Power generation alternatives

[gfbalduc]

So, I'm just back from a 2-months cruise from Genoa to Trieste by way of Corsica, Sardinia, Sicily, Malta, Greece, which was supposed to be the final shakedown before taking to the high seas next year...... /forums/images/graemlins/cool.gif

One thing that needs some additional thought is power generation: with an Aerogen6, a 100-watt solar power and a 25-Amp propshaft generator, I still had a daily unbalance of about 30 to 50 Ah (mostly due to the fridge during night hours).
In semi-coastal cruising, that would be almost OK as quite often I had to motor anyway and this took also care of topping up the batteries; I actually had to run the engine just for charging only 3 times in 2 months, which is quite acceptable, although the propshaft alternator proved to be almost useless and I'm going to get rid of it.

Different story when I will be on ocean passage: running the engine one hour per day just for battery charging would be acceptable, but I would like to further reduce that if possible, mainly to avoid accumulating engine hours (hi-output alternator and smart regulator already in place).

It seems I have two options in front of me:
- add another 100w solar panel
- buy a towed generator (Aquair or Aquagen)

some obvious pro's and con's:
- a second 100w solar panel is difficult to accomodate and pretty expensive as well
- a towed generator is somewhat of an annoyance and obviously it works only when underway

An intermediate solution could be a flexible solar panel (clearly not 100w!) to be rigged temporarily somewhere (over the sprayhood??).

Any thoughts, experiences?
Feedback on towed-generator makes? (I cannot consider a convertible water-air generator like Duogen due to possible interference with the boat's stern portal and with the wind-pilot)

TIA,

 

[Talbot]

If your fridge is using that much power, it needs fixing.

I suspect that the insulation is insufficient or of poor insulation value, thus leading to a high duty cycle - this will cause early failure. It is also possible that you are using an air cooled system which has insufficient air flow and that what air is available is not very cold - again causing a high duty cycle.

(duty cycle = percentage of time that compressor needs to run to achieve temperature)

Some keel cooled systems draw a max of 35 amp/hrs per day!

additional solar panels are good especially when trade wind sailing, but towed water generators are the best - look at 2005 ARC report on Duogen.

 

[wagenaar]

I don't understand the interference with the windpilot. The windpilot functions when you are sailing, thus when you use the generator is in the towed-mode. It is changed to the wind-mode when at anchor or in the marina and then the windpilot is at rest. I therefore do not see a reason for interference.

 

[Anonymous]

You are going to have a varied weather mix on your RTW voyage whereas your trip this year, in that area, will have given you a very high output from your solar, and probably a lot of wind? I am not surprised the the propshaft generator is useless as the prop is not optimised for generating. It is unfortunate that you cannot use a Duogen - while I have never used one I have several friends who do, and they are very happy with the product. Maybe re-think and see if there is some way you can fit one?

The thing that seems to be missing in your set-up is an inboard diesel generator. It would add to your charging and more than make up your shortfall assuming you have a good-sized charger. Aside from solving your Ah shortfall, you would have greatly improved quality of life with a generator. I wouldn't consider a portable petrol generator for liveaboard or RTW use. Diesel is the way to go.

Obviously reducing power consumption will solve the problem, but as an electrical engineer yourself, you don't need me to tell you that!

 

[gfbalduc]

Thanks all for the inputs, there's always some food for thought.

Reducing power consumption is obviously part of the equation as well and I'm addressing it.

Nav lights were another big spender during night time, but that's been easily cured by LED replacement lamps.

During ocean passages I may also consider switching off the navigation instruments (unfortunately networked Raymarine instruments cannot be switched off individually - not the ones I have, at least).

On the other side, I will probably use the SSB much more, and that's quite power-hungry even in receive mode (getting weather faxes et al).

Indeed, the fridge may need some tweaking/repair as it is running too cold when put in auto/energy saving mode: paradoxically, it seems to be fooled by the fact that batteries are always near full charge and happily runs at full power!

I already have an Aerogen which is working honestly, so I'm not entusiastic about scrapping it for a Duogen. Besides, the shape of my boat's stern plus the rear portal could make installation of a Duogen more than a bit tricky, but I may be wrong on that: worth a check, for sure.

Agreed that if I have to resort to burning fuel for electricity, a diesel genset is the best solution, but installation on a 40-footer is really marginal space-wise and also tank capacity becomes a concern.
Looks like being far too expensive and complicated just to find 50Ah a day.

The watermaker's impact is a complete mistery for the time being: I've never used it so far (still new and unused after 6 years!), but if I will this may tip the balance in the direction of the genset.

....departure date gets nearer and nearer, money is never enough and the list of things to do doesn't get any shorter!.... (Murphy's Law of ocean voyaging?) /forums/images/graemlins/wink.gif

 

[William_H]

I suggest that all your power problems stem from the fridge.
Better insulation and a keel (water) cooled condenser would seem like the solution.
Alternatively you might consider fitting a car aircon type fridge compressor to the main engine. This will give really powerfull cooling if used with a keel water cooled condenser. Sure it will require engine run everyday butfor a quite short period compared to battery charging. Without needing battery powered refridgeration you will have bags of power. You might like ton retain the existing electric (battery) refridgeration for use in port on mains power.
good luck...... olewill

 

[Anonymous]

[ QUOTE ]
Indeed, the fridge may need some tweaking/repair as it is running too cold when put in auto/energy saving mode: paradoxically, it seems to be fooled by the fact that batteries are always near full charge and happily runs at full power!

[/ QUOTE ]If you reduce the power to the fridge then the cabinet will get warmer. Monitor the temperature for a while, ideally with an IR thermometer to look at temps around the fridge, and see what is really going on. I keep ours at +2C and that is almost as good as freezing in terms of food preservation. You might welcome that on ocean passages. Downside is that your cold drinks are much colder and 'cost' more to bring down to that temperature. Though you won't be living off canned beer on ocean passages, I imagine.

[ QUOTE ]
I already have an Aerogen which is working honestly, so I'm not enthusiastic about scrapping it for a Duogen.

[/ QUOTE ] I thought you'd add a Duogen, not remove the Aerogen. Plenty of electricity is a worthwhile luxury.

[ QUOTE ]
Agreed that if I have to resort to burning fuel for electricity, a diesel genset is the best solution, but installation on a 40-footer is really marginal space-wise and also tank capacity becomes a concern.

[/ QUOTE ]We are 42 foot (but quite beamy) and it is no problem in my engine room. Tank capacity shouldn't be a big issue. When you are running to a tight fuel budget, use it less but it is there when you can afford the fuel. Anyway, the small diesels are very efficient and only burn what is needed to make electrical energy; not the most efficient way to boil a kettle, heat water or heat the cabin but it is convenient, albeit at a cost. If you are only battery charging it won't burn much.

[ QUOTE ]
The watermaker's impact is a complete mystery for the time being: I've never used it so far (still new and unused after 6 years!), but if I will this may tip the balance in the direction of the genset.

[/ QUOTE ] We find our watermaker very useful in the Med but we don't stay in marinas so finding water is difficult and/or expensive and alway very inconvenient. We can lie to anchor (or a buoy) for several weeks in the same spot and have as much fresh water as we use when in a marina. The lifestyle impact is enormous. When you are crossing oceans you will be in trade winds most of the time and should have plenty of wind power - especially if you add the Duogen. That will help to run the watermaker (if it is dc).

 

[Dave99]

Someone i know uses aqua air - it can power all instruments and fridge with reserve for radar when necessary. Then at anchor it's got a bracket rather than a pole so it can be flown between halyards

 

[landyhubbard]

Remember that trade wind sailing is, or should be, downwind so wind generators do not work- or at least ours didn't.

 

[pappaecho]

I suspect that your insulation is designed with temperate climates in mind. With say an average ambient tropical temperatures of say 22 degrees and a cool temperature of say 4 degrees, the U value should be such that you can switch off the fridge for 8 hours as see a maximum rise of just 3 degrees from 4-7 degrees.
If you cant, then perhaps the cheapest route of to make the fridge much better insulated, as after all you dont usually use the fridge at the hours between midnight & 8 am. Which means that you dont need to run the system at all, so reducing your overall demand by 30%- a few sq metres of foil backed PU insulation will cost about £20!

 

[Heckler]

i agree, on my bene 351 i have fitted a 56 watt solar panel, went down this weekend, eber on all night plus the fridge and didnt even have to think about power, (3 times 85 amp batteries) the panel charges up all week/weeks and when i go at the weekend power is not an issue.
Stu