Solar hot water - 30°C

This morning it was 8 °C outside in the world when I started the test. The maximum temperature for the day was 9.8 °C.

Air temp in the collector was 18°C

Air temperature within the poly pipe collector was around 23 °C
And the temperature within the water tank was around 9 °C

The water tank has developed a very slight leak so the water wasn't circulating until I topped it up, thus the temperature difference. Once flowing you can actually see it flow. You see it as heat haze emited from the inlet hose and as a current swirling little bits of gunk that I failed to clean out of the hoses.

An hour and a half later and it reached 30°C inside the water tank, and 33°C within the collector.

As far as I know, my water didn't get any hotter than 30°C, but It stayed at that temperature, and still is at that temperature, even though the day became overcast and colder.

I took the temperature at the bottom of the storage tank as well and found it to be only 1°C less than at the top. This might mean I need a bigger storage tank to allow the heat to rise to the top. The flow might be enough to be stirring the water and mixing it too much. If it was a deeper tank, or the flow was less I might be seeing higher temperatures. Slowing the flow would be as easy as adding a tap. I'm not sure that I'll bother on this small test system. I think I have made the correct number of errors to allow myself to move on to the bigger version, and actually do something with the collected heat. 30°C is still 9 degrees short of my target but I think with a better made, and larger unit, 39°C should be achievable on a day like today.

Solar hot water - Poly pipe collector

It was a chilly and windy day in the hills today. But the sun was out for a while in the morning.

The ambient temperature was around 11°C as I added the rest of the T junctions to my new poly pipe collector, and I was almost confident that I'd sooner or later, be making some solar hot water. 

The water temperatere was around 10°C from my rainwater tank.

It was interesting to note the temperature of the collector was very close to the temperature of the storage tank, and the air temperature in the collector stayed low. (digital thermometer is testing water temperature and the glass one is testing air temp in the collector) 
No doubt this means that the heat exchange area of the black poly pipe is sufficient. This came as a bit of a surprise to me, although in hindsight it would appear that the transfer rate is self governing to some degree. The hotter the water gets, the faster it will flow and thus the more heat exchange will occur.




Final temp before it started raining and I went inside was only 22°C, and it didn't get any higher in the overcast, windy and rainy conditions, even when I went outside hours later. But, I think it was actually a success. I doubled the temperature of the water and it only took an hour and a half. 


Given I only used two sheets of corflute for insulation, and the insulation for the top, bottom, and sides was just tape, which isn't really insulation it's really just tape, It did about as well as I hoped.


The experiment served its purpose in that I learnt a few things and didn't cost anything as I'll be pulling it apart and using all the bits in the real thing.


Lessons learnt ...

• Air bubbles are not your friend. Don't let them collect.
• You don't need a lot of tubing to shift a lot of heat from a collector.
• Insulation is amazingly important. (tape leaks heat so that you can feel it leaking)
• A tube based solar siphon regulates itself, so there wont be any issues with the collector overheating.
• Even at the rate this poorly constructed solar collector collected heat, it would still be worth using it as a bathroom heater or something*. On a bigger scale without changing anything except scale I could heat my house by building a wall out of water tank and simply circulating the water to my collector.
• Collecting free energy is a worthwhile pastime.
• I'm not very skilled at gluing.
• there was a reason I collected all that 19mm poly pipe for all those years, even though it had holes in it every few metres, and kinks in the sections between the holes.

*Hmmm towel heater...

Solar hot water - Poly pipe

My too hard basket brimmith over.

I have patches on my patched patches. I think it's time I gave up on my solar hot water heater.

And tried a new design!

For a change I thought I'd try taking advice from people who know much more than I do. I thought I'd try a different method. There comes a point where a project can leak more than one can safely ignore. Especially when wiser folk are suggesting I try something else.

So the new plan is to use poly pipe hose fittings to pass the water through the solar collector. I'll use two layers of corflute to insulate.


Also, it's possible to be too frugal.

Say, for instance buying enough T junctions to make only one half of my new design.

I'll get the rest tomorrow and test it rain or shine.

I suspect I'll need to add a second layer of these pipes in the grown up version to extract all the heat from the collector, but only a test will tell because I have no Idea how to calculate such stuff.

Solar hot water - New, bigger corflute collector

It's still a test, but I've started making my new, bigger corflute collector.

This time I'm using my new glue gun to make everything stick, and I'll be using two sheets of corflute glued on to the back of the collector as the insulation. By doing so I can make it a bit bigger than the first test, and make better use of my glass. I will glue the entire thing to the glass to give it some structure.

At the moment it's upright, full of water, and leaking all over my front steps.

It turns out making a solar hot water service involves an awful lot of water leaking out of stuff. In fact, generally speaking, I've noticed that a lot of my projects involve leaks.

This time I anticipated my poor craftsmanship, and held off on painting it until I had repaired the inevitable leaks. I've marked where the leaks are so it should be easy enough to fix them.

And I forgot to sand the surfaces so the glue would stick better. The hot glue gun glue sticks well to the corflute but does't seem to like the black hose. I suspect roughing up the surface a little will make it stick better.

Solar hot water - My first solar collector

Its done. Or at least its as done as its ever going to be. Now all I have to do is sit back with a tea bag at the ready and wait for all my hot water to collect.

I have a recommendation.

Paint stuff.

I've never really been into painting things. I'm more of a "just let it rust" kind-a-guy. But now I'm not so sure. Very small sections of this thing actually look as if it were made by someone who could make stuff. And all it took was some black paint, and a camera that cant deal with contrast.

Now all those people who say things like "If a jobs worth doing its worth doing properly." don't seem quite as insane as they did in the past. It occurs to me that when this thing springs a leak, even though its just an experiment, I'm really going to regret that decision to use that old tube of silicone I had lying around. A piece of junk left behind your garden shed is just junk, but paint it, and you leave that same piece of junk in plain sight where it belongs.

I should put this to the test by painting pieces of litter I find in the street.

Tomorrow I test my painted junk to see if I can collect some heat.

Solar hot water - Corflute collector part 1

Corflute collector part 1 will indicate to all just how bad I am at applying old silicone sealant to a home made corflute solar collector.

This gives some indication of the general idea. Tubes attached top and bottom will carry water up through hundreds of tiny tubes in the corflute (white thing pictured here side on) where they will be collected at the top into a bigger tube (black and end on) and sent to the storage tank. Actually that pic doesn't really look like its anything to do with this project but I promise it is. It's looking down the length of pipe that runs across the bottom of the sheet of corflute. The black hose will be siliconed on and a stopper put in place to block one end, and the inlet hose from the storage tank will be attached to the other end. The same will be repeated across the top)

My camera is really struggling to take pictures of the corflute, I think because its so bright white.  (I might have to make photography a "thing").

According to the instructions there is meant to be a nozzle that isn't packed with solid dry silicone. 

My work looks nothing like the suggested use pictured on the tube. My work looks like leftovers from "ice your own birthday cake day" at an infant school.


Oh well. At least I'll get some more practice when I have to do it all over again tomorrow, after I test for leaks.

Solar hot water - Corflute collector part 2

No photo today because my photo-journalistic skills are simply not up to the task of making pics of drying silicone look interesting.

There were only two small leaks in my corflute collector, but they will take at least until tomorrow to dry so there will be a part three to the construction of the test corflute collector.

In spite of my poor craftsmanship I actually have a tip or two to pass on. 

• Black hose is best worked after it has been laid out in the sun for a day or so to straighten it. Tie one end to a fence and the other to a brick or something, so you can pull it tight.

• If you cut the black tubing along the side of its natural bend it will sit straight against the edge of the corflute. For some reason its tempting to make your cut on the inside of the curve. Doing so will make your hose pull away from the corflute when siliconing.

• Get a grownup to do your silicon work if you are as unskilled as I am.

• Make sure your flutes go from top to bottom before you make any cuts or glue anything. I didn't make the error of getting it sideways, but I can imagine it would be a pain if I did.

• Create a slight slope on your top cut in the corflute so that any bubbles will flow up to the exit hose. Bubbles are not your friend and any place where air can be trapped will collect air as soon as your solar collector starts working.

• making solar hot water is much more exciting than I make it look in this list.

Solar hot water - Corflute

Just as there is for most things in life, there is a product that seems to be perfect for collecting solar hot water. Luckily it's something people throw out because its also good for advertising.

Corflute is a plastic product that we in the western world need a surprisingly large amount of. This is odd because we dont really use the corflute. We use it to make us want to use other things. Different things. Things other than corflute. We use corflute to make advertising signs. These signs are rarely, if ever, trying to sell us corflute. More often than not these signs are trying to sell us real estate.

A few days ago, when doing some research, a found a website where someone very clever had used corflute as a solar collector. Painted black, insulated, and covered with glass, this should make a very useful solar collector. I cant remember the website and have been trying to discover it again. If you know it, or you made it, please let me know and I'll link to it. The genius behind using this is in the plumbing. It seems a lot of people have made solar collectors from copper pipe. This involves a stack of soldering and a stack of time, money, and skill. I have time, but no skill and no money. Corflute is just what the doctor ordered. The secret is to cut some plastic hose lengthways, and slot this onto a sheet of corflute top and bottom. Silicone it all up and you are now the proud owner of a few hundred pipes all plumbed together. It should only take a few minutes and even fewer skills.

The plastic that corflute is made of doesn't conduct heat very well but its thin, and because each tube is square, and has a huge surface area of water carrying pipes that we can expose to the sun, it should work well.

If you need some corflute and don't want to pay for it, you could try putting your house on the market and stealing your own real estate sign from your front lawn.

Re-reading this post makes me wish I had arranged some sponsorship from whoever makes corflute.

corflute corflute corflute

Solar hot water - Hot water system

If we create the bottom half of a thermosiphon by putting a black hose into a foam box and cover it with a sheet of glass, we will see the beginnings of a (hopefully) slightly efficient (albeit temporary and largely useless) solar collector.

If we use a large insulated drink bottle to concentrate collected hot water as the top half of the thermosiphon, we will see the beginnings of a temporary and largely useless solar hot water system.

Its night time.

Its not collecting much heat.

It's not very well designed. There are bits where the tubes form loops, and all tubes go down in through the top. My head says it should work a bit. The rest of me is not so sure.

We shall see when the sun next shines.

Solar hot water - Greenhouse

Anyone who has left a hose out in the sun on a hot day will know how much heat its possible to collect. Collecting heat on a hot day is easy. What we need to be able to do is collect heat when there isn't much around. One way to do that is to flatten out your hose to increase the surface exposed to the heat. The downside to that is you also increase the hose's ability to radiate or lose heat.

What we need is a flat, large surfaced hose that's insulated to prevent heat loss. Unfortunately what we also need is a big flat hose that's exposed to the sun and isn't insulated in any way. In fact what we need is a big flat hose that's both, a conductor of heat, and well insulated.

Some years ago in Rome, someone accidentally mixed a flux of some kind into their beach party's fire. The same thing probably happened in China as well. Some time after that, people started making glass. Others may have a slightly different or more complex  history of glass, but I'll leave it to the reader to decide on their preferred history.

Normally when the sun's radiation hits something it gets warm. If the object becomes warmer than the surrounding environment, the object starts to radiate energy to share the warmth. Heat and light (and microwaves, and for what it's worth, puppies and beer) are all basically the same stuff. There is a very cool characteristic that glass has. Light, unlike puppies and beer, to a large degree can pass through glass. Once it hits something that it cant pass through it is either reflected away or is absorbed. If it's absorbed it is absorbed as heat. Normally when something outside is heated, the heat radiates away and warms up the air or whatever else is around it. This air then rises and disperses away. But you can use glass to stop that hot air escaping, or at least to slow it down. If you used glass in this way you will have built a greenhouse.

It seems to me, in order to make a solar collector, what we need here is some kind of big flat matt black greenhouse hose.

I think I understand the main principles involved here so It's time to do some experiments.