Winter Sun

One of the things that's become clear from looking into running our house off solar panels is that the most difficult time of year will be winter, when the sun is lower in the sky. Our place is in the midst of much taller buildings, which are going to block out even more of the sun.  Basically, if I can design a system that will get us enough energy in winter, it'll work for all all year round.

So how much sun is blocked out in winter?  Well, my handy app drew this diagram:

...which was not overly encouraging, as the "Winter Soltice" line in blue is rather interrupted by grey building shadows. Even worse, I had a strong suspicion that my prime spot for some panels would be totally overshadowed by our water tank in winter (the water tank is too near to appear in the diagram).

So the only thing to do was to wait until the depths of winter and check out the shadow situation. This is a photo taken every half an hour or so, on 19 June (3 days before the soltice):

My supposedly sweet spot for panels is the area on the bottom right. And sure enough, from about 1:30pm onward, it's completely in the shadow of the water tank - i.e. it only gets morning sun, and even then, until about 10am, it's streaked with shadows of chimneys and antennas - shadows like that reduce the amount of energy generated by panels, because the cells in shadow drag down to performance of sun-bathed cells in the same circuit.

An alternative spot I'd thought about for panels is the wall that can be seen in the background - the top-right of the photos.  This gets quite a lot of sun, but also lots of pointy-thing shadows.

The other thing that's clear is that, from 3:15pm, all of our roof is in shadow.

So this is probably bad news for a regular photovoltaic system with lots of panels in the same circuit.  The only way I can see to get this to work would be to get creative, and have panels on different circuits, optimised for different positions at different times of day.

Tricky...