Solar panel install advice needed

[skripo]

I purchased a 135 watt semi flexible solar panel that I planned to mount on the curved roof of my TT. The panel is roughly 2' by 5'.

I was originally planning to mount it dead center from front to back but am now wondering if I should mount it side to side. We only camp in the summer, which way is more efficient?

[westend]

skripo wrote:
So I finally got it all up and running but am not sure it's working correctly.

I believe I get 54 volts at 100 watts, 2 amps in full sunlight. Am I not supposed to get close to 270 watts (2 x 135)?

I suspect I do not understand the math properly. I also may have misstated the amps but will check again tomorrow.

How are you measuring the output?

[skripo]

So I finally got it all up and running but am not sure it's working correctly.

I believe I get 54 volts at 100 watts, 2 amps in full sunlight. Am I not supposed to get close to 270 watts (2 x 135)?

I suspect I do not understand the math properly. I also may have misstated the amps but will check again tomorrow.

[skripo]

Hermy,

Thanks for the comments and of course I realize that. That's why I went with 2 panels even though I feel it is overkill, especially when you factor in the fact that we don't even have an inverter.

[hermy]

Remember that the number of watts of solar you need is totally dependent upon your specific needs and how much sun is available in the area you are camping. I disagree with an earlier reply saying that 135 watts could barely sustain you thru a 3 day weekend. We have no problem boondocking for unlimited time with a single 135 watt panel. We have a small inverter to run the television and to charge devices and have converted most lights to LED but have been off shorepower for as long as a month with no problems.

[skripo]

I have a TPO roof and after seeing that it is not uniformly glued down I decided against gluing it to the roof. I will use the 4 grommets with washers and screws instead. I will also use Dicor self levelling on the leading edge to avoid it grabbing the wind when driving.

Any comments?

[skripo]

Just ordered the second one.

[skripo]

pianotuna wrote:
Since the die is cast, I would get three panels in total. I have a hunch these panels may disappear.

Its a good suggestion but I have been considering these panels for 2.5 years and they are still available.

Nonetheless, you make a valid point, I may order an extra one now.

[scrubjaysnest]

westend wrote:

pianotuna wrote:
Hi westend,

My panels are on aluminum "bodies", so they are installed in the same manner as the more traditional glass and aluminum format.

I was thinking this may be the best, a panel of aluminum would definitely dissipate a good amount of heat.

For the OP's situation, just using the factory adhesive back may be enough. I don't have any experience with them so can't say it will or won't be adequate. I do know that 3M VHB tape is very strong. In fact, we have a few members here that have used it for solar module installations and has been a good solution. Some have used it just on the "feet" of mounting brackets. That is a small amount of square inches in relation to the larger area of a big solar module.

The suggestion to purchase three modules while they are available is a good one. Most MPPT algorithms and the system don't get along good with mismatched modules. I bought one of the USA made MX Solar modules at Solar Blvd. It's a good module but MX Solar closed their US plant and availability is scant to no more. As with most solar hobbyists, I'd now like to have more power harvest but getting the same module is going to be a challenge.

As long as Vmp is within 10% of your current panel any will work; my system is 2- UL-Solar, Vmp 18.1 volts and 1 Kyoreca Vmp 16.9 volts. They play well together.:)

[westend]

pianotuna wrote:
Hi westend,

My panels are on aluminum "bodies", so they are installed in the same manner as the more traditional glass and aluminum format.

I was thinking this may be the best, a panel of aluminum would definitely dissipate a good amount of heat.

For the OP's situation, just using the factory adhesive back may be enough. I don't have any experience with them so can't say it will or won't be adequate. I do know that 3M VHB tape is very strong. In fact, we have a few members here that have used it for solar module installations and has been a good solution. Some have used it just on the "feet" of mounting brackets. That is a small amount of square inches in relation to the larger area of a big solar module.

The suggestion to purchase three modules while they are available is a good one. Most MPPT algorithms and the system don't get along good with mismatched modules. I bought one of the USA made MX Solar modules at Solar Blvd. It's a good module but MX Solar closed their US plant and availability is scant to no more. As with most solar hobbyists, I'd now like to have more power harvest but getting the same module is going to be a challenge.

[pianotuna]

Since the die is cast, I would get three panels in total. I have a hunch these panels may disappear.

[pianotuna]

Hi westend,

My panels are on aluminum "bodies", so they are installed in the same manner as the more traditional glass and aluminum format.

[skripo]

westend wrote:
The only way the efficiency of the module could change with orientation is if you park the RV in a certain direction, continually, or have shade interference issues. I guess I would orient it with the least amount of forward edge facing the front. A lot would depend on future plans.

Have you investigated any efficiency differences regarding mounting the module on a rigid substrate? I'm thinking that you may be able to keep the module cooler by elevating it above the roof surface. That may pay a significant dividend with power in warmer climes. Maybe not. Pianotuna has similar type of modules on his Class C. He might be a good source of info about installing or using these modules.

Another thing noted: You're paying more than market rate $$$/watt. You may have considerations about installation of rigid frame modules or ease of installation we're not privy to. Basic consideration is that a rigid module has better $$$/watt and the price of aluminum angle mounts is much less than the difference in price from the bendable module.

The main reason I chose flexible is that I have a curved roof made from foam laminate. The top skin does not hold screws that great, as I found out when replacing my old fan with a Fantastic fan.

I was also concerned about the wind at one of our favorite campsites. It is popular with kite surfers and it gets so windy that shopping carts need to be brought inside at the local shopping centers. I realize this may be more fear than fact but nonetheless, it factored into my decision.

You raise a good point about heat. Concerning price, I am only going to be buying 2 to 3 panels max did not make such a big difference in the end.

[westend]

The only way the efficiency of the module could change with orientation is if you park the RV in a certain direction, continually, or have shade interference issues. I guess I would orient it with the least amount of forward edge facing the front. A lot would depend on future plans.

Have you investigated any efficiency differences regarding mounting the module on a rigid substrate? I'm thinking that you may be able to keep the module cooler by elevating it above the roof surface. That may pay a significant dividend with power in warmer climes. Maybe not. Pianotuna has similar type of modules on his Class C. He might be a good source of info about installing or using these modules.

Another thing noted: You're paying more than market rate $$$/watt. You may have considerations about installation of rigid frame modules or ease of installation we're not privy to. Basic consideration is that a rigid module has better $$$/watt and the price of aluminum angle mounts is much less than the difference in price from the bendable module.

[skripo]

This is the panel I purchased. I do plan to get one, possibly 2 more. I bought a 4215BN 40 amp MPPT controller to allow for this.

I already have LED lighting throughout. The only real load is the water pump and 2 Fantastic Fans. One is used sporadically, the other when we sleep at about 40% power.