Alternator + Inverter vs Generator

[s/v Jedi]

I have noticed that it is standard practice in the USA to heat water with the AC powered electric element. In the EU, every boat uses the heat exchanger in the water heater instead, plumbing it into the genset or engine coolant loop.

Doing that saves you a lot of energy/fuel because you use the waste heat from the diesel, improving it's efficiency. It is also much faster. We only use the electric element on shore power or to accelerate making hot water when there's enough AC capacity left.

If you run a 10A (1,200W) element for one hour it cost you 1.2kWh. When you use the heat exchanger, you have water of the same (very hot) temperature after 15 minutes with zero energy consumption.

Heat exchanger: After removing the exchanger from our old genset and cleaning it, I couldn't find a single indication of corrosion or other problem. We very rarely flush the genset with fresh water, only during haul-out's so that is once every 3 years. It is a cupro-nickel element and I guess that makes the difference.

I dislike electric cooking (like every chef dislikes it ;-) but I am looking into it because propane is what we run out of first. We have 2 x 20 pound propane bottles and it lasted about 6-7 months without using the BBQ too much. Now we changed baking bread with a breadmaker instead of the oven and it lasts us about 8 months. Still less than our diesel and I would like to use the BBQ more. So the choice is an extra 20 pound bottle or more electric (diesel).

Highlander: you are fine with your water setup, but that is because you are always near a good source of water. When we leave for the San Blas again, we will be on our own for 6 months. There are some Kuna villages that have a water faucet in the village center but it isn't drinking quality and they need it for themselves anyway. It would also mean sailing back to that village every week (which can take days) and a day of hard labor hiking up and down with jerry jugs between dinghy & faucet etc.
Most boats in the San Blas without a watermaker only stay for a week or two (sailors, not cruisers) or beg for water with boats that do have RO. You just need RO there and in every similar area.

ciao!
Nick.

[Joli]

Using the main propulsion engine to make ice cubes gets expensive quickly. Buy the genset and back it up with alternators and inverter.

[motion30]

I used the honda and an inverter for a while Found a used westerbeke on craigslist did the istall myself, I love it no need to haul gas cans, quiet all the power I could ever need By the way my small miro wave run tru the inverter uses 100amp dc of course it is needed for a short time

[Highlander40]

Nick,
Yes we have a main engine hot water loop too but that only works when you pick up and go. Everything is sized a bit smaller. The hot water tank is 6 gal. The time to heat electrically is maybe 20 min.

Most of these boats are not used for more than long weekend trips. We are the oddballs at the yard. Always wanting things to work! Trying to get the most out of what we have. Putting in a bigger/better fridge was great and switching all lighting to LED helped too.

The cool thing with this boat is the shallow draft, 22" so rather than travel far afield we can go where few can. Right now we want to go to the Delmarva peninsula and see the wild ponies on the beach. Very skinny water behind the barrier beaches.

Last summer we went to the SE corner of Cape Cod MA between South beach and Monomoy island. Not one cruising boat to be seen. Natural ocean beaches with full -grey seal escort for all excursions.

Not that I wouldn't want to be where you are but we can have adventure wherever we are.

[Highlander40]

Nick , about the cooking element, They are just coming out with inductive heating units for boats. I would swap one in but don't know if it will fit.

Anyway, the Dashews have been using one and like it.

[Dockhead]

Originally Posted by s/v Jedi

I have noticed that it is standard practice in the USA to heat water with the AC powered electric element. In the EU, every boat uses the heat exchanger in the water heater instead, plumbing it into the genset or engine coolant loop.

Doing that saves you a lot of energy/fuel because you use the waste heat from the diesel, improving it's efficiency. It is also much faster. We only use the electric element on shore power or to accelerate making hot water when there's enough AC capacity left.

If you run a 10A (1,200W) element for one hour it cost you 1.2kWh. When you use the heat exchanger, you have water of the same (very hot) temperature after 15 minutes with zero energy consumption.

ciao!
Nick.

All the boats I've ever looked at, EU and US, all have at least two ways to heat water -- electricity and main engine waste heat. In the UK where most cruisers have a Webasto or Eberspaecher central heating system, there's a third way -- a loop off the hydronic heating circuit.

Waste heat and electricity are complementary, not competitive -- when you're motoring you use the engine, of course, to heat your water. If you've on a dock, you will not be running your main engine, but if you've got a power connection, you can heat water with electricity.

On our new boat the heating is running most of the year, so the water is always hot and we don't bother with the other methods.

By the way, electrical water heating has another use -- to make a load for the generator. It's not too good to run your gennie at only 40% load, so you can consider a kW or so of power used for water heating as "waste heat", too, if you don't have enough other electrical loads, while you're running your generator.

[s/v Jedi]

What I know is that the Northern Lights dealer in Ft Lauderdale never had the question on where to connect the waterheater to the genset's coolant loop before. They just don't know sailboats, it all motorboat stuff they do.

So, we don't use the main engine for hot water, just the genset.

On heating and Cape Cod and stuff. Well, you guys want to come south but we're coming up the US east coast ;-))
So, we'll have to install heating too. I ripped out the old Webasto years ago, didn't even try it first. I plan to install a big Webasto or Eberspacher plus extra heat exchangers for both engine and genset. It will become a big loop and include the water heater too. If I would add electric circulation pumps for genset and engine coolant loop, I can even pre-heat them from the Webasto or heat stored in the water heater ;-) So many options there. Currently, my only heat is the reverse cycle of the A/C

On electric cooking: nah, no induction for me because a good wok needs flames. I will stick with propane I think.

cheers,
Nick.

[Dockhead]

Nothing wrong with reverse cycle of AC if you're on a dock with external power. It's a particularly efficient heat pump (sea water as heat source). I would run that in preference to the Eberspaecher, if I had AC on board. Our old boat had that, but had no generator so was no use in cold anchorages.

Really interesting idea about your big loop. I would get some professional consultation before just hooking it up, however. The hydronic heaters have pumps built in and very complicated fail-safe controls. I'm not sure if they will passively take an externally pumped flow of water. Will be great, though, if it works. One loop to get heat from whatever happens to be running.

I have an Eberspaecher heater on an old Land Rover, which, besides for cabin heat, I use to preheat the engine in cold weather (without which, it would never start, about two minutes preheat for every degree below zero C). Ought to work on a boat too.

[bobfnbw]

Originally Posted by s/v Jedi

On electric cooking: nah, no induction for me because a good wok needs flames. I will stick with propane I think.

cheers,
Nick.

Nick, induction cooking is the future. Seriously, it cooks better. Period.
For wok, then you use propane. But when cooking with induction, there is less heat in the cabin, less moisture, and less hassle going for gas. You can run it off a inverter with the smaller ones. It costs are low. Yeah you need special pans, but you might have them already.
I have a resturant quality, gas stove in my home, and prefer the induction cooktop I have. Its just quicker, and you can control the heat better. Clean up is fast too.
Sure gas is great to cook with, but I believe we will use the portable 1800 watt induction more that a propane stove. I will reserve the propane for the grill or oven. And a convection microwave might take care of most of the oven stuff.
But a generator is necsessary first. That is still down the road.
Bob

[s/v Jedi]

Yes, a combination of induction and propane would be great. I'm not sure about finding room for that though....

cheers,
Nick.

[akio.kanemoto]

Originally Posted by s/v Jedi

Hi Akio,
Your charging system sounds fabulous and much like our setup. Now, you only need to install a generator ;-)

*grin*

I say that because no, you have no optimum balance at all. Let's do some math:

you have 2 x 120A alternator. When you take the output of those directly into an inverter, this is what you get: 2 x 120 = 240A @ 13V. That is 3,120W into the inverter which is 95% efficient so you end up with 2,964W. Let's make that 3kW. Now, after 1 hour you have generated 3 kWh of energy at the cost of 4 liters, let's say 1 gallon.
My 6 kW genset: when I run it for 1 hour at full load, I get 6 kWh and consume 0.5 gallon of fuel. That makes the genset 4 times (!!!) as efficient.

Now, let's just say you run that 1,000 hours in a year and I generate at half output so equal power ,also 1,000 hours in that year. You consume 1,000 gallons of diesel while I consume (at 3 kW load 0.35 gallon/h) 350 gallons. The difference is 650 gallons of diesel and now it comes down to the cost of diesel. Here in Panama diesel currently costs $2.63 per gallon so you just lost 650 x 2.63 = $1,700. When you do that 8 years in a row, like we did with our genset, your extra cost is 8 x 1,700 = $13,600. I paid $7,400 for my genset and even if I deduct that, I end up $6,200.- cheaper than you but hold on: you also have 8,000 extra hours on your main engine. And your engine still takes much more oil than a genset (40 oil changes for 8,000 hours means 80 liters extra oil at how much per liter?) more expensive filters, more noise, heat, more expensive replacement parts and the list goes on.
You will never beat a genset because it's like negrini wrote in his post: the genset is tuned in a way that you can never beat with the propulsion engine.

Just as an additional point - it's only 4L/hour because I made a mistake with my rpm and pulley ratios - I calculated based on 2800 rpm, as I was getting too excited and started with by looking at the efficiency curve instead of required power... so I chose the most efficient spot for fuel consumption and went from there - but don't need the full 27HP at that rpm... I only need about 10HP...

So going with 2200 rpm - I could have had this down to 2.3L/hour - but your math still works out better... (but the difference is not as hideous as before.

On a 40' boat you can find room for a genset. If not, you can make room. You are on the small side for one but I have seen 36' boats with a genset. Believe me, I had to make room too and make compromises for accessibility even. If all else fails, you can buy a gas-powered Honda generator and still save significantly.

Believe me, I am really short on space (and waterline).. this is an old racing boat with quite a narrow beam that I've totally ripped out the insides of and redone, but unfortunately the hull is still the same size as when I started... I was feeling romantic at the time so thought against buying a brand new beneteau (we'd have been "out there" for about 4 years by now with that option... *sigh*) .... but this is another story..

On the Honda - yes I have an EU2000i and in fact bought it specifically for this reason originally, thinking of the better fuel economy etc - but there are again various limitations which I've been wracking my brain over and can't resolve.

I have 250L of diesel tankage and 200L of water. Philosophy here was that "I can always make water, but not diesel"...

Batt bank is approx 700AH AGM. Chosen such that running my hideous 240A alternator combination, I can pump the bank full in about an hour. During that hour, I can also use the watermaker (cat 247 pump) on the engine (bought already.. oops) - to produce about 100L of water... about half the tank - meaning no limitations on water usage.

The only thing left here is hot water - still an unresolved issue. I have a raw water cooled engine - so no heat exchanger.. meaning that even if I take the hose off the exhaust manifold and run it though a really efficient/long externally mounted separate heat exchanger unit before plumbing it back into the mixing elbow, I'd probably only take the chill off the water since the engine will only be running at ~40degC anyway.. this part I'm not 100% sure of and will have to see when the engine is commissioned to see how hot I can actually get the water. (I have a very small hope that it will warm the water sufficiently... but not holding my breath..) If this doesn't work - then I need another solution.

Now the theory here was that at 4L/day diesel consumption - I'd get water, power and maybe hot water and assuming efficient usage/timing with moving around etc - it means 62 days without refuelling - away from civilisation. If I redo the pulleys - this will come down to 2.3L/day - meaning 108 days without refuel... much better.

Now on the Honda option - at the moment, I have no petrol tankage at all. Just jerry cans. Assuming say a max of 80L worth of jerry cans stowed around the place - the Honda eu20i will drink about 1L/hour at full load. Meaning 80 hours of runtime max - and if and only if I can complete charging etc in 1 hour per day - that means 80 days between refuels - which is not too bad. (Please note - I value days between refuels much higher than saving $)

Now comes more complexity - with the Honda - I will need a charger... it has been explained to me that the Honda won't power much more than a 75A charger... so this is way less than the alternators, and won't "saturate" the AGM acceptance rate on the bank... so it's probably more like 2-3 hours to charge the batts..

But, with all the power going to the charger - there's also no power left to run a watermaker with an AC motor.

One saving grace here is that with a Honda - I can buy an intant electric waterheater... and shower with that... but again, not all within an hour.

So to make the honda work - I'd have to do it in series - 2-3 hours charging, 1 hour watermaking, then shower. So we're now back to 4 hours or runtime... and 4L/day.... and with less petrol aboard than diesel - we're down to only 20 days between refuels (not counting outboard usage.. but we'll ignore that for now).

So since I really can't fit a diesel genset - (I really mean this - even the Honda would have to be stored in the cockpit in a purpose made box and will barely fit) - I have limited options for making this work - either somehow massively increase petrol tankage for the Honda, or just run everything off the main engine.

I would greatly appreciate wisdom and solution to this dilemma - but no matter how I look at it, the only way I can solve/optimize the problem is using the main engine.

Of course, I remain open to education and BetterSolutions(tm).


(By the way - there will also be a solar panel in the mix as well to help top up the batts as well.. no windgen though)

The alternator thing you did is great and it will save the day now and then... it does for us. But I would put the watermaker pump project on hold until you're very sure it's the way you want to do it. Why not couple it to an AC motor and run it through your inverter?? That way, you can always opt for a genset later.

Unfortunately the Cat 247 pump just arrived.. but the other thing I just remembered is that to run the 247 at max output - you need an approx 2.5HP motor - which the Honda can't start due to the inductive load at start... :\ So if I couple to an AC motor - I'd have to run a smaller motor and run for longer... thus again increasing fuel consumption...

As you now have a 3kW system, you can look into smaller gensets. They will cost less and use less fuel than my 6 kW at half output. They are also much smaller. When you couple it to a Victron 3 kW charger/inverter with their PowerAssist mode, you can still handle 6 kW (3 kW from genset plus 3 kW from inverter... they get added when needed) during peak usage times. Find the Victron document negrini described, it's an eye-opener.

The problem here is that the last remaining bit of space I could possibly manage for a diesel genset is about the footprint of a Honda eu20i. I've just googled what is available here and there's nothing much smaller than something about twice that size... The only other crazy thing I can think of is to buy a really small air-cooled portable diesel genset - remove the frame and try to wedge it in somehow.. :\

[s/v Jedi]

Well, if all the room you've left is barely enough for a Honda, then you're out of options.

So tell me, where are you going to store your fenders, dinghy, sailbags, bucket, liferaft, provisions, mooring lines etc.? You have no lazaret or other cockpit locker?

cheers,
Nick.

[akio.kanemoto]

Originally Posted by s/v Jedi

Well, if all the room you've left is barely enough for a Honda, then you're out of options.

So tell me, where are you going to store your fenders, dinghy, sailbags, bucket, liferaft, provisions, mooring lines etc.? You have no lazaret or other cockpit locker?

cheers,
Nick.

Howdy,

I have very shallow cockpit lockers - enough to store lines/fenders etc - but outside storage is *very* limited. Even this storage didn't exist before and is being created by shrinking the cockpit width (which is too wide anyway) by extending the seats, adding another front face, installing access hatches and using this space underneath. The cockpit is split in two by the traveler beam - so just aft of the traveler is where the lpg tank goes, and two jerries in a box (or the honda). The good news is that ply/glass work is easy and I have options on fabrication, but no space with which to exercise said creativity.

Sails and other bulky items etc - I will sacrifice a double berth for this below decks. Dingy goes on deck while sailing (flush deck, stainless mounting frames with webbing/tie down). There's also plenty of space for small things - so there's no problem with general items.

Large things and tankage is the issue... I have loads of space for small things (don't know about weight though - but volume is ok)... But the only large place left for a proper genset would probably be right smack in the middle of the cabin sole - where there's about 85cm x 60cm left, and if put there, then we're really climbing over it to get in and out - but could pretend that it's a part of the design of the companionway steps - but this does not really give me warm fuzzy feelings... The other alternative is to cannibalize a quarterberth - but there would be zero access from the side and would further upset an already suspicious trim... and I can't open a hatch on deck to the quarterberths either because of winch placements. Bah.

I could probably fit it athwartships near the bow under the vberth - but this is also getting pretty hard, not to mention an exhaust run of about 12m and the added weight right up front.

For the honda option, I could perhaps find space belowdecks for more petrol stored in bite sized chunks in jerry cans - but that's not a good feeling either..

If I can get the diesel consumption down to 2.3L/day using the main engine - I'm actually relatively happy with it - it's not optimal, and doesn't give me the refuelling once per year option like yourself - but the best I can do in this situation I think. The only thing I don't have any real solution for is hot water. Any ideas on this one? :\

12V water heating/immersion elements... or instant water heating through inverter at 240V... ?

[s/v Jedi]

I think the sewing machine sized Kubota will fit in your cockpit lockers.

For some ideas, look here: Aquamarine, Inc -
28"L x 13.5"W x 15.75"H makes power & water. Check out all the info on that site!!

Also:

http://www.cruisersforum.com/forums/...mbo-14330.html
http://www.cruisersforum.com/forums/...ions-4349.html
HOW TO BUILD YOUR OWN WATERMAKER
NEXT GENERATION POWER ENGINEERING INC.

ciao!
Nick.

[Bash]

Originally Posted by akio.kanemoto

I have very shallow cockpit lockers - enough to store lines/fenders etc - but outside storage is *very* limited.

If my outside storage was that limited, the last thing I'd do is store fenders in the cockpit lockers.

Many cruisers tie their fenders to the pushpit rails when they're not in use. This practice leaves room in the lockers and lazarette for more important uses.