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  1. #11

    Re: Energy Efficiency and Solar Power on a 53MY

    While I believe you understand the physics what I'm missing is the spreadsheet.

    Write a budget where you list and add ALL your usage. Find the wattage of everything (you'd be surprised what a laptop uses) add it all up. Figure/estimate how many hours a day what runs.

    This is your need.

    Then figure your feed. Panel wattage, generator hours, shore power etc. Build scenarios.

    Then balance it out in a budget with the cost in the last column and tweak until it makes sense, or not. Having gone through this exercise numerous times I can tell you that payback is a LOOOOONG way down the road and in the meantime you'll be sitting there wishing you had more power, and you'll be looking at the panels (never enough) and all the holes in your deck.

    BTW, $.25 a KWH is a ripoff. I would move.
    1978 53' Motor Yacht "LADY KAY V"
    Hull number 524
    Chesapeake Bay

  2. #12

    Re: Energy Efficiency and Solar Power on a 53MY

    FWIW, I was told this week by a marina operator in Marathon that they were legally prohibited from making a profit re-selling electricity. I don’t know if that is a state or local rule or what, but it sounds like MD needs something similar!
    Michael & Beth
    Hull Number CV312
    63’ Cockpit Motor Yacht
    1986 model launched in August 1987

  3. #13

    Re: Energy Efficiency and Solar Power on a 53MY

    This thread is confusing. Limiting generator use (while away from shore power) is a whole different task than limiting shore power usage. The former obviously involves an inverter, and is limited to to low amp/watt stuff, which generally excludes anything involving heat or A/C. A 1200 watt 36v heating element will pull 30+ amps, which will wipe out a 280AH battery bank in 6 hours, and that is not counting all the low amp stuff. And then you have to put that energy back. And there is the cost of the batteries, inverter, etc. In the end, the break even point is usually much less ambitious. An inverter, battery bank and alternator to run all the little stuff and using the generator a few hours a day to charge, heat water and cook. If you are t talking dock-to-dock, then usually the generator is not even needed as the alternator(s) and batteries will keep you going till you plug back into shore power. You will be able to use a microwave, and the water will stay hot for the trip. But if you are going to anchor then you will have to use the generator a couple times a day.

    Now, regarding the different task of reducing the electric bill, hot water is generally not the main culprit. A/C and heat are the main culprit. And btw, a heat pump is far more efficient than a space heater. One of my A/C units will heat the whole cabin while a space heater only provides minimal comfort as long as it is pointed right at you and it isn't too cold. Yet, they use almost the same electricity. In any event, you have the same problem solarizing a boat as you do a house. The cost of a lot of solar panels to run the A/C. And the additional problem of where the heck to put them all.

    In my opinion, using an inverter + batteries + alternator to save some fuel and wear and tear on your generator when you are away from shore power is practical. You can even throw in a few solar panels, but you still won't be able to run the A/C. But trying to compete with shore power, even at 0.25/KWH is going to be tough. These boats are not easy to cool or heat, which is why they have 4 tons of A/C on board. The diesel heater idea has merit, but I suspect that to will not be cheaper.

    I guess my main point is that it is one thing to limit generator use when away from shore power, but something different to limit shore power use. Tread wisely.
    Last edited by Photolomy; 09-19-2020 at 02:37 PM.
    Prometheus
    1978 53' MY Hull #529
    Viera, FL

  4. #14

    Re: Energy Efficiency and Solar Power on a 53MY

    Lol... in the Bahamas some marinas charge as much as $0.85 Per KWH... I ve had bills of up to $180 a day for an 84 footer!
    Pascal
    Miami, FL
    1970 53 MY #325 Cummins 6CTAs
    2014 26' gaff rigged sloop
    2007 Sandbarhopper 13
    12' Westphal Cat boat

  5. #15

    Re: Energy Efficiency and Solar Power on a 53MY

    Quote Originally Posted by Westfield 11 View Post
    Can you clarify: are these Li-on batteries or LiFePo batteries? If Li-on then your tolerance for risk in much greater than mine!
    LiFePo4
    Thom Price
    1984 Hatt 53 MY Tiramisù
    Harborview Marina, Baltimore, MD
    gondolaguy@gmail.com
    Liveaboard

  6. #16

    Re: Energy Efficiency and Solar Power on a 53MY

    Its crazy to think you can out engineer the engineers.

    By the time you add a bms system and custom charger or modify one to work with the batteries your not ahead of the curve.. add in the alternators and 32 volt system your trying to tie into and your behind.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  7. #17

    Re: Energy Efficiency and Solar Power on a 53MY

    I understand you’re talking about living aboard, but if you want hot water cheaply you can run a coolant loop either from your genset or from one of the mains through a water heater, and get all the hot water you want for nothing besides the cost of the setup. Obviously, this only applies when the boat’s been running.

  8. #18

    Re: Energy Efficiency and Solar Power on a 53MY

    Quote Originally Posted by oscarvan View Post
    While I believe you understand the physics what I'm missing is the spreadsheet.
    Oh, but I do have several spreadsheets, that I update regularly. As an energy auditor, I couldn't agree with you more about the analysis of data. There are two approaches and I believe that we use different ones: one is to model the energy usage based on how much you think you will use an appliance over a period of time, and the other is to measure how much energy you actually use over a period of time. The first is faster and will get you in the ball park while the second is more accurate. Then there are climactic factors that come into play for which you can make heat gain/loss calculations based on square footages, R-values, air leakage, outdoor air/water temps, and indoor temps, but again you have to use historic weather data to predict what the weather will be in the future, which is still only accurate up to a certain point.
    My approach is to start small and expand, adding panels, batteries and charge controllers as needed. I'll keep my different voltage systems mostly separate from each other with the ability to use inverters as needed, but to try to reduce that as much as possible to avoid system losses.
    Thom Price
    1984 Hatt 53 MY Tiramisù
    Harborview Marina, Baltimore, MD
    gondolaguy@gmail.com
    Liveaboard

  9. #19

    Re: Energy Efficiency and Solar Power on a 53MY

    Quote Originally Posted by Westfield 11 View Post
    FWIW, I was told this week by a marina operator in Marathon that they were legally prohibited from making a profit re-selling electricity. I don’t know if that is a state or local rule or what, but it sounds like MD needs something similar!
    I'll look into that anecdotal information, but even if it is the case, I'm not sure I want to fight that battle. It's the total annual cost that I'm interested in and I factored this in when I chose the marina. At least this is a factor over which I have some degree of control, and it is an incentive to become more energy efficient.
    Thom Price
    1984 Hatt 53 MY Tiramisù
    Harborview Marina, Baltimore, MD
    gondolaguy@gmail.com
    Liveaboard

  10. #20

    Re: Energy Efficiency and Solar Power on a 53MY

    Quote Originally Posted by Photolomy View Post
    A 1200 watt 36v heating element will pull 30+ amps, which will wipe out a 280AH battery bank in 6 hours, and that is not counting all the low amp stuff.
    Well, I'm not trying to heat a hot tub with it. It would only need to be on long enough to bring 19 gal. of water up to temperature. I keep the water heater turned off until I need to use it, and I've added additional insulation to the tank. Hot water can also be a good way to store excess energy from the solar panels once the batteries are full. That's why I chose to spend those $18 dollars on the new element.
    Thom Price
    1984 Hatt 53 MY Tiramisù
    Harborview Marina, Baltimore, MD
    gondolaguy@gmail.com
    Liveaboard

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