Hi all, I’ve put in my 2 arrays, and I’m getting very low forecasts:
I add these together, and you can see actual is 4kw higher right now
we actually have other things like cloud cover I would have expected forecast to be higher than actual.
I’m trying to use something like the forecast next hour to control my automation instead of using actual instant generation which will be affected by cloud cover can be more volatile
One array ‘front’ and one array ‘rear’ suggest, like myself, that they face 180 degrees apart, yet your peak production is only 2 hours apart. Assuming Australia, around solar noon, you appear to have both arrays facing South to West.
Configuration settings must be accurate. Location, elevation from horizontal, array peak generation, and azimuth (which is measured differently in Forecast Solar) are critical. Then the inverter capacity figure limits the solar forecast should this exceed the maximum the inverter can deal with.
After that, it is a forecast. Based on clear sky estimates for your location / array orientation, but reduced for weather and atmospheric conditions. On a clear sky sunny day, with the correct settings, the actual should match the forecast. Issues with alignment have been noted.
Weather accuracy is another subject. Note that the integration uses an EU based estimate / forecast, which may not be as appropriate when in the Southern Hemisphere.
In my experience, ratio of actual production to day forecast can vary from around 0.5 to 2, and for myself averaging at around 1.3 over time as my array is shaded early & late.
Hourly forecast figures can be very inaccurate. I continue to collect daily solar and weather forecast and actuals in the hope that I might find a model that can be used to better estimate day and hour ahead values.
I have solar analytics setup and I have copied all these figures fromthere.
my Orientation: 128 and 308
That’s what I should use right?
I need some way of working out how much solar I’m producing so that I don’t react to cloud cover like this
I thought the this hour or next hour would be the thing that could give a useful number.
The integration configuration in HA uses north 0 east 90 south 180 west 270, which is different to the forecast solar API and possibly everyone else. I suggest your figures may be incorrect.
To deal with sudden cloud cover, I have tested using statistics platform sensors, based on rolling averages or smoothing over a time period of 15-30 minutes.
There must be an issue in the integration.
https://doc.forecast.solar/find_your_azimuth
However you can’t put -ve in HA.
In any case it’s clearly wrong I can’t have two panels facing opposite sides with peaks one hour apart as you said. Is the integration just clearly useless then?
WHat Statistics are you using? I’m not a mathematician I’m not sure what would smooth out the graph. Eg red line
Because in Home Assistant we apply a 1 to 360 degree value and in the code we then translate the value to what the API should use.
In that case my settings are correct the only number I’m not sure about is the inclination 25 which I copied from my system but I haven’t measured myself.
As you can see, it’s generally 1-2kW under real
As a first step, the settings have to be absolutely correct. My solar panels face east-north-east and west-south-west, so the HA integration azimuth figures used are 75 and 255.
The elevation should be measured with a clinometer or by depth-height to calculate an angle. Zero is flat, my UK house roof is 35 and quite shallow. Free standing ideal is I think closer to 50, so 25 maybe incorrect (and the flatter they are the closer the two array solar peaks will be).
The basic solar pv model is accurate for South facing arrays, but becomes increasingly unreliable away from due South. North of East and West seems to be particularly difficult since the sun faces the panels near dawn/dusk, when atmosphere and horizon shading are most prevalent. Solar noon gives the best sun and estimates, but the sun is glancing incident on the array.
The weather is unpredictable. Cloud will reduce solar pv to about 15% of clear sky.
My forecast for the past hour was 600 Wh, I got 200. On a clear, sunny day, outside of December to January, I get a good match.
Personally, I don’t see that the 'next hour forecast is accurate for my practical use.
In time, based on either the solar forecast, the’ clear sky’ estimates, and/or my own ‘best day’ history, used together with my local weather forecast, I can see an opportunity to develop a better-fit next-hour estimate by down-rating based on cloud cover forecast.
My cloud cover is 100%. All day. I expect about 1.8 kwh today, not the 5 kwh forecast.
To try and answer your other question, only forecasting will give you an idea of what the solar pv will be in the next hour.
However, the statistics platform can offer averages and other figures, sampled over a given time period. Using a linear average sampled over 1hour, periods of passing cloud for 5-10 minutes can be “averaged out”. This is very much back-casting, and assumes that the next hour will be about the same as the average of the last hour.
I am most certainly not a statistics wizard, so I continue to explore and experiment from time to time to see if I can get a better model. A simple linear average would be an easy place to start.
Hi @Biscuit ,
Can you share more details about your dashboard , eg the solar vs forecast? I cover 3 of the 4 available side on my roof and I would like to mimic you dashboard with the 2 orientation group. Could you please share how you built your dashboard?
My solar forecast project is now almost 2 years old, and I did an update on the Node-RED code I used mid last year. This NR code is now too big to post in this forum, so I posted in the Node-RED forum
https://flows.nodered.org/flow/bbde517b1e592ce804f553da80dbb4c4
Looking at this, I probably should redo the documentation and pull everything together into a Github repository… Another job for another time.
Here is a link to the update post in the main thread regarding my work. You can find the details above / below this post if you care to dig through the thread.
https://community.home-assistant.io/t/access-data-from-forecast-solar/435964/50?u=biscuit
Hope this is of use to you.
Not sure whether you already tried, but judging from your nick 
this should fit your needs better than forecast.solar:
I also have wrong graph shifted 1 hour. Please share which file you are touching.
I will just add +1 and solve all my graph problems.
How do you run Home Assistant?
I’m also facing some strange behaviour. 2 Directions, South (2.5 kWp) and West (5.8 kWp). Inverter can do 6kWp so i added these numbers to 2 services. I only see a max of ~4kW. Mornings and evenings are usually pretty correct.
Do i miss something ? location, Azimuth and declination are correct.
thanks for any hint
Hi,
I tried to access https://forecast.solar/ to get an API key, but it seems to be down. Am I trying to access the wrong site, or do they have problems right now?
Problems right now. My numbers have been unavailable all day.
Hi all,
New to the world of PVs and HA - but having fun learning.
I have added Forecast.Solar as an integration and created three services, Home-East, Home-North and Home-West for my three arrays. I have measured the declination of the arrays (22°) and azimuth (105°E, 15°N, 285°W).
East array - 7 panels @ 440 W = 3,080 W
North array - 11 panels @ 440 W = 4,840 W
West array - 5 panels @ 440 W = 2,200 W
The inverter is a GoodWe 8kW inverter.
I have entered the above values in the corresponding three services and included the three forecasts in my Solar Panels Energy graph.
I understand this is just an estimation of energy production, and not something I should ‘hang my hat on’, but still I thought it would be closer than this … (only able to add 1 image to this post … see image in next post).
If I enter the Total Watt Peak Power for my entire system in to each service (i.e. 10,120 watts) instead of the Total Watt Peak Power for each indvidual array the resulting prediction resembles more closely the actual energy generated … (only able to add 1 image to this post … see following posts for next image)
Am I misunderstanding how Forecast.Solar needs to be configured?
With Total Watt Peak Power on each of the three services set to total peak power for entire system (i.e. 10,120 W) …
Probably not. After years of trying everything to get a good match, I find for myself that the solar forecast integration this year is almost consistently half actual generated in summer and double actual in winter.
Solcast, on the other hand, is running at 90-105% actual to forecast, day after day.
Here is yesterday and today…
For yesterday:
forecast.solar, up to 09:00, gave a total forecast for the day ahead of 11.2
Solcast, at 02:00, gave a total forecast for the day of 16.1
The actual generated was 15.2, hence Solcast was 94%, and forecast.solar was 136% (actual/forecast).
I think that the figures speak for themselves.
