Any advice on solar panels for boats?

[MAFWeiss]

It is five and a half years since I last posted on the forum, but I thought it worth revisiting to seek assistance on the question of solar panels for motor boats. Given the incredible increase in the cost of electricity in the southern Italian marinas that I frequent, on average a 250% increase, this has meant that in my home berth when we are away from the boat but connected to shore power to just keep the batteries and anti-corrosion system running, the monthly cost has leapt from around 100 euros to nearly around 250 euros a month. And when on board in the marina in summer, with the air-con and ovens in use, the daily cost of being on board has gone from around 55 euros to well over a 100 euros a day. And in marinas that used to offer free power, they now of course charge also, and since in high summer the cost of a berth for my 21m boat is expensive enough as it is, the additional cost of power is becoming something of a concern. So we already are now spending even more nights at anchor than we usually do, but therefore needing to run the noisy generator for the aircon since the heat and humidity makes sleeping without it difficult.

So I was wondering if it would be worth looking into flexible (movable) solar panels that could be laid out over the bow seating area, and up over the windscreen if neccessary, during the long periods when not on board in our home berth to at least keep the batteries fully operational, and then even also the fridge and freezer going, without the need to be connected to shore power. And if then they could be rolled up and stored ashore in our storage unit whilst we we are away cruising. Any advice gratefully received!

 

[sailorman]

im following with interest as i have used an aeroged for 40 yrs; nxt boat being a mobo will be solar panels

 

[dunedin]

Perhaps try a post on the Practical Boat Owner forum - lots of experience of solar on sailing yachts. Indeed solar is pretty much mainstream, and wind generators largely abandoned.
I would have thought a motor boat would have plenty of cabin deck space to permanently site semi-flexible panels.
We have two 50W Photonics Universe semi-flexible panels, plus a third on a roving cable, plus a Victron MPPT solar controller. Fitted 6 years ago and worked well, keeping batteries charged and runs fridge 24x7 when on board.
Panels have been seriously mistreated but worked fine - now considering replacing panels with new ones.

 

[LiftyK]

My experience:

Rigid panels
+ longer lasting and more reliable than flexible panels
- heavy - not easy to get out on demand

Flexible panels
+ easier to move around, face the sun and take in to prevent theft
- less durable

My current favourite is a folding set, using flexible panels on a lightweight substrate.
12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine

 

[dunedin]

My experience:

Rigid panels
+ longer lasting and more reliable than flexible panels
- heavy - not easy to get out on demand

Flexible panels
+ easier to move around, face the sun and take in to prevent theft
- less durable

My current favourite is a folding set, using flexible panels on a lightweight substrate.
12V solar panels charging kits for caravans, motorhomes, boats, yachts, marine

Re the “less durable” of semi flexible panels, it may depend on make - but ours have lasted 6 years, and as about £300 for two 50W panels happy to replace every 6 years or so.
The 100W rigid panel we got at the same time is lasting well - but mainly because it has been in the garage for the last 5 years unused, as too bulky, heavy and sharp edged. Ditched and replaced by another semi-flexible after 6 months. Might be different if permanently mounted on a rigid arch or similar.

 

[vas]

size of mobo, amps demand, f/b/open/h/t, size of possible area to fit, etc would help in suggesting.
if for example you plan on having a full size fridge/freezer running 24/7 on a 50+ ft mobo with a 3kw inverter, plus alarm/charger/etc don't expect to run them from a couple of flex 200w panels...
so give a bit more info

PS. flex panels don't really last much under the med sun, they seem to be fine in the UK. Only v.expensive ones seem to survive for 5+ seasons down here, budget ones delaminate/milk fairly quickly

 

[MAFWeiss]

size of mobo, amps demand, f/b/open/h/t, size of possible area to fit, etc would help in suggesting.
if for example you plan on having a full size fridge/freezer running 24/7 on a 50+ ft mobo with a 3kw inverter, plus alarm/charger/etc don't expect to run them from a couple of flex 200w panels...
so give a bit more info

PS. flex panels don't really last much under the med sun, they seem to be fine in the UK. Only v.expensive ones seem to survive for 5+ seasons down here, budget ones delaminate/milk fairly quickly

Thank you VAS and and others for your replies. And yes, sorry I should really provide a bit more info as you have suggested. My boat is a 21m LOA 2016 Prestige 680 Flybridge. The space available that could be used to lay the panels over would be primarily the front bow sunbed area which measures roughly 3.5m x 2.5m. The length could be further extended by covering also upwards across the windscreen by another 1.5m or so. So in square metres of space available, this would be from 8.75 sq.m to 12.5 sq.m. The very least I am looking to keep powered would be to the batteries and the anti-corrosion system, and the maximum would be also the main galley 61w fridge freezer. Given what I regularly spend running and keeping the boat to highest possible standard, I would not be looking to buy budget, but to invest as far as possible in longevity and the best possible products.

 

[vas]

I vaguely remembered it was a big boat (hence my asking...)
I'd carefully look at what Mike (Hurricane) has done on his P67. Used the "eyebrows" for four semi-flex panels.
laying and retrieving flex panels on the sunpad area sounds complicated, easily nicked or lifted by the wind, problematic in terms of getting decent IPa lot glands to pass the current across to the inside, ripping a fair amount of upholstery to lead them in and down to the e/r or wherever the batteries are. Doesn't sound v.easy, clean or even visually appealing tbh.

Mind I'm talking about a permanent installation here, not a temp thing. cannot think how a temp install would look good on such a boat!

V.

 

[jrudge]

I have some sympathy. In Palma electric use to cost close on e100 per day some 4 years ago.

What it costs now does not bear thinking about

It is the only place where I turned off ac when I left the boat. In cala dor it is included and the a. Is on for months !

 

[Bigplumbs]

The Dokio ones are quite good. See my little video

 

[Bouba]

I put my solar panel on a rail frame that can be tilted to face the rays or folded flat...the flybridge rails are the best place because they won’t interfere with neighbors when Med berthing

 

[MapisM]

Given the incredible increase in the cost of electricity in the southern Italian marinas that I frequent, on average a 250% increase, this has meant that in my home berth when we are away from the boat but connected to shore power to just keep the batteries and anti-corrosion system running, the monthly cost has leapt from around 100 euros to nearly around 250 euros a month.

The 250% increase is high, but not crazy in the present environment.
It's the previous €100/day that sounds already OTT.
What was/is the cost per kWh that they were/are charging?
In my marina, €100 used to buy 500kWh last year - a consumption which is beyond a joke, for a sleeping boat.
And this year, €250 would buy 600kWh (since the unit cost increse has been "only" 210%), which is even more absurd.

For comparison, when I'm not onboard, even now after the cost increase I'm in the €1/day ballpark.
Ok, my 56' boat is smaller than yours, but I don't think my battery charger (100A max) needs much less current than than yours, when constantly in float mode. Also because we leave one 24V fridge on - the smaller one, and of course staying always close its compressor runs pretty rarely, but it's still an additional consumption anyhow.
Besides, I have an AC de-humidifier constantly cycling, plus the router and a couple of cameras.
Overall, this translates into a ballpark consumption somewhere between 70 and 80 kWh/month.
I can't even imagine how to use 500kWh/month if I wanted to, let alone 600!

So, I think that either you are charged some completely OTT prices, or your boat is using way too much electricity, for reasons that escape me.
Do you have a way to check the real time absorption onboard, turning on/off each device?
And what on Earth is the anti-corrosion system?!?

 

[MAFWeiss]

What was/is the cost per kWh that they were/are charging?

The cost per Kw/h was € 0.33, it is now €0.84 including VAT.

Overall, this translates into a ballpark consumption somewhere between 70 and 80 kWh/month.
I can't even imagine how to use 500kWh/month if I wanted to, let alone 600!

Having just checked with the marina, when we are not on board we are currently consuming around 9 Kw per day, which equates to around €7.50, up from around €3 per day pre the energy crisis.

So, I think that either you are charged some completely OTT prices, or your boat is using way too much electricity, for reasons that escape me.
Do you have a way to check the real time absorption onboard, turning on/off each device?
And what on Earth is the anti-corrosion system?!? See below and, if you are still bemused, google it.

As previously stated, whilst we are away from the boat, we only have the house electrics cable attached and live to keep the batteries fully charged, and the Volvo Penta ACP (Anti Corrosion Protection) system fully charged too. All other electrics on the boat are switched off at the main electrical control panel.

I will now check with Prestige to see if the daily consumption of around 9 Kw when everything on the boat is switched off is normal and to be expected, but maybe by the sounds of it, based in what you say you consume when away from your boat, there is something eating up power unnecessarily somewhere!

 

[terranova]

Hi MAFWeiss

Our boat, although a slightly smaller 62ft Princess uses a similar amount of power to yours whilst ‘at rest’. We kept the boat in Sardinia for the first 3 years of its life, where in Marina di Olbia electricity is included in the berthing price. Thus, we didn’t notice how much electricity we were consuming.

This Summer we moved the boat to Marina di Loano (mainland Italy) where electricity is charged separately - the current price is 0.77 per KWh (it was 0.35 a few months earlier when I agreed the annual contract).

We were using around around 20KWh per day with ‘normal’ things running in September - a bit of air con, 2 fridges, freezer water heater, coffee machine etc. At around 16 euros per day, I thought there was a mistake, but assumed that the air con was the biggest draw. As the weather grew cooler in October, we stopped using the air con and switched the water heater off when we didn’t need not water, but our consumption was still relatively high at around 10KWh per day.

I asked the Marina to send an electrician over to check things out. He installed a separate meter to double check the dock meter’s accuracy (it was spot on) and then we powered things down on the boat whilst looking at the meter to see what was consuming the power. Turns out that the battery charger was by far the biggest draw ; I can’t recall the exact fridge consumption but they matched the draw when I checked the manuals.

We have 6 x 115Ah service batteries, but they weren’t really doing much apart from powering a couple of fridges, an hour of TV per day and a coffee machine twice per day. I was amazed by this and have asked for an electrician to check all of my systems over the Winter period.

As a side note, Marina di Loano does not allow shore power to be connected whilst you are away from the boat so ours is currently disconnected. They told me that this is law across Italy, which I find strange although I only have experience of keeping the boat in Sardinia for long periods. We have a technician on board weekly and he connects to shore power for 5-6 hours to keep the batteries charged up (everything else is turned off so there should be no power being drawn from elsewhere)

I am told that many, if not most, marinas on mainland Italy charge separately for electricity although the unit price is very high compared with France and Spain. Apparently electricity prices in Italy have jumped more than other countries as they do not have nuclear power stations. I’m not sure if this is true, but the high electricity costs (and water too, although this isn’t expensive) in addition to the standard annual berthing fee is certainly a gripe as I’ve never experienced it before.




Hi MapisM

I think the anti corrosion protection system referred to is a Galvanic Isolator - we are having one fitted this Winter too.

 

[MAFWeiss]

Thank you Terranova for your post. Is the cost of 0.77 euros you quoted inc tax? We have ten x 140ah Exide Dual AGM 1200 batteries, so by the sound of it the consumption of 10kw a day may well just simply be down to the battery charger, but I will try get more advice on that.

 

[Hurricane]

In answer to the OP.

Our Princess 67 is about the same size as your boat.
Without shore power and without using the Air Conditioning (i.e. at anchor).
Our boat consumes about 5Kw hours per day (Vas - I think I have the units correct this time!! )
Thats running an "under counter" fridge for drinks and a full height fridge freezer along with all the usual boat electronics (not navigation/radar though)
We have a small cool box on the flybridge but at anchor, we usually leave that off.
So, thats 5Kw hours of electricity being used per day - in domestic (home) terms, thats 5 units per day (No A/C)
I fitted 4x150 watt semi flexible solar panels to our flybridge "eyebrow" - see in this pic:-



On a good day - and I mean on a GOOD day (in the middle of the Med summer) - we can harvest a little under 3Kw hours (3 domestic units) per day.
My point is that our 600w of solar panels isn't enough to keep your fridges running whilst you are away.

OK, so you are suggesting that you should cover the fore deck with removable panels whilst you are away.
Do you really want that extra hassle just before you leave the boat?
I find it hard enough setting the boat up when I leave - let alone fitting temporary solar panels.
What is the weather like in your marina during the winter months - I seems to remember that you are based in Marina d'Arechi.
Do they get winds strong enough to damage a temporary solar panel setup ?
In order to be any more use than our panels, you would need a large surface area which would behave like sails in strong winds.
Personally, I wouldn't want to leave a boat with that kind of worry.

Also, how much do you think it would cost to fit such an array pf panels.
Remember, you would need quite large cables to reduce the electrical losses between the panels and your batteries.
My cable sizes weren't insignificant.
Don't forget that you will also need a suitable size solar controller and safety switch gear.
Remember, there is power coming from the panels that needs to be connected safely.
You can't just run cables "ad lib" across the decks.
So you would, inevitably, end up with a semi permanent installation.

I think what I'm saying is that, if you keep the fridges running, whilst away the idea is a "non starter".
Couple that with the life expectancy of the fully flexible panels being 4 or 5 years maximum.
Don't you think that it would be better to spend the money that the panels would cost on paying for the shore power?

Alternatively, turn off the fridges and all your DC systems whilst away (I do).
Then, a small set of portable panels could be used to keep the batteries "topped up" with a floating charge.
(My 600w can do that easily)
But, then again, if you shut all your DC systems down and switch off the fridges, your electricity bill for shore power would be reduced anyway.

Nice idea but not a practical solution - IMHO

BTW - I am currently replacing my ice maker.
I have recently run some tests on the new replacement.
If left on 24/7, I reckon an ice maker will consume about 1.2Kw hours (1.2 domestic units) per day
We usually make a stack of ice, switch it off and keep the ice in the freezer.
I have always felt that these devices are hungry on the electricity - after these recent tests, I am now sure.
I will be sticking to making our ice in batches and keeping it in the freezer.
Don't forget that my figures above exclude any ice makers - so thats another Kw hours (1.2 domestic units) per day per ice maker to add to the ships electrical load.

One final point that might be useful to some people.
About 4 years ago, I replaced our main upright galley marine fridge - supplied by (Dometic).
I replaced it with a modern Bosch high efficiency domestic unit.
The difference is amazing - the domestic unit consumes about half of the energy that the marine fridge consumes.
I put it down to better insulation - but the domestic fridge only incorporates a single compressor - the marine unit had one for the fridge and one for the freezer.

 

[MapisM]

Hi MapisM
I think the anti corrosion protection system referred to is a Galvanic Isolator - we are having one fitted this Winter too.

There should be no current absorption in a passive galvanic isolator, AFAIK.
My guess is that the ACP thing mentioned by MAFWeiss is somewhat "active", instead - but I never came across that bit of kit.

Regardless, you are correct in suggesting to turn on/off every electrical switch and see how the Amp-meter reacts.
I'd expect it to be present in MAFWeiss electrical panel, but missing that, a multimeter clamp costs peanuts these days.

Ref. your marina asking to disconnect shore power when the boat is unattended, it's not the first time I hear of such requirement, but I really don't think it's triggered by any Italian law.
Much more likely a Marina choice, possibly oriented to minimize the risk of an onboard fire, that could also spread to other boats due to an inevitably more delayed reaction compared to a boat where someone is onboard.
And saying that it's a legal requirement leaves less room for debating that...!

 

[Portofino]

There should be no current absorption in a passive galvanic isolator, AFAIK.
My guess is that the ACP thing mentioned by MAFWeiss is somewhat "active", instead - but I never came across that bit of kit.

Regardless, you are correct in suggesting to turn on/off every electrical switch and see how the Amp-meter reacts.
I'd expect it to be present in MAFWeiss electrical panel, but missing that, a multimeter clamp costs peanuts these days.

Ref. your marina asking to disconnect shore power when the boat is unattended, it's not the first time I hear of such requirement, but I really don't think it's triggered by any Italian law.
Much more likely a Marina choice, possibly oriented to minimize the risk of an onboard fire, that could also spread to other boats due to an inevitably more delayed reaction compared to a boat where someone is onboard.
And saying that it's a legal requirement leaves less room for debating that...!

You are right about the fires .They have had two biggies .Before my arrival time in Loano end of summer 2019 there was fatality incident on a iirc 20-22 M FB German registered.They got trapped in the mid cabin no second escape route .
Since then the marina authorities do play the “switch the thing off if unattended line “
Maybe they have done a risk assessment and / or it’s driven by there insurers ? Dunno

There was another fire last yr a ferretti jumbo 100 or what ever …..u tube shows it started in the engine room .Thankfully no one was on board it just sank .Later the sunken wreck removed .

@ tera nova just dock walk and see what everyone else does .Some live locally and regularly visit.

When onboard in Loano ( summer season) I tend to burn through about € 4-5 / day .Fortunately we have a Frigomar Aircon 42K BTU ….at bit over specced for the boat .The thing being a AC to D.C. inverter tech with variable speed D.C. motors running the single compressor it’s got a tiny current draw . Blurb says as low a 2 A .I must stress it was specced for it silence not current draw .

If we don‘t go out its on 24/24 and if we do for a swim its back it’s on from 4 pm to 11 am next day .
Electric hob and two fridges .

One more thing not touched upon ……well briefly by hurricane changing a fridge .and reading your post your electrical guy who discovered your charger consumption.
A few yrs ago our OEM charger packed up circa 2002 so nothing unusual.

It was rated at 30 Ah for domestics of 2x180;Ah .lets just park the same size engine batts assume the just sit after a day out ready for tomorrow s trip .Need no charge worth mentioning .

The same guy a boat sparky that fitted the Aircon did his maths 2016 ish and came up with a 80 Ah all singing and dancing multistage charger .
My point is this the new 80 Ah one can stuff up the batt bank (s) quicker get its self down to its trickle / float + lowest mode faster .
If the smaller OEM 30 Ah was still alive apart from the basic fewer functions it would probably be for want of better wording “ revving it nuts off “= net result burning up more shore power to keep the batt charged than the bigger 80 Ah floating ….if you see what I mean ?

Not sure what the maths are for charger size ? I just went with his professional advice.You know the fraction of charger size / Batt capacity-
Was 30. /2x 180 or is it 30 / 4 x 180 if you inc the what should be the full engine bank ?
Now it’s 80 / 2x180 when we park up assuming the engine banks topped up on the run out ?



As far as charging PAYG in this instance for us we prefer it .Last yr ( pre Putin ) I think we went through £3-400 a year max .
Where as in La Napoule our service charge for a 14x 3.8;M berth was almost €4000 payable in advance in two instalments.

There are more folks who spend more time than us and have by todays standards inefficient kit on board .
Dividing it up ( with a size delta ) masks them and punishes the more frugal .Having had both tariffs PAYG works better for us .

 

[MapisM]

end of summer 2019 there was fatality incident on a iirc 20-22 M FB German registered.They got trapped in the mid cabin no second escape route .
Since then the marina authorities do play the “switch the thing off if unattended line “
Maybe they have done a risk assessment and / or it’s driven by there insurers ? Dunno

I remember that very sad story.
I'm pretty sure that the boat was a Maiora, and when the fire started two couples were sleeping onboard, but only one lady managed to escape.

The logic of introducing the "no current when unattended" rule as a consequence of that accident is really hard to understand, but... Hey-ho!
They must have thought it was better than nothing, since introducing a "no current even when onboard" rule would have been a bit hard to digest.

 

[terranova]

Thank you Terranova for your post. Is the cost of 0.77 euros you quoted inc tax? We have ten x 140ah Exide Dual AGM 1200 batteries, so by the sound of it the consumption of 10kw a day may well just simply be down to the battery charger, but I will try get more advice on that.

Yes, the 0.77 euros is including tax (thankfully ?). As well as our 6 service batteries, we also have 4 engine batteries connected to the same charger so the same amount as you, albeit slightly smaller batteries.