Just upgrade to a new panel - data is in

[Jim Cate]

FWIW: We frequently have seen over 400 and as much as 450 watts peak from our two 200 watt panels here in Tasmania (~43 deg S) this summer. These are seen on bright days and with relatively low SOC in the nominal 440 a-h golf cart bank. These are transient readings, of course, but they occur often enough to be "real"... as shown on the Victron MPPT data page.

The panels are monocrystalline, relatively high OCV (44), parallel connected, fixed horizontal mount with little shading under most sun angles, going into a Victron 100/30 controller.

I guess the point is that your panels should be doing better IMO. One possible reason for lower charge rates is that the batteries are not deeply discharged and your observed currents are all they will accept. Another reason could be that the batteries are sulphated, which can also reduce their acceptance rate.

Jim

[billgewater]

All the commentary probably explains just why many people build a frame aft. The frame can be used for davits, antennae, Radar, wind generators, provide a shaded aft deck area etc. This allows for many more panels that have much better exposure to sunlight. Panels situated aft also don't interfere with other things on a busy deck. Yes, the big problem is the sheer cost of the metal framing to support the panels and act as davit system as well, but it's generally what I see people doing. The structures range from self fabricated aluminium models - looking a bit agricultural - to very spiffy expensive SS versions. Usually, the diesel gen set goes up for sale - not needed and the $'s go towards paying for the frame, panels and associated electronics. Usually a bigger battery bank is installed as well.
An acquaintance recently sailed across the Pacific (Bavaria 48) using four panels (I think) and from what I understand managed without running the engine at all.(not allowed to stop anywhere) His boat has a water maker, freezer, auto pilot . . . all the usual stuff. So it can be done.
Sailing is supposed to have a "solitude" facet. Solar panels certainly allow for this, whereas a gen. set is quite capable of driving you and your neighbors bonkers.

[markcouz]

Originally Posted by Jim Cate

FWIW: We frequently have seen over 400 and as much as 450 watts peak from our two 200 watt panels here in Tasmania (~43 deg S) this summer.

Jim

This is a common occurrence as a result of cloud edge effect.

Your flat mounted panels will be quite well pointed in summer in Tasmania, so normal recovery at midday with low SOC and cloudless skies (so panels maxed out) will give a very good indication of normal max output (somewhere between 300 and 350W i guess).

If you watch your panel output on a partially clouded day you will see output jump up momentarily as clouds approach/pass the sun as direct rays + deflected rays reach the panel.

[markcouz]

Originally Posted by mvmojo

We had ten 100w panels on MOJO (1,000 watts total for the math challenged), all mounted flat on the roof (trawler, not sailboat). With a MPPT controller we routinely generated 300 a/h per day from the sun, even in Long Island sound during the summer months all year long in the Bahamas and the Caribbean.

Great info for anyone planning a solar installation on a yacht for use in the Caribbean and surrounding areas.

1kWp mounted flat and not shaded (trawler) has routinely provided (~300Ah x ~13V = ~4kWh) giving an efficiency factor of 4 over a prolonged period.

Energy recovery on a yacht is unlikely to improve on the above because of additional shading issues.

So if planning an install on a yacht and able to install aft on a radar arch, (out of shading from dodgy wind generator, huge radar umbrella, and smorgasbord of antennas) then you can take your total panel power rating and multiply by 3 to 4 to get an estimate of expected power recovery.

Thanks mvmojo!

[derfy]

For you data-driven types, here is an update.
I believe the daily cumulative Energy delivered kilowatt hours, and amp-hrs.
They are very consistent and credible, as they are accumulated across the day.

But, I am highly suspicious of these max and min voltages and currents. I think they are captured glitches (ie transients). I never let the house get below 12.2V, and usually 12.3. And, I never saw the solar panel deliver any more 12.9 to the house at blazing midday. No way did it deliver 14.3 - that would require about 80 amps into the House 12v (based on my Xantrex Charger in Absorb state). I disbelieve the max PV current also, as that would equate to over 800 watts of peak power at 35 volts. These are all transients from switched loads, etc. The Outback is simply sampling at a high rate, and not filtering or signal processing these parameters.


I have not seen Max power above 260 w at midday, so I am suspicious of the 320 w log value, which I believe is a transient.


Guess I will have to figure how to connect a serial port to this Outback gadget (in my spare time).

[derfy]

Originally Posted by markcouz

This is a common occurrence as a result of cloud edge effect.

Your flat mounted panels will be quite well pointed in summer in Tasmania, so normal recovery at midday with low SOC and cloudless skies (so panels maxed out) will give a very good indication of normal max output (somewhere between 300 and 350W i guess).

If you watch your panel output on a partially clouded day you will see output jump up momentarily as clouds approach/pass the sun as direct rays + deflected rays reach the panel.

This is very interesting. This might explain why I never see the max power that is being reported in the log. I believe it is a transient condition of some kind. It is not sustained.

[derfy]

Originally Posted by billgewater

All the commentary probably explains just why many people build a frame aft. The frame can be used for davits, antennae, Radar, wind generators, provide a shaded aft deck area etc. This allows for many more panels that have much better exposure to sunlight. Panels situated aft also don't interfere with other things on a busy deck. Yes, the big problem is the sheer cost of the metal framing to support the panels and act as davit system as well, but it's generally what I see people doing. The structures range from self fabricated aluminium models - looking a bit agricultural - to very spiffy expensive SS versions. Usually, the diesel gen set goes up for sale - not needed and the $'s go towards paying for the frame, panels and associated electronics. Usually a bigger battery bank is installed as well.
An acquaintance recently sailed across the Pacific (Bavaria 48) using four panels (I think) and from what I understand managed without running the engine at all.(not allowed to stop anywhere) His boat has a water maker, freezer, auto pilot . . . all the usual stuff. So it can be done.
Sailing is supposed to have a "solitude" facet. Solar panels certainly allow for this, whereas a gen. set is quite capable of driving you and your neighbors bonkers.

Well, I am sitting in solitude this morning, listening to my Westerbeke pour 70 amps into my batteries. The reason I am in solitude is my wife stayed home (cause she does not love the smell of diesel in the morning), and all the other boats anchored downwind ran away ...ha, just kidding.


But, the reason I am running the generator is that I have just enough battery capacity to get me from sundown to sunrise, if I am fully charged at sundown. About 180 Ahr is needed at night (the load goes up to 14-15 A for lights and fans). Across the night, my 12v drops from 12.8 down to 12.3. I recharge at 12.3.



So, to eliminate my trusty Westerbeke, I need to pump 180 Ahr into the house bank, using solar mainly in about 5 daylight hours (from 10 AM til 3 PM), in addition to handling my daytime house load of 12 A. Take requires a sustained 180/5=36 amps for five hours, plus my 12 A load, I need 48 Amps from 10 AM to 3 PM. Charging requires 13.5 V (bulk) up to 14.3 V (absorb), so lets call it 13.8 average. That means 48 A x 13.8 V = 662 watts sustained for 5 hours.


Since radiation varies across the five hours, I really need probably about a kilowatt of real, non-transient max power into the 12 volt rail at noon. I am sayin' that means about 1.5 or 2 kw of panels. That is a factor of 4x to 5x above what I have now.


If I want to make water or make my water hot (yeah, I know...it's the Caribbean ... but I have to wash dishes, right? ... and mama won't ever come back aboard without hot showers).. Nah. Sorry, I gotta have my Westy.



Gotta go change the oil in it right now. Thanks for the great discussion.

[markcouz]

Your 180Ah at night can be multiplied by 12.5V (ave nighttime voltage) which gives 2.25kWh required.

If you take 2.25kWh and divide by 4 (approx unshaded efficiency factor in the Caribbean) it shows that an additional 562 panel watts required, call it 600 so a total of 1kWp would get you mostly off the generator.

These would need to be unshaded, so aft radar arch with no garbage mounted above.

Depending on how much you want your wife with you on the boat this may or may not represent good value ;-)

[derfy]

Originally Posted by markcouz

Your 180Ah at night can be multiplied by 12.5V (ave nighttime voltage) which gives 2.25kWh required.

If you take 2.25kWh and divide by 4 (approx unshaded efficiency factor in the Caribbean) it shows that an additional 562 panel watts required, call it 600 so a total of 1kWp would get you mostly off the generator.

These would need to be unshaded, so aft radar arch with no garbage mounted above.

Depending on how much you want your wife with you on the boat this may or may not represent good value ;-)

Yeah, you could calculate it that way if you want to assume that you get all the energy out of the house batteries that you put in them. But greedy batteries need to get back all the coulombs of charge they loose (1 Ah = 3600 coulombs). The 13.8 v I used accounts for the extra energy needed to charge the batteries. So, I believe I would need another real, sustained 1 kw. How many panels is that? So, far, looking at mid-day power levels, I see about 65% of the "labeled" power, 250-260 watts vs 400 watts). So, about 1.5 kw (label). 4 more of my panels.

Anyway, its not going to happen on this boat. I already have a stern arch. It's covered in antennas that would be very hard to move (satellite stuff that needs a clear shot at the sky), and would need a lot of stainless steel welding to make a tower in the sky anyway. And, I admit, I hate the look of it. I see other cruisers with these huge towers.

However, I was toying with the idea of stacking a second identical panel right on top of the first one, face down [yep, face down], with a hinge running along the starboard edge. When I get on anchor, I open it up and hang it with a halyard off the starboard side, over the water. It provides protection for both panels when I am under sail, and acts as an awning when it is opened. More than doubles the power, since I can tune the angle to the sun's altitude with the halyard. I also have the wiring right there, so the electrical connection is really trivial. Whattaya think? Totally Crazy?

[markcouz]

Originally Posted by derfy

Whattaya think? Totally Crazy?

I think creative rather than crazy. If you devise a method to support the swing out panel from below using the existing bracket and get rid of the shade producing halyard it would be a great way to double your current output with the space available.

[BillKny]

Originally Posted by derfy

The panel comes nowhere near supplying enough power to handle the total house load, and simultaneously recharge my batteries that have drained overnight. At the end of the day, the house batteries need a good recharge from the generator. I need to make water and heat water also at this time, which I must do with the generator.

You are running this completely the wrong way round!

You should be running your generator in the AM, before the solar panels start charging, and bring your batteries up to 80 to 90% SOC. THEN let the solar panels charge the balance during the sunny part of the day.

Charging the tail end of the battery charge curve with the generator is VERY inefficient, because you are burning 50% of full load fuel, and generating 5% of the full load power.

Use the genset to pump the batteries up the steep part of the charge curve, where is is reasonably heavily loaded, then let the solar panels do the light work of running the batteries up toward full.

[stormalong]

Looking at your picture it appears that the boom extends over the center of the Bimini. Solar panels are very susceptible to shading. Even the slightest amount kills the power output.

Can you move the panel outboard to reduce the shading? A second panel could provide power when the first is shaded but they must be in parallel, not in series.

[Quadrille in JB]

I have to agree with Billkny. Use your genset in the morning and let the solar panels top off the batteries during the rest of the day
My 2-360W Sunpower panels routinely put out the rated current of 60 amps through 2 Victron 100/30 mppts. We have 840 ah of AGMs that are only discharged down to about 93% overnight acoording to our Victron 702 monitor. We run separate fridge and freezer and our Seawaterpro water maker(1 hr daily). The only time we use the genset is after several overcast days. Its nice to have the little NextGen 3.5 kw diesel to back up our PV system and to run the A/C on those really hot breezeless days.
The attached screenshots show the output of both panels at about the same time.

[derfy]

Originally Posted by markcouz

I think creative rather than crazy. If you devise a method to support the swing out panel from below using the existing bracket and get rid of the shade producing halyard it would be a great way to double your current output with the space available.

I'm thinking about how to do it simply and elegantly. It could work. Maybe more of a project than I want to do while down island.

[derfy]

Originally Posted by BillKny

You are running this completely the wrong way round!

You should be running your generator in the AM, before the solar panels start charging, and bring your batteries up to 80 to 90% SOC. THEN let the solar panels charge the balance during the sunny part of the day.

Charging the tail end of the battery charge curve with the generator is VERY inefficient, because you are burning 50% of full load fuel, and generating 5% of the full load power.

Use the genset to pump the batteries up the steep part of the charge curve, where is is reasonably heavily loaded, then let the solar panels do the light work of running the batteries up toward full.

Thanks. This a very helpful suggestion. I read it early this AM, got up, and cranked up the genset. Besides, told you I love the smell of diesel in the morning. It is sooo obvious to use the solar on the back end of the charge cycle. Duh. Very good.