Electric boats are certainly not new; the first one was invented by a German in Russia as early as 1839. However, using solar panels to keep on-board batteries at full or optimal charge is a pretty recent development that is becoming increasingly popular with owners of yachts, sailboats, boats, houseboats, and even dinghies. The technology is getting more refined with each year too and costs have come down significantly.


Why change to solar?


If one asks boat owners what one of the biggest problems they have is, the chances are that the majority will say, “Keeping the batteries charged”. Even if it is just a day trip the demands placed on the batteries are high; refrigeration, lights, and VHF head the list and – between them – may be enough to drain the battery.


Partially recharging a battery is not good for it as it may only charge up to 85%. Some remain as low as 50% which is a very long way from the 100% state of charge that the battery actually needs. According to a writer with, “Batteries like to be topped up to 100% as often as possible. When batteries are not topped up sulfation forms on the battery plates and they begin to suffer and die”. Solar means fully charged and healthy batteries.


One could stick with practices used by boaters for years in order to top up the charge on the battery. Firstly, one can run the engine a couple of times a day but that’s not ideal for obvious reasons. One could also turn off bilge pumps and all unnecessary lights etc. However, that’s not desirable and can even be unsafe. Solar seems the way to go.


Advantages offered by solar


As The Solar Action Alliance states, solar is quite simply the best “clean, reliable, and abundant source of renewable energy”. In addition, it is:

  • * Healthy, charged batteries
  • * Reduced costs
  • * Energy independence
  • * Eco-friendly and silent power.


Types of solar panels for boats


Once one has decided on solar for one’s boat the next decisions focus on panel type and where to have the panels mounted. There are several common types of panels on the market today and the distinctions in some cases have to do with manufacturing methods and composition. The primary ones are monocrystalline silicon, polycrystalline silicon, and flexible thin-film solar cells. Each of these is further subdivided into types and all have advantages and disadvantages.


Most boaters are less interested in what’s in the panel than in how it works, mounting panels, having the system installed, and having enough panels to cover the boat’s power requirements. It’s a good idea to speak to an expert for advice if there is doubt or uncertainty.


How to work out the size solar panel required


In terms of the size and number of panels needed to cover power requirements, sources such as eMarine Systems provide most helpful guidelines and formulae. For instance:

  • * If one wants to be self sufficient then the solar panel’s provision should exceed basic power requirements by 20%.
  • * In order to calculate what one needs, one must work out how many amps each light, pump, etc. on the boat uses per day. To get watts, multiply the amps by 12. Add all these subtotals together. Once one has the grand total of watts per day, divide the figure by the number of hours of sun per day to get to the wattage needed from the panels.


Solar installation


There is now an impressive range of installation options thanks to the various types of panels including the highly flexible panels. There are walk-on applications that are fitted directly into the deck. These are very rugged and hardy and, importantly, non slip. The flexible and semi-flexible panels can be installed directly onto canvas surfaces such as dodgers and biminis. There are also panels that are ideal for installation on rails and davits.


While one can save money buying items on the internet, it does not pay to take short cuts in terms of the system the panels are linked to. A charge controller is necessary and the wiring and mounting must be done properly. Care should be taken to house all the components in water resistant housing. The wires themselves should be marine grade. It is worth the money to invest in a good quality charge controller with settings for wet cell or gel batteries; cutting corners here could cost plenty later.