Off Grid Solar

[Chopr147]

$6/w?!?! I would steer clear of Goal Zero... they're absurdly overpriced

I've heard good things about Lensun panels... they're half the cost and semi-flexible.

If you're comfortable ordering from China I've ordered 300w... they should be arriving soon so I can write up a review in a few days.

Not sure what's available in the UK but I wouldn't pay >$1/w for a tempered glass PV module and inverters shouldn't cost >$0.50/w.



Do you mean 10kW?

I've got a 10.7kW system tied to a 8kW grid-tie inverter. A couple years ago I bought a Magnum Energy 4448PAE for $2200 and 8 6v Golf Cart Batteries for ~$1k. So for <$4k I can have almost full power off the array and ~4kW at night with ~10kWh of storage. If you want something more user friendly than AC coupling you can get a high voltage charge controller for ~$1500; This would bypass the grid-tie and charge the batteries directly with would in turn power the off-grid inverter.

99% of the time being 'off-grid' isn't worth it but having some backup power can we worth its weight in gold if there's an extended grid outage.

No I mean 10 kwh. I have a 10kw system but it's only good for an hour
Confused my S with my house I guess

 

[WentOffGrid]

I'll say specifically that the utter key to a good system is an adequate battery bank. -

Yes, for sure!


Side note- the benefit of "selective grid-tie"... when we are at 94% SOC and it's sunny, the grid-tie switch connects, so all excess generation then goes back to the grid instead of our panels being forced to reduce output (a waste of perfectly good sunshine)

 

[miimura]

Good info @miimura. I figure that needs to be about $6k and then we're talking (which is just an initial guess on my part at what I think Tesla's batteries will cost, and the size of the /kwh discount this battery needs to carry to make it competitive. If they're priced the same, then I'm not seeing a compelling reason not to get the lighter weight and smaller package.

To be fair, the high price that was discussed at the show was ballparked based on a single unit marked up and installed by an independent installer. It is conceivable that they would be willing to sell these today in quantity below $500/kWh if you picked up a container-load from their dock.

 

[Lloyd]

What I would like to see is a device that acts as your utility and puts excess solar generation into storage, and also calls on a generator or queue load shedding if the batteries begin to become depleted. It needs to be a smarter system, but utilizing the existing components that a home or business owner may already have installed.

 

[nwdiver]

What I would like to see is a device that acts as your utility and puts excess solar generation into storage, and also calls on a generator or queue load shedding if the batteries begin to become depleted. It needs to be a smarter system, but utilizing the existing components that a home or business owner may already have installed.

IMO an actual utility will aways be better... since if the batteries are full and the sun is still up you're going to waste a lot of perfectly good clean energy. wk057s system is a good example of this... if he had a grid-tied system he would have displaced another ~10 tons of CO2. So with a large off-grid system you're spending more to accomplish less. We don't have the luxury of that right now

That said... we do need to apply pressure to utilities to send a clear message that their shenanigans will not be tolerated. Xcel has made it cheaper to have an off-grid system than a grid-tied system. I think that co-generation could be very promising since you're far more likely to need a generator to supplement your PV in the winter... when you also need heat.

 

[miimura]

What I would like to see is a device that acts as your utility and puts excess solar generation into storage, and also calls on a generator or queue load shedding if the batteries begin to become depleted. It needs to be a smarter system, but utilizing the existing components that a home or business owner may already have installed.

Except for load shedding based on SOC%, integrated systems like the Outback Radian already do this. I have automatic load shedding on an automatic transfer switch, but it only works if you have more connected load than a source like a generator can provide. It is the APC UTS10BI. You can configure it for the size of your UPS and generator and when you exceed the allowable draw of the generator it will cycle the loads in round-robin fashion so that things like refrigeration can still run a minimum number of minutes per hour.

 

[Lloyd]

Yes but UTS10BI is only good for 30 amps. I need a source that can supply 300 Amps minimum to supply the house. My grid feed is 400 Amps

 

[miimura]

Yes but UTS10BI is only good for 30 amps. I need a source that can supply 300 Amps minimum to supply the house. My grid feed is 400 Amps

If you get the hardwire version, you can feed it 50 amps from a generator. However, you're right, clearly someone needs to make one with much larger capacity. It is nice that it measures the power consumed by each circuit and each one is individually switchable grid/UPS/generator. I thought of daisy chaining another off the 240V circuit since I don't have any 240V loads on that panel. By setting the generator input low enough on the second panel, you could avoid exceeding the 20A rating of the 240V output of the first one. On second thought, never mind. The two legs of the 240 are never going to be equal and that output is designed for pure 240 L-L loads.

This does beg the question about how to scale load shedding to a large number of circuits. It might be easier to do it with Smart Home style controls. Communication and software integration would be the only issues there.

 

[nwdiver]

Thought I'd share some of the details on a PV system I'm donating to the Sioux;

One of the challenges at the camp is electricity... even charging cell phones and iPads appears to be somewhat problematic. I've ordered 3 100w flexible panels from a vendor on eBay. If those work out well... and depending on what I observe at the camp I plan to order another dozen or so more. For a flexible panel the cost is pretty reasonable at ~$1.50/w. Each panel has metal grommets so you can tie them down to a tent.

I have a spare Phocos 24v charge controller and a 24v 1.5kW inverter I'm going to donate and I'll pick up 4x 6v Golf Batteries on my way. Since DC-DC is a bit more efficient and less expensive than DC-AC-DC I also ordered a 24v-USB charger on amazon that can charge up to 5 devices at 2.1A. 2 of those along with 15 external power packs should keep those phones charged. Can't have the battery die when you're trying to catch police brutality on video .....

So.... the final system should look like this....

3x 100w Solar PV plan to expand to ~1.2kW 3 strings of 4; $1656

on a slightly used 30A 24v MPPT controller. $300

4x 6v 220Ah (~5kWh) Golf Cart Batteries $400

24v 1.5kW Pure Sine inverter (also used) ~$500

So for <$3k this should provide more than enough power to charge dozens of iPads, iPhones, flashlights and lanterns... at least 2 or 3 kWh per day.

I'll be at the camp next week... depending on what they need I may try to put together a 48v system... I'm traveling from NM to SD so if anyone along that route wants to donate some winter clothing please PM me.

 

[adiggs]

So a 6v golf cart battery provides 1.2kwh of storage and is in the $100 range. That's awfully good $/kwh.

It'd be nice to have alternatives down at twice the price ($200/kwh), and really nice to have alternatives at the same or lower price!

Good info @nwdiver - thanks.

 

[glhs272]

I have finally been able to make some progress on my off-grid solar system. Got some panels mounted to my shed.

Goal:
-To learn more about solar systems. Learn from my mistakes before I commit to a larger system.
-Build a system small enough to be not super expensive. But still large enough get a usable amount of power.
-Charge my car at least partially/sometimes on solar.
-Building on my garden shed so I don't need inspection/permits, not sure I would need any anyway (Rural area).
-Going to experiment with 2 different battery systems and car charging setups.

Right now I have 6 Tesla Model S battery modules. Roughly 30kWh of storage. (6) 260watt panels. Midnight Solar charge controller(s). 24volt 1800watt pure signwave inverter.

-Battery mode 1: Tesla modules. Use the solar panels & charge control to fill up the 6 Tesla modules. However long that takes. When the battery is full, charge my Tesla from the batteries and inverter via normal UMC charging. The problem with this is the fact that I live in Wisconsin and we have this thing called winter. Charging Tesla modules below 34degrees is bad for them. So need to find a solution or workaround for winter.

-Battery mode 2: Lead-Acid batteries. Just us a small lead-acid batter bank to act as a small energy buffer. Setup an OpenEVSE to modulate the pilot signal going to the Tesla to modulate the effective charge current. Limit the charging current to the solar panel output. Not sure exactly how I am going to do this, but was thinking I would add a analog to digital chip/sensor to the openEVSE controller to measure battery voltage. I would then modify the software to use that additional input to modulate J1772 pilot signal based on battery voltage, thus streaming power from the solar panels to the car without running the batteries completely dead.

Lots more to work on, need to connect everything. Just got panels mounted and wired at the moment. Will post updates.

 

[mspohr]

Thought I'd share some of the details on a PV system I'm donating to the Sioux;

One of the challenges at the camp is electricity... even charging cell phones and iPads appears to be somewhat problematic. I've ordered 3 100w flexible panels from a vendor on eBay. If those work out well... and depending on what I observe at the camp I plan to order another dozen or so more. For a flexible panel the cost is pretty reasonable at ~$1.50/w. Each panel has metal grommets so you can tie them down to a tent.

I have a spare Phocos 24v charge controller and a 24v 1.5kW inverter I'm going to donate and I'll pick up 4x 6v Golf Batteries on my way. Since DC-DC is a bit more efficient and less expensive than DC-AC-DC I also ordered a 24v-USB charger on amazon that can charge up to 5 devices at 2.1A. 2 of those along with 15 external power packs should keep those phones charged. Can't have the battery die when you're trying to catch police brutality on video .....

So.... the final system should look like this....

3x 100w Solar PV plan to expand to ~1.2kW 3 strings of 4; $1656

on a slightly used 30A 24v MPPT controller. $300

4x 6v 220Ah (~5kWh) Golf Cart Batteries $400

24v 1.5kW Pure Sine inverter (also used) ~$500

So for <$3k this should provide more than enough power to charge dozens of iPads, iPhones, flashlights and lanterns... at least 2 or 3 kWh per day.

I'll be at the camp next week... depending on what they need I may try to put together a 48v system... I'm traveling from NM to SD so if anyone along that route wants to donate some winter clothing please PM me.

I am thinking that it might be best to configure this as a 12v system rather than 24v. I know that it is more efficient to convert from 24v but I am thinking that in this situation, there will be a lot of people with 12v automobile phone chargers. If 12v is easily available, they could just plug their own charger into this system rather than be limited by the number of outlets on the 24v USB charger you are providing.
I do hope that your mission is going well... all the best to you.

 

[nwdiver]

I am thinking that it might be best to configure this as a 12v system rather than 24v. I know that it is more efficient to convert from 24v but I am thinking that in this situation, there will be a lot of people with 12v automobile phone chargers. If 12v is easily available, they could just plug their own charger into this system rather than be limited by the number of outlets on the 24v USB charger you are providing.
I do hope that your mission is going well... all the best to you.

Reporting now ~15 miles from the front lines; Took a night off from the camp and got a room at the casino.

Most people don't have anything that plugs into 12v. Almost everyone has something that needs a USB port or AC. I'm working with the camps to improve thier power availability. I got an apprentice that's going to be wintering here and I'm trying to get him to the point that he can fix anything that breaks.

After walking down about a dozen systems that have been donated a common issue I keep encountering is that there's a regular 60 or 72 cell panels with a nominal voltage of ~30 or 40v connected to a 12v PWM charge controller. This actually drops the output of the panel to the battery voltage. Since current doesn't go up much you're turning a 300w panel in to ~90w panel. By using 24v you can double the power output of the system. You can also use a MPPT controller but those cost >$100 vs ~$15 for a PWM controller.

I heard today from a senior member of the tribe that Solar City is donating $200k in equipment for a permanent building that the tribe wants to build on the camp site.

 

[mspohr]

Reporting now ~15 miles from the front lines; Took a night off from the camp and got a room at the casino.

Most people don't have anything that plugs into 12v. Almost everyone has something that needs a USB port or AC. I'm working with the camps to improve thier power availability. I got an apprentice that's going to be wintering here and I'm trying to get him to the point that he can fix anything that breaks.

After walking down about a dozen systems that have been donated a common issue I keep encountering is that there's a regular 60 or 72 cell panels with a nominal voltage of ~30 or 40v connected to a 12v PWM charge controller. This actually drops the output of the panel to the battery voltage. Since current doesn't go up much you're turning a 300w panel in to ~90w panel. By using 24v you can double the power output of the system. You can also use a MPPT controller but those cost >$100 vs ~$15 for a PWM controller.

I heard today from a senior member of the tribe that Solar City is donating $200k in equipment for a permanent building that the tribe wants to build on the camp site.

Good information and it sounds like you are on the right track.
Great news about Solar City.
I appreciate your good work.

 

[GSP]

glhs272,

Sounds like a great project. Perhaps you could add a thermal solar panel or two, and pump water-glycol mix through the Tesla modules and the panels?

Reading the module temperatures and disabling charging when below the Li-plating threshold is important. I would not expose the modules to Li plating since it quickly and permanently degrades capacity.

Good Luck,

GSP

 

[GSP]

nwdiver,

Great work you are doing. Thanks for sharing with us.

Good Luck,

GSP

 

[glhs272]

glhs272,

Sounds like a great project. Perhaps you could add a thermal solar panel or two, and pump water-glycol mix through the Tesla modules and the panels?

Reading the module temperatures and disabling charging when below the Li-plating threshold is important. I would not expose the modules to Li plating since it quickly and permanently degrades capacity.

Good Luck,

GSP

I think the Midnite solar charge controllers might be able to cut off charging when below a defined temperature threshold. I know they have a temp sensor available and cut-offs for high temp. So combined with a thermal solar panel and a pump, your idea might just work. I'll have to look into that, Thanks.

 

[glhs272]

I made a little bit more progress this weekend. Went from un-wired to mostly fully wired. Pictures posted.

I was able to do a first test run on Sunday. It was a mostly cloudy day but with a few peaks of sun. Just starting with some plain old 12 volt lead acid car batteries I had laying around, just to get the system to operate while I play around.

Conclusion: need more solar panels. I was a little disappointed with the actual output from the panels. When they got full sun in late afternoon, I got about ~550watts out power going into the batteries. Now considering I have a east-west setup, I expected that in late afternoon only the west facing panels will produce much. An considering they are not tilt optimized I shouldn't expect full output from them. So maybe 550 isn't so bad. Will need to do more testing. Looking to do a test in full sun around noon, to see what max output is when both strings near optimum.

Other problems: I was warned about buying Midnite Solar Kid MPPT charge controllers in an online review. I probably should have headed the review but bought them anyway, as I thought I got a good deal. Well I have been having an issue with getting my two charge controllers to work together properly. When I fired up the system, one of them immediately blew an internal fuse. I checked and double checked my configuration and it is exactly as it is in the instruction manual. Not sure what the problem is, more investigation needed. However, with what my panels are producing, there is no need for a second charge controller yet. With only one operating, I still haven't even near maxed it out yet. They are rated for 30 amps max each to the battery and I only got about 12 amps max on Sunday. So I need to play around with the stacking and see if I can find what's wrong or what mistake I made with it. Right now just operating on one.

So despite the clouds and charge controller issues, I did get a few miles of charge into my Tesla. Progress.

 

[glhs272]

So the last couple days I have been playing with the solar shed. My first test using plain old car batteries seemed to go ok. Not a whole lot of energy storage in those. The next test was to switch to the "lithium" mode on the charge controller. This test was just to make sure that when I connect to the Tesla modules, that the charge voltage will remain under a defined threshold. To start I am going with exactly 24.0 volts. This would give a cell voltage of 4.0 volts. That's a conservative voltage for initial testing (4.2 volts max). The initial test was using the lead acid batteries just to make sure voltage never got above 24.0 volts. That worked well. So now I am running my first test using a real Tesla module. Picture attached.

 

[glhs272]

So the last couple days I have been playing with the solar shed. My first test using plain old car batteries seemed to go ok. Not a whole lot of energy storage in those. The next test was to switch to the "lithium" mode on the charge controller. This test was just to make sure that when I connect to the Tesla modules, that the charge voltage will remain under a defined threshold. To start I am going with exactly 24.0 volts. This would give a cell voltage of 4.0 volts. That's a conservative voltage for initial testing (4.2 volts max). The initial test was using the lead acid batteries just to make sure voltage never got above 24.0 volts. That worked well. So now I am running my first test using a real Tesla module. Picture attached.

The first full charge of the Tesla Module went well. My conservative voltage limits are a bit too conservative. The charge controller switched from bulk charging to float charging a little early. It leaves a battery voltage of 23.5~23.6 volts. So for today I bumped up the voltage limit to 24.5volts. We will see what module voltage I end up with when I get home. Also need to probably adjust the cut-off amps. Right now it's set to .2amps which I think is a little low. I don't think it matters much when the module voltage is so low, but when I start pushing voltages up to closer to 25 volts I will have to pay attention to this setting. I believe typical cut-off should be around 1 to 2 amps. At least that's what it is on a supercharger I think.