renewable energy onboard

seansea

seansea

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Looking to do some extensive cruising both across tropical and temperate weather zones, trades, doldrums etc. with passages up to 2,800 miles between refueling. Boat is 12 metres long with wireless wind/speed/depth plus chartplottter, VHf and usual features. The main power draws are the fridge (72 watts) and autopilot. My calculation is daily usage will be around 1000 watt hours but it may a little more occasionally. I need to be able to charge phone and power tools for occasional use. All lights are now LED.

I have a bimini and sprayhood so was thinking of using one or both for flat flexible solar panels. I was thinking of 3 Sunware solar panels each of 50 watts, limited by the size of the bimini. There is little suitable flat space for solar panels on deck. I was thinking of fitting a wind generator as well or a hydro generator either or. It seems to me I will be lucky to generate half the boat's daily power demands. Grateful for advice on the best value and performance set up.
 
I’ve got 260 watts of solar panels on the deck and the bimini, which generates about 70 amp hours on a Greek summers day. That’s about 80% of the daily requirement so if I’m in one place for longer than a couple of days, I need to run the engine to make up the difference.
In addition, I have an Aquair towed generator which produces about an amp per knot of speed: keeps pace with the additional demands of the instruments and autopilot.
No wind turbine as the wind in the eastern Med is not reliable enough to make it worth the investment. If you’re doing long distance trade wind sailing you may find that you’ll get little benefit from a wind turbine as the wind speed over the boat won’t be enough to generate much power.
If you’ve not got much in the way of deck space, you may find it better to invest in an arch or gantry at the stern of the boat to carry three or four hundred watts worth of panels. The panels themselves are now quite reasonably priced but the gantry will probably cost £1000-1500.
 
There are calculators available online to help with this - if you google "solar calculator for boat" or something. The other thing to bear in mnd is the size of your battery bank - there's no point having a 1kw solar array if you've only got 200AH of batteries because a lot of the power generated will go to waste and conversely a 30w solar panel is never going to keep up with a 500AH battery bank.

FWIW I had a boat in Greece for a few years that only had 1 x 80w panel on an arch at the back & that kept up with a very well insulated compressor fridhe that was turned off overnight, charging various devices and the tiller pilot and instruments. I had used to angle it towards the sun as best I could throughout the day.

Sounds like a great trip you have planned, fair winds...
 
We have 720w of solar on our main domestic battery bank. We also have a Duogen that converts to wind from towed generation. We typically make about 1000w before midday when the batteries go in to float. On passage the solar and towed Duogen run the boat without resorting to the diesel generator. On longer passages we use our Wind pilot which reduces our electrical demand even lower. If you need space to mount more solar think about using the guard wires. We have done three trans Atlantic crossings with panels mounted on the guardwires. Here in the Caribbean you see a lot of boats with this solar set up. You cant have too much solar!
 
I agree with the earlier posts but would add

In terms of the battery bank it needs to be large enough to supply all your power needs at night as the passages you envisage will result in their being no solar power yet night is the time you will use most power. Worse you need to have power to run the autopilot in rough seas - when its power consumption will be at its highest. I appreciate you have LEDs but you will have all your nav lights and some internal lights on. You might want some music, you will have the VHF on and want to recharge cameras, laptops etc. You might not need the chart plotter on, there is not much to run into in the middle of an ocean (though maybe you will be running radar - if the weather is iffy).

And the following day - you need to be able to top the batteries up, ready for the next night - and I would not rely on solar as being able to top up those batteries.

At the end of the day its all about money, solar panels might be cheaper than they were - but they still cost.

We have both wind and hydro - as when they work (if its windy and/or you are tanking along) they are a boon and both work 24/7. We have an Aqua4aerogen - which means we can have wind or hydro - if we were starting again we would have both as separate units - so we could have both at the same time - and no need to faff about swapping over. Again it starting again I'd have chosen the bigger LVM wind gen the Aero6 and with unlimited funds I'd have a WattnSea(?) hydro gen (the one like an outboard). If I could buy another generator unit - I would (sadly LVM are no more). Most of the time you choose an anchorage its top redeeming feature is 'shelter' which thus means no wind power (and as you are at anchor - no hydro power either :( - so then you need solar to charge the batteries - knowing that, even in sunny Australias, we have a few days of overcast skies.

You don't mention how you will cope with water (or lack of)?

We have a house bank of 400a/hrs and separate engine start battery. The windlass runs off the house bank - but not much need for a windlass when you cross an ocean :)

On life expectancy - our , semi-flexible, solars lasted - about 10 years - our LVM wind/hydro unit is 20 years old and no noticeable reduction in efficiency.

I don't think there is an easy answer - but I would suggest you need a mix of hydro, wind and solar.

One thing we did do was duct air from the anchor/chain locker (ours is clean and sweet smelling) over the fridge compressor and then exhaust to the engine bay (which ducts to 'outside'). This has cut down on total fridge power usage. Its a fiddly instal on a cat - but might not be possible on a mono.

Jonathan
 
seansea said:
Looking to do some extensive cruising both across tropical and temperate weather zones, trades, doldrums etc. with passages up to 2,800 miles between refueling. Boat is 12 metres long with wireless wind/speed/depth plus chartplottter, VHf and usual features. The main power draws are the fridge (72 watts) and autopilot. My calculation is daily usage will be around 1000 watt hours but it may a little more occasionally. I need to be able to charge phone and power tools for occasional use. All lights are now LED.

I have a bimini and sprayhood so was thinking of using one or both for flat flexible solar panels. I was thinking of 3 Sunware solar panels each of 50 watts, limited by the size of the bimini. There is little suitable flat space for solar panels on deck. I was thinking of fitting a wind generator as well or a hydro generator either or. It seems to me I will be lucky to generate half the boat's daily power demands. Grateful for advice on the best value and performance set up.
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From my experience with smaller solar arrays in the past 300w is about the minimum allowing for cloudy days and being very frugal with power. Increasing to double that is a game changer. Days don't split in to fully sunny days and full cloudy days. There are lots of days in the tropics with some cloud. Max out your solar set up. You wont regret it
 
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geem said:
From my experience with smaller solar arrays in the past 300w is about the minimum allowing for cloudy days and being very frugal with power. Increasing to double that is a game changer. Days don't split in to fully sunny days and full cloudy days. There are lots of days in the tropics with some cloud. Max out your solar set up. You wont regret it
Click to expand...

We scraped by with 200w for quite a few years, late spring to autumn was OK but in between not good. Increased panels to 320w last winter and have not had to use engine or mains charger for 12 months. Fridge drawing 7 amps is the biggest battery killer.
 
While solar is the 'main course' for many people, it's still worth thinking about being able to get a decent current into your batteries from the alternator.
In our weather, boosting in 50A for 3/4 hour while leaving harbour gives things a head start.
It's good to have options.
 
We have 350w of solar installed and 540Ah of lead-acid house batteries. This has proved adequate for our cruising so far (Scotland & Baltic). We're heading further south now, where I presume we'll get more sun. The main consumers of power are:
- water cooled fridge (4A when running)
- Watermaker (40l/h) (8A when running)
We have a raymarine autopilot, but use the Hydrovane on longer passages - if we used the autopilot, we'd have to run the engine every couple of days to keep up with power consumption.
 
lw395 said:
While solar is the 'main course' for many people, it's still worth thinking about being able to get a decent current into your batteries from the alternator.
In our weather, boosting in 50A for 3/4 hour while leaving harbour gives things a head start.
It's good to have options.
Click to expand...
This happens automatically when you engine out of any port or anchorage but not much use if you are crossing oceans. You can run the engine but with only 150w of solar you would be running it for a couple of hours per day at least. If money was no object a Duogen and lots of solar would make a huge difference. Also making sure you have good deep cycle batteries would in my opinion, be essential.
I spoke to a couple of the rowing teams coming in to Antigua. Both had battery failures within a few days of leaving La Gomera. One team had a normal leisure battery. The other had a lithium battery. Neither guy new enough about batteries. The lithium had no BMS so was getting either over charged or under charged i suspect. Either way it died. The Leisure battery was almost certainly being deep discharged. Get your battery and charging installation right before you head off on a long passage
 
Your power use seems too low. I use over three times that.

Be careful with choosing flexible solar. They often fail early. Some last a while and I have some 20 years old. Glass fibre backed, so not really flexible. Another, a thin film design, which really is flexible also old. Most which fail early are the wafer cell type and not that stiff or not supported well. I was looking at one recently, which failed early. By bending it only a little I heard it crack, presumably a cell snapping. The Sunbeam brand I think. Others report very early failures with bimini installations unless rigidly supported.
 
geem said:
This happens automatically when you engine out of any port or anchorage but not much use if you are crossing oceans. You can run the engine but with only 150w of solar you would be running it for a couple of hours per day at least. If money was no object a Duogen and lots of solar would make a huge difference. Also making sure you have good deep cycle batteries would in my opinion, be essential.
I spoke to a couple of the rowing teams coming in to Antigua. Both had battery failures within a few days of leaving La Gomera. One team had a normal leisure battery. The other had a lithium battery. Neither guy new enough about batteries. The lithium had no BMS so was getting either over charged or under charged i suspect. Either way it died. The Leisure battery was almost certainly being deep discharged. Get your battery and charging installation right before you head off on a long passage
Click to expand...
Charging at high amperage into a modest sized bank tends not to 'happen automatically', we give it some encouragement.
If you want to get near many battery makers recommended cyclic charge profile, you'll be wanting some more volts.

Even serious world-circling boats tend to spend only a fraction of the year actually crossing oceans.
And oceans are not all coast-to-coast sunshine.

All I'm saying is, however much solar is your primary source, a few thoughts about diverse power sources may be worth it.
I'm definitely not knocking having a well sorted solar installation.
 
Thanks for all the feedback, that's great. I'm inclined to go for a rail or pole mounted solar PV set up rather than a gantry or arch. Now not so sure about the flexible solar panels on the bimini as I sometimes like to be able furl the bimini away at night and this may make the panels more vulnerable to damage and affect longevity I presume?

I do have an option to fit panels on the side decks up to 50 cm wide but it means drilling holes in the deck and chasing the wiring etc. and the panels would be walked over a lot.

Definitely interested in looking at a hydro generator but need to find out if it can fit on raked, sloping transom. More research needed also on regulators. It seems that some hydro generators can use the same regulator as for solar and wind generator which would be a bonus.

For info, I have AGM batteries 2 x 196 Ah @ 20 hours plus a starter battery. No water maker, not sure about this as not planning to do many ocean passages. It would be nice to be able to add extra insulation to the fridge but as it's moulded in, think it will be tricky.
 
I suspect I've been radicalised from spending too long lurking on lithium boating forums so do your own due diligence. There's probably a prevent programme I can be referred to.

Anyway the other factor is the efficiency of your batteries. Unlike lead acid, LiFePO4 (LFP) batteries will take whatever charge you throw at them. There's no concern about returning to full charge for longevity, and there is no voltage sag. While lead acids will increasingly resist charge over 80% SOC the same is not true for LFP. Charging from the alternator then becomes a serious additional option - so much so that standard alternators can burn-out and things like Balmars and external regulators become desirable.. Longevity (if properly cared for) and lower weight are other gains. There are of course downsides - big upfront costs, changes to charging systems and a need to self-educate.
 
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seansea said:
Thanks for all the feedback, that's great. I'm inclined to go for a rail or pole mounted solar PV set up rather than a gantry or arch. Now not so sure about the flexible solar panels on the bimini as I sometimes like to be able furl the bimini away at night and this may make the panels more vulnerable to damage and affect longevity I presume?

I do have an option to fit panels on the side decks up to 50 cm wide but it means drilling holes in the deck and chasing the wiring etc. and the panels would be walked over a lot.

Definitely interested in looking at a hydro generator but need to find out if it can fit on raked, sloping transom. More research needed also on regulators. It seems that some hydro generators can use the same regulator as for solar and wind generator which would be a bonus.

For info, I have AGM batteries 2 x 196 Ah @ 20 hours plus a starter battery. No water maker, not sure about this as not planning to do many ocean passages. It would be nice to be able to add extra insulation to the fridge but as it's moulded in, think it will be tricky.
Click to expand...
Looking at hydrogenerators, one of the problems I can foresee is fitting on a transom alongside wind steering gear if the transom is not overly wide...
 
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