Unpretentious solar water heater

[Forhorse]

Hello everybody

To follow up on the layout of my stable (https://www.econologie.com/forums/mon-ecurie-projet-de-renovation-econologique-t8678.html) and as promised in the subject about solar can heating, here is my modest contribution concerning a small solar water heater project based on PE irrigation pipe.

Here, therefore, in the form of a photo report, the main lines of the project.
Having a large length of hose available (PE irrigation hose diam 16 that I was lucky enough to be able to recover) I started by tinkering with a support for the future solar collector.
A simple wooden cross seemed sufficient for my project.
So I assembled two 4m half-rafters with wood reinforcement reinforced with frame brackets.


It remains "more than" to roll up the pipe to form a large cake. The pipe is fixed using the electric cable jumper every 3/4 of a turn and the coils are tied together with wire. The result is not very good but for a first try it should be fine.


The set is placed as is on the roof

I wrapped around 225m of hose, which constitutes a sensor with a net surface of 4.1m²
The capacity is about 45l, and in static, by a beautiful sun without cloud and without wind it takes about 1 hour to raise this volume of water to a temperature of about 45-50 ° C

The sensor is connected to an electric cumulus of 200l all that is most classic. and circulation is ensured by a central heating circulator.
The plumbing is extremely simple since I did not even put a safety group. It is the suppressor tank which will also act as an expansion tank if necessary (but that would surprise me)

Small view of my "water station"


Details of the departure to the sensor

Cold water is drawn from the bottom of the tank, and sent to the solar collector by the circulator.
The return is made on the top of the tank, by the side of the hot water outlet.


So that's my installation.
For system performance we will have to wait a bit. Since I finalized the installation we haven't had much sun (the sky is almost constantly covered ... but without a drop of rain, the kind of typical weather to get upset)

I also have to install a differential thermostat, or a solarimeter I don't know yet, because for the moment the installation works on a programmer

If this first prototype works correctly (I think it will take 2 days of bright sun to provide 200l of water at 40-45 ° C) I would then improve the sensor, probably by making an insulated box for the pipe slab (which I would do more cleanly) with a glass above.

[sherkanner]

Thinking about putting it behind a canopy, protected from the wind, to limit thermal losses from the wind

[dedeleco]

Interesting and useful.

A few common sense remarks.

Depending on the strength of the sun, it is necessary to regulate the circulation speed to keep a minimum T (30 ° C?) And the circulator does not generally have this capacity, except pulsed for a few seconds controlled by the T with the microprocessor or logic circuit elementary, and thyristor, giving pulses of a few seconds with duty cycle fixed by the output T. The few seconds must be longer than the pump start-up time.
On APPER there are other solutions.
Otherwise it may be too fast and even cool the already hot water.
The T of the water coming out is a real simple solarimeter measuring the essentials.
This seems crucial to me as a physicist.

Compare between brown cleir pipe and very black pipe which absorbs more ???

Put a transparent plastic film on it to see the gain in T especially important with wind, cutting losses by convection.
Simplistic plastic will be almost as effective as glass.

A bubble wrap sold for a cheap greenhouse can be effective in winter as a double glazing (see greenhouse on econology).

So a lot of useful tests if possible by recording the T as a function of time !!
.

[dedeleco]

Quelques idées:
Considering the 45 liters of the tube which takes a certain time to heat up even with the 4KW of the sun very well in front, the simplest is a basic thermostat with measurement of T, 1 or 2 meters before the exit of the tube in the sun, and which stops as soon as the water that comes out is too cold. 1 or 2 meters or more to be adjusted, correspond to the pump's stop time to avoid the outflow of too cold water.
It will work by itself without ever leaving cold or too hot water, if the intermediate pipes are insulated.


In weather without sun, it can be useful to preheat cold water to 25 to 30 ° C with the sensor before it enters the electric cumulus to save a lot with a low T buffer tank preheated on the arrival of cold water (or circulation of water at the bottom of the tank) ???
It is a very different assembly but economical in electricity, given its longer operation in cloudy weather.
A 3-way valve could allow you to select between the two possibilities ??????

[I Citro]

As said above, to optimize the capture it would be necessary:
- paint the pipe black
- enclose the pipe in an airtight frame and insulated at the bottom with a window.
- put a reflective surface under the tube to heat the underside of the tube since you do not use a flat sensor

The glass protects from wind and rain and creates a greenhouse effect and the resulting thermal runaway.

I leave it to others to give advice on regulating and transferring calories to the ball.

Congratulations on your initiative and your achievement.

[Forhorse]

Regarding the color of the pipe (I had no choice it's recovery ...) I am not sure that black is essential.
Indeed, what matters is the color in the infrared range (and not in the visible range)
However, the brown pipe has a matt appearance, and I think that in the infrared range it is close to black, and may even be blacker than the black pipe which has a shiny appearance.

Anyway, for the moment I don't think it's the most important.
On the other hand, as you all point out that glazing above would certainly improve performance much more, I am aware of this. But another problem arises: the price!
If I have the opportunity to recover glazing for this purpose I would, but I will not buy glass or plexi specially for this project, because in the end it would be almost as expensive as buying a real solar collector .

Regarding the regulation, I would probably apply the principle given by dedé, but I still have to buy probes.

[sherkanner]

Or a simple wooden frame surrounded by transparent plastic, it should have the same effect without the price.

[Forhorse]

Or a simple wooden frame surrounded by transparent plastic, it should have the same effect without the price.

Yeah, plastic kind of tight greenhouse ... why not!
After all the sensor in itself is not very optimized (plastic sensor) so why not stay in the same spirit.
No need to look for extreme performance, but just improve something a little simple.
I will see what is doable soon.

[I Citro]

Matt black absorbs radiation better because it absorbs a wider spectrum than brown or red ...

If painting the pipe with a spray of black mat paint (for example, barbecue, which withstands high temperatures), you mind, you can also pass your pipe black smoke (burnt cork, charcoal ... ).

15% of thermal gains are largely possible.

[sherkanner]

Then you can also isolate the pipe that goes down with what falls under your foot. Hemp, straw, something wrapped in an old sheet and taped, whatever. You just have to avoid having your isolation eaten by your equines.