Going with the wind or sun
QI have bought a widebeam with the aim of being a liveaboard and as self-sufficient and sustainable as possible. I will be a continuous cruiser so want to get as much power from solar or wind as possible. I’m a beginner to all this, what do you suggest?
Because it is a widebeam there is a large roof space for solar panels, but what are your thoughts on wind energy? How many Watts do I need to charge my laptop, power my lights, fridge, pumps and a few power points and maybe a small boiler? LIAM BERGIN, via email
AAlthough wind generators are better than nothing and have come on in leaps and bounds, they will tend to give their best output in winter when solar output is lowest; some can be noisy and transmit vibrations through the boat, too
Take care in your choice, some also require something getting on for a gale to produce meaningful output, and inland the topography, trees and hedges can often screen you. So it is usual to mount the generator on a long pole, giving rise to possible stowage problems.
I can’t really give a straightforward answer to the rest of the question, because you need to do a power or energy audit (for which you need to know the consumption of every electrical device and how long they will be running during short winter days) and then some battery capacity and charging time calculations (see tb-training. co.uk/16elect.htm#bmn68).
This will give you some idea of battery bank size needed, whether you need a larger alternator, and a rough estimate of how long you will need to run it every day assuming no solar input.
What we do know about solar power is that you get less than one tenth of its rated output in the winter, and a narrowboat cannot usually carry enough panels for year-round supply. Your widebeam can carry more, but in the darker months, you will probably require additional charging. Also get an MPPT solar controller of reputable make rather than a PWM one, as they produce up to 30 percent more usable charge.
Common diesel-fired boilers do not have an unblemished reliability record and are fairly electricity hungry, so research this very carefully. It is not without good reason that liveaboards often use a solid fuel stove with back boiler. Ideally pipe the radiators so the water circulates by convection rather than a pump.
You will almost certainly need charge monitoring instruments. An accurate and properly wired ammeter and voltmeter on the domestic battery bank will do once you learn how to interpret them.
Be very wary about battery state of charge meters that use a shunt in the main electrical cable. They are perfect for measuring amps, volts, and amp hours out of the battery, but for a variety of reasons, in many people’s hands they are confusing as far as the batteries’ state of charge is concerned, potentially causing some boaters to ruin their batteries.