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Solar panels

We are thinking of installing solar panels on our 60' narrowboat - we live aboard for long periods in the summer but the boat is often unattended for equally long periods in the winter. We want sufficient power to keep lights and water pump working on non-cruising days in summer and to keep the batteries alive in winter. Any advice would be useful, thanks.

Asked by: Lynn Barrett  | 4.12pm, Sunday 23 January

WW says:

A good starting point would be carrying out an energy audit of your actual daily needs- and then have a look at the charging requirements you really need.
The size of solar panels required is also fairly dependant on your battery bank- if the bank is too big for a panel, it won't overcome the internal resistance, to small and you might loose water from overcharging.
What you need for winter battery maintenance is quite different to maintaining a system during the summer.
For winter maintenance, a 5W panel per 100Ah of capacity if a good rule of thumb, to maintain and give gentle trickle charging, and, up to around 10/15W panels, you won't need a regulator.
A 60W panel will probably maintain a low-current drain during the summer, but if the panels are fixed flat, then the output is quite a lot lower than if they are angled towards the sun. Any shadows on the panels will also dramatically reduce their efficiency, as will dirt films.
If you have low consumption LED or fluorescent lighting, then 60W will probably be enough- but the more you fit, the better- for residential use, I would think that twin 80W panels would start to give you enough power. If you use an electric fridge however, then much larger panels might be needed.
Reputable companies give detailed performance indicators, for panels in different locations, at different times of the year, and angles, so you can work out exactly what you need. It might be more cost effective to combine wind generation with a sensible sized solar array. How they are mounted and the type of batteries they are charging is very important as well.

Mark Langley  | 6.16PM, Sunday 23 January

An energy audit calculator was discuss in the last issue of WW and is available to download in the links to the left of this page!

Mark Langley  | 6.18PM, Sunday 23 January

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