Why you might consider still keeping your generator

[Chotu]

Originally Posted by s/v Jedi

No, I am in the Abacos now and it has been horrible weather with completely overcast skies and rain all the time.

Edit: here is a graph… only 6-7 hours of reasonable solar production.

Oh, Abacos! Congratulations on being done the boatyard work and out enjoying the boat. well hopefully that weather pattern changes for you down there. You are not there to sit around in the rain I am sure. Lots of storms this year.

there is nothing actually wrong with my solar. It’s simply the lack of sunshine getting to it. It’s just the solar-terrestrial line up and the weather patterns. Darkness at a level i think you are choosing to forget. ha ha ha.

but even if you look at your data, you are getting six hours of reasonable solar production out of a 12 hour day. I have an eight hour day. Just extending the ratio, I would get 4 hours of reasonable production. however, while your sunshine is coming from directly overhead, mine comes from low in the horizon. So I actually never get the four hours of reasonable production. I get half or less of the production due to the incident angle. so figure about an equivalent of two or less hours of reasonable production. I never get actual reasonable production. But now cover the sky with clouds and fog. And you end up where I was. 20 amp hours for 2 very dark hours of actual production.

As the days grow longer and the storms grow less when spring starts, I’ll be back to normal. And then later I will surpass you unless you come up here. I will be looking at 15 or 16 hours of Sunshine in a day near the summer solstice.

I was getting normal production up until around Thanksgiving I believe. November. So on the other side of things I should be getting normal production again in February or March, barring all of the storms that come through at that time typically. Assuming sunny settled weather.

I have been dropping my worst days in this thread just because they are so interesting. I’ll take a look on a bright sunny day with no clouds and post that up next time.

[sailingharry]

Originally Posted by s/v Jedi

No, I am in the Abacos now and it has been horrible weather with completely overcast skies and rain all the time.

Edit: here is a graph… only 6-7 hours of reasonable solar production.

What a coincidence. I was laying in bed this morning looking out at the rain, and figured I should email Jedi and ask how his fancy new solar array was working... and then realized that December is NOT the time to ask someone that! And here this morning, he answered the question!

[s/v Jedi]

Originally Posted by Chotu

Oh, Abacos! Congratulations on being done the boatyard work and out enjoying the boat. well hopefully that weather pattern changes for you down there. You are not there to sit around in the rain I am sure. Lots of storms this year.

there is nothing actually wrong with my solar. It’s simply the lack of sunshine getting to it. It’s just the solar-terrestrial line up and the weather patterns. Darkness at a level i think you are choosing to forget. ha ha ha.

but even if you look at your data, you are getting six hours of reasonable solar production out of a 12 hour day. I have an eight hour day. Just extending the ratio, I would get 4 hours of reasonable production. however, while your sunshine is coming from directly overhead, mine comes from low in the horizon. So I actually never get the four hours of reasonable production. I get half or less of the production due to the incident angle. so figure about an equivalent of two or less hours of reasonable production. I never get actual reasonable production. But now cover the sky with clouds and fog. And you end up where I was. 20 amp hours for 2 very dark hours of actual production.

As the days grow longer and the storms grow less when spring starts, I’ll be back to normal. And then later I will surpass you unless you come up here. I will be looking at 15 or 16 hours of Sunshine in a day near the summer solstice.

I was getting normal production up until around Thanksgiving I believe. November. So on the other side of things I should be getting normal production again in February or March, barring all of the storms that come through at that time typically. Assuming sunny settled weather.

I have been dropping my worst days in this thread just because they are so interesting. I’ll take a look on a bright sunny day with no clouds and post that up next time.

Not sure where you get the idea… we only have 9 hour days and the sun angle is very low. It is high in the southern hemisphere, not here…. we’re far north of the tropics even. In May, our production will be double.

I don’t know how many kW you have installed but I think something is wrong if you only get 20Ah.

[sailorboy1]

Originally Posted by Chotu

leaning heavily on the generator this whole time, I have used 1/8 of a tank of gasoline. I have 3 tanks. Lasting forever!!

unless you have a magic generator those must be large tanks

[Chotu]

Originally Posted by sailorboy1

unless you have a magic generator those must be large tanks

3 tanks at 50 gallons a piece

LiFePO4 means 3 hour genset run every 3 days approximately, if i’m on the boat using heat. i’ve been gone a lot lately (snowboarding, christmas)

Generator (just one of them running - there are two for air conditioning purposes) uses about a gallon each 3hr charging cycle. so 10 gallons of gasoline in a month of full time living and heating.

It’s weird how people can’t picture or understand things different from their own boat and environment.

[Chotu]

Originally Posted by s/v Jedi

Not sure where you get the idea… we only have 9 hour days and the sun angle is very low. It is high in the southern hemisphere, not here…. we’re far north of the tropics even. In May, our production will be double.

I don’t know how many kW you have installed but I think something is wrong if you only get 20Ah.

I did mention how many watts (1500) AND how much charging capacity 120A max. but i can convert to kW for you. 1.5. ha ha ha.

Joking with you.

there’s absolutely nothing wrong with my solar installation. You’re just not picturing the situation properly. Still. For unknown reasons.

I guess a lot of people just don’t have experience using solar in these conditions, so it’s difficult for people to imagine i guess.

also you are at 10.5 hours of daylight today. 12 is a pretty common number of daylight hours in Florida for the majority of the year. That’s why I used it. this time of year it’s a bit shorter i see, but mostly it’s about 12 hours a day in Florida. 6AM to 6PM or so.

[RaymondR]

I have a highly emotive aversion to both main engine battery charging and house battery voltages below about 12.4 and in consequence installed a gas powered engine driven pair of alternators in a fairly large aluminium enclosure just ahead of the mast on my IP40.

A couple of months ago I decided to remove it as I had not had to use it for about eighteen months and, nature being the perverse bastard it is at times, a couple of weeks later experienced about a week of overcast days so am now in the process of reinstalling it under the helmsman's seat in the cockpit (for those of you about to leap in with the "just buy a Honda inverter generator and use your battery charger" I've already been through that experiment and found it wanting".

Whilst solar is the best solution for a live aboard you are going to have a need for an alternative charge system for the periods when nature becomes a recalcitrant bastard.

[sailingharry]

To add to the sparring between Choto and Jedi, my earlier post (#35) shows that according to government resources, in December, Mt Desert Island has 40% the insolation of Key West. Conversationally, that's where Chotu and Jedi are.


Curiously, even in June, the longer day-length in Maine doesn't overcome the higher sun angle in Key West, with Mt Desert Island topping out at only 92% of Key West.

[Chotu]

Originally Posted by sailingharry

To add to the sparring between Choto and Jedi, my earlier post (#35) shows that according to government resources, in December, Mt Desert Island has 40% the insolation of Key West. Conversationally, that's where Chotu and Jedi are.


Curiously, even in June, the longer day-length in Maine doesn't overcome the higher sun angle in Key West, with Mt Desert Island topping out at only 92% of Key West.

exactly. And what it doesn’t take into consideration is the weather.

it’s always Sunny in Key West. At least most of the time. It’s always gray and cloudy here. With fog. Snow and rain. That’s winter up here. that is the huge variable that I didn’t even consider either when I came up. I fully admit it. I forgot to consider that it’s often cloudy or gray or stormy here in the winter. That sunny days are fairly rare.

that’s why this whole situation is so surprising. And that’s why you should not get rid of a generator if you are going to stay up here over the winter. it’s 40% if all things were equal but they aren’t. The weather patterns are very different.

Raymond: that is a pretty interesting set up and years ago I had dreamed of building one of those myself. Do you have pictures? How much output are you getting from that?


Edit: that’s really interesting about the longer daylight not overcoming the sun angle in June. It does in August however, doesn’t it? But it gets even more interesting actually. Because it’s not very hot far north, the refrigeration demand on the boat which is actually the highest power consumption on most boats, is fairly low. so the demand also goes way down when you go north. Until you turn on heaters. Then your demand goes way way up because your heaters are fighting your refrigerators. the Low refrigerator demand is also true in the summer months. So you come out way ahead on power each day because your demands are low but there’s a lot of sun.

in the winter it’s a double whammy. You turn on three diesel heaters to heat a Catamaran, Which takes some power, but that makes your refrigerator and freezer turn on a lot more often. lose lose. Then there is no sun. It goes pretty quickly.

when I leave the boat, with the heaters off, the tiny little bit of solar I am getting is actually enough. The refrigerators barely turn on at all. There are no diesel heaters on. There is no power consumption. So it all remains in balance. Sort of. if there are a couple of sunny days a week, this is enough to keep the boat in balance. If however, each day is cloudy or raining or whatever, I can leave the boat for about four or five days before it’s down.

I went away for a week around my family Christmas time, and I came back to some weird battery behavior. I think it had gone down and got a low-voltage shut off while I was gone. however, none of the ice in the freezer or refrigerator melted, so it must have been very brief.

[s/v Jedi]

Originally Posted by sailingharry

To add to the sparring between Choto and Jedi, my earlier post (#35) shows that according to government resources, in December, Mt Desert Island has 40% the insolation of Key West. Conversationally, that's where Chotu and Jedi are.


Curiously, even in June, the longer day-length in Maine doesn't overcome the higher sun angle in Key West, with Mt Desert Island topping out at only 92% of Key West.

Exactly. This means he should get 1kWh per day. Clearly something is wrong.

It’s not about the weather, we had the worst weather out here. When the sun comes through, like today, I do 4kWh instead of 2.

[noelex 77]

Originally Posted by Chotu

Posting my results since very few people have done this. Possibly no one in a catamaran

I think it is important to emphasise that solar production is very dependent on conditions. Managining comfortably without a generator is not practical for all vessels and it is obviously not working for you, but it is a mistake to extend this conclusion to cover all vessels.

You are posting solar outputs that occur at your latitude in winter, but they are not average (unless, as Jedi suggests, there is a problem with your system) . The battery bank will average out the poor days.

I have spent a few winters in significantly more northerly latitudes than your current location without a generator and have been comfortable. For those designing their yacht systems this it is not an impossible goal, but it does require careful system design.

[sailorboy1]

In the past 30 days there have been numerous days that my 640W only did about 30ah 12V here in Jacksonville FL. Even in the winters I have spend in the Florida Keys and Bahamas there was a noticeable reduction of daily output till around April.

[s/v Jedi]

Here’s yesterday’s solar irradiance forecast for my location.

[sailingharry]

Originally Posted by s/v Jedi

Here’s yesterday’s solar irradiance forecast for my location.

So, that shows a max of about 550 W/M2. Using typical panel efficiencies of about 20%, works out to 100W/M2. A general rule of thumb is that a panel is good for 200W/M2 (rated power at rated conditions), so right now you are expecting 1/2 power. Throw on a bit more for the sun being at what, 40 degrees away from overhead? (It's about 20S, you are at 20N). COS 45 is about .7, so that gets you down to about 35% of ideal power.


I'm not actually trying to make a point here. I'm more interested in knowing if my assumptions and calculations line up with your current output -- what % of rated power are you seeing at noon?


EDIT: I love it when the math works! I just read up thread. You have 1.65kW of panels deployed. Your best hour was around 0.5kW. 0.5/1.65=30%. Gee, science works! LOL

[s/v Jedi]

Originally Posted by sailingharry

So, that shows a max of about 550 W/M2. Using typical panel efficiencies of about 20%, works out to 100W/M2. A general rule of thumb is that a panel is good for 200W/M2 (rated power at rated conditions), so right now you are expecting 1/2 power. Throw on a bit more for the sun being at what, 40 degrees away from overhead? (It's about 20S, you are at 20N). COS 45 is about .7, so that gets you down to about 35% of ideal power.

I'm not actually trying to make a point here. I'm more interested in knowing if my assumptions and calculations line up with your current output -- what % of rated power are you seeing at noon?

EDIT: I love it when the math works! I just read up thread. You have 1.65kW of panels deployed. Your best hour was around 0.5kW. 0.5/1.65=30%. Gee, science works! LOL

and that demonstrates that everything is working like it should. Reality must somewhat match theory.