Going Green with Solar

Electric power is key to having a happy liveaboard sailboating experience. Not only do you need power to run your lights, navigation equipment, and refrigerator, but on larger boats like Boundless, we have a watermaker, air conditioning, washer/dryer, etc.

On boats, producing electricity generally means burning diesel fuel, either by running the diesel engine or the diesel generator. Diesel costs money – but for me that is not the main concern. When you are living long term at anchor, the fewer times you need to hassle with a marina visit to fill up fuel tanks, the better (or worse, lug heavy jerry jugs back on your dinghy). Running the diesel is also noisy, smelly, and heats up the boat’s interior.

During our prior liveaboard cruising on Desiderata, we had a lot of power management woes – sketchy batteries, no generator, no solar/wind power, and a fridge that was cooled by running our engine, thereby warming its common wall with the fridge.

Boundless has a much better power system, with lots of battery capacity and a relatively quiet and low emissions generator. Other than charging the batteries, mainly the only times we need to run the generator are for air conditioning (very seldom outside of the muggy Chesapeake) and to run the watermaker when our water supply gets low.

We decided that we also wanted to add a “green” renewable method for charging the batteries that would allow us to not have to run the generator for a few hours each day to recharge. Ideally this would equal the number of days we can go at anchor before making water. We are still figuring out what our average water usage will be, but our target is at least three days between runs.

The two primary options for renewable power generation at anchor are solar and wind. Many cruisers have wind generators because the wind can blow 24 hours/day and they produce more power than solar. However, wind turbines are noisy. So while we may add wind in the future, we decided to start with solar.

With that decision made, we had to determine what type of panels and where to install them. We selected to install four Solbian SP-112 panels on our canvas bimini over the cockpit. These flexible, lightweight square panels each have 36 SunPower cells and are rated at 112W per panel. On a sailboat, you have to be concerned about shading of your panels from boom, mast, rigging, etc. That is why we elected to have four separate panels, each with an individual Victron BluePower regulator, so that if one panel is shaded, the others operate normally. At anchor, we will regularly tie off our boom to one side to reduce shading.

Since we will be doing offshore sailing, the panels need to be well-attached to the canvas. So we engaged a canvas shop to sew a zipper on two edges and velcro tabs on all sides. The wiring runs from the panels under canvas pockets so it is secure – and then through a waterproof gland in the cockpit coaming.

Belowdecks, the wiring is quite simple. Each panel runs into a regulator which varies its output depending on the state of battery charge. Then the four regulators output to the battery bank via a breaker. We also wired this into our existing MasterVolt power monitoring system so we can easily see how much power the solar is generating.

We are still figuring out how much power we use at anchor versus underway – and how much each device consumes. My guess is that at anchor we use around 240 amp-hours per day and the solar will generate around 65 amp-hours per day. So we are nowhere close to covering our entire daily power budget. However, 25-30% still allows us to brag that we are a “green vessel”!