Earth Notes: PV Sounds: How Does PV Grid-tie Generation Sound in Time-lapse?

Updated 2019-10-30 15:26 GMT.
Audification: listening to my roof-top solar PV #podcast #tech #audification #PV #generation
PV generation 63M Audacity screenshot
"PV sounds" Uploaded . Duration 157 seconds. Download MP3 clip 2128kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 684kB, hi-fi FLAC clip 6949kB.
Transcript:

Hi, I'm Damon Hart-Davis, and this is a mini Earth Notes podcast episode for 19th October 2019.

Following on from the "rad sounds" and "battery sounds" I decided to "audify" some PV-generation data, from a longer-running data set.

From the last "battery sounds" episode, this is my PV generation as measured by the Enphase system, with 15-minute samples for 13 months. This is more noisy than you might expect, as sunshine is significantly intermittent during each day in the UK!

[Twice Enphase-ACB-15m-PV-generation-13M-mono]

That intermittency is caused by cloud cover changing, and individual clouds' shadows passing over the PV system. Those fluctuations can have quite an effect at the local substation that many PV systems are connected to, given the substation's catchment area is unlikely to be the several miles across needed to start dampening such things.

This is what happens when I apply a low-pass filter to cut out anything much faster than a daily cycle:

[Twice Enphase-ACB-15m-PV-generation-13M-LP-mono]

I do have another source of this PV data, that runs for longer, and has faster sampling.

From July 2014, I captured grid-tie PV generation stats live via my Sunny Beam. Initially that had approximately 5-minute sampling, later improved to 1-minute sampling. Nominally, that has 'audio' content to over 500kHz or probably 25 times the top of even good human hearing! This may be enough bandwidth to generate decent video alongside an audio track in future.

(There are much-less-frequent samples going right back to February 2008, mainly daily, as the first part of the PV system was installed.)

Here is what 63 months of real-time PV generation [data] sounds like, fully covering 5 winters, with similar low pass filtering and resampling to before:

[Twice SunnyBeam-1m-PV-generation-63M.mp3]

Over five seconds of Sun-hum! Audio riches!

There's more on my "Earth Notes" Web site at Earth.Org.UK.

The Sounds

As before, I've taken (PV generation) logs and turned them into a WAV. Some at 15 minute intervals, and some at 5 and 1. All compress a year of data into a second of audio. The last one is 5-years' worth.

From last time, PV generation as recorded by the Enphase with 15-minute sampling, then N/R (.wav):

"Enphase ACB 15m PV generation 13M mono" Uploaded . Duration 1 seconds. Download MP3 clip 20kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 9kB, hi-fi FLAC clip 67kB.

Then PV generation as recorded by the Enphase with 15-minute sampling, then: Normalize, Low-Pass Filter at 500Hz with 24dB/octave roll-off (to suppress anything above 'daily' and make seasonal stand out), Normalize, Resample:

"Enphase ACB 15m PV generation 13M LP mono" Uploaded . Duration 1 seconds. Download MP3 clip 11kB (i) (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 5kB, hi-fi FLAC clip 31kB.

Now 63 months' data from 2014-07 to 2019-09, initially at about 5-minute sampling but later cranked up to 1-minute, then Normalize, Low-Pass Filter at 500Hz with 24dB/octave roll-off, Normalize again, Resample:

"SunnyBeam 1m PV generation 63M" Uploaded . Duration 5 seconds. Download MP3 clip 43kB (may not be available in data-saver/lite mode), download low-bandwidth MP3 clip 21kB, hi-fi FLAC clip 142kB.

Code

Sunny Beam

I capture live PV grid-tied generation from the 5.16kWp of solar panels on my roof (half east-facing, half west-facing) via my SMA Sunny Beam. Initially I captured about one sample per 5 minutes, but lately every minute.

cat data/SunnyBeam/20????.gz | gzip -d | sh script/mkaudio/PVGentoWAV.sh > img/audio/mkaudio/SunnyBeam-1m-PV-generation-63M.wav

There are four SMA Sunny Boy grid-tie PV inverters in the roof, each handling a separate quarter of the full PV array. A "Sunny Beam" wireless monitor listens to radio transmissions from all four of them. The stats are displayed locally on the device, by inverter and in total. The Sunny Beam is plugged into a USB port on my Raspberry Pi, which allows me to capture an aggregate generation sample each minute.

The full Sunny Beam dataset is published for the 16WW solar system.