One of the things I have learnt with this project is that (second hand) solar panels are very cheap, but everything associated with them – solar rails, clamps, cables, connectors, isolators and labour – are quite expensive. My main motivation at this stage is science: how much energy can I collect in my own back yard, and what can I do with it?
So I started out by simply leaning my second set of solar panels against the wall of the shed, as I had with the first.
But it was getting into the summer, and the sun no longer stayed to the north of the shed as it did during the winter. It is amazing how much the ancients knew about the path of the sun through the sky which is no longer taught in school today. I blame it on cultural genocide by the early Christians. But whatever the reason, I was taught about Stonehenge but nothing about why it was there, so I am having to relearn all this stuff from scratch.
Anyway, the bottom line is that as we pass the equinox, the sun starts to rise and set in the southern sky (in the southern hemisphere) and so my solar panels leaning against the northern wall of the shed were in the shade of the shed and the eves of the shed roof in the early morning and late afternoon. I therefore had to move them away from the shed wall.
They are now leaning on a set of old kitchen chairs. It looks ugly, but they trap a lot of energy. In fact I now had so much energy that I had to revisit a derivative of Ohm’s law in order to harvest it.
Someone needs to write a textbook on this stuff, with everything you need to know from soup to nuts. The YouTube vids are great but each one gives just a little bit of the picture and the ordering is more random than systematic. In some cases, such as the OFG, the poster posts whatever is in his mind at the time, which may be something he wants to learn more about, or simply something that arrived in the post that day.
My learning was also correspondingly haphazard. My first stop was to learn about batteries, because that was the driver for the whole project. I then watched a couple of vids on charge controllers, but those I stumbled across were for 12 volts camping systems and they were mostly talking about MPPT. I had some detailed discussion here about choosing an inverter while thinking about power and current and voltage, but I didn’t have a corresponding discussion about charge controllers. I went out and bought a 40 amp one, and I thought that would be fine because I had four pairs of solar panels producing 5 amps each. And when I added four more pairs, I thought it would still be fine, because that added up to 40 amps.
I didn’t realise, until I started researching why the extra solar panels weren’t giving me any more power, that the 40 amps applies
to the other side – the side connected to my 26 volt battery. 40 amps x 26 volts = 1040 watts: and that’s what I was getting. So I had to go out and buy another charge controller, and now the system is sweet.
I am harvesting, and using, close to 16 kWh per day. This is higher than I estimated I would need, and probably reflects that were are more casual about electricity consumption, now that it is free. I used to turn off the air con as soon as the house cooled down, but now I let it run all night. And each of the 304 Ah cells I purchased from Shenzhen Luyuan seems to be storing and disgorging close to 1kWh, while the voltage remains within a 3 – 3.4 volt range.
So the project has met and exceeded my expectations so far. My power consumption from the PoCo is close to zero, and with the energy I export from the front of the house during the day, my last account was a credit to me.
www.bunnings.com.au
diysolarforum.com
