Our water heater gave it up a week ago last Sunday.

[DaveEvans]

The one in the house, that is. But it reminded me that devices don't always just keep on trucking.

That Tuesday I went to the NE Boat Show, with no plans to buy any "stuff" this year.
Then I was lured by the two SeaFrost vendors to consider 12v refrigeration to replace our three-decade-old engine-driven system. But won't we then just have to run the 'beke to charge the batteries instead of the holding plate? Oh, ah, yes, solar!
Over to Hamilton-Ferris (who are also just across the canal from here) who have small 50w panels - two would fit nicely on our dodger. (Don't have a bimini.)
Most of the Sabre owners I know have moved on to 12v systems. (They're also repowering, but I don't want to go there. Although Hansen Marine said they'd rebuild our 27A, no problem. Even come and pick it up!) But I digress.
Any experience up north here with solar-powered refrigeration and its amp-hour needs? Yes, size of the box, quality of the insulation and on and on. But can 100 watts of panel cover, or at least make a good dent in, the needs of a 12 fridge system?
Always fun to have a pre-summer project! And it would open up lots of space in the engine compartment. Plus a freezer! Budget, schmudget.
Anyone can cool me down before I spend money?

 

[colemj]

Realistically, 100W of solar is going to produce ~30-35Ah per day if they have full sun and no shadows (I base this on what we see daily from our 700W). This is probably equivalent to an hour of alternator charging if you have a stock small alternator. It is unlikely that this output will keep up with a 12V reefer system unless you have a small, well-insulated box. It may be enough to keep the system running on a mooring while not in use, although several days of clouds might put you deep in an energy deficit, but you would likely be regularly charging by alternate means when using the boat. If on a dock with power much of the time, then that changes the calculus.

An alternative might be an Engle or similar portable unit and use the existing box as an ice box or storage. This could be taken home and plugged in when not in use. This way, you can keep the boat stocked and running, with the minor inconvenience of having to transport the box.

Mark

 

[Craig Cook]

A note on the portable units. I just completed the install of our new Dometic 34X this past weekend. It runs on both 12v and 120v shore power (photos coming). The down side of this setup is that these units are heavy even when empty. Ours lives on a dedicated slide-out shelf in a dedicated locker so once installed I don't plan on moving it but if you get anything larger be prepared. The 34X was a one person job to move but was awkward, this is one of the smaller units.

 

[TomY]

Interesting question, Dave. An old question but the answers are changing as panels become more efficient and cheaper, refrigeration becomes more efficient. And these days, separate cooling units are getting used onboard.

What about your battery storage? Do you have enough to utilize the panels output to store enough power for a day or two(overnight, cloudy)?

 

[Todd D]

I have a dometic 40 qt refrigerated cooler, similar to what Craig has. My 50 watt solar panel keeps up with it and 100 watts would definitely allow you to run it full time. As far as solar goes, you can buy monocrystaline 50 watt solar panels on Amazon for about $85 each and a hundred watt panel for $120 or so. Do buy an MPPT controller to get the maximum charging output from your panels. You can get an MPPT controller for around $100 so your hundred watt solar setup should cost no more than say $225 with a single 100 watt panel or $300 with two 50 watt panels. Note I allowed a bit for wiring and mounting hardware in my estimate. If you install two 50 watt panels and an MPPT controller wire the panels in series.

The refrigerated coolers have vary low amp draws when used as refrigerators (they can also be run as freezers). Mine runs about 5-8 minutes per hour after initial cool down. At 6.5 amps when running daily power consumption comes to at most 25 amp hours.

 

[DaveEvans]

Thanks all for getting past the title!
Mark, welcome back. That's a sadly low estimate of solar usefulness! One advantage of two panels on the dodger is that one of them should be unshaded at any time.
Craig, don't see any room for an extra box in the saloon. Rather use the tucked-away one we have.
Tom, batteries are certainly one of the on-and-on items. We've two 31s, say 220 amp-hours (or 110 at 50%). I need to replace them (as Maine Sail has demonstrated, AGM lose capacity big-time unless super-charged). Considering plain ol' flooded cells; not sure if room for golf carts.
Todd, there are a lot of inexpensive solar panels, but none I've seen offer 50 watts in 23" x 22". Even approaching 30" would be tight on our dodger.

 

[DaveEvans]

Oops! Just found those small, 50 watt, flexible panels.
But Todd, two panels in series? That would negate the point of two panels, hopefully at least one in the sun.

 

[TomY]

Tom, batteries are certainly one of the on-and-on items. We've two 31s, say 220 amp-hours (or 110 at 50%). I need to replace them (as Maine Sail has demonstrated, AGM lose capacity big-time unless super-charged). Considering plain ol' flooded cells; not sure if room for golf carts.

If you don't want your boats refrigeration to tell you when to sail or when to run your engine, going all in, is the best solution. How will you attach the panels to your dodger? Where are your batteries now and is there is easy space for more? How much insulation does the Sabre box have?

One more question,... what did you get to replace your homes water heater?

 

[Ron20324]

I have 2 x 40 watts on my B323, and I leave the fridge running most of the summer. Of course, extended cloud cover has some effect, but the panels still put out some. YMMV.

 

[DaveEvans]

Hi Tom and Ron,
Refrigeration does control a lot of cruising decisions. Or perhaps, provisioning and food storage.
Panels can snap on using their grommets or with Velcro. One never knows about old insulation for sure. Ocean Options suggested a simple melt-down test to estimate the BTU loss.
I'll look st the battery space this weekend.

A Rheem 40 gal, natural gas.

Ron, that sounds decent! Where are your cruising grounds?

 

[Ron20324]

Ron, that sounds decent! Where are your cruising grounds?

Chesapeake Bay, mostly, but also a Delmarva circle.

 

[Paul D13]

A Rheem 40 gal, natural gas.

You'll be very happy with the Rheem, Dave. I replaced ours with an electric Rheem water heater a few years ago.

 

[TomY]

Hi Tom and Ron,
Refrigeration does control a lot of cruising decisions. Or perhaps, provisioning and food storage.
Panels can snap on using their grommets or with Velcro. One never knows about old insulation for sure. Ocean Options suggested a simple melt-down test to estimate the BTU loss.
I'll look st the battery space this weekend.

A Rheem 40 gal, natural gas.

Ron, that sounds decent! Where are your cruising grounds?

I was on the Hamilton Ferris website. I see you are talking about flexible panels? They have helpful info, thanks.

http://www.hamiltonferris.com/products/Solar_Power/SolarFlexx_Panels/94

Have the flexible panels not come down in cost as quickly as the rigid?

 

[Captain Larry-DH]

Dave,
Another data point for you.

I've got a small Isotherm 1.5 Cubic feet, using a Danfoss compressor that draws about 3.2A when running. I have 200w of solar w/MPPT controller and it's "just enough" to keep up with he fridge in the hottest mid-summer weather at 40-degrees north latitude. In cooler weather I have a slight surplus. Extended overcast and it does not keep up.

The Isotherm has a vertical door, and overall I'm not impressed with the insulation. Certainly that's the major issue. Add in that every time you open the door it loses it's cold air; it doesn't keep up when in regular use especially when overcast.

I would recommend a top-opening fridge. Apparently from other people's posts -- the portable ones are more efficient.

 

[DaveEvans]

Larry, that's a lot of amps for a very tiny volume! I like Ron's Chesapeake experience better. Here's our box:

That gray thing is the holding plate, frozen by the conmpressor on the engine. A SeaFrost freezer bin is about the same size, so we'd have the same space, but the block would be a tiny freezer. Not big on iced drinks, but to keep steaks frozen; dare I dream of ice cream?
Not a lot of insulation under the top, but might be decent around the sides. Some measurements be worth it. Could easily add a slab of isocyanate foam under the top.
The $400 Hamilton-Ferris panels sure look a lot like the $100 ones on Amazon and elsewhere. Do they buy the A-grade panels and the others are selling the B- and C-grade? Sure, they have the clever snap fittings (they won't sell apart), but they're not worth $300 for 4. I'll drive over some day and ask them.
Feels like spring here!

 

[Sailor Sue]

Our experience with solar and refrigeration...
The 20 year old Adler Barbor Cold Machine in our boat was not very efficient so we bought a 100 watt rigid solar panel to help keep the batteries topped up on our extended cruise, without having to run the diesel at anchor. The refrigeration totally died the day before our cruise started so we never got to see how well the solar would have worked.

Last spring we replaced the A-B system with an Isotherm 2301. It draws 3.5 amps when running and is designed for a 5.3 cubic foot box. Most of the time we don't need the full volume so I made closed cell foam blocks to fill some of the extra space. (We can remove foam if we need extra space.) We also made a 2 inch thick foam cover that goes on top of the box when we aren't using it or are gone. The box is top loading, and J Boats seems to have done a reasonable job insulating it.

Last summer we turned the Isotherm on after it was installed and never turned if off until we pulled the boat in the fall. We found that our 100 watt panel was able to keep two 100 amp AGM batteries pretty much fully charged without using shore power. One week when we had two days of rain and pretty solid cloud cover the batteries were down to 65 or 70% SOC after a week.

We've been very happy with the solar panel, and the new, more efficient refrigeration.

 

[Gunni]

My 12vdc refrigerator energy budget is 80 Amp hrs / 24 hours. But I can stay well under that by freezing a system of water dispenser jugs I picked up at Malwart, turn off the compressor and use the refrigerator circulation fan to move the cold about. That can get me down to about 40 amp hours. You already have to run your engine to get cold so get a 150 amp alternator with external smart controller, beef up your battery bank to hold more amp hours ...and add the solar panels to extend the time till charge. A seawater heat exchanger would make the whole system a lot more efficient in the summer time and you have the cool water to make it work well.