Shore Power Independence

About a week ago a discussion on the practicality of operating a household size refrigerator solely with the power from a set of solar panels was started. After several dozen posts the conclusion was that “yes” it’s probably possible but “no” it’s probably not practical. A day or so ago we found a commercial refrigerator manufacturer of eutectic plate refrigerators who makes fridges that might be able to operate on the power from solar cells. The price of these fridges and whether they would actually work has not been determined. I think the forum discussion has gone as far as it practically can so now it’s up to those who are interested in solar powered refrigerators to buy one and see whether it really works.
Good luck guys. Let’s hope it doesn’t cost too much.

Over the past five years, I and a number of the members of the Murray Chris Craft Constellation forum (the Connie Forum) on the Boat US Manufacturer’s Forum site have been kicking around the concept of Shore Power Independence. Shore Power Independence means making your Connie capable of operating for long periods (days or weeks) without any connection to shore based power sources. Operational, in this case, means both providing a reasonable living environment on board as well as actually cruising. The conclusion of the forum was again that while the concept was possible it was not practical. And so far no one has attempted to actually make their Connie Shore Power Independent.

In order to determine whether shore power independence is practical the first requirements are to make an accurate determination of how much power a Connie uses when away from the dock and whether the generator and/or other power sources can provide it.

None of us had much experience in long term offshore operation but we were able to obtain some very good information from The Voyager’s Handbook; a 570 page tome on ocean crossing and round-the-world-circumnavigations. Sailors who do that obviously need boats equipped for operation for long periods far from shore power cords. The Handbook is a treasure trove of information on offshore operation.

On page 232 we found Table 9-6 which describes the electrical needs of “Highlife” a 52’, eight year old, cutter rigged ketch. The table indicated that the daily DC demands were 115 Ah for House Loads, 75Ah for Activities, and 312 AH for AC loads supplied to the battery bank via an inverter. The peak load is 502 Ah. But not all of these loads occur at the same time so the average load from these three sources is about 301 Ah.
In addition one must add in the power for the refrigerator/freezer which running 24/7 at 12 amps burns about 280 Ah per day. It is the largest power consumer on the boat. The total and average for the day is now 581 Ah.
There are also the inverter loads which include the washer/dryer, hair dryer, toaster, coffee maker, microwave, vacuum cleaner and TV/DVD. They add up to 312 Ah but average out to about 187 Ah. The total and average for the day is now 768 Ah which at 12 volts is 9.22 kWh. This completes the compilation of DC loads.

But there are also AC loads powered by the generator and delivered directly to the loads at 120 volts. They include battery charging at 5 kWh, AC watermaker at 3.4 kWh and a small amount of air conditioning at 5.4 kWh (about enough to cool down the master stateroom so that you can sleep at night). The AC load total is 15.3 kWh.

The total, DC plus AC, load is 9.22 +15.3 = 24.5 kWh which requires 1.2 hours of generator operation at full load, burns about 1.9 gallons of fuel and costs $7.68 at $4.00/gallon.

This is an enormous load and on page 235 the Handbook gives a table which states that the maximum realistic output for solar cells on a 52’ boat is about 100 Ah which at 12 volts is 1.2 kWh. This in turn is not even 5% of the boat’s requirements. There is no chance that solar cells or wind generators are going to generate 24.5 kWh. The only practical source is a diesel generator. The owners of Highlife ran their generator 20 hours a day.

So what can I do? The answer is not much. I could replace the 27 year old refrigerator with a new more efficient one which would reduce the refrigerator and battery charging loads to about one third of their previous levels. But that saves only about 5 kWh (about 1/5 of the total load) which would reduce the daily fuel costs by only $1.53. The old fridge/new fridge swap out would probably cost about $2,000 so at 30 days per year (estimated average use in the Shore Power Independent mode) it would take about 43 years to recover the cost. Not practical!

Sorry this analysis didn’t come out with a more positive answer that indicated solar cells or wind generators would work but that’s the way the cookie crumbles. At least it may have allowed you to avoid a lengthy excursion down a blind alley. In my next post, I’ll try to find a practical way to accomplish Shore Power Independence.
Pete37

Shore Power Independence

In my last post I analyzed the loads that I might have in the Shore Power Independence mode and came to the conclusion that it was about 25 kWh per day. That’s far more than solar arrays or wind generators can provide so I am are going to have to find another solution. At 25 kWh I have to generate an average of about 1 kWh per hour (1000 watts).

Let’s think about what we are trying to do. We aren’t trying to reduce power consumption because we can generate all the power we need for only about $8 per day. That’s not going to be a big financial strain on any of us.

The main objection seems to be the noise and vibration.

If we go the solar panel route we are going to have to generate 25 kWh in about eight hours. That’s a rate of about 3,000 watts. At $360 an 85 watt solar panel will provide only about 25 ampere hours per day and at 12 volts that’s 300 watt hours (0.3 kWh). That’s based on the average daily insolation. So we’re going to need 25/0.3 = 83.3 panels at a cost of about $360 x 83.3 = $30,000. Way too expensive and I doubt that you could even find space for them. In summary it’s too expensive and impractical.

An alternative would be to buy a small 4kW diesel generator for $4,000, spend $1000 to install it and buy an inverter system consisting of a 3000 watt inverter, a 100 amp battery charger and about 600 Ah of golf cart batteries for another $1,200. Total cost about $6,200. I’d run the genny at ¾ load 2 hours at breakfast, lunch, dinner and midnight snack generating about 24 kWh. A small 4kW diesel can be very quiet so it won’t disturb your meals and you need to run the genny anyway at those times to handle the heavy galley loads. The rest of the day the loads would be carried by the inverter system and you can relax in total silence.

If you already have a genny, as I do, just eliminate the cost of the genny ($5,000) and the remaining cost is only $1,200 for the inverter system. Guess which approach I’m going to take?

Pete37

Great post! Recommend as a sticky.

Hi Marty,

Peak load is the load you get if you add up all the loads and assume they all occur simultaneously. Average load is what you get if you assume they occurred randomly so that not all loads were on at the same time. For random events the ratio is about 0.6.

Pete37

Pete37 said:

After several dozen posts the conclusion was that “yes” it’s probably possible but “no” it’s probably not practical.

Click to expand...

Possibly what you meant to say is it is not practical for YOU, from what I can gather, because you cant get your head around converting a soft top bimini into a hard top covered in panels
And as far as "possible", well no possible about it, there are people on this very forum (rjtrane) that are running them and he said he is using this $1000 fridge here


Mitsubishi-MRC375CSTA-Refrigerator
And there are several other forum members who also said they run household refrigeration.

A day or so ago we found a commercial refrigerator manufacturer of eutectic plate refrigerators who makes fridges that might be able to operate on the power from solar cells. The price of these fridges and whether they would actually work has not been determined. I think the forum discussion has gone as far as it practically can so now it’s up to those who are interested in solar powered refrigerators to buy one and see whether it really works.

Click to expand...

Of course they work, but at what expense?
Like I mentioned in the other post, 300 litres of decent 12 volt fridge freezer in Australia (iceer) will cost about $10,000
This mob Ozefridge do the eutectics, but you have to build a box so I could see that costing $5k at least if not more for the box and another few grand for the eutectics.

Good luck guys. Let’s hope it doesn’t cost too much.

Click to expand...

Well that is the issue isnt it

$5000 to $10,000 for 12 volt/eutectic Vs $1000 for modern 240v

Pete37 said:

At $360 an 85 watt solar panel

Click to expand...

LOL, you're doing it wrong
Solar panels can be had for as little as $1 / watt
Ebay is full of 200 watt panels for under $200 delivered to my door

In the US, first click found this place doing 0.85c/watt http://www.wholesalesolar.com/

We spent five months in Maine last summer on the hook. Never saw shore power. No solar. 110V Ice maker, 110V cheap dorm style fridge, all elec galley, 110V WH, lite like a Christmas tree every night, three kids and wife. Didn't move the boat much at all. Ran the genny long enough in the am to make coffee and breakfast and long enough in the pm to cook dinner. 1100AH battery bank 160A/MSW inverter/charger.

Just do it!

Hi Mark,

Guess that shows that the job can be done by an old fashioned diesel generator. No need for any high tech solar panels.

Pete37

Hi Parmenter,

Any system which requires a special $10,000 12 volt DC refrigerator and a $5,000 custom built box ($15,000 total) is impractical when the same job can be done better for $1,200 if you have a generator or for $6,200 if you dont.

Pete37

Pete37 said:

Hi Parmenter,

Any system which requires a special $10,000 12 volt DC refrigerator and a $5,000 custom built box ($15,000 total) is impractical

Click to expand...

Thats not what I said

when the same job can be done better for $1,200 if you have a generator or for $6,200 if you dont.

Pete37

Click to expand...

But here it cant, not even close

And define better?
Solar doesn't use diesel daily, or cause noise and vibrations.

We are all in different boats. What works for me, doesn't suit the next guy.
I like to keep it simple, so solar would be best for me. I have limited space for a generator, and enjoy my peace and quiet. Going solar is simple and cheap as I have very little load. (gas stove, LED lighting, no A/C, small fridge freezer and large icebox) I need to add a couple panels and batteries to use the fridge while I'm on the hook, but that's it. Easy.

Quote: "The total, DC plus AC, load is 9.22 +15.3 = 24.5 kWh which requires 1.2 hours of generator operation at full load, burns about 1.9 gallons of fuel and costs $7.68 at $4.00/gallon."

Pete what size generator supplies 24.5 kWh in 72 minutes?

Marty

Hi Marty,

The Onan MDL4 I have on my Connie produces 20 kWh in one hour or 24 kWh in 72 minutes. That's pretty close to 24.5 kWh. I guess I should have said 73.5 minutes (1.225 hours) but I rounded it off to 1.2 hours. It weighs 1025 lbs. (465 kg) and is quiet as a mouse.

Pete37

Hi Parmentor,

I'm sorry that things are so expensive in Australia but I have no control over that. I and most of the people posting on this forum live the the USA so I'm quoting US prices.

I'm surprised that so many of those posting are so sensitive to noise. The $6,200 system I proposed is absolutely quiet for 16 hours of the day (it's working on batteries) and with a bigger battery bank I could probably get that up to 20 hours. For the 4 to 8 hours the genny is on(during mealtimes) it has a slight hum. It's so quiet that the only way I know that it has conked out is when I notice the exhaust water noise has quit (or when the lights go out).

As for fuel, it costs less than $8 per day. Is that a problem for any of you?

Pete37

Pete

I calculated a 20kw generator from what you said. Thanks for confirming that. Just haven't seen many that large. Are you able to load it when it is running?

Marty

Pete37 said:

As for fuel, it costs less than $8 per day. Is that a problem for any of you?

Click to expand...

Possibly

Fuel in US rises 10% (approx) a year historically


$8/day x 365 days/year = $2920/year

Year 1) $2920 a year in diesel Vs cost of 14 x 200watt solar panels CLICK
Year 2) $3212 a year (+10%) Vs zero for solar panels
Year 3) $3533 a year (+10%) Vs zero for solar panels
Year 4) $3886 a year (+10%) Vs zero for solar panels
Year 5) $4275 a year (+10%) Vs zero for solar panels
Year 6) $4702 a year (+10%) Vs zero for solar panels
Year 7) $5172 a year (+10%) Vs zero for solar panels
Year 8) $5689 a year (+10%) Vs zero for solar panels
Year 9) $6258 a year (+10%) Vs zero for solar panels
Year 10) $6884 a year (+10%) Vs zero for solar panels

Total = $46,531 for diesel Vs $2920 (initial cost) for solar panels

The above are approximate numbers for illustrative purposes

I have a genset, and some panels. The panels will happily run a 12v fridge. But when I use the eutectic fridge and separate eutectic freezer, I need and use the genset twice a day.
They are not mutually exclusive power solutions. I see battery bank size capacity as more limiting than panel capacity. Panels keep getting better and cheaper.

". So we’re going to need 25/0.3 = 83.3 panels at a cost of about $360 x 83.3 = $30,000. Way too expensive and I doubt that you could even find space for them. In summary it’s too expensive and impractical."

I bought four 120 watt panels for $190 each. So your numbers are nowhere close to realistic. But aside from the math, I think that 99% of people who would not change their lifestyle so as not to need a 20-24 KW generator aren't going to be spending very long away from a dock, restaurants, mall, and Starbucks anyway. Usually anyone who wants to set up their boat for extended anchoring is more than will to sacrifice some things for the freedom that brings.

Hey Parmenter,

Get real! Nobody uses their yacht 365 days a year. 36 days a year would be more realistic.

Pete37

Pete

I follow where your generator produces 20kw of electricity per hour. The load demands on a boat are not that high in terms of refrigeration, nor the ability to charge the batteries. I had two 135 amp chargers going and residential refrigerator and a hot water heater and did not fully load my 8kw generator. Thus some part of the 20kw is not being used in the comparisons we have been making with panels. If I am correct you would need to run the generator more than 1.2 hrs per day in order to keep the refrigeration going.

Assuming you had my set up of two chargers producing on average 200 amps per hour recharge, you would need to run a generator for perhaps 2.5 hours over the course of the day. This is what I was doing when I had residential refrigeration.

Marty

Pete37 said:

Hey Parmenter,

Get real! Nobody uses their yacht 365 days a year. 36 days a year would be more realistic.

Pete37

Click to expand...

Sorry you don't get to use yours as often as you should.
Mine will be a full term live-aboard, only marina attachment will be for resupply (fuel, water, food, washing)

There's a company on Vancouver Island that sells 5 - 100 watt panels for $500 Canadian. Plus you have to buy a controller.
Washer/dryer? Hair dryer? A 20 kW generator a big generator.

Pete37 said:

...Get real! Nobody uses their yacht 365 days a year. 36 days a year would be more realistic.

Pete37

Click to expand...

If you are planning on 36 days per year at anchor make no changes but your original post was about shore power independence.

We don't spend 365 days a year but over a 6 year period a minimum of 270 days a year at anchor with one year at 330 days for Hobo. Leave the states and you'd be surprised. Using Parameter's numbers, even at 50% of the time out, solar is a good deal.

I am seriously looking at semi-flexible panels for the top of my bimini. I can easily get six - 100 watt panel up there. It would go a long way to reduce genset time. The current price is $199 for one 100 watt panel. I have seen the prices drop 25% in the last four months on semi flexible panels. So thats about $1500 for panels and controller. The attachment to the canvas is currently an unkown price for me. There are several companies who have done this for sail boats, so the methods for attachment have been figured out.
Semi Flexible 100 Watt Solar Panel 12V High Efficiency Sunpower | eBay

Daddyo said:

We spent five months in Maine last summer on the hook. Never saw shore power. No solar. 110V Ice maker, 110V cheap dorm style fridge, all elec galley, 110V WH, lite like a Christmas tree every night, three kids and wife. Didn't move the boat much at all. Ran the genny long enough in the am to make coffee and breakfast and long enough in the pm to cook dinner. 1100AH battery bank 160A/MSW inverter/charger.

Just do it!

Click to expand...

Daddyo I'm with you on this.

A good quality, properly sized generator gives our boats shore power independance.

Pete says: "On page 232 we found Table 9-6 which describes the electrical needs of “Highlife” a 52’, eight year old, cutter rigged ketch. The table indicated that the daily DC demands were 115 Ah for House Loads, 75Ah for Activities, and 312 AH for AC loads supplied to the battery bank via an inverter. The peak load is 502 Ah. But not all of these loads occur at the same time so the average load from these three sources is about 301 Ah.
In addition one must add in the power for the refrigerator/freezer which running 24/7 at 12 amps burns about 280 Ah per day. It is the largest power consumer on the boat. The total and average for the day is now 581 Ah.
There are also the inverter loads which include the washer/dryer, hair dryer, toaster, coffee maker, microwave, vacuum cleaner and TV/DVD. They add up to 312 Ah but average out to about 187 Ah. The total and average for the day is now 768 Ah which at 12 volts is 9.22 kWh. This completes the compilation of DC loads.

But there are also AC loads powered by the generator and delivered directly to the loads at 120 volts. They include battery charging at 5 kWh, AC watermaker at 3.4 kWh and a small amount of air conditioning at 5.4 kWh (about enough to cool down the master stateroom so that you can sleep at night). The AC load total is 15.3 kWh.

The total, DC plus AC, load is 9.22 +15.3 = 24.5 kWh which requires 1.2 hours of generator operation at full load, burns about 1.9 gallons of fuel and costs $7.68 at $4.00/gallon."

I put these numbers into a spread sheet, and for the life of me, can't figure out how you came to your final numbers? I feel it is easier to use watts instead of Amps and/or AHs for calculating daily loads since watts work for DC and AC loads.

I come up with the same 581 AH/6,972 Watts/day as you. But then, I lose you. You have AC load of 5000 watts for battery charging and then add on the above 6,972 watts for DC loads? Essentially, the DC loads ARE what you are replacing in the battery, so if you add 10-15% for losses, your battery charging total should be 8KW?

Air conditioning takes about 7.5% in kW of it's BTU rating (my 8,000 BTU A/C draws about 600 watts when running). Your number of 5.4 kW for air conditioning would allow for 6 hours of 12,000 BTU - is this about right as per your usage?

Your allocation of 3,400 watts for water making - is this a daily average? How many gallons of water do you get for 3,400 watts?

Using your raw data numbers, I come up with: 8kW for batt charging (includs DC loads), 5.4kW A/C, 3.4kW water maker for a total of 16.8kW. Your one-hour plus of a 20kW seems about right.

Am I missing anything?

Since the goal is to be independent on for extended periods of time, living aboard at anchor, then most likely a combination of energy sources could be combined to work?

If, like you, you already have a generator of sufficient capacity, then nothing needs to be done. Just dinghy ashore to refill Jerry cans with diesel as necessary.

If, one is starting with a clean sheet of paper, then, depending on life-style goals and budget, other solutions may present themselves. A combination of:

1. Small Wind - a 1.5kW rated wind turbine (cost about $4.5k) will generate an average of 600 watts/hour or 14kW/day. This is an average based on east coast U.S. wind charts.
2. Solar - about 3kW of solar (cost of panels about $3k) will generate an average of 12kW/day.
3. Diesel generator - small is OK - maybe 4kW or so? On an auto-start/stop switch?
4. High-amp alternator(s) on main engine(s).
5. Big enough of a battery - to get through 24 hours - 20kW hours/1,666 AH at 12v. About $7k for Lithium, less for AGM. The bigger, the better to capture both solar and wind energy when it's plentiful.
6. More efficient fridge to save 2kW/day (new tech ones use 50 watts/hour)
7. More efficient LED lighting

Solar Panels for Bimini

fryedaze said:

I am seriously looking at semi-flexible panels for the top of my bimini. I can easily get six - 100 watt panel up there. It would go a long way to reduce genset time. The current price is $199 for one 100 watt panel. I have seen the prices drop 25% in the last four months on semi flexible panels. So thats about $1500 for panels and controller. The attachment to the canvas is currently an unkown price for me. There are several companies who have done this for sail boats, so the methods for attachment have been figured out.
Semi Flexible 100 Watt Solar Panel 12V High Efficiency Sunpower | eBay

Click to expand...

Solbian uses Sun Power cells (the most efficient commercially available) mounted in flexible plastic - these are not the kind sold at West and elsewhere that roll up or can be walked on - those are quite inefficient. Solbian has a total solution, including brackets to hold the panels to your Bimini (with air space underneath). These are costly, but the best solar solution to mounting on top of a Bimini.

Solbian Flex

Shore Power Independence-2

Hi Reuben,
Yes, the battery charging has been double counted. I’ll eliminate that which brings the total power load down to 19.5 kWh. I was following the tables in the Voyager’s Handbook and that’s the way they did it. But then, as you point out there are about 15% charging losses so the total goes back up to 19.5 +0.15 x 5 = 20.25 kWh.

The air conditioning is a bit more complicated. I have five AC units totaling 65,000 BTU. If all five are running full blast they draw 65 amps at 120 volts. That’s 7.8 kW. During the day I normally only run the air conditioning in the upper and lower salon which have 40,000 BTUs of air conditioning and draw 38 amps But these units are on thermostats and cycle on and off so it’s difficult to figure out how much power they draw. On a 90 degree day they run full blast and draw 38 amps (4.6 kW). At night the AC loads drop dramatically and I estimate about a 2kW average AC load. For a 24 hour day that makes the total aid conditioner load (16 x 4.6 + 8 x 2.0) = 89.6 kWh/day.

Air conditioning estimates are pretty much of a guess. But it doesn’t make much difference what answer you get. Solar panel power systems can’t even make a dent on the sun load. With generator power my Connie can just about break even on a 90 degree day but the noise of the air conditioning systems (not generator) is annoying. You have to make a choice; run the generator and put up with the air conditioner noise or turn off the generator and sweat. We find that fans are very useful. They can even be run on battery power. My air conditioner estimate of 5.4 kW is woefully low. It reflects running a lot of fans and running the master stateroom air conditioner for a couple hours before going to bed.

I don’t have a water maker. The estimate is just for those of you that do. But with 160 gallons I can probably make it for a week if I don’t take too many showers. The Handbook p.326 recommends 75 to 150 gallons for a couple on a trip of 30 days. I guess they don’t take too many showers. If we run out of water we can always fall back on booze. Many of us do that even when there isn’t a shortage of water.

Solar panels do provide an alternate source of power but only about 1.2 kWh per day (Handbook p. 235). Battery banks do the same thing. Four fully charged 150 Ah 6 volt golf cart batteries store 600 Ah or 3.6 kWh which equals 3 days of clear weather solar power

At $8 (about 2 gallons) of fuel a day and a 400 gallon fuel reserve I’ll only have to dinghy ashore to get fuel once every 200 days (less than two times a year). I don’t think that’s going to be a big problem.

Let’s consider your “Clean Sheet of Paper” comments.

1. Small wind turbine: They don’t seem popular with the blue water sailors – solar panels are preferred and at $4K they are almost as expensive as a small diesel generator.

2. Solar power : A good source of alternate power in case the engines break down. Popular with the blue water sailors.

3. Small diesel generator: An excellent choice for alternate power. They start at about $4k, provide 4kW to 6 kW, work in any condition, are quiet and provide additional resale value to the boat.

4. High amp alternators: Fairly popular with blue water sailors; provide up to 300 Ah (3.6 kW) each, can be installed on both engines for redundancy. But they have high belt failure rate and run the main engines at low power output causing premature engine wear and failure. A good emergency source but don’t use them regularly.

5. Big Auxiliary Battery Bank: Almost a requirement for off shore power independence. All of the blue water cruisers seem to have very large battery banks.

6. More Efficient Fridge: Yes, by all means change your old fridge out and replace it with a new one. They only burn about 30% of what an old one does. But, paradoxically, if you have a large generator all it will do is reduce your fuel burn rate by a small amount. And, if the fuel cost savings are small the savings may not pay for the swap out of the fridge for several decades.

7. More efficient lighting: I’ve been changing out my incandescent lights for several years and replacing them with fluorescents or CFLs. This is due more to longer lifetime than to efficiency. It means that I don’t have to change them so often. Incandescent lights in a high vibration environment (such as an engine room) have a very short life. No point in changing out your old fluorescents though. They seem to last forever and have very good efficiency. LEDs are good but avoid halogen bulbs.

Pete37

If you only plan on 36 days a year, that is 3 days a month, or one weekend a month. The generator choice is obvious. If you liveaboard 365 days a year as I do, the solar choice is obvious. I don't want to feed, listen to, or maintain a diesel genset. It goes back to how you use your boat. Their is no "one" right answer for everyone.