How Does Energy Work on a Sailboat?

Annapolis – 0 miles sailed, 0 kilometres walked

I was up at 6 after an early night. I had a list of jobs to do and I wanted to get as many of them done as possible. I started by running a new 12 volt circuit up to the v-berth which had never been outfitted with one despite the other two cabins having one. Until now we’d used the 120 volt system for that, but then we have to run the inverter all night which uses up battery unnecessarily. That took longer than expected, so I had lunch then dinghy’d into town and had a nice decaf coffee at Bitty & Beau’s (look it up, amazing place) and used their wifi to publish a few days’ worth of journals. I then went on a fruitless search for a propane refill then returned to the boat and installed these neat plastic/rubber distance indicators on our anchor chain, which makes it very easy to see how much chain we’ve let out. Once I had all the chain hauled out on the deck, I went headfirst back into the anchor hold to remove the crappy sealant I used on the first attempt to fix a leak. Once it was cleaned up, I put fresh Sikaflex compound on the suspect crack. It will take a day or two to dry, but hopefully that fixes the leak. After that I washed the hull then zipped over to Ben and Kate’s for a one drink sundowner.

 

So since there wasn’t much of interest to report on today, I thought I’d write a bit about sources and uses of energy on a sailboat. With our recent battery problems and the prospect of living for the next six months off the grid, our energy needs and management thereof have taken on much greater significance.

 

The Wind

The wind powers the sails, and with the magic of vectors and wing physics, propels the boat forward and allows us to travel in the most environmentally friendly way possible. There are two devices some sailboats have (we do not) which makes supplementary use of this energy. Wind generators are miniature windmills that use the wind power to create electricity to charge the batteries. The other are hydro generators, which are devices either integrated into the propellor, attached to the underside of the boat, or towed behind the boat. They contain an impeller which is spun by the force of the water to generate electricity. Lastly, the wind can also be used to remove energy or heat from a boat by opening the windows and hatches.

 

The Sun

That big energy ball in the sky shines on our six solar panels to produce a lot of electricity. The theoretically maximum amount of energy our panels can produce is about 1300 watts but realistically it’s probably about 85% of that. The solar panels transform photons into higher voltage electricity which is taken by the three solar controllers on board and turned into 12 volt electricity which charges the batteries. The sun also produces thermal energy by hitting the boat and heating up the surfaces which increases temperature inside the boat.

 

The Ocean or Lake

The water we travel through affects the energy levels on the boat. Cold water cools the hull, absorbing interior heat, and dropping the temperature while hot water does the opposite.

 

Food and Drinks

A lot of muscle power is required to make a sailboat work. The obvious ones are pulling on lines to raise and trim sails, or pulling up the anchor, or rowing the dinghy, but all the repairs and everyday tasks on a sailboat require human movement. And this movement is fueled by food and drinks.

 

Gravity

We use gravity to store potential energy on our boat. The best example I can think of is our Brita water filter device. We fill it up with tap water using our muscle power and the energy required to run the pump, then whenever we want a glass of water, we push the spigot and water runs out, courtesy of gravity. Gravity is also used by the boat rigging and sails to make the whole thing move.

 

Diesel

Our sailboat engine runs on diesel and without it we are in big trouble. The diesel is stored in a 50 gallon tank and is sipped by the 54 horsepower engine. This energy is transformed into forward momentum by the spinning shaft and propellor, and a great deal of heat from the engine which warms the cabin as well as the water in our hot water tank, which is used later for showers and washing dishes. The diesel also powers the engine’s alternator which produces electrical current to charge the batteries. Lastly, we have a diesel burning heater which can be used on chilly nights to heat up the cabin of the boat.

 

Gasoline

We also carry gasoline on the boat and use it for two things. First, is the outboard engine on the dinghy, which isn’t strictly necessary, but it sure it convenient for getting around, especially in strong currents and winds where rowing can become impossible. The second use for gasoline is the portable generator we have on the boat which we can use to generate electricity to charge the batteries and power the 120 volt system.

 

Batteries

We have many batteries on the boat and they all need to be charged with electricity. The house bank consists of four 6-volt AGM (Absorbent Glass Matt) batteries that can store around 600 amp hours of energy. We have a single 12-volt lead-acid starting battery used for turning over the engine. We also have rechargeable batteries all over the place – the spotlight, table lamps, solar lights, toothbrushes, portable VHF, head flashlights, phones, tablet, laptop, Ryobi tool, probably a few more.

 

Propane

We carry 24 pounds of propane in two 12 pound tanks. This is used to power the two burners on the stovetop, the oven, and the barbeque, and can also be used to power the portable generator if gasoline is not available.

 

Now how is all this energy used? The boat has a 120-volt system, which can be powered from a shore cable when at a dock, but on the water is powered by a 2000 watt inverter which is, in turn, powered by the 12 volt house bank. We use this for all the things we plug in – the toaster, the air fryer, the electric kettle, device chargers, vacuum, ice maker, heat gun, soldering gun, and beauty items such as hair dryers and hair straighteners. The boat also has an extensive 12-volt system that runs directly off the house batteries and is used for such things as cabin lighting, bilge pumps, shower pumps, fresh water pump, mast lights, navigational lights, charging ports, stove solenoid, stereo system, vhf radio, auto pilot and navigational instruments, and refrigeration.

 

Now a lot of things I mentioned above also apply to your home, but you just don’t need to think about this much in a house because things generally just work…most of the time. Unless you live on the Ring of Fire or other earthquake-prone areas, houses are generally stationary and are not subject to the vicious and frequent beatings that boats take which tends to knock things loose and shakes the systems and equipment until they eventually break. Also, the national power grid tends to be quite reliable so you don’t need to think much about how much energy you are consuming nor where you next “energy meal” is coming from.

 

And that, my friends, is why boaters have a never-ending project list. Boats are complex systems and tend to break with some regularity. So if you’ve never thought of becoming an electrician, plumber, painter, fibreglasser, woodworker, solar expert, or gas fitter, just buy yourself a boat and you will become an expert in all those things!