Energy Stats app Integration with Solcast

[BarryC]

Hello,

has anyone else found that the solcast daily limit of 10 API calls seems to get used up much quicker after Fox changed their API? I looked at the solar forecast one yesterday from Energy Stats, when I looked at it again today (more than 24 hours later) I get the "You have exceeded your free daily limit". Very frustrating

[Will]

Yes the new limits have impacted a few people. Recommended you pay for a paid account now with better API limits.

[TonyDurrant]

I suspect that the stats from Solcast do not change very often during the day, so rather than read then every time the user looks at the Summary tab, couldn't the data be retained in the App, and only refreshed from Solcast if it is more than (for example) 2 hours old?

[alpriest]

I'm very late to respond but wanted to confirm that Energy Stats caches your Solcast result for 8 hours, so if you have 2 sites (e.g. front & rear) and visit the summary tab often the most requests you'd use is 6 per day. You can force a refresh of the Solcast data from the bottom of the Summary page.

There was a bug about 6 months ago however which Solcast informed me of whereby the Android app would repeatedly request from Solcast if the first request failed (e.g. free requests had been exhausted). This was fixe.

There are changes coming soon to overlay the Solcast data on the parameters page too so you can compare prediction against your actual PV generated.

[spiral]

There are changes coming soon to overlay the Solcast data on the parameters page too so you can compare prediction against your actual PV generated.

I know this is an old thread but I was somewhat confused by the comparison between generated and predicted in that the comparison was quite high (even exceeding several 100% sometimes). I have now concluded that the comparative data must take that point in time to compare against. e.g. If it predicts 25KW for the day and in the first 30 mins you produce 2.5 I was expecting to see 10% of expected generation. What appears to happen is it compares this figure against what it expects you to generate in the first 30 mins so if it was only expecting 2KW you see 125%.
You therefore get a rolling comparison throughout the day.
I can't fathom the battery predictions though.

[alpriest]

The percentage at the top of the Power Flow screen is calculated as below. However if your Solcast data doesn't cover the full day (or was incorrect) then you could have generated more than expected. You can look on the Parameters tab to see the Solar estimates and you should be able to see.

Code: Select all

totalGeneration / todaySolarForecast

The battery estimates are the time to either full or empty assuming the battery charge/discharge rate were to remain constant. This is then rounded to hours/days.

[spiral]

With my solar forecast, the current display shows 25.85 expected today in total. Currently I have produced 6.2 which is being reported as 115% of forecast. For this to be a correct representation, it must expect my generation to be 5.4. As this is not my total for the day, I have assumed the formula must be
totalGeneration / todaySolarForecast to this point in time. i.e. it reads it the total forecast up to that point in time off of the daily generation curve.
I was expecting a reading to start out at 0 and gradually creep up throughout the day stopping between say 80 and 120% but that is definitely not what happens.

Regarding the battery, I found the app interpreted my battery as 57w rather than 5700w hence I was getting ridiculous charging/discharging times.

[alpriest]

I just checked the code in more detail and yes that's correct. The calculation uses total expected solar generation based on a rolling 30 minute window.

Would it be useful to be able to toggle to show the calculation against the whole day's expected generation instead?

[spiral]

I actually quite like the current method as it shows where you are up to relatively in the day. Do I take it that you're the apps developer? If so then a toggle which enables you to switch between the 2 modes would be interesting but if it was as a replacement then I would prefer it left as is.

[alpriest]

That's correct, I wrote Energy Stats. I'll take a look at dropping a toggle in, features are always interesting to build!

[spiral]

Yesterday I installed the app on another device. Today both of them show different forecasts for the day. Why does that happen?

[alpriest]

It depends on when each system fetched the forecast data for today and how complete each is. Eg one device may only have a forecast up until 3pm and the second may have the full day.

Solcast only permit 10 fetches per day so the all heavily caches the data. There is a “fetch now” button, but that will only work if you have enough Solcast fetches left.

[spiral]

So what determines when they fetch the data. Is it when the apps launched? Equally, does the app only make one automatic request per day and additional ones are at the request of the user.
You mention part day forecasts which I must admit, I've not seen on solcast, the forecast for current day and tomorrow always seem complete.

[alpriest]

It attempts to fetch the next 48 hr forecast when you enter the key and cached for 8 hours.

Subsequent fetches are when the cache is empty and you go to a screen needing data (or on app launch if you have that toggle enabled). So the data is then merged. If you didn’t open the app for a few days then the 48 hr forecast would be gone, and if you then opened mid afternoon you’d only have the forecast from that time onwards for the current day.

[spiral]

Thanks so it would be best (for completeness) to receive that data during a period when no generation is occurring e.g night before or early morning?

[alpriest]

If the devices were always open and initialised at the same time then they would stay in sync, but otherwise they’ll move out of sync - especially as Solcast can adjust their forecast during a day too.