Could someone check my math please?

[Na Mara]

Hscrugby

I could do the big panel aft and the coachroof. That would give me maybe 400w. Plus the watt and sea and that gets me to 1000w. That’s got to be enough for those of us who make do with iceless G and T’s and 12v fans for cooling.

[ka4wja]

EDIT: I'm afraid I haven't kept up with all the new postings here...sorry, I've been busy...


If you read all below, you'll likely see why "just adding more solar" sounds good....but, you're running pretty fast and have ignored rule #1 for solar, and that is "Unshaded" is the single most important aspect in adding solar on a boat!


If you haven't taken all shading scenarios into account, then all the discussion about what panels fit where, etc. is premature.


I understand the excitement and the urge to "do it now", "figure it all out, now"....but, take a few hours and do some more thinking on the "system", not just see what panels are for sale and what their dimensions are...


Please read below....






Na Mara,

Cool, now we're getting somewhere.


Right up front, I'd like to reiterate one important point....if you take away only one thing from all of this, please let it be this:
Install as much "unshaded" solar as you can....the key word here is Unshaded....

If you're install panels that will be shaded, you're likely wasting time/effort, and $$$....everything else is secondary...

Please, if you take away only one word, let it be: Unshaded.
[cheap, low-quality panels, installed out in the clear will work better than Sunpower panels that are shaded!]




1) I'm going to leave most of the cold weather and high-latitude sailing specifics for others that have experience there....just remember that one advantage of the Sunpower X-series panels is their ability to generate power at low sun angles...(we used to just use a bit of trig to determine a panel's projected output at various angles, but with Sunpower's cell and panel designs, they actually do provide more power at lower sun angles, than other manufacturers)....and if you're going to be doing lots of high-latitide summertime cruising, you'll have many hours of sunlight, but at low angles....that's about all my knowledge of high-latitude sailing...



Now, onto what I do know about...


2) I'm glad you're happy with your hydraulic autopilot (except for its power consumption)....'cuz, I'm not a fan of hydraulic autopilots, much preferring well-designed / installed heavy-duty electric drive units, connected to the rudder post with their own "tiller arm", etc...

But, you're good with yours, and your boat sails / tracks well under sail, so no worries.





3) Panels on deck? I'm not a fan....I think they are a bad idea...I do not recommend them...(and, that's not even taking into account, the shading of them....which is a big issue)


You will need to walk on them at some point, or something will get dropped onto them...and chances are they will fail shortly after that....

Also, they have no (or little) airflow under them, and because of surface boundary-layer effect a panel on the deck also has less airflow over them that those just a few inches off the deck....now, this might not be an issue at 50* latitude, but with higher sun angles and higher air temps (Caribbean, etc.) this is important, as panel output drops off significantly when they get hot!


And, then there is the shading, which will be significant! (please understand that shading a panel 20% to 30% doesn't reduce its output 20-30%, but rather 80% to 100% reduction....see below for details)



So....I recommend against deck-mounted panels....as well as lifeline or rail mounted panels....just my opinion, of course...


Also, remember that those flexible panels / semi-flexible panels, that are sold to be deck-mounted, etc., they do not have a long life span....and while, to some that just means spending some $$$ a year or two, or three, after installing them, to me it means I'd need to burn diesel too!!


Further, remember that they're less efficient / produce less power for the same size, as rigid panels....of course, as with all solar, "unshaded" flexible panels out in the clear will outperform rigid panels that are shaded....


Bottom line, you cannot get away from "shading issues", unless you mount / install panels where they won't be shaded.... LOL

{fyi, I'm not detailing amorphous panels, as they're much less efficient, and darn expensive....and don't produce energy as long as mono or poly crystalline cells....usually a very bad choice for boats, etc....but, their output falls off in direct relation to the shading....25% shading = 25% power reduction....but, again, these are not a practical choice as their efficiencies are pretty low...}



4) On a side note regarding panel shading....there are some variables in how any panel is shaded, that we simply can't control, so the results present a range of numbers, rather than an absolute figure...and this applies to all mono crystalline or poly crystalline panels (99% of all solar panels), whether rigid or flexible/semi-flexible...

If a panel has a minor shadow or slight shading, of just a couple percent (such as a shadow from a backstay), figure just a minor effect, of a few percent drop in output....but, further shading causes significant output reductions...


and as long as you're not shading one or two cells completely:

--- if the shadow is a bit bigger, say about 5%, figure about 10% to 20% power reduction....
--- and if 10%-15% shaded, figure on 50% or more reduction...
--- and any more than 20% - 25% shaded, figure little to no power from the panel at all....
--- also, for most panels (most lower voltage panels, at least) if you shade one entire cell you usually drop the panel output significantly (50% to 80% drop)....
--- further, shading along the length of the panel (again as long as you're not shading entire cells) is usually better tolerated than shading across the width of the panel...

---- now, ironically, this is not the same as a whole panel (unsahded) on cloudy days, where the whole panel (all its cells) is active, but just getting less "energy" into it from the sun, due to the cloudy skies...this is not "shading", as all cells are working, just not getting as much solar radiation...

FYI, a few years ago, I posted this info and another cruiser pointed me to a video showing exactly what I was saying....If I can find a video showing this, I'll pass it on....'cuz it shows a direct result of shading...much easier to see in a video.


EDIT:
I found the video link....(not a fan of "Youtube sailors", but they did a decent job explaining what I've been saying for decades...)
Have a look:

https://www.youtube.com/watch?v=1qD3mN8VotQ

Again, these are not "absolute" numbers, just a range...as this depends on what part of a panel is shaded / shadowed, and how much of any one cell (or how much of a couple cells) are shaded...

Now, higher voltage panels (50v to 60v) generally have slightly better shade tolerance, but on a boat it's generally either your panel is "shaded" (enough to significantly reduce its output), or it's not (except for the minor shadows from a backstay or halyard), so this is a minor advantage to higher voltage panels, that usually makes no difference...


The gist here is: if you have room for a panel of "x" size, that would be free of shading (or at little shading as possible), versus a panel that is twice the size of "x" but would be 25% shaded for some/much of the day, go with the smaller panel (or mount two panels, where one would be unshaded and the other subject to shade, just use two separate controllers, or wire the two panels in parallel)





5) Back to the "water-generator"....
My advice: Go with solar! And, forget the watt & sea!


If, for some reason, you cannot fit enough unshaded solar, and you still need more electrical power undersail, then consider a "towed-water-generator" (such as Hamilton-Ferris, Aquair, etc.)...


But, to be clear, even though I've successfully used mine on passages, my solar panels aren't as efficient as today's panels....so, if I had a new solar array, I'd not need my Ham Ferris towed-water-gen at all!




6) As for other matters....
a) If you haven't yet used your boat's refrigeration in the Caribbean, or Bahamas, summertime S.E US, etc. (where air temps are 80*F - 100*F, and water temps are 80*F - 90*F), you will find that you will use double the energy as it does in Sweden, and even then will probably not even come close to maintaining refrigeration temps as low as you have now...
Insulation is the key here...better insulation, and more of it...


Every "northern" sailor who has ever ignored this, has regretfully found it to be true....heck even those from California, once they get to Mexico or Central America they learn...


The only boats I've ever seen built with adequate frig/freezer insulation for the Caribbean / Tropics, have been Hinckley's and Dashew-Sundeer's.....so, please don't take it personally...




b) Please allow me to politely ask you to stop here and do nothing for a couple minutes....and just think for a minute or two, regarding your dislike of bimini tops....(I understand, you don't like 'em, and you don't want one....but, please just take a minute and ask yourself why / why not...)


You don't need to reply to me or any of us here, regarding a bimini top.....just take a minute and ask yourself why does every boat in the Caribbean have one, why does every boat in the Bahamas have one, why does every boat in the Southeast US have one....don't answer me, don't justify anything here (it's your choice, your boat, etc....no need to justify anything)






That's about it for tonight....hope this helped...



Oh, btw, on a totally-off-topic subject, I'm just curious....if you're from Sweden? or other European country? The reason I ask is because your English is very "American". That's part of why I didn't grasp where you were planning on sailing, 'cuz I though you might be from the US...
Anyway, I just wanted to compliment you...




Final EDIT:
If you can mount a panel over the radome, get a 360 - 370 watt Sunpower X-22 panel....and you'll have almost as much as you need under sail...and more than you need at anchor!!!!



Mount two of them and you're done!!

Fair winds.


John

[hscrugby]

Interesting. I never realized that the higher voltage panels would do better with shading than the 12/24v ones. That's good to know though.
I'm stealing his thread for my contemplations now.
So my plan had been two move the two older panels where one would be worthless and one might be worthless, with two small controllers. Basically along the dodger and whichever side the sail is on would be heavy shade and when anchored ideally they would both be ok.
I had thought 25-50% shade would be 50-75% max reduced, but sounds like it would be closer to 75-100% reduced.
I'll probably still go that route, and just know usually I'd only have the big unshaded ones out over the dinghy. Maybe I move them further out and put the third panel up there and only have one over the dodger. Good thing I've got a few months for trial and error. Wonder how long wife will not mind dangling wires to test... [emoji1787][emoji1787][emoji1787][emoji1787]

And back on topic... More solar=more better.
Still sticking with my thought on I've never heard someone say, "I wish I had less solar"

[Na Mara]

Ka4wja

It was because the deck panels would be shaded that I was going to break it up into 6 panels. That way any shading will only impact some of the panels and not the others. That should help if the panels are connected right or?

My American English is thanks to all my comments being typed on an iPhone with that as the default setting. I’m actually Scottish.

The x22 panel is a beast 60v output and 1558mm x 1045 mm in dimension. I’m looking for 12v charging so I’d need a control unit to step that voltage down a lot or much of the generation will be wasted. Also my poor pole might struggle with the lateral forces such a large panel would impose in a blow. It would probably need reinforcing with stays. Doable but the forward one would be in the way and the one to port might interfere a little with access to the swim step. I’ll need to look at that.

I promise that I will consider the Bimini over the exterior helm ( there is no space under the boom for one forward) but as I have said before, I have a great interior helm that is all nice and shaded with great airflow that works perfectly at sea and a easily folded cockpit tent that works as a Bimini in harbour with the side screens rolled up.

[Na Mara]

Looked at it and adding a stay across the boat to stabilize the pole won’t interfere with anything. It is already very stable for and aft and has a strut to starboard. I think a stay to port will be sufficient to stabilize it with a big panel on it.

But what about the voltage on the x22? A 60 v panel charging 12 v batteries. Wouldn’t I be better with a 175W 12v panel from victron 1450mm x 650mm or similar? Or am I misunderstanding something basic here and the voltage is a non issue?

And on hscrugby’s more solar = more better I have to say that whilst I mostly agree, there must be a limit where shading makes the panels prohibitively expensive per watt and more hassle than they are worth.

[lamadriver]

Couple of quick comments

Batteries:

If your not gogin to go Li Carbon foam fireflys are the way to go . You can really abuse the heck out of them and as previously stated they effectively double the capacity of a traditional Lead acid or AGM.

They love a charge so a big alt would be super beneficial. If your going to have a 400AH bank ( which i think for your boat and wants is a bit small) Id go CF

Watt and Sea:

I own one and have used it extensively for the past 6 years. Dont get the pod. If you lose a prop blade good look on replacing it underway., Sargaso, kelp, all sorts of other reason to not have one on the bottom . IMO build a bracket on on the transome for it to tip up and down. I Think your math is way off on generation based on experience.

Unless you have a lot of large ocean passages on the horizon IMNMO the money could be better spent.

I like mine but its an expensive piece of gear.

LD

[mvweebles]

Couple data points:

1. On another forum (TrawlerForum), a user installed two 110W panels. He showed a screenshot of production from his Victron MPPT and was averaging about 1.3 kwh/day, or around 100AH. He's in the PNW, panels are mounted the foredeck rails so no shading, and days are pretty long this time of day, but that's pretty good production. If I had to guess, panels probably produce around 1.0 kwh/day on average, 25% more in summer, 25% in winter.

2. Probably already discussed, but the OP's original energy budget estimate in his first post is likely woefully low - probably by half. From memory, he estimated 40AH/day at anchor; 100AH underway. See attached screenshot from a spreadsheet I made where I did a little research on the various components. Another good source for this type of budgeting sheet is the Pacific Cup website - scroll down and you will find two attachments.

I hope this is helpful -

Peter

Consumption 12V.jpg Views: 56 Size: 151.3 KB ID: 220462" style="margin: 2px" />

[carstenb]

Originally Posted by CassidyNZ

I suspect your numbers are wrong-way-round? 9A @ 220v = 1980W. 1980W @ 12.7v DC is about 156A.

My watermaker (for example) also draws about 9A on mains and pushes my 12v amps draw into the 150’s. I have to run a big alternator while the watermaker is running if I want prevent my batteries taking a beating after an hour or two.

Or maybe I need to re-educate myself?

I stand corrected. I should read 90 watts at 220VDC not 90 amps

[Statistical]

Originally Posted by Na Mara

Looked at it and adding a stay across the boat to stabilize the pole won’t interfere with anything. It is already very stable for and aft and has a strut to starboard. I think a stay to port will be sufficient to stabilize it with a big panel on it.

But what about the voltage on the x22? A 60 v panel charging 12 v batteries. Wouldn’t I be better with a 175W 12v panel from victron 1450mm x 650mm or similar? Or am I misunderstanding something basic here and the voltage is a non issue?

And on hscrugby’s more solar = more better I have to say that whilst I mostly agree, there must be a limit where shading makes the panels prohibitively expensive per watt and more hassle than they are worth.

Using 12V panels in parallel is one option but if you have a MPPT controller the panel voltage doesn't need to be 12V. It is going to take whatever you got and turn it into whatever is needed.

[carstenb]

Originally Posted by Na Mara

Re hscrugby. Interesting design. I had been thinking about something lower that stuck out the back more and that was entirely separate from the radar pole, but your version has some benefits to it.

1 shorter loa so easier parking and less likelihood of bumping the panels.

2 less shading from the radar on the panels.

The only issue I see with this plan is when the dinghy is hoisted it would block the view astern from the helm unless it was only hoisted halfway and secured against the push pit which is doable. Also, as I said previously, minimizing airdraft with the mast down is important so all this would need to be removable.

A lower setup on classic davits could be made permanent and stouter and would not block the view from the helm though it would stick out two foot further and be more prone to shading.

But thanks for the image. It helps me visualize what is possible.

Re Carstenb .

I take the point about light winds but that is partly why I want enough battery capacity to meet boat needs for 3-4 days rather than the standard two. Also you guys have already convinced me of the need for more solar. However, at 7-8 kn from astern Na Mara will be flying the asymmetric during daylight hours and making 3-4 kn. At that speed the watt and sea is producing about 3-4 amp, or between 70 and 100 Ah a day. That is not to be sniffed at. It’s about what 300 w of solar will give you..

Leftbrain. I will be putting a good monitor on this year. Unfortunately a regulator for the alternator will have to wait until I get hold of an alternator without an internal regulator.

First - many alternators (my electromax f.eks.) have an internal regulator that can be disconnected. But you should get a bigger one anyway.

Second, and here I'm not trying to make any claims about being a sailing guru - I'm from Denmark and have sailed the Baltic extensively. I think you will find that the swell pattern is very different in the Atlantic from the Baltic. If you set an asymmetrical in 7-8 winds and the boat is going 3-4 (our Sun Fast is a performance boat and can also do this) you'll find that the genakker will collapse as your boat is rolling and pitching.

At best, you'll not get a nice clean ride as you do in the Baltic. We've carried our genakker with us for over 4 years and 30,000nm and rarely unpacked it.

I suspect you will find that you will spend more time poled out (we do) in light winds and with the mainsail in the second reef.

But to each his own.

re the solar - As i noted previously, I suspect your usage numbers are VERY low. At anchor, we have a refrigerator and small freezer running and shut everything else down. We have LED lighting everywhere, we run our anchor alarm from an Ipad.

In the carribean and south pacific, our solar charges this up nicely - as someone once remarked, "Carsten, most people charge TO 12.7V not FROM 12.7V" When I get up in the morning, our meters show either 12.6 or 12.7. We do make ice every few days, play the radio as much as we please, sometimes watch a movie.

Even when we were sailing in Scotland, it all charged up nicely, but when it was terribly overcast - we did need to use the engine an hour a day - that also gave us hot water and if we did it in the morning, we could use our toaster

When sailing and we have everything going, we usually put our chartplotter to sleep, saving 4AH. We rarely use the radar unless sailing in fog - out on the open ocean we find little use for it - but we also always have someone in the cockpit, awake and on watch.

We have an wind vane">aries wind vane that we rig for long passages and take off when we are sailing coastal - it takes me about an hour to rig it and and an hour to dismount it.

[Breaking Waves]

I personally think this is pretty simple.

Install as much solar as you feel able, but do remember that in addition to other issues (esthetics, clutter, etc) it will degrade your sailing performance.

Get a serious alternator set-up - at least one big alternator, preferably two. And yes, you can mount them on that yanmar (I have specifically done it with that model)

Quite honestly I think you are going to be generating a decent fraction of your power by running the motor. That's not the end of the world given you say you have a quiet engine room. It is actually both highly reliable and decently effecient.

Skip the Watts and Sea. Their reliablity is not high.

Batteries . . . there are valid arguments to be made for essentially any point along the whole spectrum - from golf carts to Li. They all work, with different compromises. The important thing is to have your charging set-up (voltages and such) and drawdown points optimized for whatever you have.

And do maxmize the other side of the equation - consumption effeciencies, led lights, low power computers, etc.

As an aside - do make sure you have good spares redundancy for the autopilot. It is a lot more fatigue and use cycles than coastal sailing. Having to hand steer for long stretches sucks.

[Cheechako]

I think your at anchor calc is low. My usage at anchor tended to be 100-120 AH a day in the Caribe. Small <2 cu ft Fridge, anchor light and misc. I think most small fridges run 5-6 amps running or 3.5 or so average per hour. So that's 84 AH a day.

[carstenb]

A final note on your usage figures - I don't recall seeing a watermaker. There are several types, DC, AC and engine mounts.

WE have a DC spectra, uses about 8AH and makes 30 liters per hour. WE (my wife and I) use something like 40-50 liters per day (we take showers every day). Because we have 2 x 170 liter tanks, our pattern is generally to run the watermaker every 3 day or so for 5-6 hours. If we do laundry, then we run every second day.
We fill the in use tank and switch to the other tank.

So running the watermaker will add , say 50AH to your usage every 2-3 day - if you are like us.

Depending on how much water you use - this number could be a lot higher (probably not lower) so you definitely need to figure that into your equation.

[Na Mara]

Re carstenb

We carry 800l of water and the decks work great as rain catchers. We shower every third day or so and under sail it’s even less than that. We exclusively use merino wool and jeans clothing on board that can be worn for weeks without ponging. We won’t be needing a water maker.

My calculation for at anchor was low. I didn’t count on refrigeration in the tropics or heating in the North. 100Ah a day is more realistic. I always put the under sail figure at 200Ah a day and I still think that is about right. Basically we need to average 100Ah a day generation and 200Ah a day underway. A Watt and sea will do the 200Ah on its own at our average cruising speeds. If we don’t do that or similar I don’t know go how to meet that need reliably underway. Will 400W of solar plus maybe 400w of wind do it?

[carstenb]

Originally Posted by Na Mara

Re carstenb

We carry 800l of water and the decks work great as rain catchers. We shower every third day or so and under sail it’s even less than that. We exclusively use merino wool and jeans clothing on board that can be worn for weeks without ponging. We won’t be needing a water maker.

My calculation for at anchor was low. I didn’t count on refrigeration in the tropics or heating in the North. 100Ah a day is more realistic. I always put the under sail figure at 200Ah a day and I still think that is about right. Basically we need to average 100Ah a day generation and 200Ah a day underway. A Watt and sea will do the 200Ah on its own at our average cruising speeds. If we don’t do that or similar I don’t know go how to meet that need reliably underway. Will 400W of solar plus maybe 400w of wind do it?

well, not meaning to try to disabuse you - we spent two seasons in the caribbean and several times went more than 3 weeks without rain. I suggest you seriously work out a water usage calculation and then think some more about it.

re your generation calcs - you may get by with 100ah at anchor - but 200AH while sailing, unless you rig a windvane is low.

800L water sounds like a lot - but when you end up having to pay $.50 per liter in the caribbean for water - you'll regret not buying a watermaker.

just my two cents - we've never regretted our watermaker and we have yet to meet anyone in our travels that has said - Gee I wish I'd never bought a watermaker................... We met them that wished they bought a bigger one and we've met them that have regretted thinking they could do without one.

Water is heavy if you have to lug it several kilometers to your dinghy (assuming you can some)