New solar panel installation: panel orientation

Solar is continuing to come down, but at a lower rate in absolute terms because everything is so much cheaper than it used to be. That's not a reason not to do it now though - technology is usually cheaper/better next year, and if you waited for that you'd never buy anything.

If you go here:

Doing the sums for my garage, let's say it's 2kW of panels and faces south at 30 degrees of inclination, with 'modest' shading. It says 1495 kWh/year.

If I then say 0 degrees (flat) it's 1331 kWh/year. About 12% worse.

My take on this is that it's a garage so access is just a ladder - no scaffolding or other awkwardness. It's also not super fussy about appearance (flat roofs are never pretty anyway). That means it's feasible to DIY. If I lay the panels flat they're easier to mount, there's no planning implications, and there's fewer problems with wind loading. They also provide some UV protection for the flat roof.

Now, the next step in this plan is to look at secondhand gear. Perhaps it won't be quite as efficient as new, but the cost is a lot lower. The lifetime of secondhand panels might be lower, but then I can just go up a ladder and change them - no expensive scaffolding needed.

I hadn't thought about solar trackers, but one site suggests they add

I'd be interested to know if there's a way to make a cheapskate roof tracker. But I suspect it's not going to make sense over just buying more (used) panels, assuming you have enough roof for them.

Theo

There is one ~4kW worth on a farm near me. They have to be incredibly over engineered to survive the panel wind loading. I reckon the cost must have been around an order of magnitude more than simple mounting.

It is worth getting the angle and azimuth right if you can but you also need to be aware that mornings often have more sunshine than afternoons. Various online calculators will do the geometry for you.

Misalignment by theta costs like cos(theta).

The only panels I can think of where solar tracking might be economic are the hot water ones where there is a tube at the focus of a cylinder and there is scope for rotating the tubes.

It might be worth being able to adjust the slope of the panels on a flat roof so that you catch more sunlight in mid winter when the sun barely makes it above the horizon.

I wonder if you could do adjustable tilt with the panels having a fixed pivot at the bottom, and then a motor on a screw mechanism to wind the top up and down, a bit like a screwjack window opener. Wouldn't be that complicated, although weather and windproofing it might be annoying.

Theo

This reminds me of the debate about solar panels on motorhomes. It's often cheaper, neater, and more effective to simply add an extra battery.

Bill

The key issue is how much longer the subsidy scam will be tolerated.

Without subsidy domestic panels are hopelessly uneconomic. They also do nothing to affect global climate. So really the only reason to install them apart from virtue signalling is for the subsidy. And that will vanish without warning once the scam is exposed .

Build a solar concentrator furnace?

The other as yet unaddressed issue is how to decommission them at end of life.