Totally Disconnected

The Allures 45.9 comes standard with a shore power connection and charger.  Most boats with a house electrical system have this ability to “plug in”.  So why did we decide to forego a shore power connection?

The logic started with two acknowledgements that seem unrelated to electricity.  One, that someday we are going to accidentally hit something with the boat.  Two, that we are not the type of people who want to be waxing and polishing topsides, nor are we going to want a shiny white boat that is all beaten up from our mishaps. As an architect, I have seen how durable aluminum oxide is and how strong a 3/8” thick aluminum plate welded to a robust frame can be.  After a lot of research into aluminum alloys and expedition boats with storied histories, I was sold on an aluminum hull.

Unfortunately, almost everything in boating is a compromise and aluminum does have some drawbacks.  A potentially catastrophic drawback is that aluminum can dissolve quickly in saltwater via electrolytic corrosion. Kind of a big deal for an ocean-going vessel.

Electrolytic corrosion is preventable.  All one needs to do is assure that the aluminum does not contact a dissimilar metal and that it is electrically isolated. Arguably the most dangerous sources of electrolytic corrosion on a boat is via a shore power connection.  At the risk of oversimplification, imagine two boats parked side by side, one aluminum and one steel.  Connect both of those boats electrically via a shore power ground and you might have a giant battery. The aluminum boat won’t last long as it’s electrons are given away. There are means of protecting against this shore power risk including galvanic isolators and isolation transformers, but they add complexity and can be expensive.  So, it dawned on me that there is another option that saves and simplifies instead of complicates.  Never plug the boat in.

I asked full time cruisers with alternative energy source how often they felt they needed to plug in. Most said “never.” The reality is cruising long term requires energy independence. We plan to spend as little time as possible in marinas.  We will be keeping Gerty on a mooring and want to be ready to go on an adventure at any time. We want to avoid the maintenance, noise, and smell of a diesel generator and are happy to limit our demand to assure this.  We have happily accepted that we will never have air conditioning on the boat.  I did a detailed analysis of our anticipated energy usage at anchor, coastal sailing, and while crossing oceans, and concluded that with careful planning we could achieve simplicity, redundancy, and energy independence.

We focused on optimizing the critical components and keeping the system as simple as possible.  We started by sizing our house battery bank to be large enough to handle several days of less than ideal charging conditions.  We have a 660ah house bank made up of 6 Victron AGM batteries.

Next, we considered the best and most reliable independent energy source. As of 2017 we believe this to be solar power. There are no moving parts. To a degree, solar will work anywhere in the world, regardless of boat speed or wind speed.  Solar offers good value with a long life.  We decided to put a 600W array comprised of three high efficiency Energie Mobile HP panels (Sunpower cells) on the arch.  This was the largest array we felt would be seaworthy on the arch.  The panels are wired in series and connected to a Victron 100/50 MPPT controller.  Mounted on the aft arch the shadowing is minimized.  As shadows can have a huge impact on solar production, we decided to avoid using the arch for a wind generator or tall antennae.  Based on our analysis, in most latitudes this optimized array will handle the majority of our electrical demand.

We know we cannot depend on one energy source.  We need redundancy and flexibility.  Our second source is the 115-amp alternator that comes standard with our engine.  This is optimized by a Sterling Alternator-to-Battery Charger. Additionally, it is possible to add a second or larger alternator if we feel under powered or want more redundancy.

We recognize that our highest energy loads will be while on long passages when the autopilot and instruments will be running 24 hours a day. With a little conservation and sunny skies, our solar array will handle these loads.  However, we will be getting a water-maker (more on water in a future post) and want one more level of redundancy.  We have made provisions for a future Watts and Sea hydrogenator that will cover our usage under sail with plenty of extra power to make water and heat it with electricity.

We invested in a Victron 3000W inverter so that we can have a microwave, heat our water electrically, run power tools, and have 110v convenience outlets throughout the boat.

After two weeks sailing on the English Channel, staying at harbors, moorings and anchorages, we found the solar performed as planned.  Over these weeks there was a problem with the water heater and we had to heat our water from the batteries and inverter.  We all showered daily with hot water, including a teenager challenged in the art of short showers.  The solar panels kept up. So, even though the factory and our broker thought we were nuts, we are confident in our decision.  And if time proves we have made a mistake, adding shore power is an easy “do-it-yourself” project – we can always add a plug.