Tilting solar panels

[Albro359]

I have 2 x 130W panels and they are mounted flat on the bimini frame...I don't want to spend all my time tilting panels...I want to be cruising and enjoying life.
I get enough power out of them to keep my freezer frozen and my water maker running...but I have to say I don't go further south than about 36 degrees...
I can see that in the winter it may help to have a vertical tilt...but anything else I wouldn't bother.
Years ago I had a mate that devised an auto tilting system that used two LDRS either side of a metal plate that connected to a differential amplifier energised an electric motor to tilt the panels to keep them pointing directly at the sun...problem was the motors used more power than was gained by the all day movement to keep them aligned !!!

[Snowpetrel]

Originally Posted by barnakiel

Do tilt them if you can. Huge gains.

You can build/buy a single leg pivoting supports that will tilt in any direction. Google some, they are out there.

b.

+1 I tilted mine in one axis, huge gains the further north/south you go, and also if you are heeled.



I have some ideas for attaching the system in the photo to a vertical axis swinging arm so it can pivot in all axis and be bought inboard or swung over the stern out of the way. They might also double as davits.

[jeremiason]

One of my Marine Engineering buddys did a study for one month on the effectivieness of tilting his panels...

He manufacured an optical deivce that he could place on the panels and get the optimum angle to the sun.... OK yes, he is a geek, but I think MIT does that to you.

Anyway, he found that after adjusting his panels every hour during daylight he gained about 10% more power from his panels than leaving them in one poistion.

Thinking of the time spent moving the panels I don't thinkit is worth the trouble.

[Snowpetrel]

Originally Posted by jeremiason

Anyway, he found that after adjusting his panels every hour during daylight he gained about 10% more power from his panels than leaving them in one poistion.

What Latitude was he in? And was he comparing it to a panel at the best average angle or flat on the ground?

I got way way more by tilting them, my guess is near double the output by tilting them. over having them flat. I would only adjust them a few times a day when I was low on power, but very handy to have the capability when you need it.

[Emmalina]

Maybe you guys should look at the new semi flexible stuff around it weighs very little and you can bend it around Bimini’s etc a 100w weighs 2.5kg and the 300w weighs 9kg.
Images are of the 100w

[denverd0n]

Originally Posted by Trish Affleck

Lastly, why doesn't it matter what season it is given the sun's trajectory across the sky.

Well, you've gotten a lot of good information about the effort and problems, as well as the benefits, associated with trying to angle your panels towards the sun on a moving boat. I don't think anyone has specifically addressed the question above, so I will.

The answer is, it does. If you really want the most production possible from you panels you angle them differently each day of the year, and continuously throughout the day. That's really an awful lot of work, though. So, instead, most references will pick a best average angle for your latitude and recommend that. Then they will suggest tracking the sun across the sky during the course of the day.

Personal opinion, unless you are in a marina and pointing the same direction all day every day, I would lay the panels flat. Position them for the absolute minimum shading possible. I've seen panels that, no matter what direction the sun came from, they were constantly under significant shading from the boom, sails, an arch, etc. And then the owners wonder why they don't get much production from them.

[Emmalina]

Originally Posted by denverd0n

Well, you've gotten a lot of good information about the effort and problems, as well as the benefits, associated with trying to angle your panels towards the sun on a moving boat. I don't think anyone has specifically addressed the question above, so I will.

The answer is, it does. If you really want the most production possible from you panels you angle them differently each day of the year, and continuously throughout the day. That's really an awful lot of work, though. So, instead, most references will pick a best average angle for your latitude and recommend that. Then they will suggest tracking the sun across the sky during the course of the day.

Personal opinion, unless you are in a marina and pointing the same direction all day every day, I would lay the panels flat. Position them for the absolute minimum shading possible. I've seen panels that, no matter what direction the sun came from, they were constantly under significant shading from the boom, sails, an arch, etc. And then the owners wonder why they don't get much production from them.

Agree completely do you want to be a slave to your panels ?
I have 1200 watt of panels but expect no more than 500-600w on a good day for a mean average of 6 hours...

[jeremiason]

Originally Posted by Snowpetrel

What Latitude was he in? And was he comparing it to a panel at the best average angle or flat on the ground?

I got way way more by tilting them, my guess is near double the output by tilting them. over having them flat. I would only adjust them a few times a day when I was low on power, but very handy to have the capability when you need it.

I know he was in the South Pacific at the time, his panels were mounted on the rails and had a mount that allowed the panels not only to tilt fore and aft, but port and starboard.

I don't want to argue his conclusions... That was his advice to me when I was considering tilting panels.

I choose to mount mine flat and place as many panels as I could afford and find room for. I ended up with 795 watts, which produces between 45-49 amps per hour in peak sun times.

[hellosailor]

If you are on a sailboat, you are doing "work" every hour anyhow, since you will be trimming the sails or finding something else to look and touch on deck while you're on watch. So as you pass the solar panel, you stick a hand out and nudge it to the better angle.

No big deal as long as the mounting system allows you to do that easily.

Atom's mount appears to allow motion in only two axis, rotate and tilt but not pan. On a small panel that looks good enough, on a larger panel, not being able to move in that third axis might mean the whole panel needs a lot more clearance to be swung around.

For those among us who don't have a good "eye" for aiming things, just install a No.2 pencil or a foot long piece of something similar on the panel. When it is pointed right at the sun, it will have no shadow. If the pencil casts a shadow--just nudge the panel until the shadow goes away. No fancy optics needed.

[diugo]

If, say, 60% more power is gained from tilting, the same power could be gained by adding 60% more panels and simply leaving them all flat all the time.

With price per watt now at $1 or less, that's likely more economical than good two-axis tilting hardware---and a lot easier to manage.

[hellosailor]

"that's likely more economical than"
Your math is flawed. In order to add 60% more panels, you need to add 60% more unshaded area to deploy them, which probably means a 60% larger boat, which in turn would need 60% more panels...ad infinitum.<G>
By contrast, being able to gain more power from existing panels makes a more complicated mounting system "free" as the extra power and smaller need for real estate pay them off.

Or you could just run a genset.<G>

[Snowpetrel]

Take this example, heading from say Auckland to Sydney in winter with fixed panels. Sun at about 25 degrees north, you at 35 degrees south TZD about 60 degrees. Suns altitude is now a maximum of 30 degrees at midday. Sin(30) gives you exactly half the projected area, and half the output if my maths is right...

Now say you have NNW winds for a few days ahead of a weak front. It's overcast and you are sailing fast on a tight reach heeling about 15-25 degrees. You are only going to get 17% of the output at midday which is already low because of the cloud. Remember this is your peak at midday, your daily output will be much lower, perhaps only 10-12% of what a similar hinged panel can get. Because the flat panel will only start to see the sun when it has risen to 20 degrees and will be in the shade when it drops to 20 degrees again. Whereas with hinged panels you can get some output not long after sunrise right through almost to sunset.

Nothing beats angling the panels and watching the output soar, to me it is almost as much fun as getting the sails set correctly. And after a long dark night with the batteries down to 12.2v or so it is satisfying to angle the panels to catch the weak morning sun and see the voltage jump as the electronic lifeblood flows back into them.

This would drive me insane having to run the engine to keep my fridge cold, bad enough the heel and the bouncy conditions without the engine throbbing away in my ears, I don't much like running engines with the vessel heeling to maybe 30 degrees occasionally on the bigger seas, to much risk of lubrication issues, so I would want to reduce sail, making me even more grumpy.

If on the other hand your approach to this is to roll away your headsail, sheet the main flat and motorsail for a day or so your power problem is solved (but your fuel one might not be!).

So I guess it comes down to your philosophy on sailing. I tend to be a purist and a minimalist, mainly because I can't afford the alternatives.

Seeing how cheap solar has become flat mounting probably works just fine if you don't sail much out of the tropics in winter and have a backup for the few times the solar lets you down. Especially given the difficulty of hinging a big set of panels.

And a multihull saves the issue of heeling...

For me I will try to have at least a few hinging panels to collect the low altitude sun.

[diugo]

To answer OP's question more specifically, the season certainly does matter. Today was the March equinox, which means the sun was directly over the equator. Today at 40N a flat panel produces cos(40) = 77% of a tilted one.

The sun will continue to climb north until around June 21, when it will be directly over the Tropic of Cancer, which is 23.5N. At 40N you'll be just 16.5 degrees north of it, so a flat panel will receive cos(16.5) = 96% of a tilted one.

Your timing to 40N "shortly" suggests tilting would not be worth the trouble and expense.

Tilting really makes most sense when the sun over the opposite hemisphere. For example, around December 21 the sun is over the Tropic of Capricorn, which is 23.5 SOUTH. So 40N is 63.5 degrees away---and a flat panel only receives cos(63.5) = 45%. Winter tilting more than doubles your power.

[Pelagic]

Timely discussion as I am still in design phase of mounting my 4 x Sunpower E-20’s

What I have gleamed so far is that the best practical solution of flat or easy tilting in 1 or 2 planes is based on your chosen panel size, weight and location relative to onboard shading penalties.

That you have limited control over the dynamics of sailing angles, hunting around on a windy anchorage or tide changes etc.

I would say that the biggest priority should be a safe mounting system for storm force winds if your panels are too large to remove and store inside. (My case)

My 4 large panels have a combined windage area of 6.7 sqm. Each weighs 18.6kg + mounting system.

So far the best tilting solution I can come up with is to hinge along one longitudinal side of each 2 panel set and then tilt other side up to improve sun angle.

For my size and installation, the best tilting angle I could achieve is about 18 to 20 degrees from Horizontal

First question to those who have lived with Solar onboard:

Not quite sure if you sail only in tropics if tilting is still that important?
My cruising Latitude is between 5 to 10°N

Would that influence whether you would just simply fix to slight bimini camber on each side…Or ..still make adjustable for morning and late afternoon benefits?

Second:
From experience hunting the sun, would you make hinges on outboard side of panels (as I show in 1) or inboard (as shown in 2) ?

[GordMay]

As a very rough rule of thumb, , the tilt should be roughly equal to your latitude, plus 15 degrees in winter, or minus 15 degrees in summer.

Adjust to summer angle on March 30, or September 29 (Southern Hemisphere).
Adjust to winter angle on September 12, or March 14 (Southern Hemisphere).