DIY tilting PV

[Beau]

Looks like we are going to add a pile more PV to our system thanks to being able to get 3 phase put in.

Even though we will have around 12 kW of PV I am sure we will produce far less than we use in the depths of winter due to having an all-electric house. I have noticed how my father's PV install (next door) which is at 15 degrees is far more productive than ours at 36 degrees on cloudy days so I would like our additional PV variable angle so we can maximise production in the worst conditions.

So how's best to go about building a variable angle ground-mounted array?

Thanks Beau

[nowty]

Some people do it but as panels are so cheap now, easier just to add more panels if you can.

As its now September, my winter temporary panels are now in operation.

[openspaceman]

What I am intending is to make the base two 4mm wall thickness 4m scaffold tubes, the extruded aluminium beams will mount to the front one with U bolts isolated from the aluminium with nylon top hat washers. Similar at rear.

The panels will be portrait orientation and held in by two extruded beams for each panel from top to bottom. I am undecided about screwing clamps between each panel as I had intended to butt them. I hope to manually raise them, about 50kg of effort, by having the bottom scaffold rotate in U bolts where fixed at each end to a party wall and a parapet. The two ends will bear on unistrut so I could adjust fore and aft if necessary.

[Oldgreybeard]

I looked at doing pretty much exactly this a few weeks ago. We have a very high (around 4m) wall that runs behind our garden, that faces more or less south. My plan was to make up an aluminium frame to hold 8 panels, with that frame hinged at the top. The hinges would be bolted to the top of the wall and the whole array could pivot up and down, using electric rams. I did some rough sketches and worked out that I could fairly easily get the array to change between an angle of about 60° and 10°.

The 12V electric rams are similar to the ones used to power tailgates on cars that have that capability, so are good for a fairly hefty load. I may still get around to doing this, but at the moment my priority is to get a solar panel canopy up along the east side of the house, to give us more early morning generation. I did run three angles through PVGIS, though, to get a feel for how much the output would vary with pitch angle. The plots below were for eight 400W panels facing a bit west of south, at 10° pitch, then 45° pitch then 60° pitch.

10 deg pitch.jpg (55.39 KiB) Viewed 898 times

45 deg pitch.jpg (55.26 KiB) Viewed 898 times

60 deg pitch.jpg (56.77 KiB) Viewed 898 times

The difference is significant, and I'm sure makes the effort of a fairly simple pitch change mechanism worth trying. I did think about the level of automation that might be needed, but am in two minds as to whether it's worth the hassle. If I get around to doing this I'll probably start off with just a simple switch to select increased pitch, decreased pitch with a centre off position and see how it goes. PVGIS is great, but the the key thing I want to know is whether it's worth changing the pitch angle when the weather is like it is today, cloudy. I think a simple automatic pitch angle tracker might be the way to go, perhaps. If I get around to trying this it won't be until next year now, as my time is pretty much fully booked between now and next spring.

[openspaceman]

Apart from planning issues meaning my array needs to be flat I would optimise for maximum yield in December to January.

Rain storm just passed over and output dropped to 20W on my 4kW array. Will be lucky to charge the battery as it dropped to 20%.

[nowty]

Apart from planning issues meaning my array needs to be flat I would optimise for maximum yield in December to January.

If you build a ladder store,



Or a potting shed,



Then it's a building so no need for planning permission.

[openspaceman]

Yes but most of the garden suffers from shading. The flat roof is unshaded after 0900GMT

I do have room on a shed with a WSW facing roof but it is adjacent to a public footpath and I wonder about vandalism.

Really as I doubt I can justify the expense of a little EV (I have lots of vehicles in my fleet) I have no need of extra PV power except in those winter months.

[Beau]

Apart from planning issues meaning my array needs to be flat I would optimise for maximum yield in December to January.

Rain storm just passed over and output dropped to 20W on my 4kW array. Will be lucky to charge the battery as it dropped to 20%.

But average maximum yield or best yield for cloudy days?

They are not the same presuming the sun does come out. 0 degrees is best when cloudy which it can be for literally weeks here on the West of Dartmoor. A steep angle is best for when the sun does come out hence wanting to have a variable angle set up.

[Oldgreybeard]

Would it be worth buying a cheap low voltage panel, fitting it with a load and doing some ad hoc experiments?

Might be worth spending, say, £50 on some parts to get a feel for the percentage gain to be made by varying the pitch angle under different conditions, especially if it turns out that there is a compromise fixed pitch angle that works well enough, without adding the complexity of a mechanism to change the pitch.

I might even have a go at knocking such a test rig up. I have an old 12V nominal amorphous glass panel somewhere, and also have one or two small MPPT modules left over from making solar outdoor lights. I could have a go at putting together a test rig and trying to make some measurements. I've got a fairly decent light meter, too.

[openspaceman]

Apart from planning issues meaning my array needs to be flat I would optimise for maximum yield in December to January.

Rain storm just passed over and output dropped to 20W on my 4kW array. Will be lucky to charge the battery as it dropped to 20%.

But average maximum yield or best yield for cloudy days?

They are not the same presuming the sun does come out. 0 degrees is best when cloudy which it can be for literally weeks here on the West of Dartmoor. A steep angle is best for when the sun does come out hence wanting to have a variable angle set up.

Yes PVGIS suggests about 50 degrees is optimal for December to January and worth about 10kWh per month but flat is only about 10% less.

I may well add more panels in the future when I have a better idea of what I am doing.