Help with Solar Project at home needed, please.

[Revolvor]

I am trying to make better use of the 3kW solar panels on my roof at home. On a good day, in Summer, the generate over 20kW.

I am aware of products such as THIS which divert excess solar energy to an immersion heater, to heat domestic water.

I am considering trying to manufacture something similar, utilising an Arduino.

They work by having a “Clamp-on-Sensor” on the Incoming Supply from the National Grid to sense whether current is feeding back into the grid.

Does anyone know where I could purchase, or how I could manufacture such a sensor?

So far I can only find sensors that will sense a current, but none which can determine the direction of flow.

 

[Bolti]

I have had an immersun since 2014 brilliant piece of kit, heats all our hot water then switches over to power a heater.
The immersun ct clamp senses direction, you could also try these people.

Buy CT clamp Online Direct From myenergi | myenergi GB

zappi & eddi come with one wired CT clamp as standard. In some cases extra CT clamps are required i.e for 3 phase installs.

myenergi.com

 

[SandraL]

I built an arduino based controller that diverts power that would otherwise be exported.
It is only useful for resistive loads such as immersion heaters or oil filled radiators.
Try googling "Calypso Rae". Results with open energy might be fruitful.

 

[SandraL]

Robin's Mk2 Code variants and associated tools. | Archived Forum

openenergymonitor.org

Mk 2 pv router might be the arduino code,. That is if i found the right info........

Ok, its a rubbish image but a schematic of the circuit used, if you want a better image i could redraw and photo again.

 

[Revolvor]

Mk 2 pv router might be the arduino code,. That is if i found the right info........

Ok, its a rubbish image but a schematic of the circuit used, if you want a better image i could redraw and photo again.

SandraL Thank you for all that information and the offer to redraw the schematic, but I think it's going to have to be a long-term project, as it seems a bit beyond my elementary electronic skills, though I do have two sons who build lots of Arduino based devices.
If I decide to proceed, I will contact you, if that's OK?

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[SandraL]

No problem, I,m sure your sons could build it as electrically very simple. But you will be dealing with mains voltage.
The arduino code already exists.
Give me a shout if you want more info

 

[Bolti]

I know its nice to have a project but for a hundred quid.

<Broken link removed>

 

[jezport]

Does anyone know of installers who are fitting triangular panels. My roof would look far better with them.

 

[SandraL]

I know its nice to have a project but for a hundred quid.

<Broken link removed>

This has the advantage of not having to run dedicated mains cable from consumer unit to immersion heater. So an easy install.
Another consideration. We use the surplus power in two locations. The cable runs were easy for us and 10years ago surplus pv boxes were expensive.

 

[Revolvor]

This has the advantage of not having to run dedicated mains cable from consumer unit to immersion heater. So an easy install.
Another consideration. We use the surplus power in two locations. The cable runs were easy for us and 10years ago surplus pv boxes were expensive.

SandraL and Bolti

Thanks - great advice from you both. I would have liked to attempted a DIY solution, but for £100 this seems a good option, so I have gone ahead and ordered one.

I will report back with how I get on.

I will have to give some thought to how I get 240v to power the clamp sensor, as my Incoming Supply/Meter are in an external enclosure, but the Distribution Board is in the garage.

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[SandraL]

As long as there are no other distribution boards conected to the meter then I expect the clamp can be connected at your distribution board incoming supply, assuming that the clamp can be put on just one conductor.

 

[Revolvor]

As long as there are no other distribution boards connected to the meter then I expect the clamp can be connected at your distribution board incoming supply, assuming that the clamp can be put on just one conductor.

I need to fit the sensor in the meter cupboard, as that is closer to the immersion heater.
Fitting the clamp is not the problem. The wireless sender needs a 240v supply, but I now think I can spur that off a nearby circuit.

 

[autorouter]

So far I can only find sensors that will sense a current, but none which can determine the direction of flow.

AC = Alternating Current. It flows forwards and reverses 50 times per second. No AC current sensor can sense the direction of flow. It only tells you the current passing through that point at that time.

However if you have two or three sensors, on the solar, incoming grid and maybe outgoing loads, you can do a quick calculation and deduce whether you are for example producing more solar than the loads are consuming.

 

[Revolvor]

AC = Alternating Current. It flows forwards and reverses 50 times per second. No AC current sensor can sense the direction of flow. It only tells you the current passing through that point at that time.

However if you have two or three sensors, on the solar, incoming grid and maybe outgoing loads, you can do a quick calculation and deduce whether you are for example producing more solar than the loads are consuming.

The commercial PV units seem able to ascertain direction of flow, so I assume that is how they do it.

 

[Bolti]

AC = Alternating Current. It flows forwards and reverses 50 times per second. No AC current sensor can sense the direction of flow. It only tells you the current passing through that point at that time.

However if you have two or three sensors, on the solar, incoming grid and maybe outgoing loads, you can do a quick calculation and deduce whether you are for example producing more solar than the loads are consuming.

Not sure what trickery is a play. My immersun only has a single clamp and reacts instantly to the current going to the grid.

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[autorouter]

Not sure what trickery is a play. My immersun only has a single clamp and reacts instantly to the current going to the grid.

Yes, you're right, I'm not exactly wrong, but the meter software can tell which direction the power is flowing.

As well as the current, the meter measures the voltage. Think of it like this: if you were looking at a DC battery, it would have a positive voltage, and a positive current would flow from the positive terminal into a load. If you were to reverse the voltage, a negative current would flow into the negative terminal from the load. The point is, the voltage and current are the same polarity, either both positive or both negative.

If the battery is being charged, power is flowing into the battery. The voltage is still positive, but the current is flowing into the positive terminal, so it is negative. In other words, the voltage and current are opposite polarities.

This can be used to determine the direction of flow of power. If voltage and current are the same polarity (both positive or both negative), the power is flowing out of the voltage source. But if the voltage and current are opposite polarities, the power is flowing into the voltage source.

This applies for AC as well as DC. If there was a method to detect if the current was positive or negative when the voltage is positive, then the direction of power flow can be found.

It's phrased in different terminology, in AC-speak. If the current has a positive peak when the voltage has a positive peak, the current is said to be 'in phase' with the voltage. If the current has a negative peak when the voltage has a positive peak, then the current is said to be 'out of phase' or 'opposite phase' to the voltage. So the meter software detects whether the current is in phase or opposite phase to the voltage.