So, today we look at my parents house. By contrast, they already have tall trees on their southern side of their single-story ranch. The question is: what is their solar potential on their house roof, and how does that compare with their. largely unshaded garage roof?
Similar process as before, using r.sun.daily, though this time, we will take into account diffuse and reflected radiation with a global model: r.sun.daily elevation=dsm start_day=1 end_day=360 glob_rad=glob_rad glob_rad_basename=glob_rad_ nprocs=4 -t --overwrite
I digitized a quick reference area on the roof plus the better 3/4s of the house roof in a western and eastern facing portion to compare average available radiation across all three potential placements, analysing using zonal statistics in QGIS:
In short: the eastern facing side of the house has 97% the total output of the garage (per unit area) and the western facing side has 60%. Panels on the eastern side of the house seem to be a no-brainer. Adding panels to the garage and/or to a constructed car port to the east of the garage probably also make a lot of sense. I’ll leave to experts more august than me whether western facing panels on the house make sense, but I can say with some certainty the east facing side of the roof is not very compromised from a solar perspective.
I don’t know how much or if they would get a feed-in tariff for solar energy exports to the grid, but if you have any significant electrical loads in the afternoons (AC in summer for example), then western facing panels are beneficial.
In any case it is good to be able to spread your generation over the whole day with ~E and ~W facing panels, avoiding the huge solar noon peak with South only facing panels, which for most residences is unusable, and also suffers from minimal generation in the early morning and late afternoon.
Nice use of ODM and QGIS
You did not mention if the pv array will be grid connected, but if the electricity should also be consumed in the house, East and West facing panels are the way to go, like @Gordon mentioned.
I am living Off-Grid, so 100% self consumption of the produced electricity and I can run the carpentry and the metal workshop until 5 in the afternoon thanks to some additional North-West oriented panels. Without yet consuming any electricity from the batteries, off course.
The other panels are 20° towards East, which gives a good amount of morning electricity for laundry washing and backing
Grid connection likely. This is great. I know with our own house, we should be able to offset everything between house and garage (when that gets rebuilt…) and I have designed on battery storage as well.
If you are allowed and have the space, it’s good to go way oversized with the PV panels relative to your summer consumption, just to reduce winter grid electricity imports. Panels are way cheaper than batteries! If there is a limit on exports to the grid, you can still oversize the panels and inverter, as many inverters allow an export limit to be set.
I recently installed another set of 16 Lithium cells (LiFePO4), as some of the previous set from 2012 had very low capacity, so more generator battery charging required than was ideal.
Off-grid since 1991 here, more than half my PV panels are on trackers, the rest fixed in various directions NE to NW (southern hemisphere).
I hope to do so. The house alone covers our summer usage plus maybe an EV (if memory serves me), so the garage will be a second EV plus surplus. It certainly won’t be enough for winter, at least not winter with snow on the panels, but should help those imports a bit.
I haven’t done a deep dive into how much I can export to the grid in the summer, though I’m sadly certainly not in one of the more beneficial markets for that.
They are 400AH Winston cells, no need for any buffering The biggest continuous loads they deliver here are ~5kW, but during the day when the aquaponics water chiller starts overall battery + 8kW PV deliver spikes of up to 15kW.