Solar panels for a static caravan.

[electromonkey]

Hello all,

It's just been suggested to me from the general forum to post this post here as I'm more likely to get a better response. If I've not shared any forum posts with you before, then I should say, pleased to meet you and how do you do?

I am looking to install a solar panel set up for my in law's caravan.

They currently have a 110Amp battery supplying their electrics with a small portable solar panel connected to it. Their daily consumption if they were to have an "unlimited" power supply is around 90Amps max.

I would like to connect up a solar panel/s to keep the battery nicely topped up and would also like to install some kind of energy reader so they can keep an eye on their consumption and how much juice is left in the battery.

I'd be doing this on as small a budget as possible and the solar panels would not be permanently installed as the caravan park is closed for half of the year due to the lovely weather coming in from the Irish sea battering it during autumn and winter.

So what I am after is some info please on gear for this set up that anyone could recommend, keeping in mind that this isn't a "monies not an option" installation. Any other advice you feel I might benefit from would also be appreciated.

Cheers Ears.

Electromonkey

 

[Graeme Harrold]

Look at some of the solar set-ups for yachts, where they use flexi mats on the deck. You will need a charge controller to prevent overcharging during the day, and reverse flow back through the panel at night. (might keep the birds happy!!)

 

[Brighton Solar]

Hi Electromonkey,

Generally speaking, grid tied PV and off grid PV don't often cross paths these days. With the amazing rates the FIT's are offering, anybody with a mains supply would be mad not to take advantage of the benefits.
The main difference between on/off grid is energy storage. The grid replaces costly battery banks and simply absorbs your excess. In your case, you will need a battery bank.

There are three main areas to look at when designing an off grid system: Generation, storage and consumption.

A battery should not be discharged more than 50% regularly (as this shortens their life), so you will need 180 Ah or more. If you double up, then the 220 Ahwill be ok. These will need to be 12v deep cycle leisure batteries. If possible, stick another battery or two in for good measure (and rainy days)!

You say that your in law's consumption is 90 Ah/day. A panel can only be expected to produce its rated output (averaged over the whole day) for 5 hours a day. So to calculate the wattage of the panels we need to calculate VxA/Hrs: 12v x 90a / 5 hrs = 216W. Including losses I would say 250 watts should do it. Flexi mat panels are very expensive per watt. I would suggest standard mono/polysilicone panels mounted at an angle to face the sun.

The next issue is matching the voltage of the panels to the batteries: 13.3 -14.4v or similar. To make matters worse, this has to be specific to the charge of the battery, otherwise they will not accept the charge!
The best solution I know of is an MPPT charge controller (see:Maximum Power Point Tracking Charge Controller). This will balance the output of the panel to the exact required voltage. These cost a few quid, but increase efficiency by up to 40%! They also have overload protection and low battery functions (stops you damaging them from overcharging and over using) and a blocking diode to stop your panel taking charge from your batteries. The cost can be offset by being able to use a PV panel rated at 36v or similar. 36v panels are standard spec for grid connected systems and are in some cases costing as little as £1/watt! Where as 12 v panels are generally about £3/watt.... Using the higher voltage for production also reduces losses from cable runs.

It is most efficient to match your devices to the voltage of your batteries. There are many appliances that are rated at 12v for caravans etc. For this reason lets assume you are using 12v. If you have other 230v appliances, then an inverter can be bought, but these are expensive and reduce efficiency.

All in, excluding the inverter, I reckon you will spend £800 to get this system up and running. The best way to reduce costs is to reduce demand. Do they have a gas fridge? LED lights? Does the heating use electricity? All of these make a massive difference.

I hope this of some help.

Good luck!

 

[t4sltd]

I agree with everything Brighton Solar say bit would point out that 5 hours / day of max power is in summer. With 2 hours max power in spring and autumn

 

[Dan]

Don't mind me while I bump some threads in the solar PV forum. If they're not current or applicable topics, just ignore the threads; they'll drop off the page. If they are, feel free to chip in and chat solar stuff in the solar panels forum.

 

[Dan]

Don't mind me while I bump some threads in the solar PV forum. If they're not current or applicable topics, just ignore the threads; they'll drop off the page. If they are, feel free to chip in and chat solar stuff in the solar panels forum.