Can i keep my computers?

[MtB]

I fold them away, they are chained together and stacked up, when we are on the move, because we have only so much roof space, we take a 3 man canoe, a mountain bike, a fire pit and *ahem* a stepladder (for fruit picking) with us and we still want to leave some roof space. They don't tend to get folded out and switched on again, when we are back. We'd rather have the batteries permanently on a trickle charge off the shoreline, in the winter, perhaps that's one reason they last us so long.

 

 

Ah I see! Thanks for the details!

 

I'm tempted to get a controller like yours because this "10% in winter" figure is often quoted but no-one quoting it can ever back it up with empirical evidence. My own experience suggests the average harvest in the three winter months is about 1% to 2% of the average harvest over the three summer months, but I don;t have continuous data recording to prove it like your controller has.

[Airfix Kid]

If you use power in the winter from engine or generator or shore power you will, whilst charging, suppress the output of your solar. The physics suggests the amount of energy available from sunlight in the UK is 10:1 summer:winter so the other things being equal, i.e. your batteries are in need of bulk charge, you'll get 10% (though not at any one moment so measuring amps won't be the way to tell)

[boathunter]

OMG it wasn't simple. Simple is just turning a switch to release the pixies that live inside the magic boxes, and letting them do all the maintenance jobs while you sleep.

 

PS I need your cat and your boat

That made me laugh, but...My neighbour has that attitude, the day before yesterday he set fire to his boat through pure lack of the most basic knowlege. Now rather than setting off on their planned holiday cruise, he's replacing his batteries and dc cabling, mopping up battery acid and after randomly tearing off red hot cables in a panic, nursing his burnt hands.

 

Like it or not, some basic understanding of where possible dangers to life and limb lurk is a minimum IMO.

[MtB]

If you use power in the winter from engine or generator or shore power you will, whilst charging, suppress the output of your solar. The physics suggests the amount of energy available from sunlight in the UK is 10:1 summer:winter so the other things being equal, i.e. your batteries are in need of bulk charge, you'll get 10% (though not at any one moment so measuring amps won't be the way to tell)

 

 

Do you have a reference for that please? One that takes into account the normally cloudy weather we get in winter, and the shorter day length?

 

I've seen evidence that the 10% figure in winter is roughly right for a sunny day, but I contend that most days in December are actually cloudy, so the ratio of real life harvestable energy on a typical dull winter's day is much smaller. Compounded by the number of hours of daylight in december being about half those avaibale in July.

 

 

(Multiple speeling edits.)

Edited July 23, 2016 by Mike the Boilerman

[rustydiver]

Scrap the lot and go back to windows based rubbish I'll give e £50 for the lot. ;-).

[Airfix Kid]

here's an example : http://www.jaharrison.me.uk/Misc/Solar/index.html

 

it also shows the average daily power per season and you can see why the figures are as they are.

 

one thing he doesn't account for is any surplus in the summer would flatten the curve (basically the opposite to what you experience ) though maybe he has a way to harvest the surplus ( selling to Powergen for instance )

[Dave_P]

 

 

Do you have a reference for that please? One that takes into account the normally cloudy weather we get in winter, and the shorter day length?

 

I've seen evidence that the 10% figure in winter is roughly right for a sunny day, but I contend that most days in December are actually cloudy, so the ratio of real life harvestable energy on a typical dull winter's day is much smaller. Compounded by the number of hours of daylight in december being about half those avaibale in July.

 

 

(Multiple speeling edits.)

I suspect you're right. the 10:1 thing is probably a measure of the difference when holding a light-meter to the sky at noon in mid december and again in mid-july. You can half it again (or more) for loss of daylight hours and half it yet again for the typical increase in cloud cover in winter. On that basis a figure of 2% seems more like it than 10%.

[Linda Musgrove]

You may suspect he's right but the figures say 10:1 is the ratio of harvested energy winter to summer.

 

There was a post on this forum many years ago by a boater who posted a year's solar, so very real world.

 

10:1 is the accepted ratio for most solar installations.

 

Here's the national grid's figures;

 

http://euanmearns.com/uk-solar-pv-vital-statistics/

 

I will keep looking for a more personal take. Many have up to 5:1 ratio but I don't really accept that in the 'real' world - i.e. on the canal with a 12V system

 

I would imagine the curve to approximate to a sin² graph, i.e. a sine wave for the hours and a sine wave for the declination of the sun at midday overlaid.

 

Found it:

 

http://www.canalworld.net/forums/index.php?showtopic=51162

 

 

and another;

 

http://www.mitrajenkins.org.uk/solar-panels/

Edited July 23, 2016 by Linda Musgrove