My (large) solar thermal project

[dede2002]

Hello

I have not read everything yet ..., I remember one thing:
Painted sensors are the ones with the lowest temperature rise.
They have a lower performance, but seem appropriate given my roof angle, a sensor too efficient will suffer more empty in full sun of summer.
They are also the easiest to repair.

Otherwise I thought about my self-draining system, the fall of 13 m. and the need for a large priming flow makes me worry, as well as the passage of air bubbles in the circuit.

I modified, a pump with small flow but sufficient pressure to fill the circuit, then a solar circulator which will have less losses (bigger return, siphon primed) and will be able to go to the stop without emptying the circuit .
The drain valve must be spring-loaded for safety, how much does this type of valve consume?
The drain valve could also be controlled by the pressure: overpressure = draining?



Here is the diagram of the whole, I modified the assignment of the "disturbing" exchanger

[dede2002]

Hello everybody

I unearth my subject, which I have never buried. since i did other things i changed all my windows by myself (50m2), and my oil conso went from 6000l. at 5000l. per year.

Now it will start, I will receive my panels soon. I visited two installations that are working, and I did well to wait because the panels that I had been advised at the beginning turned out to be null in self-draining, because of the coils and the inclination of the panels there some that have frozen and farted, so it will be Rotex "ladder" panels that seemingly empty well.

12V pumps are gear pumps with separate motor.

The battery is essential for starting the pump, but then it is the pv that powers and maintains the battery charge, it will be a simple used car battery.

Regarding the maximum power of the panels, it's a bit like for cars we never use it because in summer there is too much heat (compared to my storage capacity) and between seasons when we can make the In addition, there is less power available from the sun, so the power of the pumps does not need to provide the maximum theoretical power.

I modified, and significantly simplified, my diagram. The accumulators will be used "Hoval modules", they are 200l stainless steel drums. lying and stacked, with an insulating body around. The exchangers are not coils but a double layer around the barrel, it seems very efficient, and I can modulate as I wish and not necessarily put everything in water from the network as in the diagram.

The right part of the diagram is the existing one.

There will be 2 groups of panels for practical rooftop reasons, but I think that in the summer a group will suffice.

16 inhabitants of the house use 600 at 700 l. hot water (48 °) a day ... (I put a meter at the entrance of the water heater)

A+

[Philippe Schutt]

-The coil has the advantage of setting the height of the hot element. The double-envelope balloons heat up all over the surface. So, how is stratification going?
- How will the circuit react with the water in contact with air? You do not fear rapid corrosion?

[dede2002]

Hello ,

It is a stack of horizontal drums connected by bits of tubes, it is the one of the top which heats first. We will see the use, I will be able to add other balloons in the future.

Regarding corrosion, we'll see but a similar installation runs for more than 10 years. The pipes are in multilayer, the exchangers in stainless steel, is there a risk for the panels? These panels are designed for the sake of clarity because the Rotex system works with an aerated water tank.

A+

[dede2002]

While waiting for the panels, I gamble on the pumping.

With the height of water it requires more energy than a pressurized system, that's why I plan to feed the pump with photovoltaic, otherwise the COP may be poor if I try to draw as much as possible between seasons, and also to avoid adding more consumption on the network (and my meter).

I did a test with 3 series-mounted 220v circulators, with a pressure gauge, a meter and a power meter. I am disappointed with the figures obtained, under 0.5 bar I arrive at 19 l / min, which corresponds to 15.5 W, with a consumption of 184 W, thus a yield of 8.4%.
I arrive at 1 bar and 5 l / min, 8W for consumption 174 W, catastrophic yield of 4.7% ..., and impossible to exceed 1 bar with 3 circulators given for 4 m of water height each.

My editing is certainly not hydrodynamic, I will try something else.

I will need at least 1.5 bar and 10 l / min to get to Dt 10 ° in full sun with 5 panels.

Is a gear pump supposed to be more efficient than a centrifugal pump?

I found a motor-dynamo that could do the trick, I even wonder if I could connect it directly to 2 panels 12V-100W without battery or regulator?

It consumes 3A empty under 12V, and 30A blocked (with 1.7Nm of torque).

I tried it with a small battery 6V, it starts with 2.5V and 7A and accelerates nicely up to 5V and 3.2A.

Pictures of the test setup ...

And the engine

[Philippe Schutt]

Yes, the stratification is done with balloons in series and ok if in stainless steel.

This is bizarre your thing with circulators, I would have thought that heights would add up.
With 5l / min the pressure loss of the assembly is not in question.
To reduce the electrical conso, I suggest to provide a closed circuit in normal operation and a dump / filling well split. It seems to me that it will be profitable, considering the conso of a circulator

[dede2002]

Hello Philippe and everyone,

it progresses little by little, the panels and the pipes are laid, all that is missing is the connections (for the roof, there is nothing in the cellar).

For the return pipe, I'm wondering from what speed the water coming down is going to chase all the air out and create a siphon, I could put a self-return vent valve, which opens when the pump stops.
The pump could turn harder for priming and then decrease power.

A +, here are some pictures of the roof.

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[Philippe Schutt]

At the price of garden pumps, do not bother to deprive yourself. For less than 100 € there are some that give more than 4 bars. Once the circuit is filled, switch to a normal circulator.
You pierced the tiles for the brackets of the frames? I would not have dared

[dede2002]

Yes it seems a good idea to use two pumps and fill the circuit without air. In this case, it will be necessary to have a vent valve with automatic opening, so that the emptying is done automatically in all cases.

I think I overestimated pump performance in my calculations, looking at this chart for example I calculated a yield of 11% at 14m and at best 16% at 8m ... My 400W of PV will not be enough if I circulate the water at atmospheric pressure.

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I wonder if I would not be better equipped with an inverter and pumps 220V, 24V it is not easy to find.

For the drilling of tiles I was also reluctant, but the one who provided me the panels did it at home there is 20 years and it does not move ... My roof is waterproof and ventilated under the tiles so a possible infiltration does not worry me too much, the threaded rods are screwed on the counter-rafters above the insulation and glued in the sikaflex tile. We removed the tiles to draw, then drilled with a template, there is 56 threaded rods it is very rigid.

A+

[Philippe Schutt]

https://www.2ememain.be/bricolage-const ... 32117.html

otherwise at DZ, they make stoves in 24V including to connect to the central heating. on the other hand it will be a small circulator