Generator or No generator, that is the question

[mvweebles]

As others stated, A/C is the big fork in the decision tree. I just redid my entire electrical system. Went 800w solar, 700ah lithium batteries, Magnum 3000w hybrid inverter, 225A Balmar alternator, and Northern Lights 6kw generator. I was on the fence about the generator but because my main engine was out and it needs to be out to get the generator in, I decided to add now rather than risk regret later. We have a small A/C in our stateroom and can run for a couple hours off the lithium, or while underway off the hi-output Balmar. Its an expensive system but works well

We do not use the generator much. But several years ago we were on a friend's boat in West End Bahamas. The no-see-ums were thick and there wasn't even a ducks fart for wind. Tough choice - open the ports for a little relief from heat but get devoured by the no-see-ums, or close the ports and roast. I would have paid a LOT of money for A/C that night. Which I guess I kinda did during my refit.

Good luck

Peter

[Paul L]

In the OPs original list of electric draws refrigeration is not mentioned. For a typical cruising boat it is the biggest amp-hour draw. Running Aircon without a genset is pretty unlikely and going to be impractical for most cruisers. Is aircon needed while cruising? I would have been admantly on the No side before I made it too SE Asia.
A cat offers space for a lot of solar, so for normal use it should be able to cover your needs. That said most of the long distance cats I see cruising still have at least a portable genset.
Having two weeks of rain and cloud cover is not that unusual when cruising. Most people do not want to cover that with their main engine, even though it is possible.
On passage you can have many days with limited solar due to cloudiness and sail shading. At the same time your power needs are increased due to instruments, autopilots and all frig/freezers running.

[JustMurph]

I'll chuck my setup in here as an example.

It's a 48' cat with 1.7kW of solar (latest technology commercial panels - cheap as chips and massive outputs, especially in poor lighting conditions), 5kW inverter, 40L electric hot water, 3 fridges/freezers and a 24V 10kwh lithium bank. The inverter is large, because I run my dive compressor from it (2.7kW load).

On a sunny day the batteries are full and the hot water is made by 10:30am. On such days we can run the dive compressor back to back all day and still have more than 50% in the batteries at the end of the day. On an average overcast day I still fill the batteries and make some hot water. On very overcast days, the bank will run down. There's only once in the last year since I've put this system in that I've had to run an engine to make some extra power.

There will be times where we want to fill tanks on overcast days, or when it's overcast for a week, so I plan to buy a cheap 2kW petrol genny for those rare occasions.

My suggestions:
- Forget "marine" solar panels and get the best of the chinese commercial panels (eg Jinko, Longi, Trina). You get the latest technology for a fraction of the price.
- Install as much solar up as you can. You won't regret it.
- Use individual MPPT controllers for each panel to maximise output in shaded conditions
- Go lithium. They're getting much cheaper, they're far more efficient, they can handle the big currents
- If you're going to run AC on an inverter or inverter generator, remember you need to size for the startup current which can often be 5 times higher than the steady state load.

[noelex 77]

Originally Posted by Dockhead

HOWEVER, the big problem with a large solar installation on a monohull is windage. The previous boat sailed like a pig upwind so I didn't worry about it, but this one will go upwind so I wouldn't spoil that with a giant speed brake.

Many cruising boats have poor aerodynamics. I am not sure this makes much practical difference compared to the more critical hydrodynamics, and other important factors such as the centre of gravity, but it is not difficult to significantly reduce the aerodynamic drag. For example, a streamlined shape has less than the tenth of the drag of round tube of the same frontal area.

Solar panels themselves have very little aerodynamic drag. Many of the top long distance race boats are moving over to solar power rather than a generator based system based primarily on the relative speed penalty cost with the extra weight associated with both the generator itself and the fuel required to power it.

[stormalong]

+1 for no generator and no air conditioning. Put as much solar on the boat as you can. Cook with propane, not electricity.

Save the noise, heat, fuel consumption and maintenance of a generator. Use the space for a huge battery bank. Use the weight savings of no generator and less fuel tankage to add more batteries. The only maintenance for solar is to clean the panels occasionally. If you add wind powered generators be sure not to shade the solar. Fit large alternators to your engines for cloudy & rainy days when solar is not enough.

Learn to use passive cooling. Wind scoops, air circulation, sun shading (but not over the solar panels :-).

[Dockhead]

Originally Posted by noelex 77

Many cruising boats have poor aerodynamics. I am not sure this makes much practical difference compared to the more critical hydrodynamics, and other important factors such as the centre of gravity, but it is not difficult to significantly reduce the aerodynamic drag. For example, a streamlined shape has less than the tenth of the drag of round tube of the same frontal area.

Solar panels themselves have very little aerodynamic drag. Many of the top long distance race boats are moving over to solar power rather than a generator based system based primarily on the relative speed penalty cost with the extra weight associated with both the generator itself and the fuel required to power it.

Aerodynamically efficient solar installations are certainly possible, and if I were to do a new build, I would certainly want something like that. If you build the solar panels into cabin tops and decks there is virtually no extra drag. That would be the way to go.

This is how they do it on the Vendee Globe boats:


https://www.yachtsandyachting.com/ne...th-solar-power

But flat panels mounted horizontally are awful -- according to a friend of mine who is an aviation engineer and sailor and knows how to calculate it. Heeling and going upwind the bottoms of them are presented to the wind, and they act like speed brakes. Catamarans don't have this problem, but you can't get away from it in a monohull.

I guess it doesn't matter all that much to those who believe that "gentlemen don't go to weather", but as someone who has done as much as 1000 miles upwind on one passage, it's painful for me. No solar panels for me, no bimini, no extra junk. An aerodynamically clean superstructure is one of the most important factors in getting upwind, in my experience. You're right of course that hydrodynamics are even more important, but poor either one can kill your upwind ability.

[Elleroo]

Lots of good arguments for and against a generator.

But Murphy's Law should surely be applied.

Better to have a genset and run it an hour a week just to keep it active, than to need it and not have it.


Solar setups DO break down. The inverters are the achilles heel. Along with salt.

Mastervolt are big suppliers to big marine installations, and I have a 4kw setup on my home. The first analogue inverters lasted little more than a year. The later digital inverter has run faultlessly for six years now.

So, choose your inverters well. But they will break down at the worst possible moment. Murphy knows.

[Bill O]

Originally Posted by noelex 77

Designing an effective boat system that works well with or without a marine diesel generator is quite different. This is why when questions like this crop up on the forum those with a generator cannot imagine running the boat comfortably without a generator and those without a generator cannot imagine needing one. In truth both systems can be made to work well.

Personally, I prefer the reliability, simplicity and lack of maintenance associated with designing the boat to run off predominantly solar charging and without a generator, but this is not the correct answer for everyone.

If you want to run air conditioning at anchor then a generator based system is generally better. It is possible to run some air conditioning from just solar, but only on largish cats, and the system complexity rises, defeating many (but not all) of the advantages typically found on a solar boat.

Other than air conditioning, solar equipped boats can offer all the comforts, including the greatest luxury of all, which is the reliability and time to enjoy the cruising lifestyle.

+1 Without knowing the OP's specific power needs and where/how they will be using the boat, this is the best general answer.
The OP needs to layout the specific powers requirements they will possibly encounter during normal daily use. This will help for the initial design of the solar field and battery bank size. With more time out cruising, you may need to expand your solar to keep up w/your needs.
I'm really impressed that some can run dive compressors, etc. and have plenty of power in the bats at the end of the day. Based on that and keeping things simple, would say you probably do not need a gen.

[s/v Jedi]

I recommend you get a little portable generator and spend a year living aboard before making any further decisions.

This is our first year with massive upgrade to lithium house battery and big solar array. Last year we had to run the genset three times a day for breakfast, lunch and dinner time while this year we only ran it a couple of times to see if it still works. We don’t even need it for our 40 gph watermaker.

About panels being speed brakes while sailing upwind: we installed 1,875W and our first offshore passage was a Gulf Stream crossing from Florida to the Bahamas a couple months ago. We had 15-20kts wind, at a close reach, buckling the current a bit to make Memory Rock to cross onto the bank. We easily reached hull speed at 11-12 knots through the water and if the panels are a factor at all, it is minor. The boat felt faster but that was due to removing lots of weight as we now have space to store it ashore... or simply threw it in the dumpster now that we’re back in the 1st world where everything can be had with free next day shipping

[OneKoolCat]

I have a 40 foot cat, and I don’t have a generator. I have 720w of solar on my bimini top. I have 1200 watts in foldable solar panels that I place around the boat in various temporary configs. They usually show someone holding one like a briefcase as they are hiking. They fold up small but are much heavier than I would like. I don’t use these while I am sailing. In fact, unless I am using the a/c a lot, I am usually too lazy to put them out.

I have a 1600ah lithium battery bank and a Victron Multiplus 3000. I also have 2 girls that seem to have an ever-growing list of electronics. Hot water I only turn on for showers we tend to bunch up the showers at night, so it ends up being on for only about an hour. My water maker takes a lot of juice so I either must be full-ish on the batteries, in full sun, or run an engine while I start it up. Once started it runs fine, if I stop and start it for some reason it is fine. Just LRA on cold starts.

That said, nothing wrong with a generator, but I tried get down to one fuel. My dinghy has a torqueedo cruise 2.0 and has its own solar panel. Also, I am an engineer, so it was fun for me to build these systems myself. If you don’t enjoy that kind of thing, I am sure it can be pricy. Every few years the solar gets better and off grid living gets a little easier.

[joelhemington]

Originally Posted by MarkHopk

Hi Fellow Sailors,

We are putting together a energy system for our 40 ft Catamaran.
Please can we get your suggestions on the below:-

We will be powering, lights, laptop, navigation, fans and other day-to-day household needs.
We will on occasion utilise a washing machine, aircon and small low amp dishwasher.

Could we do this without a generator and by just having the right lithuim battery, inverter and solar panels? And if so How much AH lithium batteries and how much solar Watts would we need?

Thanks.

Due to the weight, figuring a way around a big ginny would be optimal for a cat. Awhile back here Franziska (a forum member) was discussing 500 watt solar panels for her boat. If your cat has the typical hard bimini, you could conceivably put as many as six of those bad boys on and realize about 1,000 AH per day under normal conditions. 2,000 AH of FIPo4 would be nice but will need to be charged somehow. Watt and Sea makes a nice (and expensive) pod mounted hydro generator which is similar to a sail drive in appearance. A pair of these could top off that big battery bank under sail but they only work when you're moving. The downside is, you rarely use A/C under sail, but you can always run everything else and save the batteries for the hook. Aside from all that a small Honda 2000i wouldn't be bad to have. They run on the same gas you're already using in your outboard and are small enough to stow in a cockpit locker without all the weight and maintenance of a full sized ginny. Plus they're very handy for those cruiser parties on the beach With enough solar and battery banks, you could conceivably go all convection in the galley, thereby reducing the need for A/C and using Propane for the grill only with a couple of much smaller tanks.

[Cpt Mark]

A lot of good points here. My cat is 35' and came with a diesel genset. Works flawlessly. Installing 840ah LiFePO4's when they get here and building a hardtop bimini for maybe 600 watts of solar. My watermaker is 120V and I should be able to run that off the inverter. I'm hoping I can power my scuba compressor from an electric motor which would be less expensive than a small diesel engine and zero exhaust fumes to be concerned about. While I'd love to get rid of the weight on the genset it is comforting to know I can push a button and have plenty of electricity. And the fuel comes from the main diesel tank. Someday we'll get small lightweight diesel outboards and my gas one will be gone. I've eliminated propane from my boat completely. I don't have to worry or deal with finding adaptors in different parts of the world and it's one explosive gas I am no longer concerned with. Plus, induction cooking does not heat up the interior of the boat.

Would i have put in a generator had my boat not come with one? Not sure. I like redundancy in my systems and having had an electrical failure at sea before and my portable gen (not a Honda) which had always started... failed to start or ever run again. 2 days hand steering in less than desirable conditions was not something i care to repeat.

I had a reverse cycle heat pump which worked great except in the wintertime because the water was too cold for the 2 coldest months of the year. As a liveaboard that wasn't fun. I sold it and have reclaimed that space for storage which I think will make me happier in the long run. Having lived in the tropics AC is a luxury but not a necessity for most of the time.

[JustMurph]

Originally Posted by Cpt Mark

I'm hoping I can power my scuba compressor from an electric motor which would be less expensive than a small diesel engine and zero exhaust fumes to be concerned about.

Totally doable. I have a Bauer Junior II that I run purely on solar generated power. There are a few ways to do it. The issue you need to get around, is that the startup power draw of the 2.2 kW single phase motor is just over 10kW for around a second. My 5kW Victron Multiplus which is rated to do 10kW for 30 cycles, can't quite start it.

I tried using the same softstarter that Big Beakie uses on his similar setup, but had no luck. So, I swapped out my single phase motor for a 2.2kW 3 phase motor and bought a small Siemens single phase to three phase VFD (variable frequency drive). This lets me ramp the motor up to full speed over 5s, bringing the peak power down within the inverters rating. It works really damn well. The downside is that you add another layer of inefficiency to the system, but functionally it hasn't proven to be an issue so far.

[chrisr]

Originally Posted by joelhemington

Due to the weight, figuring a way around a big ginny would be optimal for a cat. Awhile back here Franziska (a forum member) was discussing 500 watt solar panels for her boat. If your cat has the typical hard bimini, you could conceivably put as many as six of those bad boys on

while i don't disagree totally with the thought, what a lot of non-cat folk don't realise is even with the big roof space it is not always possible just cover it with solar panels

eg you need access to the boom (for reefing, maintenance etc)... there are hatches to open...toys to stow...control lines

of course we all have the targa bar, but there are windage and trim issues

sure we can fit more solar than a mono, but it's not not as easy as you'd think

cheers,

[Simi 60]

Originally Posted by chrisr

while i don't disagree totally with the thought, what a lot of non-cat folk don't realise is even with the big roof space it is not always possible just cover it with solar panels

eg you need access to the boom (for reefing, maintenance etc)... there are hatches to open...toys to stow...control lines

of course we all have the targa bar, but there are windage and trim issues

sure we can fit more solar than a mono, but it's not not as easy as you'd think

cheers,

Not to mention sail shadow knocking out a large % when underway
That is, if they actually sail.
Many these days seem to motor more often than not in these parts at least.