Solar Installation on 37 Pilot House

We are considering a solar installation to keep the house batteries up while at anchor without the generator running periodically. Most of the pictures of the installations I can find look like the panels were installed on the pilot house roof, a panel either side of the hatch, although I have seen some boats mount them on or above the Bimini. I would be interested to know what others have done; mounting locations for the panels, total wattage of the panels, and do you feel it is / was worth while. Based on my calculations I think we need 600-800watts to hold the house loads and top off the house batteries on a daily basis assuming the sun is shining. Our two biggest house loads are the refrigerator and Starlink when it is running. Thanks in advance.

Different boat, but same basic idea. I have a raised pilothouse and have two 385 watt panels up there.
Huge difference. I still run at a deficit, but I can easily last three or more days before having to start an engine.
My main draws are the same as yours, but also add in microwave and coffee maker usage. Inverter is on 24/7 too.

I have a single 365W panel on the PH roof. It is what would fit. I have a collapsible Bimini over the flybridge and it would be much better if I replaced it with two large permanently mounted panels. I just didn't want to do that much work. Others have mounted panels on their deck rails, often on hinges, to give them more usable solar. This also works well, but not something I wanted to do as they would interfere with the kayaks and SUP boards that are hung there. My 365W panel has been enough to get my 780Ah AGM bank to full SOC during the summer after running the genset in the morning to get the bank from Bulk to absorb. For me it has been well worth the cost and effort and it is only 365W.

My thoughts are that some solar is great, more solar is better, and more solar is rarely "enough" solar. There are some that have been able to fully replace their daily Ah budget with solar, but it takes a big solar commitment in cost and real estate to accomplish it.

I have future plans for panels on our pilothouse roof. Same boat, so very similar issues.

That said, I heard a perspective that resonated with me. Diesel is cheap. The author said he can "replace the amp hours used in a day or two with a generator run for a couple dollars an hour and not fiddle with solar. And panels don't last much longer than batteries." Interesting. It has me thinking.

HeadedToTexas said:

I heard a perspective that resonated with me. Diesel is cheap. The author said he can "replace the amp hours used in a day or two with a generator run for a couple dollars an hour and not fiddle with solar. And panels don't last much longer than batteries." Interesting. It has me thinking.

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Everyone has to make their own decision based on how they use their boat, but I don't know anyone who has installed solar and got rid of it in favor of running their generator.

I figure the all-in costs of running my 6kw northern lights generator is roughly $10/hour. With that I can produce roughly 2kwh-3kwh of energy, about a days worth of my solar 800w panels.

Whether 800w is enough depends on a lot of different variables. Size of boat, how and where it's used, etc. What is undeniable is 800w of panels will out a helluva dent in your consumption. Depending on your latitude and season, 800w will produce 4/kwh/day. Nothing to sneeze at.

Peter

I have run solar on our 36 foot trawler for three years now, since first splash as our boat in 2022. Having enough solar wattage allows me to dock without having the added expenses of shore power. The real benefit for me is being on the hook for more than two weeks at a time and never having to run a genset at all. We have a medium size 12V fridge that runs off solar full time, and our two kilowatt inverter runs full time, mostly running house lights, TV's and computers. Of course, we're not able to run a coffee maker at the moment. (Our current coffee maker is a kettle boiling on our propane stove).


I do intend to add more power, as this year we experimented with a wind turbine, and found that its output is quite meager compared to a single solar panel on a cloudy day. Currently I have two 200 Watt panels, which are mounted to the rear of my Europa flybridge deck. I intend to add two more panels on the rear port and starboard rails, with a fold down mechanism. This summer, we were at a National Park dock one day, and ran into a Quebecker who had done the same thing. His novel clamping and fold up/down clamp was 3D printed. I thought that was kind of cool. I am also planning to add a third lithium battery to my house bank which currently runs lead-lithium. This is so we can have that much-desired electric coffee-maker running daily . It seems to work for us. At our current power needs. Anyway your mileage may vary depending on your power consumption needs.

We have 600 watts between the pilothouse and hardtop. If the sun shines we do not need the generator to keep the batteries charged. They are generally fully charged by 11:00 am every day. We have a 110 volt Summit refrigerator and run a electric coffee maker in the morning. Cooking is propane.

We only run the generator at anchor if we need hot water. I really should investigate a way to use the excess solar to heat the water.

When at our home dock we do not plug in unless we want AC.

Rob

I have 3.2 Kwp on my boat. 2000 Wp on a frame above the stern and on the dinghy deck, the other 1200 Wp is hanging on the side of the boat and I need to fold them up.
I have 1400 Ah of 24 V in lithium and during the summer, with all panels out I am able to recharge the batteries every day, however I still need to be careful how to discharge the batteries. Usually by 2 PM the batteries are full again, so then I run all the heavy equipment (washing machine, dish washer, water maker, boiler etc), which means by night I only need to cook, have the lights on and perhaps TV.
Now in autumn I cannot have the side panels extended, the frequent storms make that impossible, so I only have the 2000 Wp available and with diminished sun light I cannot recharge the batteries completely.
Luckily the alternators can finish the job when the engines are running, but when we stay in an anchorage for e.g. 1 week we need to run the generator every now and then to recharge the batteries.
Below the 2 options I have, first picture is with the side panels folded down and the second picture is with all the panels extended.
During summer, with all the panels extended, I normally get to about 2400 - 2600 W per hour, which is pretty good I think.

mvweebles said:

Everyone has to make their own decision based on how they use their boat, but I don't know anyone who has installed solar and got rid of it in favor of running their generator.

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I'm sure I would be in that group too. Like many things, including generators, they're great when they work well. Solar panels don't work forever, but probably plenty long enough for most (and at 0.5-0.8% loss per year, plenty long enough for me). Generators don't last forever either and cost a lot more to replace.

My read on the "diesel is cheap" opinion is that the guy found running his generator easy and deciding about, buying, configuring, installing, and managing a solar array difficult. It's not my opinion, but I see some logic in it.

2-225W “Marine Grade” panels installed. If I mounted them further aft another panel could have been mounted forward of the roof hatch for a total of 675 watts.
I run the generator 1 1/2 hrs morning & 1 1/2 hrs at bed time.

Loads are stock reefer freezer , large Dometic chest freezer 12v/120v, LED lights and Star link. With a 450ah house battery bank. No problems.

Nocanvas said:

I run the generator 1 1/2 hrs morning & 1 1/2 hrs at bed time.

Loads are stock reefer freezer , large Dometic chest freezer 12v/120v, LED lights and Star link. With a 450ah house battery bank. No problems.

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I guess that is the point of the "diesel is cheap" opinion. If you are going to run your generator twice a day anyway, why have solar? We have the same fridge/freezer and LED lights (plus coffee maker and water pump) loads, but no chest freezer or router. Our house bank is slightly bigger at 600 Ah, but we need just one 60 minute generator run per day with no solar. Has me thinking.

I have read advice saying to mount panels so that air flows beneath them for cooling, but I see plenty (most really) mounted directly on the deck. No matter how tight they are to the deck, the Mariner/Helmsman pilothouse roof is arched and the gaps will harbor spiders. Pros and cons of higher or lower mounts?

HeadedToTexas said:

I guess that is the point of the "diesel is cheap" opinion. If you are going to run your generator twice a day anyway, why have solar? We have the same fridge/freezer and LED lights (plus coffee maker and water pump) loads, but no chest freezer or router. Our house bank is slightly bigger at 600 Ah, but we need just one 60 minute generator run per day with no solar. Has me thinking.

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With a lead acid battery, one of the most important ways to keep it healthy is to make sure that you can get back to a 100% SOC. For many batteries, that can mean an Absorb charge phase of several hours at least.

@Nocanvas has a 450Ah battery bank. That isn't very large and he has some significant amp draws with the freezers and Starlink. Assuming he has an AGM, if he stays above 70% SOC (good for long term battery life), he would only have 135Ah of usable. 50% SOC would give him 225Ah of useable energy. Lifeline recommends a 3 hour absorb charge time for a discharge of 30-50%. It takes time in bulk to get to the absorb voltage then 3 hours at that voltage. Most of that that, the generator would be running at a very low load as the current gradually decreases during the absorb cycle. I keep hearing that it isn't good to run the generator at a very low load.

With solar, the generator can be used in the morning to do the bulk charging. Depending on the battery manufacturer, the max charge rate rate for a 450Ah AGM bank would be around 90amps. If the batteries were discharged down to 50%, it could take 1 1/2 hours to just get through the bulk phase. If they were discharged only to 70% SOC then maybe the bulk phase would be only 30 minutes. Once the absorb voltage is reached (and the sun is shining), the genset can be shut down and solar can finish out the absorb charging, getting the batteries to 100% SOC and saving house of generator run time on low load.

Anyway, that was my rational for installing only a modest amount of solar. Reducing low-load generator run-time was well worth the expense and hassle of installing the solar. Now, as I am switching to LiFePO4 batteries, I am not sure how that will change things. Getting the bank back to 100% isn't as critical as with lead acid. So even though the bank will be larger, it may result is less generator time and more Ahs available daily.

Interesting strategy. Your solar essentially handles the extended absorption phase.

I am guilty of trusting the timing of the bulk, absorption, and float phases to my Xantrex SW3000. Among its shortcomings is the lack of any sophisticated state of charge calculations. As with all of us, new batteries are in my future as the current set are from 2019. I figure on making a decision about solar as part of the battery upgrade.