By Claire
At the beginning of this year, I was at the annual AMOS Conference in Melbourne. It was Friday morning, and there wasn’t a lot of paleoclimatology going on, so I decided to head along to a session on solar energy.
Speaking in this session was Nick Engerer, a researcher from Fenner School at The ANU. Nick’s area of interest is the link between weather events and solar energy output. Now, this is an area of huge interest, especially now that we’re trying to move more towards green energy sources. But one of the key questions that keeps popping up is, “what happens when it’s cloudy?”
As part of Nick’s research, he has developed a real-time website, which shows you the weather across Canberra, and the related impact on solar energy production. Nick is working on the idea that on partly cloudy days, there will be at least some solar panels that are still able to produce power, even if some are not seeing a lot of the sun. And that’s exactly what you can see on his website.
Nick has written up a guest post for us to explain how to use his website, and introduce you to some of the cool features. I encourage you all to take a look. If you’re interested in his work, you can also subscribe to his blog and follow him on twitter.
Guest post by Nick Engerer
In honor of fixing the ACT Solar Map page by repairing a bug that was driving me mad (a minor, hidden FTP issue where I accidentally bogged my server down with 139GB of radar imagery – oops! #nerdpower), I thought I would talk a bit about the page and its purpose.
The ACT Solar Map is a perfect example of what I am interested in as a researcher – solar energy and how its power output is affected by meteorological events (namely clouds!). By putting together this image, we get live PV (photovoltaic) power output data from sites around Canberra joined with Bureau of Meteorology weather data from the Canberra Airport.
PV Data
Every 15 minutes, this map (should!) updates all of the data you see in the image. It pulls the PV data from various sources around the Australian Capital Territory (ACT), such as PVOutput.org. Right now, it has approximately 16 sites pictured, but this is set to increase in the near future – hopefully to hundreds of them in the next two years!
Each dot is a rooftop PV array, with the fill color representing its current power output, in kilowatts (kW) relative to (divided by) its installed capacity (peak), in kilowatts (kWp). This is termed the performance ratio.
Red indicates the system is performing poorly. This happens when the sun is very low in the sky, or when thick clouds are present.
Green indicates the system is performing well, as is the case during sunny conditions or thin cloud cover.
If a dot gets into the blue range, that likely means it’s a very sunny day, in the summer or there is radiation reflecting off the side of a nearby cloud and hitting the panel (termed cloud enhancement).
If you see the opacity of a dot falling (e.g. it’s becoming see-through), that means the data point hasn’t updated in a while. It will eventually disappear if it doesn’t report within 60 minutes.
In the bottom right is the average kW/kWp for all of the PV systems throughout the day. You’ll notice in the videos below, this line changes a bit throughout the day (e.g. past data points change location), this is because some data points take a while to report new data.
Weather Data
One of the coolest thing about this map, is the weather data available on the right side. By far, my favorite tool is theceilometer device – which is a laser based system that detects cloud cover and cloud height.
Cloud cover is reported in Oktas, which means eighths. 0/8 cover means it is clear, 8/8 indicates total cloud cover. If the sky was half covered in clouds, it would be a 4/8. Cloud height is reported in kilometers above the surface, and gives us the base of the lowest cloud deck. We even get a guess as to which type of cloud is present.
My next favorite toy is the satellite and radar imagery. These are taken from the Captains Flat radar and the visible 1km satellite imagery available from the Bureau of Meteorology. If we see any returns on the radar, we can be sure that opaque clouds are present in those regions. The visible satellite reveals any clouds that are present. The resolution isn’t very good for such a small region, but it is still effective for knowing if a negative ramp event is imminent (more on that later).
Lastly, you can see some real-time sky images as recorded at the Canberra Yacht Club, which is physically located in the middle of the map on the south side of Lake Burley Griffin. This is very helpful for seeing what type of cloud cover is present, and for detecting thick cloud decks on the horizon.
Weather Events
To show you how this map can be used in real-time, I’d like to share a few videos of different types of weather events with you. These will show you how a solar power day unfolds under various meteorological conditions.
First, let’s look at a day where there is a big high pressure system in place. This means there is sinking, stable, dry air over Canberra and that cloud development is not likely to be widespread, if present at all. Watch the video below, and you’ll see that it’s a pretty boring day! This type of day is very easy to forecast ahead of time.
Next, let’s look at the exact opposite sort of day. This next day is one where there was an extensive Northwest Cloudband event underway. This means there are very heavy, thick clouds in place with widespread rain and very little sunshine. You can see there isn’t much solar power being generated! This type of day is good to know about ahead of time, and is fairly easy to forecast because it slow developing and easily understood by weather models.
Lastly, let’s look at a sudden ramp event. On this day, we have a clear, sunny day, much like the first one, where the skies are very clear. But then, suddenly, a thick cloud deck appears on the horizon and quickly obscures the sun. PV power output drops quickly (aka ‘ramps‘ down). This type of event is hard to forecast, but is the most important type to catch.
Just imagine tens of thousands of PV power systems suddenly no longer contributing to the electrical grid. This is why my research solar forecasting is important for continue integration of solar energy systems into the grid.
Well there! Now you see how this map can be useful, educational and fun to use! Perhaps you’ll check back next time there is some interesting weather going on, and see how it impacts the power output from PV systems around Canberra. In the future, this map will have more systems added to it, as well as begin to update more frequently. It’s still in ‘beta’ mode at this time.
I hope you enjoyed your Solar Map tour!
Peace, Love and Solar,
Nick Engerer
OnCirculation 
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