Tuesday, November 23, 2010

Too much electricity?

This is hardly the time of year to get the benefit from a solar panel, but I know you've been itching to know whether our solar panel on Herbie is proving its worth.   I was just going to write that it's worse now the clocks have gone back, but then realised what a stupid statement that would be.  As far as I'm aware, solar panels don't care what the time is as long as there's light.

What I can report is that on our recent cruise we kept the batteries in a much better state than we are accustomed to.  Now this is not all down to the panel.  I think the new LED lights have made quite a big difference.  Instead of two or three fluorescent lights at 16watts each we were using three or four LED lights at 1.3watts each.  That's a saving of  about 89% or over a 5 hour evening, 17 amp hours.  

Working on Carrie's advice that you don't need a fridge in cold weather, we switched off the fridge whilst we were stationary for a few days at Paddington.  What little food and milk we needed to keep cold did very well in a plastic bag on the rear deck.  The result was that all the time we were there we didn't need to run the engine.  The solar panel looked after the lights, the radio, the laptop, and the water and shower pumps, even though the days were short and overcast. That alone saved us about ten quid in diesel, not to mention not having to put up with engine noise and vibration which is annoying when the boat isn't moving.  That's the main reason we got a solar panel.

However, when you are cruising, you get a different problem.  In the summer, when we're on the move each day we will get too much electricity!  We've had a taste of this already. The combined input of the alternator and the solar panel fills up the batteries more quickly and the voltage rises until it is just reaching the point where it could be a tad too high for the good of the batteries.  On summer cruises we'll reach this point fairly early on in the day.  Then the battery protection gubbinses switch in and any extra power is effectively dumped.  What a waste!  The answer?  Add another battery, so we can collect the extra.  Then we can be less frugal with our power use in the evenings.  I confess that I am a real power miser on the boat.  Last summer we sometimes turned the fridge off overnight to save the batteries.  Next summer we'll be able to leave it on and watch the telly.

The final good thing is that when the boat is left alone for long periods, the batteries won't self discharge.  I went out to visit Herbie yesterday to put in a new engine thermostat and the Smartgauge showed the batteries were at 100%.  That'll do them no harm at all.


Anonymous said...

I'm glad my recent dishonesty regarding the photo comp. has been overlooked and that you now feel you can trust some small piece of advice.(That will be £1m thank you ;-)
It's great, isn't it, not having to burn diesel to run laptops and radios etc.
Like you, I regret all the unused lecky in the summer though I reason that to buy another battery would just encourage me to buy and use more gadget stuff I don't need. One mad thought I had though, was to power a small water pump that ran canal water over the boat roof in the hottest days of summer, keeping it cool. Ok, I'll get my coat..
Carrie x

Rick said...

On winter nights you could shine a spotlight on your solar panel. That way the batteries would stay charged up all evening!

Halfie said...

What's really needed is a way of storing all that surplus energy. A battery is the conventional storage device for electrical energy, and it's commonly used because its stored power to density ratio is reasonably high. But let's think laterally. The bascules of Tower Bridge used to be raised by buckets of water falling down the tower. The water had been pumped up by a steam engine, converting the steam power to potential energy. Now you don't want to store a huge weight of water on the roof, so how about squashing something such that when it is released - when you want to use the stored energy - it can drive a motor? I can think of problems with this: the heat generated when something is compressed, and the heat taken from the surroundings when it is allowed to expand.

Or am I taking it all a bit too seriously?

Vallypee said...

Great to have the luxury of this problem now, Neil. If it really becomes an issue in the summer, maybe you could just voer the panel...or that deck pump of Carrie's might be an idea too.