I’m a member of Brixton Energy, a cooperative in South London that installs solar panels on social housing. The projects are crowd-funded by community members, with some of the profits used to support energy efficiency in the community. We are transparent about what we do and we want our investors to able to see the impact of their investments. One way we are doing this is by sharing how much electricity the panels are generating to anyone who is curious.
Opening up solar generation data
The solar generation data is logged to a website called solar log which came with the solar panel system. I wanted to integrate the data more closely with our website so I hacked together a really nasty script to scrape it from the solar log website and post the generation data to Cosm, the Internet of Things platform. In Cosm you can easily set up automated tweets based on changes to the data. I did just that and created a new twitter account @BES_Generation that tweets when electricity generation for the day exceeds 20, 50, 100, 150, 200 and 250kWh.
It’s a lovely day in Brixton! Brixton Energy Solar 1 has generated 154.723kWh of electricity so far. #solar#brixton
I set up the auto tweeting for my own use. First, to make sure that the data was posting successfully to Cosm and second, to get push notifications of how the solar panels were doing without having to visit the solar log website.
I was surprised by how cheerful and happy the tweets made me feel.
It might have been because it was March and winter was finally ending but the combination of sunshine, being involved in a cool environmental project and knowing my investment was doing well was a real buzz!
But then I was even more surprised that other people liked it too:
I love that the solar panels on the housing estate at the end of my street tweet to tell us how much energy they have just generated.
It is always a little bit sad when you have to write a instruction about how to use software. We are using Solar log to monitor our energy generation for Brixton Energy. Its really ace to see how much energy the solar panels are generating (check out our solar log page).
I read in the documentation that it was possible to export the data as a CSV, but it baffled me for half an hour on how to do os. I eventually figured it out and thought I would share how to do it so other can avoid the pain.
Exporting daily figures
Click the arrow beside Overview daily and select Overview monthly
Tick the values box on the right hand side of the page
Click the magnifying glass on the left hand side of the page
A popup window then appears with a table of values
On the bottom right of the table is the CSV link
You can use the arrows to either side of the magnifying glass to get data for the previous months
Note that the CSV is actually semi-colon (;) separated. You will need to use the import option in Excel to open it correctly. On one of the screens in the Excel wizard you can unselect commas as the separator and select semi-colons instead.
Also, I was totally fascinated by the workshop’s title. Where the hell would recyclable solar panel materials come from? The answer: typically the solar cells are manufactured in China and shipped to Europe, but they are fragile so a substantial proportion of them get damaged in transit. The damaged cells can then be bought by the kilogram as pricey scrap. The rest of the solar panels is made up of old windows, bits of plywood and a couple of random bits and bobs from the DIY shop.
We split up into four groups during the workshop and built a panel per group. Luckily there were some people in my group with more DIY experience than me. There was a wide range of people from different backgrounds at the workshop and it was really interesting chatting and working with everybody. I have written a rough outline of the process below. If you want to actually build one yourself I would strongly recommend the Demand Energy Equality site for more detailed and reliable instructions. I accept no liability for anyone trying this at home!
Grouping similarly sized solar cells
Even thought the cells are damaged they can still generate electricity roughly proportional to their size. You need to group several cells of similar sizes to make a panel. All the cells should be roughly the same size as the output capacity of the entire panel is limited to the output of the smallest cell on the panel. These cells are placed on a big sheet of plywood.
Connect the panels with tabbing wire
Next up you need to connect the cells together with tabbing wire. This involved some soldering of the tabbing wire to the individual cells. I hadn’t done any soldering in about 20 years, but aside from a burn or two it was fun. After the wire has been soldered on some transparent silicon needs to be spoldged over the soldered area to prevent galvanic corrosion. Then a slightly larger metal buss wire is run underneath the bottom row of cells.
To keep the cells in place you dab some cheap silicon sealant (normally used for bath tubs) around the cells. You then hammer a nail (!) through the buss bar. Cover the whole thing with a old window and you are (mostly) done!
I really enjoyed the workshop:
Making things with your hands is great. I definitely felt I was using different parts of my brain then usual in the workshop.
After playing with raw solar cells I now feel they can be assembled and used in more interesting and varied ways than just the standard rectangular bank of cells.
I’m no longer scared of soldering, which is great as I suspect I might be sticking a few Arduino type devices together this year.
The panels cost about 1/4 of the commercial equivalent, but obviously require some effort to build and maintain. Additionally, you may not get the FIT. At the moment I am still undecided about whether I want to build my own or not.
Coding, Environment, Brixton, Energy, Random stuff