without any cost of electricity my end goal for these Coatings is to make modular cooling panels that are easy to assemble inexpensive and made from parts that are available all over the world to make that goal a reality I realized I should probably learn more about panel design in general by first accomplishing a much easier task of making a panel that can absorb solar heat this can be done very efficiently with a good design and potentially with the right configuration a single panel could be used to both heat a building in Winter and cool it down in summer so let's build a solar heating panel and hopefully in the process we'll learn a few things that can be used for cooling later on there are many different designs for solar heating panels floating around the internet most of them starting with a large plywood box like this this is just an ordinary sheet of half inch thick plywood with a few extra boards screwed along the edges to turn it into a shallow box a heating panel can be as simple as painting the inside of this box black and then drilling an inlet and Outlet hole at opposite ends for air to circulate through it we then cover the front of this box with a plate of glass to insulate it from the outside air now this probably would not be a very efficient design as it is because air would too easily flow from one side to the other without making a lot of thermal contact with the painted surface along the way and that's what absorbs the sunlight and converts it into heat efficiency can be improved by putting baffles inside of the box so the air has to travel a longer path slowly snaking its way back and forth around these baffles before it reaches the other side and therefore giving the air a much longer opportunity to absorb heat you can also fill the empty space with various types of Darkly colored fibers which the air then has to pass through causing an even better heat transfer an example of such fibers would be black landscaping fabric now this design with those added improvements would work fairly well but I think we can do even better this is uninsulated plywood so we will definitely lose some of our heat as it soaks Through the Wood and out into the open air for best results especially if we want this panel to ever function in a cooling capacity we need to insulate it which could be done with foam board but now this project is starting to look a little bit more expensive when I started thinking about insulating this box I realized that the foam board itself has a good amount of rigidity maybe the box is not necessary maybe we can ditch it and build a panel from the ground up in layers starting with a piece of foam board what I've described so far is a heating panel that circulates air over top of the painted surface the plywood would be painted black Air would enter the Box flow directly over the paint and then out the other side the disadvantage of doing things this way is that the paint can become dirty if the circulating air is not filtered if I were using a cooling paint Not only would the paint get dirty but it might also become damp as water condenses on the cold surface in the long term that could damage the coating the obvious solution to this is to not allow air to flow over the coating but behind it now that's what I've done with this panel let's build one of these from the ground up and I'll show you how it works as we go along the surface which will collect the heat in this design is a piece of sheet metal this particular size and type of sheet metal is called a hobby panel and you can find these in many hardware stores other types of sheet metal will work just as well I've cut a piece of my foam board to be just a little bit bigger than the sheet metal itself now before going further we need to take this metal outside and paint it black this brings up a question that many people have commented on my earlier cooling paint videos asking if I could make the opposite a paint that absorbs heat very efficiently in truth yes we could make an ultra black coating that absorbs nearly 100 percent of sunlight but sunlight is so powerful that doing this seems to me like a waste of time you'll see soon enough that ordinary black spray paint which commonly absorbs over 90 percent of sunlight becomes extremely hot in our heating panel it would be easier to just increase the panel size by 10 percent then go through the effort of making a custom paint just to squeeze out a little bit more heat now we need to make an offset from the foam board so that air can flow behind this sheet metal when it's set on top to do that we will line the edge of the metal with a bit of foam pipe insulation which will double as a seal to make sure the metal doesn't cut through the foam I'll snip off the corners and cover the sharp edges with a bit of masking tape the insulation can then be pressed over the edges and held on the back of the panel with a bit more tape this isn't the prettiest solution but it's easy and doesn't interfere with the panel's performance now when I set this on top of the foam board there will be a gap behind the sheet metal for air to circulate through we just need to cut an inlet and Outlet hole in opposite corners of the foam board I bought a small solar powered fan kit to provide circulation so when I cut my holes in the foam board I want them to match the size of this fan not bad there's really only one more element to turn this into a functional heating panel and that is to put a transparent cover over the top a common choice is glass or Plexiglas but those materials will not work if I want to eventually use this for cooling they Block in for red light instead I will use a polyethylene film this works for both purposes both as an outer surface for a heating panel and it also works with my cooling paint to hold the film securely to the front of this panel I found a good option is to use the frame from a window screen these frames typically come in a kit where you cut the rails to size and then hold them together with plastic corner pieces on the ends that makes it really easy to size the frame correctly to fit our panel the plastic film is then installed in the frame in exactly the same way as you would install a window screen the kit comes with rubber cords that press into the frame holding the plastic tightly in place I think that depending on the weather conditions I would expect this film to last about one year Outdoors being tightly stretched over the frame will help prevent any damage from the wind but sunlight will destroy this film eventually overall I think this amount of yearly plastic waste is a pretty good trade for multiple months of otherwise carbon neutral heat I've left extra film overlapping the borders of the frame so that it can wrap around the edges of the entire panel covering any gaps in the seam and therefore making the whole thing waterproof to hold this three layered sandwich together I found these plastic Clips which are meant to snap onto a rain gutter downspout these are about three inches across with a little bit of a spring in them so that they can compress this foam around the sheet metal and keep everything secure of every part in this design these are my least favorite I doubt these particular gutter clips are available everywhere and they don't hold the panel quite as tightly as I would like if you have ideas for a better part that could be used for this let me know in the comments I've already thought of using C clamps and these Big Spring clamp things but these are Overkill in any case these clips will work for the moment the panel is held together and we can take it outside for a test to hold my solar powered fan to the board I'll just push a few Nails into the foam this will work well enough for a test on a thermal camera we can see quite a high temperature as we move away from the fan testing with the thermometer we get about a 20 degree difference between the air Inlet and the outlet that is a lot of heat even so the thermal camera shows that this design is not performing very efficiently there is a lot of heat once you move away from the fan that is not being absorbed by the air this can be improved in exactly the same way we talked about at the start of this video by causing the air to take a longer path from the entrance to the exit it is really easy to make changes to this panel because you just remove these clips and it comes right apart I'll direct the airflow by adding channels to the back of the metal sheet this is easily done with foam weather strips with little pieces of tape just to tack them on the ends once the panel is back together the foam will compress and be naturally held in place so now we can give this another try once again looking at the thermal camera image the air channels have become quite apparent I'm intentionally making the airflow against the grain of the ridges in the sheet metal because I suspect the turbulence will lead to better heat transfer so here is the result using a thermometer just like that we have increased the difference in temperature from the inlet to the outlet by an additional 10 degrees on top of the original 20 degree difference measured earlier the airflow seems about the same so overall this is a huge increase in efficiency well I consider this to basically be a finished panel that is ready for practical use it still needs a sturdy mounting solution and a few connections to actually move air to and from a building but those are ordinary construction tasks that don't require any Innovation from myself I'll probably use these PVC flange fittings to make my hose connections and glue this whole thing to a sturdy wooden base to keep it from blowing away the main thing I wanted to learn from this project is how to make a panel that works with the air flowing behind the sky facing surface because that is the essential feature of a panel that can also be used for cooling [Applause] while a solar heating panel is a fairly simple concept but I think what we have achieved in this video is a design that is extremely easy to assemble and very effective did you notice how few tools I used to complete this project a pair of metal Snips and a razor blade pretty much covers it now as simple as this panel is to complete we have been building on a very complex project in making and using radiative cooling paint if you feel like your science education is lacking check out my sponsor for this video brilliant.org brilliant is the best way to learn math science and computer science through interactive courses in my last video I talked about how I've been learning to program with python through a course on brilliant but for this video I wanted to see if they had anything related to solar energy it turns out brilliant has an enormous solar energy course including a section about solar thermal power to fully understand this course it does require a prerequisite of classical mechanics but if you're up for the challenge that's something you can learn on brilliant also they have thousands of lessons covering all levels of Education which can be completed at your own pace and the ones that I have completed have been extremely satisfying largely because their teaching style makes complex topics feel intuitive through practical and interactive problems most types of Education try to build your knowledge one step at a time but I think brilliant does a particularly good job of this it's very uncommon that I need to backtrack in one of their courses because I've not understood an earlier step I can't say the same for other ways I've learned things in the past using my link you can try everything brilliant has to offer for 30 days completely free that's brilliant.org forward slash Nighthawk and by using that link you can also get 20 off Brilliance annual premium subscription well I hope you find this project useful leave me comments below and stay tuned for future projects thank you so much for watching I'll see you next time

Channel: NightHawkInLight

Views: 355,352

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Id: Tg44ndqPTGQ

Length: 13min 18sec (798 seconds)

Published: Wed Aug 09 2023