Solar panels: efficiency and wiring...

last_tuesday · Post by **last_tuesday** » Mon Mar 17, 2008 1:03 pm

And just my bit on wind turbines

If you want to fit something to your boat/Bongo to keep the battery from going flat over extended periods when it's not being used, the smaller turbines are OK.

If you want to extract 'usable' power to offset battery drain on none 'hook up' locations, then something with a blade swept area of approx 1.5 sq m would help but you would need to be in a reasonably windy location.

& if you want to run a reliable 240v system 'on site' from a wind turbine, forget it, there is no such thing as a reliable wind powered mains generation system , and that includes the 125metre tall giants popping up all over the place.

mikeonb4c · Post by **mikeonb4c** » Mon Mar 17, 2008 1:27 pm

last_tuesday wrote:And just my bit on wind turbines

If you want to fit something to your boat/Bongo to keep the battery from going flat over extended periods when it's not being used, the smaller turbines are OK.

If you want to extract 'usable' power to offset battery drain on none 'hook up' locations, then something with a blade swept area of approx 1.5 sq m would help but you would need to be in a reasonably windy location.

& if you want to run a reliable 240v system 'on site' from a wind turbine, forget it, there is no such thing as a reliable wind powered mains generation system , and that includes the 125metre tall giants popping up all over the place.

I reckon we could have run a 1KW heater and still have eported to teh grid from Cartmel

But seriously, what kind of blade diameter are we talking about for a 1.5 sq.m. unit and what would the power output be in - say - a steady force 4-5 wind?

mikeonb4c · Post by **mikeonb4c** » Mon Mar 17, 2008 1:36 pm

andyfb78 wrote:The angle of the panel makes a massive difference, the ideal angle for battery charging will vary...

How very true this is. One illustration comes from the world of cross country gliding. When flying in the UK and looking for likely thermal sources, a south facing slope that is out of the wind is one of the best sources largely because the ground is more likely to be perpendicular to the suns rays (and thus receive a better investment of solar energy) than flat ground. It's interesting therefore that with the AFT you can create your very own slope to mount a solar panel on.

Similarly, I'm guessing here but an excellent type of weather is probably the 'April showers' weather with cool North Westerly airflow, clear air and very bright sunshine. It's useful to get an understanding of all this as it allows different strategies to be deployed in capturing what energy is available at various locations (we've not even discussed submersible turbines in streams yet)

last_tuesday · Post by **last_tuesday** » Mon Mar 17, 2008 2:05 pm

mikeonb4c wrote:
But seriously, what kind of blade diameter are we talking about for a 1.5 sq.m. unit and what would the power output be in - say - a steady force 4-5 wind?

For a 12v turbine with 1.2/1.5 m dia, output would be somewhere about 5-8 amps in a force 4-5.

andyfb78 · Post by **andyfb78** » Mon Mar 17, 2008 2:13 pm

I work with renewable energy technologies so some (more) thoughts:

the process really should go:
-reduce what you need
-reduce again what you really need
-work out what energy is needed, when and at what ratings.
-work out what resources there are (wind, water, sun, fuel)
-spec accordingly

Very often these simply won't match and so storage (battery in this case) is very important.

In a mobile application your resource is even more unpredictable
The only way to do it would be to have as many technologies as you can, oversize them to allow for low resource, have some way of measuring the resources and deploy accordingly....but you are still going to need storage, or some way of wasting any excess!

My feeling is, concentrate on the consumption end, not the generation end. Insulate your van, wear more clothes, use led lighting. We are outside, in the great outdoors. If you want all the luxuries, it is gonna cost you, or you will spend all of your holiday monitoring and adjusting your generation equipment.

If you are doing it just for the interest, I quite understand the fun of that, but be wary of the realities (and before you commit to cost).
Manufacturers will of course tell you how much their system generates (under ideal conditions)..... true, but it is all about the resource, a wind turbine only works when windy (windier than you thought probably), solar cells only work during the day (they do still work in overcast conditions), there are lots of rules governing the use of water courses to generate.

This sounds like I'm saying don't bother, that's not what I want it to sound like, but with recent excitement in these areas, there are lot of errrr rumours and experts, as well as manufacturers jumping on band wagons....There are many stories of money poorly spent and this gives the whole industry a bad name, when actually it has a huge amount to offer......

If you wanna do this, I would suggest you will need a large solar PV panel (maybe on a moveable mount), a turbine on a pole, and a big fat battery. Then you will need to set it up to suit what is available that day.
Sometimes it will be great, others really disappointing..... but that's the fun of the outdoors.......

Phew.......

Andy

last_tuesday · Post by **last_tuesday** » Mon Mar 17, 2008 2:45 pm

andyfb78 wrote:I work with renewable energy technologies so some (more) thoughts:

the process really should go:
-reduce what you need
-reduce again what you really need
-work out what energy is needed, when and at what ratings.
-work out what resources there are (wind, water, sun, fuel)
-spec accordingly

Andy,

Very refreshing to hear from anyone involved with renewables that has such a philosophy. Makes a nice change from those involved that seem to make promises based on snake water, fresh air and distorted statistics.

I have my own philosophies on some particular aspects of the renewable energy sector, particularly industrial wind turbines but this is not the place to air them.

It's a pity there are not more like yourself that recommend the route map to a truly sustainable future should start with conservation of energy, not a headlong rush to everything with 'eco' in the title.

andyfb78 · Post by **andyfb78** » Mon Mar 17, 2008 7:13 pm

Thank you, much appreciated kind words..... and I wholeheartedly agree with you....
Now the charge is being lead by the profiteers, lets hope we don't miss the point and go off on a tandem.

mr and mrs pips · Post by **mr and mrs pips** » Mon Mar 24, 2008 12:48 am

All good stuff..

But im confused.

I was advised that a 13w solar briefcase which can be bought at most caravan shows.

13 watts / 12(volts) = approx 1 amp per hour of sun ( In perfect conditions angle to sun no clouds etc etc)

on an absoulutly amazing sunny UK day of sun from 9am - 5pm 8 hours you could collect 8 amps for your battery

someone even said divide the figure you think you have produced by .86 to allow for wastage so lets call it ONLY 7 AMPS NOW

IS THIS AS FAIR DESCRIPTION OF SOLAR POWER ?

nothing to power your hair dryer by, But will keep the lights on, or a very efficient fridge, generally lengthen the battery life of a none hook up stop over.

any thoughts