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Quote: Originally posted by Gary Kirk on 08/04/2005

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Having searched the message board on this subject is would seem that there is an even divide as to their use and value for money.

In most circumstances, particularly those like you describe, then it seems clear that large Solar panels are a waste of money, in that you can easily do without them.

  I like the idea of using natural energy to help maintain my battery when on "green sites" rather than spend a lot of money out on a quiet generator. 

Solar panels are not a very green source of energy either, most of them will use far more energy in their manufacture than will ever be saved in the form of 'free' electricity.   

I know you can buy generators for under £100 but they are nowhere near as quiet as, for example Honda, but these cost from £400 upwards.  My battery use would be minimal and only for 2 or 3 days so my question is, would a 10 w solar panel support the amount of charging needed for that period as it would only be for lights and a 10" portable in the evening after dark. 

You need to know how much the lights and TV consume first, but ignoring that for a moment.....

A 10W solar panel will on average give you between 0.4A and 0.25A of charge current in the UK, so in a 12 hour day you going to get maybe 4Ahr of charge into the battery.

So in the 3 days you might get 12Ahr or so of charge into a battery.

Now that could be a significant amount of charge for a small battery but if your using a 110Ahr leisure battery is it worth the expense of a solar panel to add so little extra charge back into the battery ?

Hi Stuart

Re Manufacturing power vs Recovered from sun power  a 64 w panel will at worst provide 135 watt hours of power per day thats 10 ah into battery lets say

3650 ah per year

36,500 ah per decade

most are now guaranteed for 20 years so 73,000 ah

I would guess at 3 years max for energy payback 

On the 10w panel .25 to .4 is about right if aligned OK but the average Sun hours for UK I am guessing would be lower than for Australia and their figures are 3 to 6 hours per day so I would say use top table here and divide by 6.4  gives roughly the Figure you have calculated allow for conversion losses and that the UK as lower Sun Hours

The above is a scan from Collyn Rivers Excellent book on solar energy for mtorhomes and campers.  http://www.caravanandmotorhomebooks.com/

A 10w panel will stop a battery losing charge while idle, ie a motorhome that is sat around a lot between uses, but wont put any worthwhile charge in.

Quote: Originally posted by GeorgeTelford on 09/04/2005

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Re Manufacturing power vs Recovered from sun power  a 64 w panel will at worst provide 135 watt hours of power per day thats 10 ah into battery lets say

3650 ah per year

36,500 ah per decade

most are now guaranteed for 20 years so 73,000 ah

I would guess at 3 years max for energy payback 

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3 years ?

Your assuming that the average motorhome\caravan\tent user can store and use 365 days worth of free energy per year. 

Thats highly unlikely to happen of course, how many people would spend say more than 2 months of a year collecting and using Solar power ?

So the energy payback in your example is realistically going to be 18 or more years.

Incidently using the figures you gave above, if you could use and store all that free energy it represents about £5s worth of mains electricity for a full year comparision, but the 2 months a year user is going to save less than £1 a year of mains electricity.

So for the average user a 65W £250 solar panel will save them less than £1s worth  of electricity.

Solar power has its place, when there is no alternative, or for extended periods away from mains electricity. But for the average camper spending £250 on a 65W panel to save less than £1 a year, is odd at best.

gary

I hope my comments will asnwer your question, we bought a 10 w solar panel from maplin last year we went away for 2 weeks with out ehu we fully charged the battery before we left. on arrival we hooked the solar panel to the battery and put on the roof and forgot about it. had all the usual stuff lights tv water pump . when we came home took the battery out to recharge thining it would be in need of it, it was almost fullly charged! so at £40 it was worth the money as a back up. the caravan and camping club did an article last aug about them and found that on average you could extend the life from a battery from 3 days to 10 we managed longer and no it wasnt particularly sunny.

Tentmad, with so much variety in power consumption, you have to do the sums in order to work out whats going to happen.

Take your example, its not very sunny, 10watt panel and the solar panel is just about keeping up with how much power you are using.

So you can work out from that you are using about 3 Amp hours per day, which is fairly frugal. 

Discharged to 50% a properly charged (before you go) 110 Amp Hour leisure battery would have lasted you 18 days, if you run it to flat then it would have lasted 36 days.

Hi Stuart

As you say you need to be storing and using the power to make it worthwhile, used only intermitantly its hardly going to be worthwhile.

The only time it seems worthwhile is as a battery maintenance charge (unless you are using the motorhome a lot ie to live aboard)

I dont support solar in general in most cases its just not worth it.

Tentmad that is really low consumption you must have.

George

WOW, WHAT A CAN OF WORMS   Thank you all for your kind input but OMG I still dont know what to do :o)  My main reason for offering up this question on solar panels is that I am going to the British Grand Prix this year and will be up there without EHU for 4 days.  Most of my time I hope will be spent at the circuit with all the other anoracks but in the event of bad weather I might be reliant on using the caravan more, hence the heavier use on my 130Ah battery.  Usual things, tv lights etc are things that I did not want to have to ration should I be needing them.  I will also need to use my Invertor to keep the video camera and phone charged. Perhaps the middle ground would be to purchase another leisure battery (130Ah) and keep it with me as a spare.  Cheaper than a Generator and I dont have to use a calculator trying to work out how much sun time I need to generate additionl power.  Oh my poor head hurts  :o).   Thanks again averyone.

Hi Gary

Thats one of the other major bug bears, when its sunny you are out and about, when its raining and you are inside no power generation.

Extra batteries and a good charger far better.

George

Hi Gary,

It's really thee cost thats the issue ...it's the freedom to go and do what ever you want, not to be reliant on 240v mains yet still have all of the comforts given with 240volt supply (see answer to Nigels question further up the forum page) Ideally 2 x 130amp leisure batteries hooked up to a 60 to 70 watt panel (see my homepage for a picture) Use a separate charging circuit in the car, this charges the leisure batteries as you drive (the car battery is charged separately) Then use the solar panel when at camp.

If you have an LCD TV, then these draw a lot of current, we use an LCD TV, marine fridge freezer, DVD, free view, shower and more plus all the lighting from this system ...wicked! It's the freedom that counts not the cost of manufacture or how long it will take you to get your money back!

Birty1

Quote: Originally posted by Skatty on 09/4/2005

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There is a competition to win one at the mo !! http://www.ukcampsite.co.uk/competitions/1012.asp

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From the competition page?????

For the competition question and your chance to win click here. Closing date for the competition 13th June 2005

That buggers that up though?