Proper prior preparation prevents piss-poor performance. This is a notion that was driven into my brain throughout my time at Maine Maritime Academy. Questionable eloquence aside, it rings true over and over in both my career and personal life. Throughout the last six months, which brought blizzards in March and endless rain in April, I’ve been slowly and methodically planning our new solar panel installation. Knowing that we’d be leaving the marina life and moving out to a mooring, the pressure was on to get it right the first time.
Installing solar panels on a boat is not particularly difficult for the average user, but can become increasingly complicated for full-time living. The more you use the boat, the more power you consume, and the more solar energy you will need to harvest. Technology has significantly increased the efficiency of solar panels in the last few years, allowing more power to be harvested in a smaller footprint. Still, fitting enough panels onto a sailboat can feel like a game of Tetris.
The goal of my planning was entirely sustainable, off-grid living from May to November. During the winter months, we will continue to use shore power from the dock. All of our systems will run off of our 12-volt battery system, charged primarily by solar and additionally by wind generators. Our options for mounting locations are somewhat limited, and we decided to focus on the top of our hard dodger and over the stern.
Looking to maximize power production within the constraints of the space available I compared dozens of panel sizes and combinations. Ultimately, I discovered that Panasonic manufactures a highly efficient 325-watt panel which fit these locations perfectly. As explained by Panasonic, these panels “lead the industry in efficiency at over 19%, producing up to 36% higher production yield per square foot compared to conventional solar panels.”
We were able to install two of these panels for a total of 650 watts. Given that Maine experiences an average of 4.5 hours of daily insolation (full sun hours) annually and closer to 5.5 hours in the summer we could theoretically produce over 3 kWh on a single sunny day. Realistically it will be less as the system will never be perfectly efficient. Nonetheless, that’s a lot of power!
Additionally, I installed a maximum power point tracking (MPPT) charge controller. This smart device regulates the power from the panels to protect our battery bank from overcharging and step the voltage down to the appropriate level. An MPPT controller is a must have for our large panels, taking the 70-volt output and stepping it down to approximately 13 volts while simultaneously cranking up the amperage. Because of the relationship described in Ohm’s law (power = current x voltage), this maximizes the potential of our system.
The best part about the installation is, of course, the renewable energy it produces. Yet an incredibly close runner-up would be the ability to monitor the power generated via a Bluetooth-enabled application on our phone. From anywhere aboard we can see our current battery voltage, instantaneous solar wattage, charge current, and a 30-day history. It is surprisingly addictive; we are complete data nerds now.
In our first week of off-grid living, we have experienced everything from a soaking nor-easter to brilliant sunshine. On the rainiest days, we produce nearly 1 kWh, keeping our batteries healthy even while running an inefficient dorm fridge. On sunny days we reached full charge by noon, having produced nearly 2 kWh. This means that the system will, as predicted, be able to produce much more in a single day if it is needed.
“Needed” is the key word here. When the batteries are already topped off the controller will restrict the power to float charge the batteries. If we were to consume a lot of power throughout the afternoon, however, the daily production would continue to climb towards the theoretical capacity of 3 kWh as calculated before installation. By contrast, as you can see in the screenshot above for days 3 and 4, when the batteries are already charged by the engine or shorepower, the panels only needed to produce a few hundred watt-hours.
So what is our initial reaction? Bliss. Optimism. Giddiness. Gratitude. Accomplishment. Satisfaction. We are incredibly excited to monitor the performance of our setup in the coming months and will be sure to check back in down the road for an update. The ability to absorb power from the sun and convert it into refrigeration, light, and water pressure is simply incredible.