Solar options for home in 2022.

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1524 posts

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#3294380 8-Oct-2024 10:57

HarmLessSolutions:Why are you limiting your HWC to 60 degrees? We have ours at ~72 degrees w

Thats a point, dont know what ours is set too!

Anyhow inspection completed, just waiting for the new meter now.

HarmLessSolutions

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#3294381 8-Oct-2024 11:02

RobDickinson:

HarmLessSolutions:Why are you limiting your HWC to 60 degrees? We have ours at ~72 degrees w

Thats a point, dont know what ours is set too!

Anyhow inspection completed, just waiting for the new meter now.

Important that for safety's sake make sure your tap delivery temperature is controlled by a tempering valve or similar (as it should be by law) if you're cranking up your HWC thermostat.

https://www.harmlesssolutions.co.nz/

RobDickinson

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#3294383 8-Oct-2024 11:04

It is, the HWC was replaced couple years ago and its all pretty modern and up to code

HarmLessSolutions

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#3294604 8-Oct-2024 14:07

This SMH article could just as well be directed toward our government: https://www.smh.com.au/business/the-economy/if-you-give-voters-free-solar-batteries-they-might-keep-you-in-power-mr-albanese-20241002-p5kfaf.html

Paywalled but easily accessed with the right app.

https://www.harmlesssolutions.co.nz/

SumnerBoy

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#3294658 8-Oct-2024 14:23

So do you guys have any thoughts on the question of "is a diverter necessary when you have a battery?"

RobDickinson

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#3294662 8-Oct-2024 14:28

It depends. You can feed it direct from the battery but thats power that you may not get to replace until the sun is out again, rather than using spare sun.

You are talking 3-5kwh to heat water that may not be available for other stuff

SumnerBoy

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#3294673 8-Oct-2024 14:46

Yep you are correct - but the idea with the way I have my system setup is that I will only "turn on" the HWC when the PW > 80% and solar > 3kW. This means I am only attempting to divert to the HWC once the battery is almost charged and we are generating enough to cover the HWC element.

90% of the times when the battery is > 80% and solar is > 3kW it has been a high solar gain day and there is loads of excess PV to divert to the HWC. The benefit of the battery in the system is that it is able to cover any short term drops in solar generation (clouds etc) or short term peaks in house usage (boiling kettle etc) without the need for a high-accuracy diverter - the PW effectively becomes the diverter in essense.

Plus there is the issue of two closed loop systems trying to balance the grid supply to zero.

RobDickinson

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#3294674 8-Oct-2024 14:49

So you effectively have a diverter? Thats what one does.

SumnerBoy

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#3294676 8-Oct-2024 14:51

Yes exactly - the PW is the diverter - my question is with that setup does it still make sense to have a second diverter (for your HWC directly).

It is something I have been mulling over since before I ordered my PW for the new house we moved into 15 months ago. And I have been mulling it over ever since.

Just interested in other folks opinions to see if I am missing anything.

RobDickinson

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#3294682 8-Oct-2024 14:59

SumnerBoy:

Yep you are correct - but the idea with the way I have my system setup is that I will only "turn on" the HWC when the PW > 80% and solar > 3kW. This means I am only attempting to divert to the HWC once the battery is almost charged and we are generating enough to cover the HWC element.

How are you doing that bit ? That is the diverting bit. Why would you need something else ?

SumnerBoy

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#3294684 8-Oct-2024 15:04

RobDickinson:

How are you doing that bit ? That is the diverting bit. Why would you need something else ?

Using NodeRED. I am running this in docker which polls my PW and provides a nice API for checking state of charge and various meter readings. Definitely worth a look if you have a PW, I think they have gotten it working for PW3 now as well.

The "away mode" just disables the middle element boost when we are away from home.

SumnerBoy

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#3294687 8-Oct-2024 15:13

Sorry - I see what you mean now - the NodeRED logic is "the diverter" - I guess you are right - it is very crude and basic, but yes it is acting as a very raw diverter. The reason it works though, is thanks to the PW which is able to mop up all the excess/shortfall in between the times I am running the logic above - i.e. every 10s.

HarmLessSolutions

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#3294688 8-Oct-2024 15:15

RobDickinson:

It depends. You can feed it direct from the battery but thats power that you may not get to replace until the sun is out again, rather than using spare sun.

You are talking 3-5kwh to heat water that may not be available for other stuff

"Calculate the kilowatt-hours (kWh) required to heat the water using the following formula: Pt = (4.2 × L × T ) ÷ 3600. Pt is the power used to heat the water, in kWh. L is the number of liters of water that is being heated and T is the difference in temperature from what you started with, listed in degrees Celsius."

So, our 250L HWC consumes ~9kWh to heat up by 30 degrees C (i.e. 40 - 70 degrees C). Not quite the energy demanded to charge a PW but still a significant reduction in grid consumption (or generation being exported).

In context 9kWh will use most of a PW's storage so not a practical strategy to do that. Also worth having this as a secondary 'storage' capacity after the PW has reached full charge so prioritise the HWC and PW accordingly depending on your own use case.

https://www.harmlesssolutions.co.nz/

RobDickinson

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#3294689 8-Oct-2024 15:16

That looks cool may have to have a play with it.

But yeah you effectively have a diverter between the software triggers and your HWC element controls?

SumnerBoy

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#3294690 8-Oct-2024 15:21

RobDickinson:

But yeah you effectively have a diverter between the software triggers and your HWC element controls?

Yes. Am interested to know if you see any issues with your system, i.e. dedicated diverter plus the PW. They are both closed loop systems trying to balance the grid feed to zero. In my experience this caused issues (as detailed above).

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