Solar Panels - Angle of incidence?

[Tim Good]

I’m not exactly sure of the correct terminology or if angle of incidence is even the right word. But I’m trying to figure out what angle of the sun on a horizontally laid panel will produce what efficiency or percentage power output.

For example in northern Spain at the moment at solar noon the Sun is altitude is around 31%. currently we are only getting about 50% if max power output and I’m curious if there is a graph or calculation which shows what you should theoretically get at a certain angle. Clearly 90° Solar Altitude to a panel where the Sun is hitting the panel head on his best.

 

[Bilgediver]

Google is your friend:-

Tilt and Orientation and Solar Energy

 

[Roberto]

With two/three modifications of the inclination: morning - noon- afternoon I measured about 20% increase in total daily output. Anchorages in tidal areas are of course specific.
If (I'd say "when") one forgets the panels with the wrong angle then total output collapses

 

[roaringgirl]

Each panel is made in 'strings' my 250W panel has 3. You can figure out how they are laid out by looking at the connection strips on the sun-side at the ends of the panel. Try usimg a piece of card to cover each individual string one at a time to make sure they're all working. If covering any one of them doesn't cause a drop in output, you know you have a problem.

Bear in mind that panels are extremely sensitive to shading - *any* shadow (eg from a piece of standing rigging) over a cell will stop that entire string from producing.

 

[lustyd]

Some modern ETFE panels have a sort of bubble lens pattern on top to capture the sun better without worrying so much about the angle. If mine are anything to go by this is very effective as I often get more than max rated output for several hours in a day.

 

[Graham376]

With two/three modifications of the inclination: morning - noon- afternoon I measured about 20% increase in total daily output. Anchorages in tidal areas are of course specific.
If (I'd say "when") one forgets the panels with the wrong angle then total output collapses

Every anchorage and marina berth will present a different angle to the sun and we've found a big difference in output by being able to tilt our panels fore and aft at different times of the day or tide direction.

 

[Roberto]

Every anchorage and marina berth will present a different angle to the sun and we've found a big difference in output by being able to tilt our panels fore and aft at different times of the day or tide direction.

Yes especially during the first hours of the morning -or late afternoon of course: with the panels in horizontal position one sees a tiny amperage, once they are tilted it immediately goes up to a (more or less) relevant percentage of total possible output. IMHO a worthwhile modification, of course if one has hundreds and hundreds of watt it may not be worth the hassle.

 

[Stemar]

If you want to change the angles - height and direction - throughout the day, you'll get more out of the panels. As a lazy git, I fit mine horizontally, and put up with the reduced efficiency when the sun's low, when the intensity is at a minimum anyway

 

[ghostlymoron]

If you want to change the angles - height and direction - throughout the day, you'll get more out of the panels. As a lazy git, I fit mine horizontally, and put up with the reduced efficiency when the sun's low, when the intensity is at a minimum anyway

I'm with you, Stemar, being a slave to my panels doesn't appeal. Likewise the issue of a small amount of shading isn't something I've experienced and certainly new panels have features that improve their performance in these circumstances. Rather than tie yourself to a regime of adjusting them three times a day, I would fit a larger area of panels to compensate and fit the panels round about horizontal. I have a swinging mooring so having panels matched to the angle of the sun in one orientation may drop significantly when the boat swings with the tide. Its a mater of compromise and I'm not always aboard which makes trice daily adjustment.

 

[Spirit (of Glenans)]

Some (amateur) astronomical telescopes can be fitted with a small, very low-geared electric motor that will traverse and elevate the apparatus, in time with the movement of the celestial bodies, i.e. they can track the Moon. Perhaps something similar could be fitted to solar panels so that they are always perfectly aligned to the Sun.

 

[HissyFit]

Some (amateur) astronomical telescopes can be fitted with a small, very low-geared electric motor that will traverse and elevate the apparatus, in time with the movement of the celestial bodies, i.e. they can track the Moon. Perhaps something similar could be fitted to solar panels so that they are always perfectly aligned to the Sun.

This video is a small scale implementation of just this. It's not boat specific, but it goes some way to showing just how important array alignment can be. It is shocking to see the haphazard setups on some boats, and yet their owners still moan about their poor charging..

 

[Tim Good]

Every anchorage and marina berth will present a different angle to the sun and we've found a big difference in output by being able to tilt our panels fore and aft at different times of the day or tide direction.

Indeed. From late spring onwards we don’t really need to as the output of our 500w panels can give us up to 2Kwh a day. But for winter cruising being able to tilt fore and after can make a huge difference if we want to continue to boiler the kettle, run the heater and charger laptops without even running the genset.

 

[Tim Good]

Google is your friend:-

Tilt and Orientation and Solar Energy

Yeah I’ve seen all those but it doesn’t really answer the question. Look at the graph and at 90 degrees it’s still outputting. Therefore it’s taking into account the angle as the run rises and falls. Everywhere on that graph shows an output but that can’t be possible if the sun is at 90 degrees to it.

 

[oldmanofthehills]

The sun rises to about 50 degrees in the UK (thus median is 25 over the day) going to 73 in high summer noon with 37 median. Most panels are non-ideally flat though light bubble technology helps.

 

[Stemar]

This video is a small scale implementation of just this. It's not boat specific, but it goes some way to showing just how important array alignment can be. It is shocking to see the haphazard setups on some boats, and yet their owners still moan about their poor charging..

I saw that and though it was cute, but how would such a setup react to taking a wave full in the face?

 

[lustyd]

I saw that and though it was cute, but how would such a setup react to taking a wave full in the face?

Given where most panels are mounted I wouldn't consider that a design requirement.

 

[HissyFit]

I saw that and though it was cute, but how would such a setup react to taking a wave full in the face?

My consideration of this as a possible boat installation ended with the phrase " It's not boat specific." Industrial servo motors are available, at a cost, as would be the heavy gauge mounting hardware.

If one could take care of the rolling of the boat by a purely mechanical pendulum driven mechanism, the energy harvest would no doubt improve over a purely static mount.