Go­ing with the wind or sun

Canal Boat - - Back Cabin: Experts - TONY REPLIES…

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.

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