What wattage of solar panels should you try for as a liveaboard.

[sailinglegend420]

Reply 2

....What wattage of solar panels is realistic for meeting the average liveaboards lifestyle?

The problem with the question is what is an "average" Liveaboard, and what is "realistic" for the size of a solar array. This can depend on lifestyle and what other charging sources there are and how often shorepower is used.

Lots of posters have given feedback on what works for them, but this highlights the differences of opinion.

The simple theory is that you should size them to replace your average Ah daily usage, so those figures are easy to work out.

?...., we use around 100-120Ah/day; laptops, instruments/GPS while out at anchor and fridge (50-60Ah/day) are the main users. I installed 200w (4x50) of rigid solar panels about a month ago.... All parallel is delivering 50-60 amp hours a day (in Greece), series was giving 10-15 Ah less....

Taking this example which is probably "average" then we can see that with a 120 Ah usage per day and only 50 Ah produced from the 200 watt panels gets no where near to charging up the batteries. If you don't have a controller that tells you your daily Ah usage you can work out roughly what to expect from the panels by dividing the wattage of the panel by 3 in the summer months and dividing by 4 early and late in the season.

So taking 120 Ah as the usage you would need for a 9 months Liveaboard season 120 X 4 = 480 watts to replace what's used. But to actually store this in the batteries you might need an extra 30% to overcome the charge inefficiencies. That would make a solar array of 624 watts, which is probably not practical on most monohulls. When sailing the Ah usage would be even higher! Motoring or shorepower charging would get the batteries to about 85% and the solar will then take over.

......having a controller that allows data collection and setpoint tweaking enables me to see whats going on on a daily basis and change the preset values to match my system.

This is a must for Liveaboards to be able to match the solar controller to the size of your battery bank so that it doesn't switch down to float too early.

..... Even a bit of shade cuts out most of the output so placement under boom etc is a waste of excess capacity.

This is the biggest mistake people make, radar and aerials on an arch serious effect the output. It's important to understand that a small shade across several cells can cut the output current to almost zero. If the panels are connected in series then the current from the unshaded panel will not pass through the shaded panel, with no extra bypass diodes added. This is a complex subject.

...When the sun shines I am fully charged by mid day....

... we have 2 rigid domestic panels which provide all the power we could possibly need

.....Our 250 Watts gives us more power than we know what to do with in the summer....

This highlights the problem, everybody has been had by the "Charging Gotcha" where the charge controller switches to Float well before the batteries are fully 100% charged.

Which Solar Panel Type is Best? Mono- vs. Polycrystalline vs. Thin Film for a boat?

It's probably the brand that's more important. Don't go with cheap Chinese!

And the weight. On my extremely modestly sized boat by Med standards we are always stern-down with an arch and two panels exerting quite a bit of leverage, plus a radar pole and scanner.

This picture from an American boat shows how stupid some people can get!

 

[Nostrodamus]

sailinglegend420,
Thank you taking the time to post the last.. it makes it a lot simpler for idiots like me to understand.

 

[SamanthaTabs]

Originally Posted by SamanthaTabs
... we have 2 rigid domestic panels which provide all the power we could possibly need


I simplified as don't understand the full rigmarole, Seamanstaines ditty is more in depth.
No charging gotcha was harmed by this post

 

[Midsummer_Energy]

When you are sailing in the sun and anchoring off as much as possible power aboard becomes a real issue.
We need to fit new solar panels this year and obviously the more the better.
Given the choice we would tow Chernobyl behind us to meet our power requirements but we have to be realistic.
What wattage of solar panels is realistic for meeting the average liveaboards lifestyle?

Hi Folks

If you would like any assistance with solar or wind turbine, battery related issues please feel free to message me.

Establishing the size of solar panel array you will need is determined by several factors.

1.Power Consumption
2.Location
3.Time of Year

The fist thing you will need to do is establish how much power your going to need to generate. This can be done by establishing all your different electrical loads. You will need to then find out how much power they us in Watts and how long you want to run them for per day. If you can only find an Amps figure for a certain device you can calculate the Watts by multiplying the amps figure by the system voltage.

Example

Bilge pump draws 2A from your 12V battery bank

2A x 12V = 24W

Once you have done this you can calculate your daily power consumption

TV runs at 60W for 3 hours a day = 180Wh (60W x 3 hours =180Wh)
Water pump 20W for 1 hour a day = 20Wh
Navigation Equipment 10W for 10 hours a day = 100Wh

Total daily is 300Wh

If you find this hard to follow you can use our free solar panel calculator to do the maths for you.

Once you know how much power your going to need to generate you can then look at seeing what size solar panel you will need. If your solar panels are fitted to a boat in the UK then you can use the following as a rule of thumb. A solar panel in the UK in winter time will output around 1:1 for its given rating. Meaning if you bought a 100W solar panel you could get around about a 100Wh out of a panel. On an average day you would get around 1:2 of the solar panel rating. So a 100W panel may give you around 200Wh. On a really good day in summer you might get as much as 1:5, so your 100W solar panel will generate up to 500Wh of power.

Its worth noting that the power you generate from the solar panel is not the same as the power you will get out of the battery. Your solar panel may output 100Wh over the day but you may loose up to 20% of this in the charging/discharging of your battery.

If your outside the UK you can use the PVGIS website to establish how much power your solar panel can generate. It uses google maps so you can drop a pin on your location and enter then number of installed kilowatts of solar you have and it will establish your monthly yields. Please note that it required you to enter the amount of Kilowatts of installed solar so if your fitting a 200W solar panel this would be 0.2kW.

Its worth remembering that your going to get grey days when your solar panel system under performs with this in mind you should have a suitably sized battery bank to cover your for a few days of bad weather.

 

[ip485]

By way of an update I used two Benq panels each 330 W and weighing in at a very reasonable 18.5 kg each. They are on a purpose built arch but I dont think it looks ugly or top heavy and the panels stay within the width of the boat - just! The arch is a very convenient mount for the Tracvision and Fleet Broadband, and other aerials. I am glad to hear its enough in the Med. Our summer two week cruise in really sunny weather for the UK proved it wasnt enough to keep up albeit without any consideration to the amount of power being used - lots of lights, fridge, freezer, TV, etc., etc. However it was pretty good and the Genset required very little use. In any event if you want hot water it seems to me you are going to run the Genset (or engine) for a time each day. In my case the engine is very inefficient at heating up the water, whereas the Genset will do a very good job within an hour. The combination works very well. However for year round use in the UK 660 watts would certainly not keep up and it was noticeable that with cloud cover all day the power drop off was significant.

 

[sailinglegend420]

Hi Folks
If you would like any assistance with solar or wind turbine, battery related issues please feel free to message me.

Establishing the size of solar panel array you will need is determined by several factors.

1.Power Consumption
2.Location
3.Time of Year

This is a commercial posting and as such should surely NOT be allowed on here, especially as he doesn't seem to have brought anything new to the party.

His example of daily usage is worked out in Watthours where we all should be using Amphours - that is how our battery capacities are measured and that's how all Battery Monitors measure, although some may show Wh as well. His calculation for power consumption suggests estimating usage, the best way is to use a battery monitor on board and disconnect ALL charging for 24 hours, this will calculate the actual Ah used automatically. This needs to be done several times, both at anchor and whilst sailing to get an average Ah usage.

 

[Monique]

I had 140w of semi flexible which were on top of the saloon roof. The panels developed blisters and after only 2.5 years use will only work briefly in the morning and just before sunset. The company who made them (GB Sol were totally unhelpful and would not answer any of my questions about them or give technical support). I would never buy semi flexibles again even though they did offer to replace them at cost price plus VAT plus transport.

GB Sol... had the same problem. (Texas warranty = if it breaks in two, you own both halves)

 

[Nostrodamus]

GB Sol... had the same problem. (Texas warranty = if it breaks in two, you own both halves)

Also worst customer service of any company I have come across. Basically we have your money so stuff you.

 

[oldvarnish]

We have the usual fridge, computers and music running a lot so the consumption is quiet high.

You could always try switching stuff off.

That's not meant as a snide comment, but I see lots of boats anchored with instruments left on, autopilots powered, stereos powered up but not being used and iPad chargers left plugged in when charging is complete, computers switched on but not being used, monitors too.

I've never lived aboard, but I'm guessing that one of the secrets of success is realising that you're no longer at home.

I keep meaning to put an ammeter in the negative line just to see how much power is being wasted by idle bits of kit - I think it might come as a bit of a shock.

 

[Nostrodamus]

You could always try switching stuff off.

That's not meant as a snide comment, but I see lots of boats anchored with instruments left on, autopilots powered, stereos powered up but not being used and iPad chargers left plugged in when charging is complete, computers switched on but not being used, monitors too.

I've never lived aboard, but I'm guessing that one of the secrets of success is realising that you're no longer at home.

I keep meaning to put an ammeter in the negative line just to see how much power is being wasted by idle bits of kit - I think it might come as a bit of a shock.

Mr Old Varnish, I didn't take it as a snide comment and I agree with you. The trouble is at the moment we have no solar panels (well ones that work) so we rely on a portable generator or my wife peddling like mad on an exercise bike. The trouble is I need her occasionally to cook, wash and such things which means that on those occasions we have no power going into the batteries. Although I may have a fit wife life would just be a little easier with solar panels.

 

[RichardS]

Although I may have a fit wife ...............

That's enough bragging already!

Richard

 

[oldvarnish]

Mr Old Varnish, I didn't take it as a snide comment and I agree with you. The trouble is at the moment we have no solar panels (well ones that work) so we rely on a portable generator or my wife peddling like mad on an exercise bike. The trouble is I need her occasionally to cook, wash and such things which means that on those occasions we have no power going into the batteries. Although I may have a fit wife life would just be a little easier with solar panels.

Aaaahhh, we single handers can only dream....

 

[Nostrodamus]

Aaaahhh, we single handers can only dream....

or change hands! :encouragement:

 

[Koeketiene]

Aaaahhh, we single handers can only dream....

A wife: I thoroughly recommend it - she can take care of all sorts of boaty jobs.
Not to mention the useful by-product of junior crew.

 

[sarabande]

At the moment I am looking at about 380w of solar panels (4x95w)
I have found a company which have been the most helpful I have come across yet with very quick response time and good technical knowledge.
http://midsummerenergy.co.uk/index.html
They apparently bought out all the Kyocera panels when the Japanese company pulled out of the UK so can do them at discount.

The bigger, more reputable companies are moving to next generation solar panels, which are (?) 10% more efficient. A large number of good quality panels were dumped in the UK by China, so there is a surfeit of 'old' panels which are waiting to be sold - hence discounts.

 

[Nostrodamus]

The bigger, more reputable companies are moving to next generation solar panels, which are (?) 10% more efficient. A large number of good quality panels were dumped in the UK by China, so there is a surfeit of 'old' panels which are waiting to be sold - hence discounts.

The Kyocera panels are Japanese and are a quality panel. Quiet a few people have suggested them to me.

 

[charles_reed]

The Kyocera panels are Japanese and are a quality panel. Quiet a few people have suggested them to me.

Kyocera, though a Japanese owned company, apparently make most of their panels in Schenzuan province.

I've had their panels for the last 4 years and can recommend them as extremely high quality - mainly for domestic use (in fact they do not guarantee their panels in a marine environment).
Their KD panels are the latest - and are about 18% efficient - the output voltage varies according to the # of modules - 36 produce 16v, 54 48v. This means that you need an MPPT controller to convert the panel output into 12v nominal to charge your batteries.
12v panels as offered on e-Bay and most other outlets are obsolescent and expensive way of producing electricity from solar.
I have some of the early KD panels 36-cell units in parallel to output 24/32v into a BZ 500 MPPT 500 amp unit. This is optimised for an input @ 48/54 volts. In hindsight I'd have done better to get two of the 54 cell units rather than 4 x 36.

Here's the information http://www.kyocerasolar.com/residential-solutions/solar-panels/current-products.htm

Though I have a commercial arrangement with their UK importers, they are not cheap - my 290 watts in 2 pairs of panels cost £1200 and I had to get them to Greece.
Some have plaintively spoken of the weight if PV panels - as you can see from the Kyocera data sheet they're not heavy, any support structure is likely to weigh more. However the price of outdated technology is inefficient mass and cost.
If you need further information please PM.

PS Only BP Solar officially made panels for marine use and they've now been absorbed into Solarex, another producer of quality products, if somewhat expensive and outmoded.

 

[sarabande]

The Kyocera panels are Japanese and are a quality panel. Quiet a few people have suggested them to me.

I know they're Japanese (originally made in J, but now ? )and good; I have two 100W ones


The EU was involved last year in anti-dumping from China.

http://www.theguardian.com/business/2013/jun/04/eu-tarriffs-dumping-china-solar-panels

 

[demonboy]

When you are sailing in the sun and anchoring off as much as possible power aboard becomes a real issue.
We need to fit new solar panels this year and obviously the more the better.
Given the choice we would tow Chernobyl behind us to meet our power requirements but we have to be realistic.
What wattage of solar panels is realistic for meeting the average liveaboards lifestyle?

You should definitely start with a rough calculation of your requirements. What's the average amperage pull over a 24 hour period, factoring in night-sailing, if relevant? It's a good starting point because, if nothing else, you'll be more aware of your actual power consumption rather than taking a punt or basing your calculations on other yachtie's requirements (though I don't think it is unusual for the average liveaboard to run laptops, charge phones, watch films, as well as do the usual like running fridges these days). Once you know this, you have a guide to work from and a target to aim at.

FYI, we have 6x40w Kyoceras and they cope well. However we invariably run the batteries down eventually so sticking the motor on or the portable generator every three days or so is not unreasonable IMHO. Someone else suggested that you move on after three days. Not so in our case: we've been at anchor for weeks at a time, but I still run the engine since we have a 100amp alternator that charges the batteries quicker than our shore-power charger. I reckon another 60w would be good though.

I've seen cats with massive arrays on the back of their hulls. I get quite sick with jealousy, but then they do have freezers, washing machines and jacuzzis to run, so it's all relative

 

[Nostrodamus]

Well, we have ordered the arch and solar panels (380w of Kyoceras) and a good Mppt box (morning star).
There is an excellent web page for fitting and using solar panels on boats here

http://roadslesstraveled.us/sailboat-solar/

They suggest fitting the panels in Parallel as it is better for any shade. Also interesting that that do not suggest fitting to the legs to the boat with sikaflex as a sealant.

Does anyone have experience of the best way to wire up multiple panels.. Parallel or series.
Again, thanks for any help.