rvupgradestore.com Composet Products Fridge Defend
RV Life Magazine RV Park Reviews RV Trip Wizard

Author Topic: Grid tie panels?  (Read 1501 times)

drish

  • ---
  • Posts: 21
Grid tie panels?
« on: October 09, 2019, 01:13:49 AM »
Grid tie panels are much higher voltage, but you get a lot more watts for the price:

$1.85 per watt https://webosolar.com/store/en/12v-24v-solar-panels/2382-solarland-175w-12v-monocrystalline-solar-module.html

vs.

$0.59 per watt https://webosolar.com/store/en/grid-tie-solar-panels/2138-canadian-solar-cs6k-300ms-300w-monocrystalline-perc-superpower-panel.html

Do people use those on RVs and convert the voltage down to 12V? Any drawbacks that make it not worth it?

solarman

  • ---
  • Posts: 381
Re: Grid tie panels?
« Reply #1 on: October 09, 2019, 07:06:40 AM »

Grid tie as you call them are just commercial 60 or 72 cell panels, any panel can be configured in practice for "grid tie"
but as you have discovered, cost is the driving factor.

it is more economical to manufacture a larger panel, the 72 cell panels are physically larger than 60 cell panels and require less mounting hardware
on roofs etc.. so they are the preferred style for off grid use..

the higher panel voltage also means lower current so again is beneficial for large arrays.
these panels are big and are typically connected in series for high voltage MPPT converters.
as an example, I have designed large systems with multiple strings of 300 Watt panels often 10 panels in series
and four or more strings in parallel.. 10 of these in series will net 360 Volts at full power and over 450 V open circuit, hence the use
of 600 Volt MPPT controllers. High voltage also means low current, so easier wiring..

for RV use the biggest, and I think the only drawback is their physical size, finding space for a panel of 66 inches by 40 inches ( 5.5 ft by 3.3 ft )
is not easy on an RV roof. it's achievable, but for most it's a non starter hence the smaller so called 12 and 24 Volt panels with 36 cells.

electrically, there are no issues with converting panel voltages to 12,24 or 48 volts with any good MPPT controller.
PWM controllers are unsuitable for these panels.

KZ MXT20 480 W solar
ORV 24RKS 960 Watts solar
48V LFP, 2000W inverter/charger
Ram 2500 CTD

John From Detroit

  • ---
  • Posts: 23994
  • ^My New Home^
    • Diabetics Forum
Re: Grid tie panels?
« Reply #2 on: October 09, 2019, 01:10:36 PM »
MMPT charge controllers buck/boost as needed so in theory.. If they are within the range of the MMPT controller.. should work.. Waste of money with PWM controllers.
Nothing adds excitement like something that is none of your business
My Home is where I park it.

Tom_M

  • ---
  • Posts: 167
Re: Grid tie panels?
« Reply #3 on: October 10, 2019, 07:47:46 AM »
Do people use those on RVs and convert the voltage down to 12V? Any drawbacks that make it not worth it?
With the higher voltage of grid-tie panels you have to use an MPPT controller which costs more than a PWM controller. With 12 volt panels you can get by with a much cheaper PWM controller.
Tom
2005 Born Free 24 Rear Bath
Towing 1978 VW Bug Convertible

drish

  • ---
  • Posts: 21
Re: Grid tie panels?
« Reply #4 on: October 10, 2019, 12:33:51 PM »
The price of the panels makes up for the price of the controller though:

300w = $178
300w = $178
TS-MPPT-60 = $598
Total = $954 for 600W

vs

175w = $325
175w = $325
175w = $325
TS-60 = $232
Total = $1207 for 525W

solarman

  • ---
  • Posts: 381
Re: Grid tie panels?
« Reply #5 on: October 10, 2019, 01:59:05 PM »
With the higher voltage of grid-tie panels you have to use an MPPT controller which costs more than a PWM controller. With 12 volt panels you can get by with a much cheaper PWM controller.

for low wattage installations, then yes, a PWM controller would cost less, however as the wattage increases, the efficiency gain and
usability of the mppt shines through. in fact these days i would not even consider a pwm and 12 v panels.. the extra cost and
weight of thick cabling can easily be avoided with mppt. certainly my experience in the RV world..



KZ MXT20 480 W solar
ORV 24RKS 960 Watts solar
48V LFP, 2000W inverter/charger
Ram 2500 CTD

Frank B

  • ---
  • Posts: 1367
Re: Grid tie panels?
« Reply #6 on: November 23, 2019, 07:51:24 PM »
Grid tie panels are much higher voltage, but you get a lot more watts for the price:

$1.85 per watt https://webosolar.com/store/en/12v-24v-solar-panels/2382-solarland-175w-12v-monocrystalline-solar-module.html

vs.

$0.59 per watt https://webosolar.com/store/en/grid-tie-solar-panels/2138-canadian-solar-cs6k-300ms-300w-monocrystalline-perc-superpower-panel.html

Do people use those on RVs and convert the voltage down to 12V? Any drawbacks that make it not worth it?


We did exactly what you are suggesting.  After 3 years, I am still totally satisfied.  Please note that at the time we bought, there were two types of 72 cell panels -- one using 6" ingots for the cells, and another using 5" ingots.  The ones with the smaller cells put out the same voltage (less power, of course), but were narrow enough to fit on each side of center on the roof of our RV.


See my post here:


http://www.rvforum.net/SMF_forum/index.php/topic,106669.msg1003893.html#msg1003893
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Lou Schneider

  • Global Moderator
  • ---
  • *
  • Posts: 10336
Re: Grid tie panels?
« Reply #7 on: November 23, 2019, 10:39:26 PM »
The price of the panels makes up for the price of the controller though:

300w = $178
300w = $178
TS-MPPT-60 = $598
Total = $954 for 600W

vs

175w = $325
175w = $325
175w = $325
TS-60 = $232
Total = $1207 for 525W

I'll do you one better ...

New SunPower P17 340 watt panel $170 ($0.50/watt) or Used 275 watt panel $55 ($0.20/watt).  Add an MPPT controller and you'll have a high power system for not much money.

https://www.santansolar.com/
596 E. Germann Rd.  Gilbert (Phoenix), AZ

« Last Edit: November 23, 2019, 10:43:15 PM by Lou Schneider »

rbTN

  • ---
  • Posts: 113
Re: Grid tie panels?
« Reply #8 on: November 26, 2019, 05:22:35 PM »
I'll do you one better ...

New SunPower P17 340 watt panel $170 ($0.50/watt) or Used 275 watt panel $55 ($0.20/watt).  Add an MPPT controller and you'll have a high power system for not much money.

https://www.santansolar.com/
596 E. Germann Rd.  Gilbert (Phoenix), AZ

Lou, this may be one of those questions that you know if you have more exposure to solar than I do, but can you tell me why the used say they would need to be used for off grid applications on the site, vs grid tie - not that an RV install would be grid tie, just wondering if you know why they would state that
middle TN
was - 2001 Ram 2500 4x4 5.9 cummins, auto, camper pkg, trailer pkg (still have the 2001)
now - 2014 Ram 2500 6.7 Cummins, CC long bed SLT 4x4
2007 Thor Denahli 26RL
Equalizer hitch
300 watt Renogy system with 40amp mppt Rover

solarman

  • ---
  • Posts: 381
Re: Grid tie panels?
« Reply #9 on: November 27, 2019, 10:00:04 AM »
Lou, this may be one of those questions that you know if you have more exposure to solar than I do, but can you tell me why the used say they would need to be used for off grid applications on the site, vs grid tie - not that an RV install would be grid tie, just wondering if you know why they would state that

power companies will insist on CE/UL certified panels connected to their grid, insurance will also be somewhat picky with that.
these used panels have their labels stripped, so that info is lost.. hence off grid only.
KZ MXT20 480 W solar
ORV 24RKS 960 Watts solar
48V LFP, 2000W inverter/charger
Ram 2500 CTD

rbTN

  • ---
  • Posts: 113
Re: Grid tie panels?
« Reply #10 on: November 27, 2019, 06:33:57 PM »
thanks solarman, makes sense
middle TN
was - 2001 Ram 2500 4x4 5.9 cummins, auto, camper pkg, trailer pkg (still have the 2001)
now - 2014 Ram 2500 6.7 Cummins, CC long bed SLT 4x4
2007 Thor Denahli 26RL
Equalizer hitch
300 watt Renogy system with 40amp mppt Rover