We are an island unto ourselves, our own floating self-contained little world. It has been over 6 months since we’ve been ‘connected’ to shore power – that is – dependent on plugging in to a marina to have power on board and charge our batteries. We’ve had the opportunity, but since Netzah is fitted with a European rated (220 volt) charging system, this hasn’t been a possibility in the US. It’s just as well, as this has forced us to be more diligent in the management of our resources and has demonstrated that its fairly straight forward for us to live for extended periods, ‘off the grid,’ outside of any land based support.
Netzah is equipped with 3 sources of power generation: A 250 watt array of solar panels, a high output alternator (fitted to the boats diesel engine and gives a full charge at idle speed (unique for an alternator)), and a wind generator. Although I’m dubious of the actual output of the wind generator as it only seems to move the amp meter when its spinning like a mad man. I plan replacing it in the future with a more effective unit. The energy from these sources is stored in a 440 amp hour bank of 3 AGM (Advanced Glass Mat) Lifeline Batteries.
Our primary power draws are the refrigerator (1.5 – 3 amp hours) and the auto pilot (3 amp hours), used when underway. This means our maximum drain from our battery bank over a 24 hr period would be 144 amps (6 amp hours x 24) or about 30% of our bank – if there is no input. We also have a 12v to 120v inverter that we use to charge our computers and run power tools on board, but will only use this while running the engine as the energy draw is significant. We keep a very close eye on our battery levels with a Balmar Smart Gauge and never let it fall below 80%.
If the sun is out, the solar array has no problem with keeping up with both the refrigerator and the auto pilot. However, if its cloudy or during an over-night passage we’ll have to run the engine for a bit to charge the batteries. Netzah carries 70 gallons of diesel in two tanks and as we can charge at idle we use very little fuel doing this. However, it’s pretty inefficient to use such a large engine to simply run an alternator. Many voyaging boats are equipped with a small (2- 3 hp) diesel generator for this purpose. These use very little fuel and most importantly save wear and tear on the main engine. If we can find the money and space for it, such a generator may be in Netzah’s future.
Another alternative for powering during longer passages is a water generator like those made by Watt and Sea. These units have a small propeller that’s lowered into the water while underway. The forward movement of the boat spins the prop and generates power. A lovely system that can generate enough juice day and night to run all systems on board. The drawback to installing one is the high price ($4000). But if our future plans include ocean crossings then such a system makes a lot of sense. There is another brilliant system that’s been around for some time that utilizes the fact that if you leave the engine in neutral while sailing, the prop will rotate the drive shaft. By attaching a pulley to the drive shaft you can spin an auxiliary alternator. Unfortunately, we couldn’t use the off the shelf system that Nanni (our engine manufacturer) offers as we didn’t have the clearance for it. I’ve seen DIY systems that work great and are inexpensive and may consider fabricating something custom in the future.
In the mean-time there are a few efficiencies that we can work on to curb our resource use. Our current fridge is quite old and has one setting, full-blast. It runs continuously and freezes everything if left on for too long. The work around has been to shut it down a night. It’s replacement would certainly use less power. Secondly, the auto pilot does draw considerable power as it needs to run continuously on a passage. We are going to experiment with a much smaller unit that uses the physical power from our wind steering vane (another type of auto pilot on board). This may only work in certain conditions, but would reduce the power draw to a trickle. I plan to do a post in the future on all of our AP systems – as their operation is involved and quite interesting. Not to mention the fact that we use them to steer the boat 98% of the time.
Other draws on board are fans and lights, most of which I’ve replaced with low amp LEDs. I’ve also installed several USB plugs throughout the boat for charging iPhones and iPads – avoiding the use of the inverter to do so. Besides refrigeration and the vast amount of food storage we have throughout the boat, Netzah is also equipped with two 330 liter fresh water tanks. We top them when we have the opportunity, but have yet to run out. We also have a rain catching tarp that we can string up during downpours to fill the tanks. My past experience with a water maker (expensive, power hungry, and fragile) convinced me that a boat with sufficient tankage and the ability to sail well when fully loaded was the way to go. Fully provisioned and fueled we could conceivably go for months without restocking and even further without dependence on shore power.