Solar - Flat vs Tilt

[r4dent]

Pointing panels directly at the Sun all day can actually reduce the efficiency of solar panels. The hotter the panel gets can reduce the output slightly.

The important word being slightly.

Not pointing directly at the sun can reduce the output significantly.

The lower the angle of incidence (i.e. the lower the sun is in the sky) the greater the loss of output.

In the UK the sun (even at noon) is usually less that 45 degrees incidence.

At 45 degrees the loss is over 30%.

Even allowing for the loss of efficiency from heat, a panel pointing directly at the sun will always produce more power than a flat mounted panel.

 

[maingate]

The important word being slightly.

Not pointing directly at the sun can reduce the output significantly.

The lower the angle of incidence (i.e. the lower the sun is in the sky) the greater the loss of output.

In the UK the sun (even at noon) is usually less that 45 degrees incidence.

At 45 degrees the loss is over 30%.

Even allowing for the loss of efficiency from heat, a panel pointing directly at the sun will always produce more power than a flat mounted panel.

That's the difference between us I think. You sound like you are quoting from text while I actively used sloping panels for a lot of years. As an Engineer by background I tested various angles and configurations and noted them down, my Ammeter being a sound guide to solar output. The second line of your post is just wrong as there is a surprising amount of leeway on panel placement (as tried and tested by me).

 

[merl]

That's the difference between us I think. You sound like you are quoting from text while I actively used sloping panels for a lot of years. As an Engineer by background I tested various angles and configurations and noted them down, my Ammeter being a sound guide to solar output. The second line of your post is just wrong as there is a surprising amount of leeway on panel placement (as tried and tested by me).

You're right that there is a surprising amount of leeway but that is when you're deviating from the 'ideal'. 20deg either side of perfect ie straight on won't have a massive difference but if you're already at a poor 45deg then 20deg either side of that will make a huge difference because you'll be either 25 deg off perfect or 65 deg off perfect. 25 deg off will be pretty reasonable but 65 deg off will be pretty crap.

 

[r4dent]

That's the difference between us I think. You sound like you are quoting from text while I actively used sloping panels for a lot of years. As an Engineer by background I tested various angles and configurations and noted them down, my Ammeter being a sound guide to solar output. The second line of your post is just wrong as there is a surprising amount of leeway on panel placement (as tried and tested by me).

We must agree to differ.

I maintain that the greater the angle of incidence the more power is produced.
You maintain that your field observations disprove this.

I will not convince you that what I believe is true, and vice versa

Other members must draw their own conclusion.

 

[maingate]

You're right that there is a surprising amount of leeway but that is when you're deviating from the 'ideal'. 20deg either side of perfect ie straight on won't have a massive difference but if you're already at a poor 45deg then 20deg either side of that will make a huge difference because you'll be either 25 deg off perfect or 65 deg off perfect. 25 deg off will be pretty reasonable but 65 deg off will be pretty crap.

I have 3 used leisure batteries in my shed (removed when they got to 5 years old or thereabouts) which are still in decent condition. They stood from around September last year to a couple of weeks ago and the lowest showed 12.41 volts. I have an old (but not often used) 8 watt good quality solar panel (I never bought cheap solar panels from the likes of ebay etc.). I just prop it against the shed at approximately the right angle and facing roughly South. One battery is fully charged, the second one is just about there and the third will probably get its turn tomorrow. I cannot see all the fuss about precision, after all flat panels are nowhere near the optimum but they keep batteries topped up for nearly all of the year (assuming little or no motorhome use over Winter).
When I used a ground mounted tilted panel on our trips I had 2 settings. 1) Short stick (Summer use). 2) Longer stick (Spring, Autumn and Winter use)*. Efficiency always checked with ammeter.

* The 2 wooden sticks were free issue from woodland next to a campsite and hand whittled.

 

[merl]

I have 3 used leisure batteries in my shed (removed when they got to 5 years old or thereabouts) which are still in decent condition. They stood from around September last year to a couple of weeks ago and the lowest showed 12.41 volts. I have an old (but not often used) 8 watt good quality solar panel (I never bought cheap solar panels from the likes of ebay etc.). I just prop it against the shed at approximately the right angle and facing roughly South. One battery is fully charged, the second one is just about there and the third will probably get its turn tomorrow. I cannot see all the fuss about precision, after all flat panels are nowhere near the optimum but they keep batteries topped up for nearly all of the year (assuming little or no motorhome use over Winter).
When I used a ground mounted tilted panel on our trips I had 2 settings. 1) Short stick (Summer use). 2) Longer stick (Spring, Autumn and Winter use)*. Efficiency always checked with ammeter.

* The 2 wooden sticks were free issue from woodland next to a campsite and hand whittled.

But to be fair you ARE tilting your panels, leaving the panel flat on it's back without any sticks and you'd be well down on charge power especially in the winter.
I think what r4dent is getting at and which I agree is that he's not advocating tilting to gain precise alignment in order to extract the ultimate last few percentage points of power, he's tilting the panels (like you do) in order to maybe double or triple the available power because the angle of incidence is so low in the winter with a horizontal panel.