Choosing solar panels for your 24 volt system
A pair of our Unisolar peel'n'stick panels on a narrowboat roof
Virtually all solar panels have an output designed for 12V systems, so if you are trying to find a 24V solar panel... don't bother. There are a couple of panels that are manufactured to give a 24V nominal voltage, but they are huge beasts, designed for big grid-connected applications rather than for boats or mobile homes.
Don't stop reading though! Luckily, there are two simple solutions. The traditional approach is just use two 12V solar panels, and wire them in series. In practice, that's all a 24V solar panel is anyway, so electrically you won't notice the difference.
Technology has also come to the rescue in the form of the new MPPT regulators. These advanced devices are able to convert whatever voltage your panels produce to the correct voltage for your battery. This not only boosts the power harvested by up to 30%, but some - including Emponi Sol-1 MPPT - will happily charge your 24V battery bank from a single 12V panel.
Types of panel
12V solar panels are readily available in a wide variety of sizes and formats, from dinky but sturdy 5 watt framed panels, to the remarkable and powerful Unisolar flexible peel'n'stick panels. They give an excellent output in summer, although of course in winter they produce a lot less as there are fewer hours of daylight (and it's often cloudier too).
If you want to know roughly how much power you can expect from a solar panel array, take a look at the solar panel calculator from Midsummer Energy.
Read on: Mounting your panels