Air Conditioning & Watermaker on a no-Gen cat - AC vs DC

[3cdad]

We plan to take delivery of a Seawind catamaran in 2022. It will have a robust solar and lithium system, and no generator. The manufacturer is currently spec'ing out AC air conditioning and AC watermakers. But that means that the inverter will have to get involved, which also means a significant loss of energy from converting the lithium's DC to AC. In boats without generators, but with ample lithium and solar, doesn't it make more sense (as in energy efficiency) to install DC air conditioning and a DC watermaker?

[IslandInfedel]

Unless you have miles of solar, you probably are only running AC with shore power, my understanding is running AC cooling takes tons of power, a water maker you wouldn’t really need at the dock as you likely have water at the dock.

I’d go AC for the AC/heatpump

I’d go DC for the water marker

[mako]

The DC air conditioners that I’ve seen are extremely energy efficient. However they are like 3-4X the cost of a “normal” aircon.

If you have a large enough battery capacity you could consider installing just a single unit. On typical 50% duty cycle you may be able to cool your stateroom through the evening.

Of course the next day you need to recharge those batteries. Catch-22

[sailorboy1]

My boat has factory air conditioning. It didn't come with a factory generator.

I bet this isn't all that uncommon.

[Statistical]

If you don't have a generator your air conditioner use will be limited to shorepower so AC is fine. As for watermaker DC may be marginally more efficient but AC also works fine too.

[NaClyDog]

Originally Posted by Statistical

If you don't have a generator your air conditioner use will be limited to shorepower so AC is fine. As for watermaker DC may be marginally more efficient but AC also works fine too.

Not true. Many newer cat builders are including air conditioning without a generator. If the customer has enough battery capacity and solar panels it isn't a problem.

[Statistical]

Originally Posted by NaClyDog

Not true. Many newer cat builders are including air conditioning without a generator. If the customer has enough battery capacity and solar panels it isn't a problem.

Ok however that is a huge if. In the vast majority of cases boats don't have sufficient solar to run AC for an extended period of time and AC is limited to generator or shorepower.

We are talking about a LOT of solar and a very large bank if you don't want to lose air conditioning on low generation days. However I do concede it can be done. If that is the case then DC and the most efficient air conditioner you can find is probably worth it.

[sailjumanji]

It's surprising that they spec an AC powered watermaker. Are you sure about that? When I ordered my Seawind - albeit built in second half of 2018 - they were installing Spectra system watermaker. I have a smaller one, and it is very efficient and we we have no issue running it with the solar panels. Downside is that they are fairly expensive.

We dont have a permanent generator either. We do have the factory air conditioning though, but its an AC setup. We either run it at the dock, or use our Honda 2200. It will power the 18k btu unit. However, most times we just open the hatches as air flow is excellent.

[Dtm67]

It depends on which part of the world you are in and how good of a solar day is typical.

We have 1200watts of solar and in the Mediterranean summer are typically 100 percent SOC by 2pm. We have enough excess to run our 8 amp 220volt AC watermaker for an hour (120 liters per hour) and still have more than enough to get to the next day and repeat if we choose too. Draws 1750 watts from the inverter while running. Days we don’t make water we turn on the 1200 watt calorifier for hot water. Our 5kva inverter handles all of that along with induction cooking off of 600ah lifepo4 batteries.

A cloudy day means no water without firing up the genset...but those are rare in summer here.

By fall we find ourselves firing up the genset gradually more and more. More solar would help...

We run 220v Aircon off batteries in one cabin all night while at anchor but need the genset to get us back to where solar can do the rest. It would take at least double my solar array (maybe more) to have it run that way off the sun.

[Augi]

Originally Posted by 3cdad

We plan to take delivery of a Seawind catamaran in 2022. It will have a robust solar and lithium system, and no generator. The manufacturer is currently spec'ing out AC air conditioning and AC watermakers. But that means that the inverter will have to get involved, which also means a significant loss of energy from converting the lithium's DC to AC. In boats without generators, but with ample lithium and solar, doesn't it make more sense (as in energy efficiency) to install DC air conditioning and a DC watermaker?

As you suggest going with DC air conditioners and DC watermaker is more efficient. My understanding that going with AC air conditioners and AC water maker the losses are 30-40% versus DC.

Other things to consider are even though what Seawind is specing for you will likely cost more there are advantages to have everything come for the factory in terms of less hassle, running wiring, running ducting, all the components ought to be complementary, potential warranty issues maybe can be avoided if a manufacturer of one comment will not honor their warranty because they say their component is not compatible with a componet you installed.

I think Seawind will run the ducting, wiring, prep the electrrical panel, etc for a generator or air conditioning. If you are sure you want air conditioning have them run the ducting, wiring at least at the factory.

I think Seawind will install larger Master Volt alternators on the engines. Depending on your climate, how much you motor, how much capacity lithium and solar you are going with that set up may provide enough juice to satisfy your need for air conditioning when not connected to shore power. Air conditioning is the big power drain. Before spending the money on being able to run air conditioning including maintenance when not connected to shore power consider going with more 12 V fans, wind scoops, hatch fans, etc

Another option instead of a generator is to go with a new alternator / generator( run by a special CPU that Nigel Calder helped develop that you can put on one or both engines( see links below). At max RPM Calder says the alternator / generator will generate 8KW to 9KW and at a high idle will generate approx. 4KW. At low idle Calder says enough load is put on the engine to not cause the problems/ inefficiency associated with running engine with low load to charge the batteries. If it does what Calder claims it is more efficient, weighs less and requires less maintenance/hassles of having an independent generator. The installation does not look like it is a lot different than installing a new alternator. The company says they will do all the engineering for whatever the specific engine, solar capacity, batteries chemistry / capacity for whoever does the installation. It is a new product so check it out carefully, get an in person demo. From what I know Nigel Calder is not apt to sell out and put his name on a product that can't do what he says it can do.

https://integrelsolutions.com/

https://www.youtube.com/watch?v=0uTNjfb3MNQ

https://www.youtube.com/watch?v=5hHf8qII1Bg

If you have not already seen it, checkout the video below about setting up a Seawind for long term cruising.

https://www.youtube.com/watch?v=6AsQEg-7oks

[wathey]

Great thread. Some quick research yields a DC Mabru unit at 12k btu is about 5500 US. A similar dometic AC, AC unit is 3500 so there's a few $k difference but relative to a new Seawind this is a nominal expense. Bigger question is whether Seawind will take on another manufacturer relationship if their current AC supplier doesn't have a similar product. I don't agree with the statement you must have a genset. I do agree that you must have a monster sized Lipo pack. The Mabru states it draws 40 amps. If you have three you may be limited to running specific hulls or 1 hull and the saloon to achieve the desired runtime. The largest lipo pack on a cat of that size I have seen in person was (6) 280ah lipo units to achieve 1680ah. That boat did have a smaller genset to charge the pack on rainy days when they were at anchor when the 2800 watt solar array could not do the trick. But seriously that battery bank was likely around 22,000 US and the solar setup another 20k, at least , I don't have specifics but that was aftermarket installed the factory pricing could be significantly higher. My guess is that your plans will bump the purchase price by at least ten percent. I think the videos they have posted are great for understanding the math involved. Also check out sailing Uma and their elctrobeak series. It's about using a forklift battery as a main engine but they do a great job explaining amp heures, watts, DC controllers and the difference between AC and DC electric motors.
Important is where you are cruising. In many areas we only run our AC just when we are cooking at anchor and it gets over 80 in the saloon. Further south like Panama you will run it much more.
It will also be interesting to see how this effects resale value but only time will tell how the market responds to these DC based boats. I think there are others heading in that direction. There have been a few threads about DC gensets over the past few years which is ultimately where this is going.

[Augi]

Originally Posted by wathey

Great thread. Some quick research yields a DC Mabru unit at 12k btu is about 5500 US. A similar dometic AC, AC unit is 3500 so there's a few $k difference but relative to a new Seawind this is a nominal expense. Bigger question is whether Seawind will take on another manufacturer relationship if their current AC supplier doesn't have a similar product. I don't agree with the statement you must have a genset. I do agree that you must have a monster sized Lipo pack. The Mabru states it draws 40 amps. If you have three you may be limited to running specific hulls or 1 hull and the saloon to achieve the desired runtime. The largest lipo pack on a cat of that size I have seen in person was (6) 280ah lipo units to achieve 1680ah. That boat did have a smaller genset to charge the pack on rainy days when they were at anchor when the 2800 watt solar array could not do the trick. But seriously that battery bank was likely around 22,000 US and the solar setup another 20k, at least , I don't have specifics but that was aftermarket installed the factory pricing could be significantly higher. My guess is that your plans will bump the purchase price by at least ten percent. I think the videos they have posted are great for understanding the math involved. Also check out sailing Uma and their elctrobeak series. It's about using a forklift battery as a main engine but they do a great job explaining amp heures, watts, DC controllers and the difference between AC and DC electric motors.
Important is where you are cruising. In many areas we only run our AC just when we are cooking at anchor and it gets over 80 in the saloon. Further south like Panama you will run it much more.
It will also be interesting to see how this effects resale value but only time will tell how the market responds to these DC based boats. I think there are others heading in that direction. There have been a few threads about DC gensets over the past few years which is ultimately where this is going.

Lithium batteries store energy. They don't generate energy. If the Op wants to run air conditioning, for example 10 hours at night(with no noise), on consecutive nights when not connected to shore power optimally he needs a way to charge the batteries as quickly as possible the next day before the next night when he will want to run the air cond. 10 hours again + maybe run the watermaker + run the rest of house, etc. So if the plan is to not to motor that day(and it happens to be cloudy so not much from solar), then the OP needs an independent good size generator or large alternator / generator connected to the aux. engine(s) to charge the batteries as quickly as possible. Lithium batteries can take huge input so they can be charged quickly if you have ample ability to generate energy. In the above example if no independent generator or large alternator(s) / generator(s) connected to the aux. engines the OP would have to run his engines to charge the batteries all day(with the noise), at low load possibly damaging the aux. engines and at high cost(low efficiency), in order to run the air conditioning for 10 hours that night and consecutive nights.

It all depends on the OP's needs, wants, and desires for his intended use. If he is going to motor a lot every day, has lots of solar, big capacity of lithium batteries, wind generator, hydro generator, almost always clear days and he can live without air cond. sometimes he does not need an independent generator or large alternator(s) / generator(s) connected to the aux engines.

If possible the best way to go if it works for the OP is be able to live without air cond. except when connected to shore power. Consider if the alternatives such as more 12 V fans, wind scoops, hatch fans work well enough when not connected to shore power. The other big users of energy that the OP may potentially want like watermaker, washing machine, mircrowave don't have to be run for long periods of time every day as air conditioning does if the OP wants to be cool for long periods of time daily away from shore power.

[IslandInfedel]

So if you want AC cooling at sea you need a gen set

[joelhemington]

Originally Posted by 3cdad

We plan to take delivery of a Seawind catamaran in 2022. It will have a robust solar and lithium system, and no generator. The manufacturer is currently spec'ing out AC air conditioning and AC watermakers. But that means that the inverter will have to get involved, which also means a significant loss of energy from converting the lithium's DC to AC. In boats without generators, but with ample lithium and solar, doesn't it make more sense (as in energy efficiency) to install DC air conditioning and a DC watermaker?

Think about where you'll likely be using theses items. Most cruisers won't use A/C while at sea but will use them in a marina at a dock - no problem for the AC unit since you'll be plugged in. But you really don't want to be making water in a marina - so the DC option would be better while under sail. If you have the battery capacity, the extra cost of the DC A/C might make perfect sense to you if you get caught in some steamy doldrums at 90 degrees and 80% humidity.

[Augi]

Originally Posted by Augi

Lithium batteries store energy. They don't generate energy. If the Op wants to run air conditioning, for example 10 hours at night(with no noise), on consecutive nights when not connected to shore power optimally he needs a way to charge the batteries as quickly as possible the next day before the next night when he will want to run the air cond. 10 hours again + maybe run the watermaker + run the rest of house, etc. So if the plan is to not to motor that day(and it happens to be cloudy so not much from solar), then the OP needs an independent good size generator or large alternator / generator connected to the aux. engine(s) to charge the batteries as quickly as possible. Lithium batteries can take huge input so they can be charged quickly if you have ample ability to generate energy. In the above example if no independent generator or large alternator(s) / generator(s) connected to the aux. engines the OP would have to run his engines to charge the batteries all day(with the noise), at low load possibly damaging the aux. engines and at high cost(low efficiency), in order to run the air conditioning for 10 hours that night and consecutive nights.

It all depends on the OP's needs, wants, and desires for his intended use. If he is going to motor a lot every day, has lots of solar, big capacity of lithium batteries, wind generator, hydro generator, almost always clear days and he can live without air cond. sometimes he does not need an independent generator or large alternator(s) / generator(s) connected to the aux engines.

If possible the best way to go if it works for the OP is be able to live without air cond. except when connected to shore power. Consider if the alternatives such as more 12 V fans, wind scoops, hatch fans work well enough when not connected to shore power. The other big users of energy that the OP may potentially want like watermaker, washing machine, mircrowave don't have to be run for long periods of time every day as air conditioning does if the OP wants to be cool for long periods of time daily away from shore power.

Maybe a good way for the OP to go, may be have Seawind prep at the factory for the boat to receive an air conditioning, an independent genset, and to easily use portable rain main water maker. That is run all the electrical, duct work, prepare the main electrical panels, install lots of 12 volt fans. Then see how it goes including try out wind scoops, and hatch fans, etc to see if going without air cond. works. If the OP knows he wants air cond. when connected to shore power then obviously have it installed at the factory. Next step up to consider to install at the factory would be larger Master Volt alternators for each engine. After having the boat for awhile if the daily energy needs exceed what only the above can provide inlcuding with what the OP already has specified then add good size independent generator or something like the Integrel large alternator / generator that connects to the aux engines. One of the good things about the Integrel product is it does not need it's own through hull.