Ground Mount or Roof Mount on Shop?

[live4soccer7]

I am looking at a 25kw installation, however I am torn between whether to go with a ground mount install or a roof mount on my shop which is a 50x100'.

I always thought I wanted to go ground due to accessibility for maintenance, replacements, cleaning, snow removal, etc.... I also figured that roof mount would inevitably cause leaks and then if you have to work on the roof then you have to REMOVE the solar system which would be a massive PIA. I do have space on the ground in a field near the shop somewhat. The shop would sit on the north side of the panels.

Roof Installation pros/cons from my perspective. They'd be out of the way and off the ground and would probably get a little better productivity as there would be no possible obstructions from the shop or other trees in the far out distant.

Anyone have any suggestions?

 

[HRTKD]

All things being equal, I would take a ground install over a roof install.

 

[live4soccer7]

Would you mind expanding on why you would prefer ground mount?

 

[Steve_S]

I had the option of Roof or Ground mount and it came down to a matter of efficiency, maintenance capability and simplicity. Simplicity because the roofing system I used does not lend itself to such things, as it is a Cool Roof System that works incredibly well. REF for Cool Roof System: http://www.houstoncoolmetalroofs.com/cool-roof-information/cool-roof-design-texas/ (Never underestimate how much difference the roof can make, and even here in Canada)

I did go with Ground Mount as it allowed me to set the best averaging angle for all 4 seasons, which for me is 45 Degrees, so unless I had 12:12 Pitch roof I would have lost generation potential. Depending on your location and the Roof Pitch (if it is close to the "Average") it may be fine. Due to my location, I had to concern myself with Snow Removal which even at 45 degrees angle still needs doing. I used a Sea Container (my site storage) as the back part of the "rack" which I built using 2x6 Pressure Treated @ 24o.c. & 4x4 PT posts. The aluminium Rails (kinetic solar) are isolated with rubber pads (prevents galvanic reaction) and using only Stainless Screws & Bolts.

** NOTE: Ground Mount is not difficult to do with a bit of smart planning. You do have to factor in various issues depending on your locality though. Such as proper anchoring if you're in a Tornado / Hurricane, snow shedding/clearing capability and so on.

To determine the "Average Angle" typically that is March & September (Spring/Fall) for North America, I suggest using this Solar Angle Calculator at the bottom of the page here at: http://www.solarelectricityhandbook.com/solar-angle-calculator.html

Pitch Angle Calculator for builder's (handy tools for anyone building anything here) https://www.blocklayer.com/pitchangle.aspx

Hope it helps, Good Luck
Steve

 

[HRTKD]

Except for the installation of a pedestal to mount the panels on, a ground based system is likely faster to install, easier to maintain and like Steve said above, gives you the option to easily modify the angle.

Let's say you install a ground based system. Five years in, you change your mind, or decide you need the land for something else. All the panels can be moved to the roof still. All you're out is the cost of the pedestal and the wiring to get from the building to the pedestal.

 

[live4soccer7]

Thank you both very much for that insight. That definitely helps.

 

[Off grid Colorado]

A ground mount is by far cheaper, by code you have to be able to switch the array off safely for the fire department, it adds complexity and more cash to mount on a roof.

 

[live4soccer7]

this is all great information. I really appreciate it.

 

[live4soccer7]

Is there a "sun sensor" or something I could put outside that would allow me to take daily readings on the hourly direct sun? I probably won't do panels until next year or possibly the year after, so I could gather a full year's worth of data in a couple places to help determine if ground mount would really be the best for me or if I'd gain better exposure on the roof.

 

[HRTKD]

Is there a "sun sensor" or something I could put outside that would allow me to take daily readings on the hourly direct sun? I probably won't do panels until next year or possibly the year after, so I could gather a full year's worth of data in a couple places to help determine if ground mount would really be the best for me or if I'd gain better exposure on the roof.

Good question. Looking forward to an answer.

 

[mandrews44]

I use Ambient Weather Station. You can use any device lilke this that monitors 'W/m' solar radiation for finding what to expect due to shadows from trees, etc. One thing you can do is use a raspberry Pi, ADS1115, a low current sensor (ASC712 5A) and a small solar cell, running on linux and dotnet core to gather this data. That is how I started my system with these conponents, including the UPS, Solar Tracker and Solar Monitor. I could create this in a weekend but I've done it before.

 

[live4soccer7]

I use Ambient Weather Station. You can use any device lilke this that monitors 'W/m' solar radiation for finding what to expect due to shadows from trees, etc. One thing you can do is use a raspberry Pi, ADS1115, a low current sensor (ASC712 5A) and a small solar cell, running on linux and dotnet core to gather this data. That is how I started my system with these conponents, including the UPS, Solar Tracker and Solar Monitor. I could create this in a weekend but I've done it before.

I've always wanted an excuse to get a pi. I'm fairly competent on the computer and in linux. Do you have more detailed information available for this setup? I'd love to build a couple of these and just let them collect data.

 

[mandrews44]

Actually, I could do it with an ESP32, much cheaper and lower power.. The entire thing could be solar powered.

 

[live4soccer7]

I'm actually running several temp sensors off of an ESP32 units now.

 

[mandrews44]

All the information you need is online. the ASD1115 is a 4 port A to D converter. the ASC712 is a 5 amp hall effect current sensor. Take a small solar panel and connect it across the ASC712. It will output an analog signal that you would read with the ADS1115. ADAFruit has these parts as well and they also have libraries to be used with Python with samples. I think the ESP32 is the better way to go since it has sleep mode and could run off the small solar panels.. 3 for power, 1 for sensor.

 

[mandrews44]

The ADS1115 runs of I2C and would work with your temp sensors (assuming they are I2C and not 1wire.

 

[mandrews44]

I used these panels for this project. https://www.amazon.com/gp/product/B073Y5PLS1/

 

[live4soccer7]

Thanks! I'll look in to this. My esps connect back to an MQTT server, however I think that it may be too far away to connect to any wifi. I don't think there is much storage capacity on an ESP32 unless I could write to a USB stick or a micro sd card.

 

[mandrews44]

I used these panels with a powered raspberry pi but I just realized they are 4.5v so if you use it with ESP32, you won't even need a battery. Just have it post to a website on the network that is either on your local computer or a raspberry pi that does the data logging.

 

[live4soccer7]

That's the problem though, I don't think it will be able to reach my wifi.