A few thoughts about robust, reliable, redundant energy system architecture.
Flexible solar panels have improved (hopefully) in the past few years, however efficiency versus age compares poorly to high quality domestic panels. Part of the problem seems to be degradation of the transparent protective coating. Economy of scale production costs make the cost of lightweight flexible panels very expensive versus watt output. The trick with solar panels is robust mechanical support to support wind loads and accelerations from boat movement, installation in or above the plane defined by the cockpit top if not above for maximum exposure to the sun during the day, and installation method that will guard against the main sheet, loose reefing lines or other items that may snag a solar panel, either damaging the panel or chafing / cutting the line. Domestic panels have hard edges and sharp corners which might cause a crew injury. Routing electrical cables into the boat interior can be challenging, and long cable runs produce both electrical losses and excess weight gain. Ultimately the esoterics of hard panel installations and their associated cabling may detract from the beauty and sleekness of the vessel, however from the crew’s perspective high output solar can be a beautiful thing.
Individual solar controllers for each panel may not dramatically improve system efficiency but a case may be made for system performance in partial shading conditions. Oversize controller do offer the advantage of redundancy; should a single controller fail, we can re-wire our system so that two panels can be managed by a single MPPT controller. An overabundance of solar power in an ideal solar environment will minimize, but not eliminate, the requirement for auxilary charging sources in a poor solar environment.
Excess solar power leads to house batteries being topped up early in the day. At that point the crew has the option of implementing an automatic load dump to a hot water heating element. For full time live-aboards like us, we can elect to turn on the inverter and run the water maker or the hot water heater or use the electric kettle or inductive cooktop with reckless abandon. It’s all about making the most efficient use of that free energy and still having topped house batteries at sundown. Those who would point out that LiFeP04 house battery banks can operate down to 20% SOC (state of charge) might not have thought about tomorrow’s weather. Thus, cooking dinner solely with electrical power might increase the frequency of being forced to use a fossil fuel fired energy source to bring the house batteries back up the following day if the solar input is marginal or less.
Hot water for showers, even in the tropics, improves crew morale on JollyDogs. In retrospect, rather than fit a blown air diesel heater, we should have fitted a fluid heating/circulating system that would both warm the boat and heat the hot water tank. While a good bit more expensive to acquire, installation is much easier (try routing 3” diameter ducting ANYWHERE through the boat), and ultimately the hot fluid heating system offers much more utility, even in warmer climes, as sometimes just drying the boat out inside helps control mold and mildew and make things smell nicer. For full time live-aboards who can write the check, it’s worth considering.
Next time we’ll think about refrigeration, water makers, induction cooking, and perhaps generators. . .
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