Wind generator -v- Solar Panels

[Ray_G]

For my Med cruise, starting next spring the next purchase (and the last I hope in this fitout!) is to add some further battery charging through wind or solar power. I already have an 80amp alternator and Adverc management system as well as a 4KVA generator which powers a 50 amp Sterling charger. Battery power is 3 No 135amp domestic bank and a 135 amp engine starting battery.
For Med sailing, should I be going with wind or solar power? I am sure there are plenty of you guy's out there who can advise from personal experience.

Thanks, and have a Happy Christmas folks.

 

[ccscott49]

For the med, it has to be solar. But I wouldn't fit one now, they are cheaper in Portugal and spain. Also with the genny etc, I would thionk the costs of a solar, would outway it's usefulness, you can buy a lot of diesel for your genny! You will also be doing a fair amount of motor sailing, to keep your batteries up and trying to point the panel at the sun, when anchored to get the best out of it etc. I went through this same decision making scenario myself, in the end decided not to bother, for me to get a decent wattage array, being a little power hungry, would have cost 1200 quid, even a small array was 600, just couldn't justify it.

 

[Paulka]

Agreed.
Unless you are extremely power hungry (air con, etc.) your equipment will be sufficient. You'll probably motoring a lot anyway, thus recharging the batteries with the alternator. Power is available in all marinas.
Except for a small Honda 450 W generator, which I use about 1 time a year, I don't have anything more than the engine generator, and a battery charger.
No solar panel, no wind generator.

Paul

 

[MedMan]

It all depends on what you wish to achieve. With the battery reserve that you have, the high-output alternator and a substantial generator I doubt if you will need more power. However, if you would like to be able to spend 3 to 4 days and nights in a secluded anchorage in peace and quiet you may wish to have a silent form of power generation. IMHO that means solar power. Wind generators are seriously noisy beasts when they are producing power and useless ornaments when they are not!

 

[colin_jones]

The big battey killer is the fridge. With long summer nights, you do not need to worry about power for interior lighting and if you pick your berth well, even an anchor light can be dispensed with in many places... or you find an alternative power source for it.

So, the bottom line is coping with the fridge.

When this is pulling most juice, it is generally a hpt, windless day, so your Wind Bugger et al will not help.

Even if it is windy (and sunny) solar panels still work.

I have 2 x 30watt flexible solar panels rated at 1.9amps, but probably giving 1'5 (3Ah in total) and these cope with what the fridge needs (Waeco 60 litre with modern 30W comprssor. The panels cost about £200 each and have been worth it on 8 trips to Med and home. We keep them on strings and when we are aboard just occasionally reorientate them to best sun angle.

We expecy to stay on an anchorage (if you can fine one in W Med nowadays) for abt 5 days without flashing up the dsl main engine.

 

[charles_reed]

I think you're boxing yourself into a cul-de-sac in querying whether you need wind or solar power.
The truth is you will need both.

You don't specify which part of the Mediterranean you will be, so the relative merits of each power source cannot be specified exactly.

For example, if you're in the Golfe de Lions, your wind generator will be producing far more power, outside the summer months, than your solar panels.

In essence I'd agree with Colin - the major consumer of on-board electricity is the fridge. Living without one in 38-42C is not particularly feasible and most unpleasant.

So before discussing power-sources could I'd exhort you to look closely at the insulation around your fridge-freezer. This is the most critical factor in determining your re-charge requirements.

My top-opening 50 Litre fridge has 100-120mm of closed cell foam around it and runs the ASU unit about 10 times in 24 hours for about 18 minutes each, at summer temperatures, which pulls 5.5 amps on start-up and when on supercool, dropping to 4.2 amps.

I have a 100 amp alternator feeding 300 AH of battery capacity through an Adverc as well as an Ampair 100 wind generator and an 85 watt BP solar panel.

I keep one battery as a standby and find the remaining 200AH lasts about 5 days before the engine needs to be started to re-charge - this takes about 60 minutes at 1200 rpm.

I will confess to finding the recieved wisdom of keeping a battery solely for engine starting particularly crass - why not use the storage capacity you're carting round?

Could I suggest the most productive method of analysing the problem is to start with the 24-hour power usage on the boat.
Your available battery capacity should amount to 2-3 days usage under way and 4-6 when at anchor.
Your charge capacity needs to allow you to recharge on motor within about an hour - I note you're proposing to have a separate charger, which may make you very unwelcome to your neighbours in the more scenic anchorages.
The shape of your alternator output is more important than its maximum rated power output - you need the output fairly low down the rev-range (but not so low down that it stalls the motor on start-up).
The Airmarine chargers make the most claims for power output, but sound like Concorde on take-off in any wind (another source of neighbourly irritation).
As a rule of thumb, the more blades a wind generator has the less noise it makes.

The most efficient solar panels are the crystalline variety (the ones you can't walk on) and probaly the best of these are the BP panels (now only supplied to OEM). It used to be cheapest to buy your panels in Portugal - but I believe EC tax standardisation has reduced this benefit.

Of course most people in the Med marina-hop so the shorepower charger is their most important ancillary - but that can be very expensive in high season.

 

[rickwat]

More batteries cost effective?

It might be worth increasing the size of your battery bank. This way you could have a bigger reserve of power and get more useful charge in a shorter period of charge (I think because the alternator could get more amp-hours into the bigger capacity before the voltage rises and regulates the charge downwards). Buying more batteries you could also just have them as reserve in the first instance to see if you have a problem at all.

 

[MedMan]

Re: More batteries cost effective?

Someone with more knowledge than me may well disagree, but I think the opposite is true. If you only had one small battery, the voltage would drop quickly under use and, when you came to charge it, it would accept a high rate of charge. If you had a huge battery bank, after the same amount of use the voltage would have dropped very little and it (they) would only accept a low rate of charge.

For the fastest re-charging you need to operate your batteries between 75% charged and 50% charged. When you start charging at 50% they will accept a high rate of charge. By the time they are back up to 75% it is starting to taper off and it takes ages to put the last 20% in.

www.geocities.com/yachtretreat/

 

[Strathglass]

Re: More batteries cost effective?

If the alternator used it's inbuilt regulator, a single battery may charge quicker, as the lower voltage of a single discharged battery would initially get a higher current from the alternator. But with multiple batteries where the voltage would be higher a built in regulator would be higher up its charging voltage/current curve and it would give out less current.
The output current tails off well before the fully charged state is reached with a built in regulator.

If one of the smart regulators was fitted it, where the output current is steady and high until the fully charged state is reached, then, it would be advantageous to have additional batteries.

Iain

 

[Guest]

DONT BOTHER - THE 4KVA GENERATOR WILL BE WAY MORE EFFECTIVE.

WIND GENERATORS SUFFER FROM NOISE / VIBRATION TO VARYING DEGREES. MET VERY FEW PEOPLE WHO DID NOT TIE THEM OFF AT NIGHT. SOLAR PANELS NEED TO BE QUITE LARGE TO GET A SERIOUS AMOUNT OF POWER OUT OF THEM. IN PRACTISE, YOU WILL FIND YOU MOTOR WAY MORE OFTEN THAN YOU EXPECT, AND FOR THE OCCASIONS WHEN YOU ARE AT ANCHOR / SAILING FOR A LONG TIME, THE GENNY WILL CHARGE . IT WILL TAKE A LOT OF GENNY HOURS TO USE UP THE COST OF A WINDVANE / SOLAR PANELS

SORRY ABOUT THE CAPITALS - DIDNT NOTICE CAP LOCK WAS ON UNTIL TOO FAR INTO MY POST TO RE-TYPE.

 

[James_Hunter]

Solar, Solar, Solar!!!!!

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[James_Hunter]

Not so! The most efficient solar panels on a boat are the amorphous or thin-film variety. They are shadow resistant and lose only a very small amount of their output when shadowed by rigging etc.!

Regarding the fridge, try turning it off every night before going to bed and back on again first thing in the morning. You should find that this 8-10 hour off period in the cool of the night (despite the extra work it has to do when turned on) saves a lot of amps, without having any real noticable effect on the refrigeration process in general.

It is unwise to use your starting battery for house requirements UNLESS it is the same type and make as your house batteries - and absolutely necessary. In most cases - and correctly so - the starting battery is specifically designed for engine starting and as such, should not be discharged, or charged, in tandem with the house batteries.

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[Guest]

Having lived afloat for 20 years or more in the tropics, I agree with much of the advise given with a few exceptions here and there. My advise is:

1. Have as many DIFFERENT means of charging as possible that is within the limits of your pocket, solar, wind, alternator AND shore power connectors and cables for charging from the mains where available.

2. Enlarge your battery capacity to the maximum that your pocket and boat space will allow.

3. Buy deep cyle batteries with a reputation of long life.

4. Try to keep your useage within 25% of your theoretical battery capacity in order to keep the charging time within reasonable limits and to ensure longevity of the battery's life.

5. Endevour to have the insulation on any fridge that you have, made as thick as is practical in your circumstances. Six inches being the target.

6. Keep the temperature setting as warm as possible within the limits of keeping the contents edible without going bad.

Cost wise, solar panels are the better buy as good ones last over 20 years or more.

However, with windy conditions a wind generator is useful, BUT make sure that it is the AC type WITHOUT brushes but including diodes. I have had both types and the brush types need constant maintenance.

An inverter/charger is also an asset, but you have an AC generator. Personally I don't.

For charging I prefer the 12 volt alternator connected to a small diesel engine for my daily charging, with exactly the same make and sized alternator on my main boat's engine as the auxiallary one. This enables me to have one spare alternator that can be used on either engine.

One last point.

If you have automotive alternators fitted, do bear in mind that they are NOT rated for the CONTINUOUS use at the high outputs that is required on a boat.

An automotive alternator rated at 90 amp for use at a contiuous high output should be down rated to around 65 amps, namely around 30% lower. If however, you buy the more expensive continously rated alternators you won't have this to consider. In the part of the world where I am, the expensive ones are not so easily obtainable so I go for the cheaper automotive types.

Lastly, I have used my starting battery as part of my total system for some 15 years, without any problems. The advise on the starter battery being the same make and capacity as the others is VERY important. Mine are all the same.

In my opinion a separate battery for brief useage, for starting or winches, that is kept isolated from the rest of your system, is a scenario for a battery that is going to die very quickly. Lead acid batteries like to be used constantly, they don't last long when only used briefly with long periods of idleness, even when charged regularly. I realise that this is not the current popular opinion on starter batteries.

I hope this info is of help to you, and the best of luck with your planned cruising.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by djcrib on 30/03/2003 03:51 (server time).</FONT></P>