Solar panel utilization

[Bobgar]

Hi all!

I have finished my DIY grid connected install. I had some extra panels leftover and I'm trying to find a cheap way to utilize them. they are 370 watt panels. I don't want to sink anymore money into it at this time, at least not more than a couple hundred bucks. It seems a shame though to just have them sit in a closet. Any thoughts on what I might be able to use them for?

 

[sunshine_eggo]

"some"?

The issue is that to utilize your power, you have to invest in an MPPT. Then you need a battery. Then you need an inverter. You're almost certainly already over "a couple hundred bucks" even for the needs of a single panel.

 

[Bobgar]

"some"?

The issue is that to utilize your power, you have to invest in an MPPT. Then you need a battery. Then you need an inverter. You're almost certainly already over "a couple hundred bucks" even for the needs of a single panel.

Thanks for taking the time to reply! I have six extra panels. and one extra micro inverter. I don't think i can make the micro inverter work off grid. I was kind of hoping I could do something with the DC power and skip an inverter entirely. Maybe just something with a resistant heater element to get some extra heat during daylight hours in the winter. But I'm not sure if such a thing would even be practical.

I'm not looking for anything sophisticated with this, or even particularly efficient. This seems a case of something is better than nothing.

 

[dfw_dude]

heh happens to us most -- I'm wrapping up the main install of my off grid system (6000xp, two EG4 indoor batteries, and 16 solar panels-- 370W aptos panels)

Originally I was going for a 10 panel setup, but they were so cheap I figured I'd just buy 20 and be covered. Was able to find room for about 16 in my backyard. 8 being mounted optimally, the other 8 on a separate string are not in the best location for full day production, but something is better than nothing)

I'll be sitting on what looks like 4 extra panels when all it said and done, could sell them for 1/2 of what I paid I suppose but will probably just stash them as spares if any of mine ever get damaged somehow.

 

[zanydroid]

You would need at least a PWM controller to efficiently utilize the solar, since solar panels are weird crappy current sources, and the PWM will limit the current drain from your heater. Or, if you want to be creative, you can attempt to build a PWM with an Arduino.

Also, if you math out how much you can get in the winter (IE with PVwatts), it's probably not worth it except as edutainment.

 

[Bobgar]

heh happens to us most -- I'm wrapping up the main install of my off grid system (6000xp, two EG4 indoor batteries, and 16 solar panels-- 370W aptos panels)

Originally I was going for a 10 panel setup, but they were so cheap I figured I'd just buy 20 and be covered. Was able to find room for about 16 in my backyard. 8 being mounted optimally, the other 8 on a separate string are not in the best location for full day production, but something is better than nothing)

I'll be sitting on what looks like 4 extra panels when all it said and done, could sell them for 1/2 of what I paid I suppose but will probably just stash them as spares if any of mine ever get damaged somehow.

I was shooting for a 30 panel set up. There was a 31 panel pallet and a 36 panel pallet. The company advised I order extra because if 1 or 2 break in shipping they cant send a replacement order that small. I opted for 36 as it was only like 300 dollars more. No panels broke in transit and they accidentally sent me an extra micro inverter, so here I am. Thinking I might expand the system eventually, but not for a year or two as i observe the performance of what I installed.

Just would like to put the panels to use in the mean time.

You would need at least a PWM controller to efficiently utilize the solar, since solar panels are weird crappy current sources, and the PWM will limit the current drain from your heater. Or, if you want to be creative, you can attempt to build a PWM with an Arduino.

Also, if you math out how much you can get in the winter (IE with PVwatts), it's probably not worth it except as edutainment.

PWM don't look to be terribly expensive. Is there a certain kind or brand you would consider. I see some real cheap ones and some not so cheap ones. I'm curios what the difference is? I'm not sure I have the skills to build my own with an Arduino. I took a programing class once...it did not go well.

And edutainment is just fine by me

 

[zanydroid]

ve. Is there a certain kind or brand you would consider. I see some real cheap ones and some not so cheap ones. I'm curios what the difference is?

The challenge here is that the most common PWM and MPPT controllers expect a battery but the resistive heater will not look like a battery. A small buffer battery in parallel with the heater would address that but then this gets into the escalating cost territory.

There are a few direct solar to heat threads here you can consider looking at. The direct dump load to resistive water heater is electrically the same as using a space heater.