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philipl avatar image
philipl asked

VRM API NODE - Solar Forecast (NodeRed)

Hi,

The new solar forecast can be very useful, I am just having some trouble making sense of the returned data.


I am using the VRM API NODE in NodeRed.

I am calling the following, and then looking at the totals.

Installation Stats - Solar Irradiance Forecast

totals: vrm_solar_irradiance_fc 1921


So here I get a total of 1921, does that mean a total of 1921 watt/hours for the day.

So if I have a 35kw of panels, can I then argue I will generate 67.235kw for the day (1921 x 35)? Does the forecast include system losses?


If I look at the

PV Yield solar forecast:

vrm_pv_charger_yield_fc 19 211.72

I get 19 211.72, is that watts? This is not what I would expect, I would expect much more than that, a value above about 65kw. Also, does this include system losses, if it is a forecast for the system, I would argue that it should include all losses factored in.


I would appreciate any information as to what exactly the vrm_solar_irradiance_fc and vrm_pv_charger_yield_fc is giving me.


Thanks


VRMsolar
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13 Answers
nickdb avatar image
nickdb answered ·

found the same confusion and have raised it with the dev team.

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philipl avatar image
philipl answered ·

Thanks Nicdb, I agree that the values doesn't make sense. I used forecast.solar and the forecast for tomorrow is 90kw, compared to Victron's vrm_pv_charger_yield_fc of 19kw. So the VRM forecast is way too low.

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Rob Fijn avatar image
Rob Fijn answered ·

Hello,

I just have here own question for you:
First for what purpose do you need this Solar Forecast?
Second, how accurate is this ?

Thanks, Rob

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philipl avatar image philipl commented ·

Hi Rob, Solar Forecast can be used for many purposes. It can be used to drive high power loads that you don't want to run if there isn't enough solar power.

In terms of accuracy, the VRM API forecast is brand new, so we still need to see how accurate it will be.

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nickdb avatar image
nickdb answered ·

The node isn't passing start/stop times to the API so the default response will be the last 24 hours.

You can either make the call the old fashioned way, or wait for an expected update to the vrm api node in node red which will correct this.

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conkev23 avatar image
conkev23 answered ·

It looks like the vrm_solar_irradiance_fc totals object is the total of W/m^2 stored in the array for the length of interval requested for the given start/end times passed to the API call.

24hr = 1 sample/24hr
1hr = 24 samples/24hr
2hr = 12 samples/24hr

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philipl avatar image
philipl answered ·

If I use the vrm api node in node red, I get the forecast data for the last 24 hours.

I notice that you have said the Vrm API node needs to be updated, has that been done? I still can't get the forecast in node-red for the rest of the day or the next 24 hours.

Or is there another way to get that data looking ahead?

What is the old fashioned way that you refer to?

Thanks

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wolferl avatar image
wolferl answered ·

Hi

it works for me so far, but is there a chance to get a forecast for more than 24h? Looking at the VRM online, at least for the irrideance I get 7 days. In node red this seems not possible...

Thanks


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wolferl avatar image wolferl commented ·


I solved it by myself

To have more options for time periods you need to edit the html file of the API node in node red: /data/home/nodered/.node-red/node_modules/victron-vrm-api/src/nodes/vrm-api.html

Pull request is put on Github and already merged. Thank you @Dirk-Jan Faber for the fast response!!




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philipl avatar image
philipl answered ·

Can someone help me, no matter what I do, I only get back historical solar forecast data from the API.

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conkev23 avatar image conkev23 commented ·

What are your node settings?


Mine are like this and I get the forecast for tomorrow.

1692838070589.png

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philipl avatar image
philipl answered ·

Hi, that is the problem, I don't have the additional parameters that you have, and I don't know how to get them. I only have the following:

So I don't have Interval, Start or End, how can I get that?


1692854759675.png



1692854759675.png (6.7 KiB)
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philipl avatar image
philipl answered ·

I solved it, I had to go to manage palettes, and then upgrade my "victron-vrm-api"

Now I have the additional parameters. Thanks

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conkev23 avatar image conkev23 commented ·
Thanks for the update tip, I was a version behind myself.
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philipl avatar image
philipl answered ·

Hi,

How can I get the total forecasted kWh value for the day (total generated so far + what is forecasted for the rest of the day).

The API only return the remainder of the forecasted kWh for the day.

I want the total for what has already been generated + what is remaining for the day.

It is theTotal value that is shown on the dashboard.

For example:

Solar 20 kWh

Forecasted 5 kWh

Total 25 kWh

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fish avatar image
fish answered ·

Any thoughts I've updated the node and its pulling a forecast but having run it at midnight for the next 24hrs it gives a total forecast of 2380 !? which bears no reasonable resemblence to the VRM forecast of 36.4kwh

Does anyone know what I'm doing wrong?

Cheers


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fish avatar image
fish answered ·

Right think I've got most of the answers if it helps people or if someone can confirm or deny!

To get the correct forecast it isn't the solar irradiance fc but a combination of in my case adding both the PV inverter yield forecast and the PV Solar Charger Yield to gether as I have both AC Array and MPPT to battery array. These then when rounded give basically the correct figure although it is slightly out which I think is the UNIX stamp using UTC and the forecast being local? The Solar Irradiance I think is just the w/m or something ie strength of sun..

Hope that helps, if anyone could confirm how to get it time wise to match the local forecats that woudl be great..


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