2200 watts of solar on the roof?

Peter_n_Margaret

Adventurer
I had 600W of panels all rafted up together (3 x 80W + 3 x 120W), ventilated underneath and hinged along one side to allow cleaning underneath.
There is a bucket full of leaves and twigs underneath.
Note also, the rail along the top edges of the 'box' that protects the panel edges from overhanging trees. That rail also channels the water to the corners of the roof so I can collect it with a hose to run into the tanks.
I am currently replacing the panels with new ones that will be glued down to the roof with no ventilation. We will see how they go. :)
There is always more than one way to skin a cat.....
16-06-27 1E.JPG
Cheers,
Peter
OKA196 motorhome
 

Alloy

Well-known member
I had 600W of panels all rafted up together (3 x 80W + 3 x 120W), ventilated underneath and hinged along one side to allow cleaning underneath.
There is a bucket full of leaves and twigs underneath.
Note also, the rail along the top edges of the 'box' that protects the panel edges from overhanging trees. That rail also channels the water to the corners of the roof so I can collect it with a hose to run into the tanks.
I am currently replacing the panels with new ones that will be glued down to the roof with no ventilation. We will see how they go. :)
There is always more than one way to skin a cat.....
View attachment 586005
Cheers,
Peter
OKA196 motorhome
The supplier of my panels said the back will reach 150F and I've read of it reaching 175F. Do you want that heat being pushed though the roof?
 

Alloy

Well-known member
We've got a height challenge, and we don't want to give tree branches an opportunity to remove our solar panels. The solar panels will probably be mounted directly to the roof with 3M VHB double-sided tape. Thinking of using Panasonic HIT panels, because they reportedly run cooler...
From the Panasonic HIT install manual:
Clearance between the roof surface and module frame is required to allow cooling air to circulate around the back of the module. This also allows any condensation or moisture to dissipate. The required clearance between the roof surface and the module is more than 4 inch.


 

dreadlocks

Well-known member
mine haven't broken so far at >11ft in the air:
IMG_20190504_190738 (2).jpg

Mine a good 10in above roofline tho to get above AC and powah vent.. another thing to consider is how your gonna keep em clean, ripping down dirt roads makes em all kindsa muddy.. I gotta climb up w/a bottle of water and a squeegee/scrubber pretty much every camp if I want maximum output.
 

Peter_n_Margaret

Adventurer
The supplier of my panels said the back will reach 150F and I've read of it reaching 175F. Do you want that heat being pushed though the roof?
I agree.
That is why I also added 50mm (2" for you non metric people) of closed cell polyurethane insulation under them PLUS 30mm of EPS foam (because I had some) inside the panel frame. The typical RV fridge/freezer has about 35mm of closed cell polyurethane insulation.
Cheers,
Peter
OKA196 motorhome.
 

Alloy

Well-known member
I agree.
That is why I also added 50mm (2" for you non metric people) of closed cell polyurethane insulation under them PLUS 30mm of EPS foam (because I had some) inside the panel frame. The typical RV fridge/freezer has about 35mm of closed cell polyurethane insulation.
Cheers,
Peter
OKA196 motorhome.
What's the % of solar panel loss from heat going to be or the temp coefficient of the panels?
 

Jman99

New member
The first thing that comes to my mind with such a large rig is finding sunlight is much harder than a small rig.
I may not be a quantum GEDC electrical engineer, but my outdoor activities have always showed 3 facts:

1: roof panels are more for show, plenty of caravans with 400-600W struggle to stay on top of their big fridges...
2:you try & keep the power consumption as low as possible while maximizing the reserve capacity of the bank, ie. use a fanover air con.
3: you do all your battery charging & air con running from a small reliable generator, maybe honda 2.2 w/ extended tank or the yam 2800 11L tank?
the air con I only use at night as those few short sunhours are small & when the sun goes, you have the insides warmed back up in a hour.

I would say that 2.2KW is shaved off 20-30% its wattage at max nominal conds, like in most temperate climates due to sun being lower in sky or the high heat in tropic areas. In winter the panels really need to be perpendicular to the sun at all times or else the total watthours is terrible, in summer you got more flexiblity as the sun is higher in sky, but the mountains & clouds will get ya. Off the top of my head I can honestly say most places I have gone there have been clouds 70-80% of the time.
 

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Joe917

Explorer
The first thing that comes to my mind with such a large rig is finding sunlight is much harder than a small rig.
I may not be a quantum GEDC electrical engineer, but my outdoor activities have always showed 3 facts:

1: roof panels are more for show, plenty of caravans with 400-600W struggle to stay on top of their big fridges...
2:you try & keep the power consumption as low as possible while maximizing the reserve capacity of the bank, ie. use a fanover air con.
3: you do all your battery charging & air con running from a small reliable generator, maybe honda 2.2 w/ extended tank or the yam 2800 11L tank?
the air con I only use at night as those few short sunhours are small & when the sun goes, you have the insides warmed back up in a hour.

I would say that 2.2KW is shaved off 20-30% its wattage at max nominal conds, like in most temperate climates due to sun being lower in sky or the high heat in tropic areas. In winter the panels really need to be perpendicular to the sun at all times or else the total watthours is terrible, in summer you got more flexiblity as the sun is higher in sky, but the mountains & clouds will get ya. Off the top of my head I can honestly say most places I have gone there have been clouds 70-80% of the time.
The sun seems to hit our truck as much as smaller vehicles.
1, our 630 Watts of roof solar run our electrical needs 95% of the time no issues, including our 6.8 cu ft fridge freezer.
2. running air con off solar is not normally feasible unless specifically designed for.
3. Generator charging is about the most inefficient ways to charge a lead acid bank (apart from bulk stage)
Tilting panels is highly overrated and makes no difference in overcast conditions when a large array will still provide power.
 

nathane

Active member
I am gradually building up experience of my solar set up.

Quick reminder I have 4x 175W and 1x 360W Victron monocrystal panels on my roof. All mounted flat. I have 450AH of LiFePO victron batteries and a Victron Multiplus 300W inverter charger. I am UK based and whilst my box is still work in progress the solar is set up and working so even though I'm not travelling I am building an understanding of the potential of the system.

At the moment we are having a really nice weather window here. Its c25 degrees and clear blue skies. My panels are generating around 700W - 900W between 11am and 6pm. I am running a Dometic Freshwell 3000 ac unit in the box and When I run it for 12 hours continually 8am-8pm with a target temperature of 16 degrees I am dropping to around 60% battery capacity by the time the sun has fully gone down. I'm running around 50W of other stuff at the same time (fridge not yet installed) on the DC circuit. The AC is not powerful enough to get to 16 degrees with the amount of windows and roof lights we have but it does maintain around 18.

I'm pretty pleased with this performance, it should enable us to achieve a sensible temperature in the box to be able to sleep.

Hope that is useful for folks.
 

nathane

Active member
Yes, just pushing it to see what's possible. I wanted to ensure it ran continually to see the battery drain effect. 20 will be fine I think.
 

ohiobenz

Member
After reading this entire thread, I'll share a couple suggestions.
First, the system I'm building consists of four 340W 48V monocrystaline PV panels, which fills my entire roof space. They will be tiltable side to side.
The battery bank is planned to be 2 Tesla 24v units.
I have a 3.5KW Onan 28v genny as backup.

As I did with the cab roof, the habitat roof will be coated with a white Ceramic Thermal Barrier coating by Lizard Skin to further reduce heat transfer into the living space. It has made a HUGE difference in the cab temperatures.

AC is planned to be a 9K mini-split.

No other fuel aside of diesel, I have approximately 150 gal fuel capacity with a dedicated aux tank for the genny and Eberspacher heat exchanger.

There are a lot of details to work out yet.....

I would highly recommend looking into Ceramic Thermal Barrier coatings for the roof, and the Tesla batteries with an appropriate BMS are very affordable, high capacity units.
 
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