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Forum Index : Solar : Deciding if I should build this solar heater
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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 02:23am 12 May 2021
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Don't really think it matter much. For backyard purposes, I'd classify any wide non paper tape as duct tape and it does not really matter what it is. Long as it holds, job done.
The cloth tape is great but sometimes too good for temporary use and is relatively expensive. Can be a mongeral to get off if you want to especially after a bit of time.
Dunno about that! Good mate of Mine owns an AC company that takes on the most High end jobs in the city. Not the biggest but the most detailed, critical and Complex. Operating theatres, Clean rooms, Military installations etc. He get the work because he has a reputation of doing things once and doing them right.... and of being the most expensive out there. :0)
He's still flat out with work and apart from a period last year he took off for an operation and had everyone else just doing maintenance, has never slowed down even in the last 12 months or so.
Helped him a lot of times and only remember using the foil tape on some exhaust Duct out of a high star rated furnace exhaust that was supposed to be under 40oC. The rest of the time it's the black plastic type tape.
I have the foil, the cloth and the plastic tape up the back thanks to him and he's fussy on the brand he gets and gets loads of it he keeps in stock in his little warehouse. He's also fussy about the amount of wraps that go round each duct you do, both layers and where it is positioned.
For 95% of backyard purposes, the regular plastic type at least in a decent brand is good enough.
Foil Tape Might look good on my Ugg boots though, might even start a trend! More like Moon boots of safety boots when casting molten metal. Be more comfy than the steel cap ones I wear when playing with the furnace now.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:31am 12 May 2021
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You guys have this all wrong...
Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 03:35am 12 May 2021
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I think there is Volts/ Amps Type equation with heating. You can bias it to one or the other but the goal is really the watts. You could have higher temps at lower airflow, more airflow at lower temps but you still need a certain amount of KWH of energy to do the job.
The drawback I perceive is that it backs onto the laundry. I usually close that off in winter because obviously does not need heating and eliminated another window and door. then again, the Mrs has relegated feeding the dog in there with her water so probably going to have to stay open now. I'd be happier if that wall back onto a living area.
The other thing that will quieten fans is to put them in the middle of a duct so there is no direct exposure to the fan blades itself. If that's not practical, just put some duct on the end to suppress the noise that can be heard outside.
I'm wondering how liner the output of the tubes would be to a panel? Efficiency is different but response should be fairly similar for the most part I imagine. Back to the idea of having a fan run by a solar panel. Less sun, less heat, less power to the fan. I was thinking a resistance in the solar output ( put it in the duct and get 10W more heat! ;0) ) but might be easier/ simpler to choke off the air intake. Spinning the fan faster through being unloaded I think would keep the pressure up while limiting the volume.
I doubt you need this to be critical, really just to make the best of what is available. The other thought was to have the fan output stepped rather than linear. Use a solar cell or even a couple of LED's to give a reference signal and then have say a 10 Stepped output.
Now that the fridge has stopped, I can hear it from where I'm sitting, but it's no louder than a fridge or aircon running. Certainly louder up closer though.
My inverter fans howl in summer. Bout the only place you can't hear them is at the letterbox but doesn't really worry me. I was watching some Vids on Silencing the Diesel heaters. Haven't fired mine but I doubt that's going to be loud enough to worry anyone here either. The Ducted AC Fan isn't exactly silent when it runs and no one worries about that.
The Mrs is smaller than I have ever known her in the almost 40 years we have been together. It's disturbing, like being married to a 16 Yo. Even though I feel loosing weight has made me weak as a Kitten, I nearly threw her over the fence I was supposed to lift her onto the other day when we were taking pics. She thought I was being a smart arse, Daughter saw the surprised look on my face and was cracking up. Effing expensive though, now she needs a whole new wardrobe and has 100% REASON to buy new clothes. Dammit!!
I just keep drilling new holes in my belts.
It's been good for me. My diabetes is pretty much where it should be now. If I get under 100kg I can go for a Joy flight at the local glider club which I'd like to do.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 03:37am 12 May 2021
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Is that for temporary repairs and fixing leaks on Ducks? Poor little things!
InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178
Posted: 05:03am 12 May 2021
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I guess it's a regional thing. Every tradesman has a roll of duct tape like Tony posted, but where I'm from, it would be considered a hack job to actually use it to seal up ductwork with it . A long time ago that's what it was for, hence the name, but the HVAC trade in the US and Canada abandoned it probably in the 70s for foil tape or duct mastic.
As far as heating goes, energy is important but power is what matters most. Having a bunch joules available but only letting them trickle in slower than they can leak out results in a cold home.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 05:40am 12 May 2021
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I think that is where running a fan heater for a day or so in a particular room, and judging the comfort level against the measured Kwh used, may give a useful indication of the required heating energy required.
Once that is compared to the measured available solar heating energy, its then possible to judge the potential success of the whole project. Even a fairly rough and ready estimate is better than no data at all.Cheers, Tony.
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852
Posted: 08:31am 12 May 2021
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The results for today were also very encouraging.
Forecast was for a high of 18 and partly cloudy.
I swapped the fan to outside to reduce the noise and even re-used my 1970's duct tape.
I remembered to start both loggers together so the graphs match ... at 9:00am.
Was probably too early because the output wasn't that exciting, but worth doing to see what happens.
Looks like 4:30pm is the limit at the moment because by then the sun is behind the trees on the other side of the road and temperatures drop quickly.
I attempted a power test which I had to cut short ... but was exciting to see the result ... and I also did a comparative pv panel power test.
I'll detail that in the next post.
Here's a overview of the results.
Cheers, Roger
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:16am 12 May 2021
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That is quite a significant rise.Cheers, Tony.
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852
Posted: 09:52am 12 May 2021
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I forgot two things.
First, I ran the fan on low all day ... 42 watts
... and I also forgot to mention that I dragged out the reflectors that came with the tubes and fitted them to my stand ... around 11:30 this morning.
Looks like they've had a bit of a rough life, but still reasonably shiny.
I'll have to wait for a clear unchanging period and remove them temporarily to see what happens to the figures. And also keep my eyes open for some large mirrors.
Tony, you asked about doing a comparative power test with a normal pv panel.
As mentioned previously, the evac tube array is 1,415mm wide and my 250 watt pv panels are close to a meter across ... so I need to allow for 2 pv panels as an equivalent.
Before and after the power test on the evac tube array, I checked the output of just one pv panel. I used a gutsy 5.62 ohm nichrome wire resistor across it and had a high of 28.51 volts.
That equates to 144.6 watts ... so for 2 panels equals 289.2 watts.
The other power test was a bit more exciting.
As before, I fitted an extension on the hot air outlet and slid my 1,200 watt hot air gun element up the spout.
The hot air outlet at that time was 40.7 degrees ... so I was aiming for 81.4
I wound up the variac and ended up at 240 volts ... and my temperature had just gone over 70 degrees ... but with the element glowing at full heat it was a bit too much for the plastic tube.
I shut it all down before it caught fire or worse .. then had to open up the doors for half an hour to get rid of the burning plastic smell. Luckily my wife saw the funny side of it.
I probably need to work out a better method of containing the heat from an element and combining with the air outlet if I want an exact power level ... but at this stage I am pretty confident to say that the system was putting out over 1,200 watts this afternoon.
If that is the case ... then this evac tube setup was outputting over four times the output of the pv setup.
Once again, it is looking really promising to build a double size system to mount on the roof. To potentially get 2,400+ watts for periods of time on a good day is very alluring. I do have plenty of tubes ... maybe it should be three sets wide ... 54 tubes. Plenty of room up there.
I was starting to worry about my datalogger, so I didn't push it ... though the tube is a lot longer than it looks here.
Cheers, Roger
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:30am 12 May 2021
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Whatever the actual final figures turn out to be, it certainly seems beat photovoltaic panels very easily. And if the blower was running all the time, those temperature rises are quite amazing.
Should be even more impressive in a clear blue sky, all very encouraging indeed.
If that style of blower turns out to be objectionably noisy, there may be some quieter alternatives. Edited 2021-05-12 20:34 by WarpspeedCheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 11:30am 12 May 2021
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I perceive there is still energy loss for the area with the reflector. There is a highlight in the pic which is the sun bouncing back to the camera. If it's hitting the camera, it's not hitting the tubes. How much might be lost and if it's worth trying to recover is a different thing.
The other thing I wonder about is the mirror. The reflector is angled so is always going to bounce the light to the side where it will ( mostly) hit a tube. A mirror will tend to bounce back straight which at Midday and around, again reflect the light back out and not allow the tube to capture it.
I'm still of the mind that a 2 layer set up of tubes would be more efficient BUT, If you have the roof space ( Did you say you wanted that for PV or am I confused as usual? ) Then multiple single tubes would get more exposure and be more efficient still.
Can't help it but looking at the back of that reflector, I'm wondering how much heat could be gained from enclosing it and pumping air through? You could paint one side black and compare the combined heat reflector output with the shiny reflector side when you turned it over.
Not that it matters, the margin is too wide anyway but you are more looking at something around 200W because you allowed 2M of PV and under 1.5 of tubes. Even with a 25% advantage, the PV lost badly!
Pretty sure they shouldn't be glowing that bright. I would suggest you consider turning the air up next time which will lower the temp you have to reach and cool the gun element as well.
Thinking about this, if you had a T piece in the output of the tubes, you could put an intact heat gun in there as long as it was relatively sealed so as not to induce cold air and measure the power that way.
Impressive.
The heater here in the office is about 900W on low and even with the door open, it heats this 4x4 Little room too hot. 1200w should put some worthwhile heat in any room and if you double or triple it....
Better still but if you are thinking of doing any PV which you can also use in summer to offset cooling costs, a mix of both systems may be the best all round outcome. Just trying to be the killjoy of reason and suggest that your lowest total year round energy costs may be the better goal not getting the max heating 3 months of the year... which by the sounds of it you can meet with another low cost, healthy workout solution. :0)
Pv will do the hot water as well which is a year round requirement or you could divert that half the year or so when you did not need heating or cooling.
No doubt though, this is an excellent outcome. The only reservation I can see will come in about 5 weeks or so when we hit winter solstice. Shortest day of the year so although the input power may not change a lot, the time available will. It hammers my PV output and will be proportionally the same for any solar energy capturing devise. You have an Idea of the KW Now but the KWH may be the real question.
Well done in any case. The world needs more people to get off their arses and try this stuff. We have all learned a lot though your efforts and I thank you for the knowledge I have gained with these things already through your time and hard work.
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852
Posted: 11:54am 12 May 2021
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Yeah thanks, I was really encouraged.
I think what makes it even more impressive is the full picture ...
If you see the shaded section ... that is all open to the lounge room and we can't close it off. And today, even the main bedroom was open, so there was a lot of space soaking up all that heat.
Yes again, there is no doubt there's a big difference between the two. Admittedly today was a pretty nice day ... a lot better than the last week probably.
I purposely ran the fan all day because if it's off, the temperature builds up in the tubes and when you start the fan the temperature rise for the first 5 minutes can be really impressive ... but not sustainable.
This way I can see fairly smartly when the energy level is being depleted ... and I guess that would be the time to slow down the fan or stop it altogether if the output temperature gets too low.
With the fan outside, the noise level is quite okay ... though if we end up with a variable speed system, I can't see noise being a problem at all.
As Dave suggested, having the fan inline with the duct in the ceiling should be quieter again. Some careful mounting should keep it super quiet.Cheers, Roger
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 12:02pm 12 May 2021
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Like many things, Large and slow Moving are generally quieter. If you look at the fans on the condensers of AC units, they are quite large and slow Moving. This isn't because the Coils need to be spaced out, it's to keep the noise down.
Something like an enclosed car radiator fan may be quieter or Roger could go to a scrap yard and get an AC condenser fan. There are always piles of scrapped units whenever I go to my local place or ring an AC company. My mate has bins full of the things he replaces. The fans rarely give out on them.
I'm not sure about the air pressure though although being large, with the right housing ( could take the panel work off the original AC unit as it generally has a shaped Lip) should be OK and could even provide the air for multiple setups.
I took all my fans Back up the shed today after bringing them down a week ago ( of course) to dry the carpet after I got a cleaner and gave it a once over.
The Jumping castle fans put out large amounts of air at high pressure but are loud as hell. They are centrifugal blowers rather than fans. Still, Outside in their application I doubt they can be heard over the screaming spawns of Satin yelling their lungs out.
I have a really old Blower that has a 1/2 Hp motor on it and is made of cast. Bigger than a jumping castle blower and that thing is Impressive! It's older than me and was used for vacuuming down material on a printing press. They really don't make them like that any more.
Other one I have is a really high pressure Blower that has a separate induction motor that is overdrives the blower with a belt and pulleys. That one came out of a Church and was used to provide air to the the organ. It's old too but apparently was uprated to give more sound. I uprated the thing myself when I removed the blower cover and noticed the inlet was only about half the diamater of the inlet area of the blade, where there are none in the middle. I opened the cover hole up with the MIG and the improvement was huge. Don't know why it was built that way, maybe to meet a specification but it sure puts out a lot more ait and I believe pressure now! Pretty loud though although that's mostly the sound of the rushing air outlet.
I have a 12" inline, I'd call it more a radial really. Large diameter with a large motor in the middle but only fairly short blades and many of them. Bit like the proportional spacing on a gas turbine engine. It does the same power as the jumping castle fans but Much quieter. I suspect the airflow is similar if not more due to the outlet size difference.
The 3rd Type is a proper AC inline tube fan, I think that's about 90W flat out but still moves good air and is quietest of the lot by a good margin. One thing I noticed years ago with this fan... Although it has curved stators to straighten the airflow, they don't work that great. I used this primarily to blow Models hair round in Photo shoots and I found that by putting that plastic square mesh grid material used for for Lighting, the " Thrust" of the fan was improved greatly.
I did some tests and with smoke one could see how the air spiralled and as if under it's own weight expanded beyond the width of the fan immediately where as having the grid inserted, the air came out in a direct stream that expanded very little over the length of where it was noticeable and lost inertia. Much like the grid was designed to do to control spill lighting.
I suspect that having the grid would help the airflow in a duct by causing less back pressure due to friction with the walls of the pipe, especially if it was flexible and corrugated type.
Never realised how many of these things I have till thinking of them just now. Plenty more smaller ones as well!
InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178
Posted: 12:03pm 12 May 2021
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I'm sorry that my observation of the world around me has offended you, madam. I retract everything I said and declare that HVAC tradespeople in this hemisphere do, in fact, use duct tape to attach ductwork. I was wrong to assert that the trade had moved to a different type of tape in recent decades as materials improved. My previous statements were sexist and insensitive to the vast duct tape-using communities of the world.
I would also like to apologize to women and people of non-binary genders on this forum for my use of the outdated and hurtful term "tradesmen" in my previous post. I recognize now that people of the many genders that enrich our world can be in the HVAC trade, even though such a trade continues to consume energy and resources that disproportionately affect communities of color. Edited 2021-05-12 22:05 by InPhase
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852
Posted: 12:46pm 12 May 2021
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I have to admit I hadn't given reflectors a lot of thought ... it was only the prompting from you guys that reminded me I had those reflectors ... and seeing the sun shining nicely for a change helped me decide to drag them out.
I've seen research papers on tubes with reflectors ... but all the stuff I've seen was only using one tube ... so their reflector was a great wide trough perhaps 12 inches wide or more. It didn't seem to fit when using 18 or 36 tubes.
I'm surprised that these reflectors seem shaped quite well really, being little troughs and not just like corrugated iron ... though a fair bit of them has been bent out of shape somewhat.
That had crossed my mind too ... but will be hard to prove. The only one constant I can't control needs to be constant to make a definitive comparison ... though I suppose I could set up a test with a couple of each perhaps.
Having said that, the sun seems to be overhead for such a short time, I wonder how much difference it will make.
I can fit about 12 meters of tubes up there ... 3 sets would only take up 4 and a half meters.
Any pv I fit will go on the shed roof ... there's room for about 40 panels on the north facing roof ... with perhaps an additional 10 or so if I put them on landscape, so I wasn't especially worried about saving the house roof for pv.
Not sure about that, hadn't given it any thought really. The only thing I can comment about was that while it was sunny this afternoon and they'd been out there for hours ... I was actually shocked that the shiny stuff felt cold. I thought they'd be warm. Even the front side was cold. How does that work.
I even gunned them to see and they measured 25 in some spots ... but they didn't feel anywhere near that warm. I must have more of a look (and feel) tomorrow.
I was feeling pretty confident so I gave it a head start.
Yes, definitely needed more air. I need to find a fan heater one that is physically bigger ... and funnel the air through it well. Like tony suggested at the start.
Yes, understood. That's why I keep thinking more tubes ... just like you and pv I suppose.
I had been encouraged by results even on miserable days, and todays results may be as good as I'm ever going to get ... but still confident it's worth pursuing.
Thanks Dave, that means a lot ot me. And I appreciate your support and questions and input. Helps me to think through why I believe what I do and what things to try to prove the results one way or the other.
And thanks to you too Tony. Always lots of good questions when you can see I don't know what I'm talking about or haven't thought something through.
I think when this is all finished and I've got my Warpinverter going ... I might open a kebab shop.
Cheers, Roger
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 02:05pm 12 May 2021
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I can answer that one for you, I am presently in my caravan and have just fired up the 5KW (Chinese) diesel heater. It roars a bit after startup, mainly noise from the intake, but once its up and running nicely (~5 min max) the fan is quiet. The fan in my all electric caravan fridge is louder. I believe the outside exhaust noise is a little louder at startup but I can't hear that inside my 'van. For some reason my diesel heater came with two exhaust mufflers, I put them in series.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:44pm 12 May 2021
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Noise is really a function of tip speed. Dave is quite right, large and slow is the path to silence. You can also do it with a really small diameter but wide rotor, the type of double ended barrel fan you see in domestic space heaters. Centrifugal will more easily generate the higher pressures that you may need for a lot of duct work. A propeller fan will need to run fast to generate much pressure and will always be a lot noisier.
One crazy idea... How about a blower with a dc motor driven directly from a solar panel? It may work well enough by itself without needing any type of additional control system.Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 11:48pm 12 May 2021
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I have been playing with a Cabin blower from a subaru. XV I think I pulled it out of but all of them are much the same, Liberty,impreza, Forester. The only difference is some of them have 3 Phase motors and some are just ordinary DC.
This one is the Normal 2 wire type. I cut and modified the housing a bit and used a heat gun to shape some 100mm DWV pipe to fit and give me a standard outlet. I duct taped around to seal a couple of little spots the housing and the pipe did not fit perfectly.
The blower is about 117W flat out and pushes Significant air and has good pressure. If one looks at the vents these fans have to push air through, particularly to the rear of the vehicle,it can be seen they are rather flat, narrow and not too wide, yet the air pressure is quite strong.
I'm playing with this for a Burner and it has loads of air. If Rogers current blower is being set to 42W, this one would have plenty in reserve. I have been controlling it to try and get down to a sustained 10 KWH oil burn with a little digital PWM controller so I have actual numbers to relate to with another timer on the fuel pump.
It does make some roar at full power but at 75% or less, thing is almost silent. The controller I am using has a 6-40V input so would work well on a solar panel to limit the speed but should give a linear output depending on the panels level of radiation.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578
Posted: 12:39am 13 May 2021
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Good point. Probably not a lot. Like I have said in relation to PV, it's not the Peak output that makes the KWH, it's getting them started early and finishing late and keeping the numbers as high as possible the whole time. No reason why this would be any different.
Rightio then! Space is definitely not a problem. :0) 40 x 250W panels is 10 Kw. A good size array. Should make 50 Kwh easily in summer and take care of all your power needs. With the winter fall off and heating being a big power draw, The tubes will offset a lot of that requirement and you'll still have the wood burner and need it even less.... Or enough power in reserve to fire the AC.
Very well it seems! If it's sitting at 25 I would not think there was anything worthwhile to be gained there. I was wondering if you were going to enclose the tubes but have my doubts on whether that would be worth while either. Do they leave them bare normally or enclose them for protection?
Aw geez mate, Don't loose your mind like I have! You will end up with a yard full of Tubes like I have panels. I'm actually getting sick of the sight of the things myself. They sneak up on you.
First you are after all you can get for your own use. Then you get to learning where to get them and when you are all set up, the things keep appearing so you grab them to sell. Then you find better ones so get them to replace what you have and sell the old ones. Then as time passes the newer and better ones keep coming along so you grab them and before you know it, the things are piled up everywhere!! No, one more final Re do then that's it. Spent more time on the roof than any sane person should with these things.
I think if you do the tubes and the panels you will be significantly energy self sufficient and lower your power bill a lot. That's always worth pursuing!
That's a pretty cool party Trick! I'd get some tubes just for that. Be exactly the sort of thing family and friends would expect from me. :0(
rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852
Posted: 04:25am 13 May 2021
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Sounds a bit like a certain pool pump solar system.
Certainly some merit there because on average, the more sunlight, the more heat buildup that's available to be blown out the tubes ... and also the more energy is available to run the fan a bit quicker to make use of that heat.
When the sunlight drops, so does the heat and the fan speed.
So that's a barrel type I assume.
Now that I have an anemometer I am able to get more of a feel for windspeed and also volume. For a bigger unit one of these might be a good fit, especially seeing it's DC.
I'm going to have to watch this development. Even if my system ends up working well ... we're still going to have that gap from the early mornings and until we get a bit of light from 9 or 10.
Maybe end up with wood, air and oil.
Haha, yeah. Am still kicking myself for not having fitted solar years ago. But better late than never.
Yes, totally out in the open. The bottom of the tubes have the nipple where they are evacuated and then welded closed ... and they sit in a plastic or rubber cup to protect from breaking that and letting the air in. The other end plugs into a manifold of some kind but the rest of the tube is out in the elements.
You'd think that hailstones would be a problem, but some of the testing claims are pretty remarkable. The glass must be stong!
Haha, at least they don't take up a lot of room. It took my wife 5 minutes to find them in the shed after I'd brought them home and stacked them away. 140 solar panels would have been a bit more obvious.
Looks like we have the same genes. That sounds perfectly normal to me.
Yeah, I can't really not carry on after all the experimenting and the results I've got, even though it's going to be a big job.
Haha, I've been thinking of doing it for ages. I can see a string of sausages being slid down in there ... put a bung in the end to retain the heat ... and occasionally rotate the tube to roll them around.
Bit hard to wash out the tubes, so maybe just wrap the food in alfoil and job done.Cheers, Roger
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. A long time ago that's what it was for, hence the name, but the HVAC trade in the US and Canada abandoned it probably in the 70s for foil tape or duct mastic.
