Solar options for home in 2022.

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2023 posts

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#3290211 2-Oct-2024 20:06

The Paladin has an output for driving DRED capable heat pumps, which essentially allows them to run at preset rates - 25/50/75/100%, depending on the manufacturer.

Essentially, when the solar generates a certain amount, the HP will run at a reduced consumption rate. Increase the solar, HP draws more.

As far as the Paladin was concerned, the idea I believe was to run pool pumps or other devices that are DRED enabled, once the hot water tank was full. I imagine there are ways to do the same without the Paladin, I am unsure if there are HWHP with this option built in.

dantheperson

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#3290268 2-Oct-2024 21:09

I did have a chat with the paladin creator about the DRED control. My takeaway was that's it's for air conditioning units, to ramp up/down in summer. He wasn't aware of any hotwater heatpumps (HWHP) with DRED support.

Regarding timer, most of the hotwater heatpumps already have timing capabilities built in. Some of them also support a solar relay so that they can turn on when your inverter indicates that there is excess solar.

But as mentioned you don't want a heatpump turning on and off allot. My plan is to install one and just set the timer to run in octopus shoulder periiods. So you wont be pulling from the grid during peak periods. During the shoulder/inter-peak period it's only drawing 700 watts or so and so you are generally heating the water from solar. On a particularly grey winter day you might pull some grid power but so be it, that's why we are grid tied rather than off grid right?

With a resistive/immersion hotwater cyclinder (HWC) it's different, it's pulling 3000 watts and so its going to be pulling from the grid far more often. The paladin is a great system and will perfectly match your excess production to capture it all precisely into the HWC, you wont be pulling from the grid on a grey day unless it's the 3rtd grey day in a row.

In constract, the HWHP by using 1/3 to 1/4 of the power, i figure t's going to mean your exporting allot more power, and that extra export will be far more than any grid import.

Some variable to consider:

1) the cost of the HWHP. They cost more than a regular HWC, will you recoup the extra capital cost? The cost varies allot. Tradedepot have a new 270L R290 midea model for 3K that looks nice. Or you can pay 9.2K for a Rheem. Consumer have HWHP marginally ahead over a resistive HWC over a 15 year lifetime. (https://www.consumer.org.nz/articles/electrifying-your-home-vehicle-how-it-saves-you-money-and-reduces-your-emissions#article-water-heating)

2) How much hotwater do you use? Larger households using more water, are going to save more with a HWHP. This consideration is not solar specific, but with solar you are going to export more or import less with a HWHP.

3) Longevity. Regular HWC is probably going to last longer, but then a HWHP typically has a backup element for when ambient temperature is < 0, so even if the HP fails, you still have a traditional HWC (but then you'd want to add a diverter like the paladin).

Terciops

26 posts

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#3290412 3-Oct-2024 11:16

Ge0rge: The Paladin has an output for driving DRED capable heat pumps, which essentially allows them to run at preset rates - 25/50/75/100%, depending on the manufacturer.

Essentially, when the solar generates a certain amount, the HP will run at a reduced consumption rate. Increase the solar, HP draws more.

As far as the Paladin was concerned, the idea I believe was to run pool pumps or other devices that are DRED enabled, once the hot water tank was full. I imagine there are ways to do the same without the Paladin, I am unsure if there are HWHP with this option built in.

I lost track of this thread, but if I may jump in here to clear couple of things up :

There is a add-on LoRa transmitter for Paladin which broadcasts a full data stream of Paladin info every 5 seconds. The 'road map' looks thus :

A monitor box - which is essentially another LoRa ESP32, a screen and a 3 position switch. also sends data into the LoRa stream, mainly about the switch position - which is Auto / Off / Max. The DRED receiver that is added to the AC compressor interfaces with the AC's DRED and controls the AC operation. This assumes that the AC head unit is selected ON with the user's remote.
OFF and MAX are obvious, AUTO is a fairly simplistic AI (Ant Intelligence?) that aggregates data from Paladin (or a stand alone transmitter - more below) and decides what DRED selection to make given the excess solar, water temperature and transfer activity present in the 5 second window in play.

The 'nice' (in the proper sense of the word) thing about having that Paladin as the front end is that the following basic rules can be applied :

If the water is below 50C - only use exported solar to calculate DRED activity.
If the water is above 60C - use exported solar and 50% of transfer to calculate DRED activity.
Water between 50C and 60C use transfer values pro rata.

This gives a lot more flex to the DRED in keeping the DRED value as high as possible for given solar activity whilst still maintaining water heating.

DRED is a fairly coarse tool on its' face, but in reality, since the compressor power demands are so variable, depending upon the evaporator activity, the 50/75/100 sequence is perfectly adequate since Paladin will always pick up the slack and use it for water heating. Thus you can run that AC with sufficient flex overhead to avoid using mains power at all, except in rapidly changing circumstances - and then only briefly.

The key process is one of timing and reactivity. The AC compressors can be notoriously erratic in their reaction time to upward DRED changes - particularly a restart after an OFF. This is to do with the DRED 'black box' protecting the compressor pump from a restart or acceleration when the internal pressures are high enough to stall or overheat the motor. Without DRED trying to second guess this would be impossible over any range of manufactures / models. But DRED provides a 'black box' and you just throw it the command(s) and it does what it can when it can and it is the manufactures' problem.

Finally the stand alone TX. This only provides a value for GRID activity, and the DRED Rx AI will happily work with this, but the coarseness of the DRED values is more apparent as their is nothing to scoop up the overflow.

As you can see from the roadmap (which is complete) the LoRa matched with some simple AI is an effective and flexible concept. LoRa has great range and although it has limited data speeds and volumes compared to WiFi, it has none of the range and interference issues.

I am working on a simple ESP32 / WiFi plug in for the Monitor that sends data on request to Home Assistant. The depth and range of Data that is available from Paladin is very useful in HA if you have the fortitude and YAML skills :)

fastbike

201 posts

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#3293239 5-Oct-2024 18:09

Terciops:

I am working on a simple ESP32 / WiFi plug in for the Monitor that sends data on request to Home Assistant. The depth and range of Data that is available from Paladin is very useful in HA if you have the fortitude and YAML skills :)

If you have a Mitsubishi Electric heatpump (most models) there is a well supported github project that allows access via an ESP32 device and a few wires to the CN105 port on the control board. It provides a two way interface to control the heat pump via various home automation systems such as HA, OpenHAB etc.

I'd guess being open source it would not be too hard to get it working with Paladin.

https://github.com/SwiCago/HeatPump

Otautahi Christchurch

RobDickinson

1520 posts

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#3293295 5-Oct-2024 19:12

RobDickinson:

Have gone with world solar, 9.24kw+pw3 at $33k

So install was Tuesday, apart from a late addition of a scaf tower (I had assumed they would need one anyhow) it went very well, super tidy job everything looks good and is working (outside of the post install inspection and new meter coming later).

I also had a smartish hot water cylinder control thing put in ( green catch power)

Weds/thur wasnt the best weather but still managed to do ok, today we ran everything, charged everything, heated hot water, overall even capped we generated 37kwh

so overall happy with the system!

HarmLessSolutions

955 posts

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#3293312 5-Oct-2024 20:37

RobDickinson:

RobDickinson:

Have gone with world solar, 9.24kw+pw3 at $33k

So install was Tuesday, apart from a late addition of a scaf tower (I had assumed they would need one anyhow) it went very well, super tidy job everything looks good and is working (outside of the post install inspection and new meter coming later).

I also had a smartish hot water cylinder control thing put in ( green catch power)

Weds/thur wasnt the best weather but still managed to do ok, today we ran everything, charged everything, heated hot water, overall even capped we generated 37kwh

so overall happy with the system!

Interesting usage graph. Is the Powerwall's maximum input 5kW? What was the 'home usage that came on around 10:30? The Powerwall soaked up your generation pretty efficiently until then and after that just about up to capacity?

What HWC (diverter?) did you decide on? Do you have use of your generation prior to inspection?

Sorry if this comes across as an interrogation but I'm interested on how other solar owners maximise their ROI.

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

RobDickinson

1520 posts

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#3293314 5-Oct-2024 21:14

HarmLessSolutions:

Interesting usage graph. Is the Powerwall's maximum input 5kW? What was the 'home usage that came on around 10:30? The Powerwall soaked up your generation pretty efficiently until then and after that just about up to capacity?

Yes the PW can only charge at 5kw max

I manually set the hot water to start heating at 10:30, It should be smart but I am not exporting anything yet so it cant really do its thing. I also started charging the car later to soak up some more.

HarmLessSolutions:

What HWC (diverter?) did you decide on? Do you have use of your generation prior to inspection?

HWC diverter is the green catch power from here

https://www.catchpower.com.au/

The system has been live (powering our home) since install but no exports allowed until inspection

This is the graph for the day, big chunks unused due to no export

HarmLessSolutions

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#3293316 5-Oct-2024 21:51

Okay. So essentially your generation is restricted by the amount you can consume. Interesting perspective.

The Catch Power diverter looks similar to how our Paladin works but the 500W threshold is far less reactive and so midway to that of our Evnex EVSE with a 1.4kW minimum EV charging rate. Either way any component that automates self consumption based on export monitoring is key to optimising your solar system.

Your ability to export will widen your PV's capability and based on our experience (also export capped to 5kW, from an 8.2kW system) the best strategy seems to be to cycle your consumption over the course of the day in order to use enough to reduce the 'spillage' to export to under 5kW, particularly at peak generation periods. Throttling inverter performance to satisfy an export cap is pure waste.

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

RobDickinson

1520 posts

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#3293975 7-Oct-2024 14:30

Couple interesting things the pw3 seems to export some power even tho its set to no export allowed, people have suggested this is just voltage balancing or switching something

So mostly running in 'off grid' mode at the moment but it drops out of that overnight for some reason also...

SumnerBoy

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#3294021 7-Oct-2024 16:33

Interesting thread. I have had a PW2 for the last 12 months and until recently had a DIY PV diverter heating my HWC. However due to the way the PW and diverter are both closed loop systems trying to "soak up" excess PV they had a tendancy to interfere with one another.

They both had a CT clamp around the grid supply but the HWC was "inside" the house load. This meant that if the diverter detected "export" to the grid it would turn on the HWC and wait till the grid supply changed to "import", when it would switch off the HWC. The problem was that the PW would detect the HWC load and if it exceeded whatever was being generated by solar, it would start discharging the battery to ensure zero grid "import". So the diverter would never see the grid supply change to "import" and it would just leave the HWC on, draining the battery.

It didn't always do this, since sometimes the PW would be a little slow to detect the switch and thus the diverter would successfully turn off the HWC, but it was not a very effective system.

I have since decommissioned the diverter and have a few simple automation in NodeRED which will simply turn on the HWC if the PW charge > 80% and solar generation > 3kW. This means I only boost the HWC once the battery is pretty full, and if there is enough solar to run the 3kW HWC element. If the solar is below 3kW then any excess will be used to charge the PW - i.e. the PW is effectively a diverter.

I have been trialling this new simplified system for the last few weeks and it is working very well. In my mind the battery works very well as a type of "energy buffer" which all but eliminates the need for a diverter.

Interested to hear others thought on this? And how your diverters are working out if you have a battery in the system as well.

RobDickinson

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#3294103 7-Oct-2024 18:30

how do you make sure the HWC has got to temp?

HarmLessSolutions

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#3294107 7-Oct-2024 18:40

RobDickinson:

how do you make sure the HWC has got to temp?

In the same vein, how do you ensure a minimum HWC temperature is maintained (for health and practical reasons)?

In the case of the Paladin there is a hard minimum of 40 degrees C below which the usual solar excess protocol is overridden and grid supply is used to reach this temperature.

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

SumnerBoy

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#3294325 7-Oct-2024 22:31

Yep, valid questions. And the reality is there is a little bit more to my system. The HWC has two 3kW elements, middle and bottom. The diverter logic I was outlining above applies to the lower element. So excess solar is used to heat the entire 350l cylinder, from the bottom.

However I also have a timer which runs between 4am - 7am, and 12pm - 3pm, which will run the middle element irrespective of PW charge or solar generation. This ensures the HWC is heated from the middle up to 60C at least twice a day. The morning boost is timed to run in off-peak rates and ensure we have hot water for the morning showers. The midday boost is designed to run when we are most likely to have the highest solar generation, and after enough time for the PW to get some charge. So if there isn't much solar it will be boosted by the PW.

Both elements on the HWC have thermostat cutouts which shutoff at 60C.

HarmLessSolutions

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#3294367 8-Oct-2024 10:30

SumnerBoy:

Yep, valid questions. And the reality is there is a little bit more to my system. The HWC has two 3kW elements, middle and bottom. The diverter logic I was outlining above applies to the lower element. So excess solar is used to heat the entire 350l cylinder, from the bottom.

However I also have a timer which runs between 4am - 7am, and 12pm - 3pm, which will run the middle element irrespective of PW charge or solar generation. This ensures the HWC is heated from the middle up to 60C at least twice a day. The morning boost is timed to run in off-peak rates and ensure we have hot water for the morning showers. The midday boost is designed to run when we are most likely to have the highest solar generation, and after enough time for the PW to get some charge. So if there isn't much solar it will be boosted by the PW.

Both elements on the HWC have thermostat cutouts which shutoff at 60C.

Why are you limiting your HWC to 60 degrees? We have ours at ~72 degrees which is close to the Paladin's maximum so that we maximise our energy storage ability which optimises its 'battery' potential and provide greater hot water supply to avoid running into the 40 degree hard minimum situation I mention above. Of course our HW system is regulated by way of a tempering valve to ensure safe tap delivery temperature.

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

SumnerBoy

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#3294369 8-Oct-2024 10:35

TBH that is what the plumber set it to when it was installed and I have been meaning to increase it.

On a nice sunny summers day the HWC is up to 60C and the PW is full by 11am, so there is definitely room to "store" more energy in the HWC.

In winter I would prefer the HWC only get heated to 60C and any excess go into the PW tho, since the reduced sunshine hours means we don't often get everything fully charged up during the day.

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