Considering going solar

[Lollygag1]

My finicky generator is acting up again. Likely a fuel injector. Before I lay out more dough for this I am considering adding solar panels on the roof and an inverter. We never run the AC so just need juice for fridges and general usage. Any idea on what I am looking at for cost? Thoughts on solar vs generator?

 

[DavidM]

You can buy 100+ watt solar panels for about $1 per watt from Amazon or eBay. You will also need a solar charge controller for about $100. Wiring can be done for maybe $50 or as much as $100 if you use pre made up MC-4 cables and connectors. Maybe another $50 for L mounts and other hardware.

Or you can pay about $5 per watt for a professionally installed system.

There are several articles in the Library section (upper right icon on this screen) on this subject, some of which I wrote.

David

 

[AusCan]

It's impossible to answer your questions clearly without knowing how much power (in amp-hours) you use daily for "fridges and general usage".
Also - how much space do you have for mounting solar panels?
What is the house bank capacity? Do you have space to add additional batteries? How long your maximum expected stay at anchor?

 

[JLD]

It's impossible to answer your questions clearly without knowing how much power (in amp-hours) you use daily for "fridges and general usage".
Also - how much space do you have for mounting solar panels?
What is the house bank capacity? Do you have space to add additional batteries? How long your maximum expected stay at anchor?

First thing you need to do is an energy audit of your power needs. You can't plan for the number of panels or the size of the battery bank until you do this.

Are you going to be one night on the hook, or ten?

Will you run the engine at all while away from the docks?

Once you calculate how much power you actually need you can start the delicate balancing act between the number of solar panels and the number of batteries. If you don't have much space to mount panels, you might need a larger battery bank, although, again, it depends on how the boat will be used.

Inverter size is dependent on the power draw at any one time. A higher draw will require a larger (and more costlier) inverter.

Also, don't forget the federal tax credit for solar systems in your decision making. For 2020, the credit is 26% and drops to 22% for 2021.

Jim

 

[O C Diver]

While solar may be a good idea, you should do the energy audit to determine need, and then evaluate cruising style and your ability to recharge batteries off your engine alternator.

For me, energy consumption was reasonable and my cruising style was to generally move every other day. As a result a larger house bank and bigger alternator with multi stage external regulator allowed me to sit for a day and then completely recharge the bank on the next cruising day. There is no one right answer all the time, it's very dependent on on how you cruise.

Ted

 

[Jeff F]

How do you cook?

 

[rsn48]

You will be told to figure out your amperage as suggested above but if you are lazy, don't. The reason I say this is you can't have too much solar and the limiting factor is how much room you have for the solar panels. So if you can add 4 panels go for it, if you can add 6 panels go for it. Go for whatever your boat can hold without looking weird. A rough guestimate is 30 amps per panel per day.

Go google "Will Prouse" who is a young guy who has done significant research on solar & battery usage for RV's. He puts out decent "budget" recommendations he has researched. Also consider panels that have cosmetic blemishes but are other wise fine and work just as well as the unblemished panels. Will also informs you on what you need for a system.

Here is a video of a "local" guy and a member here but not very active who has installed panels on a sister boat to his that he is helping to fix up. He has a link to a reasonable deal on panels, controller, etc. all in one package at a decent price.

If you have leaded acid batteries, you might consider a swap to AGM's or Firefly batteries. Three Firefly batteries is equal to 6 flooded lead acid batteries., a 2 to 1 ratio. So if you have four flooded lead acid batteries the energy output of 4 Firefly replacements will be the equivalent of 8 FLA's. Combine this increase in available energy, combined with solar, combined with maybe adding or increasing the amperage of your alternator and the results is substantially significant increases in available energy for the boat on the hook.

Will Prouse:

Travels with Geordie:

 

[Ken E.]

Solar is great. I installed 2x350 watt panels a couple years ago and love them. Panels are not the lowest-cost alternative for charging batteries but there's no maintenance, fuel, noise or fumes. And they are always-on during daylight. Add as many as you have room for or can afford. You should also investigate adding bigger alternators to your main engines. If you can get by without a genset depends on the energy budget for your boat, as mentioned above.

 

[C lectric]

I will add that solar panels can simply mean the difference between a one day stay or multiple days away even though you may not be able to garner enough recharge to run the boat electrical fully on solar.

Many people take solar as needing enough to operate the boat entirely in that manner. Not the case. Any solar will help you last another day or two on the hook or at a powerless dock. Ours has 160 W total and it makes the difference between three days on batts. alone or 5 -6 days at which time we need to move regardless. Assuming the sun is out at all.

Take a serious look at what you are running and at what you can change inexpensively , well relatively so, to REDUCE load. Make sure the fridge is operating effectively, a muffin fan to exhaust waste heat from the fridge cavity will help. A good fan operated by the fridge to run only when the fridge runs uses approx. 150 to 180 mA ,use a ball bearing fan only, and it will make a big difference in how long the fridge runs and for how often. The additional fan power will more than make up for the fridge run time reduction.
Also shade the fridge externally depending upon how the fridge is mounted. Some fridges are totally inside, some have the backs to the salon exterior wall and sun hitting that wall can add a big heat load reducing the fridges ability to cool.

Led lighting for living area lighting will reduce power several times compared to incandescent of any type, even flourescents.

So take a look also at load reduction.

 

[Ken E.]

Further to C lectric's comments, you can do other things to reduce your electrical needs that work in concert with the panels. In my case, I changed to DC-only refrigeration and freezing, formerly having AC household-type appliances. This was expensive but has almost eliminated the need for running the genset, which I now see as being in more of a backup role. This is a huge improvement since we spend most of our time on the hook.

 

[ScottC]

In case it's of use...
I have 6x300W = 1800W of solar panels on the roof of my boat. Since I have no fly bridge, the panels cover the entire roof. They are fairly heavy glass panels, but one cannot walk on them. With these panels, at 55 degrees north latitude, I can see up to 22 amps from the panels coming into my 240Ah 48v battery, all while the refrigerator and 12v battery charger are running (via 230v on inverter). Solar panels are rated at maximum potential, implying the sun is directly overhead (90 degrees). This doesn't happen in Scandinavia. Maybe we have sun 45 degrees above the horizon during the summer where I am in southern Sweden. BUT...here the sun rises around 04:30 and sets around 22:00 in the summer. So, there are many hours available for charging, albeit at sub-optimal sun angles. Anyway, with net inflow of 6 amps in the early hours, ramping up to ~22 amps midday and then decreasing again, I can charge my 240Ah 48V battery (from "empty") in 2 "blue sky" days.


If your panels are photo-voltaic panels, then you can even expect respectable power production (i.e. ~50% reduction) on overcast days.


One interesting thing I've noticed since I moved my boat to the Mediterranean last year is that I don't generate any more power than I did in Scandinavia, even though the sun is at a much more optimal angle. This is most likely because the temperature is so much higher in the Mediterranean region and heat reduces the efficiency of the solar panels.


One last thing you should keep in mind... Your panels will probably be hooked up in series. ANYTHING causing a shadow to even a small part of one of the panels will knock your entire output down by 80-90%. So, no dinghy or inflatable on the panels. No fenders or fender boards on the panels. NOTHING. Leaves and bird poop must be regularly rinsed off, etc.


I apologize that this is was not a very scientific explanation, but it's definitely a "real world" explanation, which I hope you will find useful!

 

[ScottC]

I will add that with 6x300W panels, and 230v electric everything on board, we could last on the hook indefinitely (if I use the 230V air conditioner sparingly and manage the 230v hot water heater carefully).

 

[rsn48]

Since I will also be boating off season, frequently in our cloudy rainy PNW and coastal BC weather, I added a 210 Efoy (I was fortunate to find a used one, not easy to do, trust me) as back up during the summer days, and main supplement other than the alternator in the dreary season up here.

 

[socalrider]

One last thing you should keep in mind... Your panels will probably be hooked up in series. ANYTHING causing a shadow to even a small part of one of the panels will knock your entire output down by 80-90%. So, no dinghy or inflatable on the panels. No fenders or fender boards on the panels. NOTHING. Leaves and bird poop must be regularly rinsed off, etc.

This is good info. Question: Are there good ways to keep the birds off? I’m looking at solar on our flybridge Bimini - the normal bird repellers would all cast shadows. Wondering if it’d be possible to rig up something with fishing lines or the like to keep them from landing but low profile enough to avoid shading.

 

[ScottC]

I've seen all sorts of bird-deterrent contraptions over the years. Some are very wirey and small...and seem like they would not make a very constant shadow. Nevertheless, I have never bought one, because it's something I would have to take down almost every time I leave the harbor. They wouldn't stand up to much wind.


I try to avoid docking under trees (which often contain birds) because I want full sun to hit the panels. I also think twice about mooring in a harbor that's primarily a commercial fishing harbor. These attract huge numbers of sea gulls and all their droppings.


The bird poop isn't a huge problem, as it's easy to wash off with a telescopic brush connected to a hose. Nevertheless, it's a nuisance.

 

[Comodave]

This is good info. Question: Are there good ways to keep the birds off? I’m looking at solar on our flybridge Bimini - the normal bird repellers would all cast shadows. Wondering if it’d be possible to rig up something with fishing lines or the like to keep them from landing but low profile enough to avoid shading.

We found the spyder type of bird deterrent to work very well. Don’t know if the small wire would shut down solar or not. But it would be easy enough to do a test and find out.

 

[Rebel112r]

That’s 22 amps at what voltage from 6 x 300 watt panels. On a good day you should see 120 to 150 amps. I have seen 25 amps at 12 from a single 330 watt panel.

 

[mvweebles]

I found 36" square panels of 200w each so have four mounted. This will generate around 300AH of power equivalent per day on average (roughly 20% more in summer, 20% less in winter). I have matched to that a lithium bank of 6x100AH batteries. This is roughly twice my energy budget of around 135AH/day with a well insulated fridge, a separate and well insulated freezer, and normal stuff for a 36-foot trawler with a couple aboard. We can stay off grid virtually indefinitely as long as no AC running.

Solar part of the system is relatively cheap - probably under $1500 for the panels, wiring, controller, and a decent meter. Decent PSW inverter (which you probably already have) is around $1500. The expense is in the batteries. Battle Born 100AH are around $950/ea plus cabling and switches. Pretty easy to have $5k-$7k into the battery bank but it should last 10-years of solid use, maybe longer. All in all, cheaper than a generator, but still no AC. Another expense item is a decent alternator to charge underway with 3-stage regulator. Balmar 150A alternator will run close to $1k plus any mounting notifications needed.

Also, the above system is for long term use. If only for weekend use, you could halve this system and cost and still get decent benefit, though not off grid capability.

 

[ScottC]

We found the spyder type of bird deterrent to work very well. Don’t know if the small wire would shut down solar or not. But it would be easy enough to do a test and find out.

I don’t think a small, moving wire would make any noticeable difference, Comodave.

 

[socalrider]

I don’t think a small, moving wire would make any noticeable difference, Comodave.

We have the spider type on our Bimini currently. Sounds like it’d be worth a try just keeping it.

I’m going to take some measurements today and try to figure out the best way to retrofit the current structure. Rigid vs semi-flexible seems like the first decision to make.

 

[Comodave]

On a previous boat in San Diego we had a huge problem with bird poop on our bimini and sundeck tops. It was terrible. I tried the bird sweep type. The birds would just step over it as it came around and then we had a huge storm and the sweep got tilted over and literally cut a 180 degree arc in the $2000 bimini top. That wasn’t good. So a friend said he had good success with the spyder type. After replacing the bimini top for $2000, did I mention that, I mounted a bunch of the spyders and no more poop. The bimini on that boat was 12’ x14’ so it took a few of the spyders to cover it, but the birds didn’t like the spyders so it was great.

 

[foggysail]

In case it's of use...
I have 6x300W = 1800W of solar panels on the roof of my boat. Since I have no fly bridge, the panels cover the entire roof. They are fairly heavy glass panels, but one cannot walk on them. With these panels, at 55 degrees north latitude, I can see up to 22 amps from the panels coming into my 240Ah 48v battery, all while the refrigerator and 12v battery charger are running (via 230v on inverter). Solar panels are rated at maximum potential, implying the sun is directly overhead (90 degrees). This doesn't happen in Scandinavia. Maybe we have sun 45 degrees above the horizon during the summer where I am in southern Sweden. BUT...here the sun rises around 04:30 and sets around 22:00 in the summer. So, there are many hours available for charging, albeit at sub-optimal sun angles. Anyway, with net inflow of 6 amps in the early hours, ramping up to ~22 amps midday and then decreasing again, I can charge my 240Ah 48V battery (from "empty") in 2 "blue sky" days.




If your panels are photo-voltaic panels, then you can even expect respectable power production (i.e. ~50% reduction) on overcast days.


One interesting thing I've noticed since I moved my boat to the Mediterranean last year is that I don't generate any more power than I did in Scandinavia, even though the sun is at a much more optimal angle. This is most likely because the temperature is so much higher in the Mediterranean region and heat reduces the efficiency of the solar panels.


One last thing you should keep in mind... Your panels will probably be hooked up in series. ANYTHING causing a shadow to even a small part of one of the panels will knock your entire output down by 80-90%. So, no dinghy or inflatable on the panels. No fenders or fender boards on the panels. NOTHING. Leaves and bird poop must be regularly rinsed off, etc.


I apologize that this is was not a very scientific explanation, but it's definitely a "real world" explanation, which I hope you will find useful!

My 4 each 295 watt panels are connected with 2 parallel pairs connected in series. I can assure you that their output DOES NOT get killed with shade. Yes, the Vmp will be lower and the Victron controller adjusts to that change. Operating panels in series offers benefits. The higher output voltage relaxes the wire sizes needed from panels to the controller and for me that is a huge benefit.

 

[firehoser75]

Some good advice so far. I have never heard anyone who went solar say, "I put too much capability into my system. I wish I had less".
First thing, do not scrimp on your solar controller. Better yet, a separate controller for each panel if shading is going to be a problem. Anyway, go with a MPPT style controller, not a PWM unit. They cost more, but are definitely the way to go.
Flexible vs hard. If you can, hard panels are the better way to go, but sometimes due to mounting options, flexible may be the only way to make it work. Panels do not work as well if there is not "air flow" under them. Cooling is important as our friend from Sweden alluded.
Real world stuff:
I have 2 fairly large (285 watt each) panels on my pilothouse roof using one Morningstar MPPT controller. We also have a generator on board, and have a 650 amp hour battery bank. Our normal electrical usage is all 12 volt. Fridge, separate freezer, lights, recharging things like IPads, phones, etc., some TV/DVD player, sound system, and some electronics such as anchor alarm.
Other than on days with no sun (a few times thick fog til 2-3 PM), we reach back to full 100% recharge every day. I only run the generator if we want hot water. On days with fog, I run the generator for an hour in the morning, and let the solar do it's best from there. We can easily stay at anchor til our holding tank is full even during cloudy weather.

Solar is noiseless and requires little attention or maintenance. As others have stated, your system does not have to get you fully back to 100% by itself to be worthwhile. Just reducing generator time, or extending how long you can stay in one location is worthwhile. For the freedom and options it will give you, I highly recommend going that route. It is a larger "up side" if you are the type that likes to stay in one spot for a few days rather than moving regularly.

If you have to go to flexible panels, do not go cheap. Do some research. Some brands do not hold up well or put out the rated power.

Good luck.

 

[Comodave]

What type of fuse or circuit breaker do you use on solar panels? Where did you mount them? Close to the panels or close to the controller?

 

[Ken E.]

What type of fuse or circuit breaker do you use on solar panels? Where did you mount them? Close to the panels or close to the controller?

One breaker between the panels and the controller (I put mine at the controller for ease of access) and one close to the batteries.

 

[Comodave]

Anything special as to fuse?

 

[Ken E.]

My MPPT controller is 40 amp. I believe they are 40 amp breakers as spec'd by the controller owners' manual. I have seen 40 amps coming into the controller from the panels and it hasn't tripped. I used Blue Seas flush-mounted breakers.

 

[Comodave]

I meant special like ANL? Or just a regular breaker/fuse.

 

[Ken E.]

Mine are just garden variety circuit breakers.

 

[Comodave]

Ok, thanks.