"200 watts" of solar doesn't seem to generate anywhere near 200W, is this just normal

[tx2sturgis]

Ok, a year later and I'm still often disappointed by the amount of solar power I get. How about this question... Does a rigid panel output more power in the real world than a flexible one?

What doesn't make sense to me is that I have read that rigid panels are more efficient than flexible ones. But yet, if you shop around for a rigid vs flexible 100W panel, they are a similar size to one another. So what is the deal? Are flexible panels being over rated, or does a rigid panel not really put out much more power than a similar size flexible?

All other factors being equal, a flexible panel and rigid panel, side by side, both rated at 100 watts, should both put out about the same amount of power. (same level of sun, same angle, same temp, etc) when they are both brand new.

What does change is that as a flexible panel ages, it can degrade sooner than the rigid glass panel, so that in 3 or 4 years the flexible panel, assuming it is still working, will have begun to yellow, maybe some cracking and peeling of the plastic, etc, and it will not produce the same that it did when new. It could be as low as 50% of what it was when new. As far as I know, there are no flexible panels with a warranty much longer than about 2 years. (someone correct me if they know one that is)

Meanwhile the glass panel in 4 years will be happily putting out 95% of what it did when it was new. They typically have a warranty of 80% power output (when new) for up to 20 or 30 years.

 

[Carla618]

Ok, a year later and I'm still often disappointed by the amount of solar power I get. How about this question... Does a rigid panel output more power in the real world than a flexible one?

What doesn't make sense to me is that I have read that rigid panels are more efficient than flexible ones. But yet, if you shop around for a rigid vs flexible 100W panel, they are a similar size to one another. So what is the deal? Are flexible panels being over rated, or does a rigid panel not really put out much more power than a similar size flexible?

Will discusses heat spots on flexible panels (and heat cameras) and why he is opposed to flexible panels in general:

 

[thebarefootbadger]

I found even with panels on the roof of my house professionally hooked to the grid, which you could consider an empty battery, I rarely got more than 70% of what the panels were rated for. I always assumed the sun angle and intensity, dust on the panels, high temperatures on the roof, distance of electricity transport and probably many other variables were to blame.

 

[afblangley]

I ask this in all earnest. If solar panels have such low efficiency under normal conditions, what makes them worth all the roof space they take up compared to other things (ie. MaxxAir fan, Thule boxes, Artic Tern access hatch, observation deck) that could otherwise occupy that space?

 

[Happy Camper]

Even at low efficiency they can put out enough electricity to make life more convenient. No point in a Maxxfan if you don't have the juice to run it. Or have to pay to generate that juice.

Since a lot of people here seem to have chairs and outdoor setups, there's probably more incentive to have cold food and air in the summer, and whatever else one wants to do that electricity provides.

You can also do a portable or reduced install to have space for that deck or hatch. You'd just need to watch your energy usage accordingly.

 

[Spaceman Spiff]

.....If solar panels have such low efficiency under normal conditions, what makes them worth all the roof space they take up compared to other things.....

The big one is: solar panels power refrigeration, which allows me to stay away from 'civilization' for 2+ weeks at a time while eating a fresh food diet. They also charge my electronics, run LED lights, power a booster for a weak cell signal, power my MaxxAir and other fans. All without me having to run a generator to recharge my battery bank.

P.S. I do have room for a MaxxAir fan and other stuff on my roof too.

 

[jacqueg]

I ask this in all earnest. If solar panels have such low efficiency under normal conditions, what makes them worth all the roof space they take up compared to other things (ie. MaxxAir fan, Thule boxes, Artic Tern access hatch, observation deck) that could otherwise occupy that space?

If you want a refrigerator, get rooftop solar. If you don't want a refrigerator, you don't need rooftop solar. A smaller "solar generator" will take care of your laptop/phone/LED lights and occasional electric cooking, and if you drive frequently enough, you won't even need the portable solar panels.

But once you get rooftop solar to run your refrigerator, it is very handy for lots of other things. It all depends on how you travel.

I started without rooftop solar, and did just fine, wasn't sure I would ever get rooftop solar. But once I got tired of the ice chest - and I had a GOOD ice chest - I got rooftop solar.

 

[Happy Camper]

I'm hoping at some point we can eliminate the label of solar generator from a fancy battery pack. One of my pet peeves that I can't get past. It's so disingenuous.

 

[wayne49]

Especially since the prepackaged battery and inverter in a box doesn't come with solar panels or any charging equipment. The battery tends to be small and they don't rate them in amp hours, they are rated in Watt hours to have a larger number for marketing.

 

[maki2]

There are walkable solar panels that can be used for a rooftop deck surface. However they are considerably more expensive than the common types of solar panels. I have seen a few videos that featured them being used that way by nomads.

 

[Happy Camper]

Those were probably thin film panels. Not nearly as efficient, but they are good for their application. I considered them at one point.

 

[jacqueg]

I'm hoping at some point we can eliminate the label of solar generator from a fancy battery pack. One of my pet peeves that I can't get past. It's so disingenuous.

Alas, it seems to be catching on...

It's a pretty dumb name, but there's no denying that "solar generator" has fewer words/letters than "portable power station"...

 

[bullfrog]

How about “ a battery with a multi input charger and inverter with lots of outputs in a sealed box so it isn’t serviceable that costs too much for the amount of power you can get out of it.” $2,500 is a good deal? Yes it is, a good deal of money!

 

[frater secessus]

I ask this in all earnest. If solar panels have such low efficiency under normal conditions, what makes them worth all the roof space they take up compared to other things

Q. if MPG doesn't reach the number on the window sticker under normal driving conditions why do we still buy cars and trucks?
A. because they are useful

What solar offers, IMO, is excellent "time on task"; it's out there making power whenever sunlight is hitting the panels no matter what we humans are doing or if we are even present. It does this silently without maintenance in the normal sense.

Example: my budget system ($423) averages 1.7kWh/day in all seasons, with the maxxfan in place. It was making power this morning before I started making coffee, As I start this sentence it's 7:41am local and the panels are making 124.3w, steadily climbing as the sun rises higher. That's enough to cover my background house loads and start charging the bank. The house bank will be charged by ~11am, well before local solar noon when the system would make its best numbers. Max I'll see today is probably ~60% of rated power. Totally happy with that since my needs are 100% met.

Having said that, solar is a tool and will not be required in every build. Like a car is not required for every household. People with frequent access to shore power might have no use for solar. Same for folks who drive enough to use alternator only. OTOH fulltimers who boondock in place for long stretches will probably use solar as a major source of power.

 

[frater secessus]

I'm hoping at some point we can eliminate the label of solar generator from a fancy battery pack.

Preach! The name confuses so many newbies. I am reminded of the SNL Coffee Talk skit: "A solar generator is neither solar nor a generator. Discuss amongst yourselves."

thin film panels. Not nearly as efficient, but they are good for their application

IMO thin film got betamaxxed by "flexible" crystalline panels. The lower Vmp of amorphous panels makes them a natural fit for folks running PWM controllers. And they're actually flexible.

 

[Happy Camper]

Thin film is still viable for larger area usage. When I had my G20 I thought about putting 2 sheets of it on the roof they were roughly 2x6 feet and would have put out around 200w give or take. I forget as it's been a while.

Figured if I taped them to the roof they wouldn't even be seen. They hold up to damage and can even be stood upon if needed. I liked the idea that they would be very stealth. Sold the van, and haven't really thought about it until now lol.

 

[sithigh]

I'm hoping at some point we can eliminate the label of solar generator from a fancy battery pack. One of my pet peeves that I can't get past. It's so disingenuous.

Oh I definitely agree. It's also hard to believe anything that is only used to sell something. Even the reviews they list can be manipulated. But seriously, it's a meaningless hype word for an unknown assembly of optionions in a box. You need to go through all the specs with a lot of salt.

 

[Happy Camper]

They definitely have a place, and are completely worth it in certain situations. I have one sitting less than a foot from me that I bought for someone that was going to need it. Their situation changed so I kept it. It's handy and wasn't one of the crazy expensive ones.

It's the naming convention I take issue with.

 

[2slo]

I have a 400watt panel and I think the most I've seen going into my 'solar generator' is around 350w. It's usually between 100-300 but charges me to 100% before the sun get's high in the sky. I love being able to park the van and not worry. I can come back after days and the drinks are still cold and the van is still ventilated.

 

[wayne49]

You could be under clear skies and not get close to the rated wattage. Higher relative humidity will impede the photons on their path to the panels.

There are test bench laboratory numbers, then there are real world numbers.