Motorhome Solar (Flexible V Rigid)

nailer8

I am looking at fitting a solar panel to the roof of my camper.
I was looking at the flexible solar panels which you can walk on (in theory). Has anybody any experience with these.
Can you really walk on them?
Are they worth the extra price?
I carry two large surf boards on the roof so space is limited and i need to be able to move around easy enough to drag up the 10ft Sup board.


I mainly wild camp so plug in not an option and find my 200ah of batteries are getting a bit low by the 2nd day. (mainly due to inverter working numerous chargers, baby monitor, laptop & occasionally a low power microwave). The camper power controler records about 20ah usage per day but i am not sure what is going into the inverter as it is wired directly to the batteries.

I was thinking 100w should be enough to keep things fairly topped up, should give c.35ah in summer time.
Would 100w be ok or would you need more or would less do?

Any advice is much appreciated.

paddyp

Whats pretty low? 40% making 60Ah per day usage.

You'll never see 35ah in the batteries from a 100w panel in ireland you'd need to be a lot closer to the equator for that. Don't forget the charging efficiency of lead acid. Reality will be less that 20ah average in the batteries for the summer months may, june, july in ireland.

Cheaper flexible ones are less efficient than rigid so they'll be bigger and for similar efficiency you'll be paying 4 times the price of a rigid cell. Why pay the premium unless you need it to be flexible.

nailer8

paddyp wrote: »

Reality will be less that 20ah average in the batteries for the summer months may, june, july

Thanks for the feedback. 20ah is fairly dissapointing, hardly worth the hassle.

Anyone ever try a small wind turbine. My wild camping trips are usually for kitesurfing so its always windy where we go.

paddyp

nailer8 wrote: »

Thanks for the feedback. 20ah is fairly dissapointing, hardly worth the hassle.

Anyone ever try a small wind turbine. My wild camping trips are usually for kitesurfing so its always windy where we go.

It probably pays for itself in the medium term by keeping batteries topped up when not in use.

Regarding wind, small turbines are usually specced to produce their rated power at 12m/s or more i.e. a good force 6 they won't produce any power at all until about force 3. Then you have to look at the average windspeed - garrettstown cork / castlegregory kerry is 7.5m/s / 8.5m/s at 50m above the ground.

At 3m it will it will be more like 4/4.5 at that speed you're 500w turbine will be
generating about 100w.

Then theres mounting you obviously can't leave a 3ft - 4ft wind turbine attached to your van as you drive around so you'll be taking it down and storing it inboard. If mounted directly to the van the van will act as a soundbox and amplify all the noise that the generator makes so you'll be looking at putting it on a pole. On a pole it will have to be well above head height for safety so you've talking 7ft/8ft + 1/2 blade diameter + whatever portion you bury in the ground. So you;re looking at carrying around an 11ft/12ft pole (could be in sections) and a 4ft diameter turbine (could be dismantled).

At that height it will need guys for stability and will have to be take down gale force winds for safety.

Or something like this and take it down in lower winds: http://www.bizrice.com/upload/20120106/350W_Caravan_Windmill_Wind_Generator_.jpg

In the end the cost would be similar to 2 250w solar panels which would just stay on the roof forever and cover you for most things.

Really though you should think about getting rid of the heavy inverter loads. if you want to stay off grid without running a generator or hassle.

I don't think flexible panels are that great an idea as they will be more likely to suffer from partial shading or in-equal absorption.
Bare in mind that a module that's 10% shaded will not output.
The solar industry suffers from a lot of gimmicks where you really have to take a close look yourself at the comparative price per watt to overcome.

I'm averaging 30Ah p/d from a 150watt rigid solar panel this Summer Ireland and Europe.
About 5-10Ah p/d on overcast days 70Ah p/d with maximum exposure.
Anywhere around the Mediterranean had my module operating at peak output most days.

I could add 40% to this with tiltable brackets to face the panel directly perpendicular to the sun....or parking on slopes :rolleyes:.
I wouldn't be inclined to walk on the module but it's pretty durable so laying surf boards over it would not be likely to harm it at all.


I don't think the wind turbine is a very practical idea, unless it's a small scale plug and play jobbie that only gets put out in high wind conditions on a low stand. I've seen boats do this as a third generator but I suspect they'd be subject to high maintenance in ground level turbulent conditions. From what I've looked at they're not really practical with wind speeds under 7m/s (which if you are at the coast often wouldn't be hard to achieve).
Also with a turbine you have to consider the need for a regulator, an over-charge diverter and dump loads.
For camper purposes I think solar is a much better suited technology.
Here's a link to DIY turbines by the Wind Guru Hugh Piggott if you want to have a closer look at the undertaking.

A good solar set-up pays for itself in battery maintenance.

The lead acid charge efficiency (80%) is not as troublesome as you first imagine. If you use the system as circumstances allow, you can run most of the heavy loads and battery chargers in daylight, and the solar module will power these directly, the battery charging from the leftover current.

Like any renewable system however in order to make it work the first step is a significant reduction of consumption.
Using DC power supplies instead of an inverter and DC transformers will save you ±15%.
Also an idle inverter or regulator will still use current. Resistance/voltage drop due to rust, poor connections, thin or non-stranded cable, long cable runs also take a toll.

Large inverters use more operating current; it's often better to use appropriately spec-ed inverters for the loads rather than just using one big one for everything.

If you are using 20Ah a day standing, I'd say 120watt/150watt tiltable will be adequate most of the time on a good system, else a 200watt flat array.

paddyp

paddyp wrote: »

Or something like this and take it down in lower winds: http://www.bizrice.com/upload/20120106/350W_Caravan_Windmill_Wind_Generator_.jpg

Nice, I love the way the satellite is shading the solar module...

Sir Liamalot

Sir Liamalot wrote: »

I'm averaging 30Ah p/d

I've been thinking about this and thought it best to clarify it a little. Peak harvest is 11am to 5pm. So this averages about 3-5Ah p/h over this period and the rest in the remaining lit hours.

Because you are on a battery system the maximum harvest will only be when A: the batteries are < 80% charge (bulk charge) or B: batteries are > 80% (absorption charge) and you have another load running.
The nature of the charging system is to reduce charge as the batteries become full, so often a lot of what you are harvesting is being dumped by the solar controller to preserve the battery.

A result of this is when touring my state of charge usually sits about 80% - 90% after most days. It will take a full day or two with my system at idle to reach full charge and float after substantial use.

This is where a good solar controller shines. All things being right, the solar controller should quickly compensate the current required to power your daytime load, maintain the residual charge for what the batteries are requiring for their stage of the charge cycle, and dump the rest.


Another energy saving to be made is in the laptop battery, charging the laptop battery will consume about 3 times the current with the laptop on (about 2 times with it off) as just running it without the battery, so I only charge my many laptop batteries when I have an abundance of photons (good luck with that one on a Mac ) and run them down at night when I'm feeling frugal or close to < 12.4v.