Long time listener, first time caller from Dateland, AZ

You mentioned using Growatt battery-less. That won't support a starting surge higher than instantaneous PV output. Capacitors only supply for a fraction of a second. A string of four car batteries for 48V, which have CCA rating of 700A (at 7.5V) would probably deliver 350A while staying above low-voltage cutout (about 10V per battery). That would be 14kW, enough for whatever Growatt was willing to do to kick over a motor. But don't cycle the batteries; shut off A/C or whatever as soon as batteries start to discharge because PV can't keep up.

There's only a little mention of wind on this forum. We know that most wind turbines don't perform as advertised. Some, like Bergey, are supposed to be pretty decent (but not cheap). Studies I've read found that even with an anemometer measuring wind speed, turbine produced a fraction of what rating said for that speed. Issue appeared to be turbulence; like an airplane wing, the blades "stall" and fail to produce lift when wind doesn't pass over them at the right angle. If you can build a guyed tower 90' tall for a 300W or so turbine, it might do OK. Has to withstand your highest wind speeds as well, of course.

Someone linked a video from a guy in Australia who runs his house off a washing machine. Put a (Pelton or other) water wheel on it and ran it as a micro hydro generator. Found out the hard way bearings last 2 years of continuous use but not 3, so now replaces bearings every 2 years.

I think a chest freezer (or any freezer filled with a bunch of jugs) and ducted air vents would work, but total BTU per day is limited to its compressor capacity. And mixing room air with it's working air would probably cause too much icing. If you know how many Wh/day the A/C consumes, that's about how much freezer is required. An AC system with evaporator coils in a tank of water, and air duct heat exchangers through the water, might work. But that might be a development project not suitable for someone on a shoestring budget. Usually, what we hear about are commercial systems that build ice at night when rates are low, and chill with cold water during the day.

You have water? Earth-sheltered home with sod roof?

Hedges said:

That won't support a starting surge higher than instantaneous PV output.

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I was curious about that myself. But the company says right on the web site (https://watts247.com/product/spf-3000tl-lvm-es/?wpam_id=3):

48V battery is OPTIONAL, in other words, it can run with nothing more than some solar panels connected.

...be prepared to have some interruptions in supply if your load is higher than the solar input.

Some of our customers in AZ use them for directly powering air conditioners during the day.

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I messaged with one of their technicians who assures me that a 5S3P array should work just fine with 4000 watts in from PV and 3000 out from the inverter.

As for wind, we routinely get consistent 20 mph wind at ground level out here in the desert.

I like the IDEA of an ice-based cooling solution, but the implementation seems outside of my wheelhouse. Although, a simple ice-fed swamp cooler has been on my mind lately. As it is, the swamp cooler goes through about 5 to 6 gallons a day. That will probably double in the Summer, and ice would be a nice addition.

Earth-sheltered home with sod roof?

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Nope. I wish. Panel covered trailer with a weak floor and piñata walls with no insulation.
I do have really clean well water though from the local community water treatment plant.

I messaged with one of their technicians who assures me that a 5S3P array should work just fine with 4000 watts in from PV and 3000 out from the inverter.

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awesome!

I hope it's true. I reached out to Mr. Prowse on his YouTube channel suggesting he test this claim during his upcoming review. I hope he finds this useful information for his viewers.

"Surge Capacity 2* rated power for 5 seconds"


That is good, 6000W AC for 5 seconds. Enough to start a 1200W motor. But you won't get it without 6000W of PV, or a battery.
If you have 4000W of PV and sun hits them at a 45 degree angle, they will only produce 2800W. Or less, if that was 4000W (STC) and the weather is hot.
A string of four car batteries that aren't completely dead will provide a few seconds of "cranking" power, plenty to start a motor. They wouldn't last long with cycling, only good for a brief surge, so you need to shut off A/C when battery begins to supply the load. If you have a small window A/C that might only draw 500W for use later in the day, and a big one could provide more cooling when there is more sun.

Yeah, I thought that was curious. Max PV input on one device is 4000 watts, but then somehow the inverter can surge 5 seconds at 6000? How does THAT work?!

As for the sun angle concern and lowered array output, doesn't the MPPT compensate to some degree?

Luckily, I have two very efficient Frigidaire window A/C units; one 5,000 BTU (460 watts), the other 10,000 (916 watts). Also, I'm hoping to rely on the built-in failover controller in this device to switch to the backup trailer hodge-podge array and battery to keep the A/C running when the Growatt can no longer pull enough from it's own array. Additionally, I have thirty 270 watt panels to create two 4000 watt arrays and parallel two Growatt systems for single phase 6000 watt total output. That should also resolve sun angle issue, et al. However, in order to parallel them, the manual does indicate that a battery must be used, so I'll probably cobble together some cheap lead acids just to keep them talking.

A PWM controller simply shorts the panels to the battery. Whatever PV panel IV curve shows as current at voltage equal to battery, that's how much current you get. Something less than Isc, slightly higher than Imp.

An MPPT controller is a switching power supply, acts like a transformer for DC. It can take in 1200W, 12A at 100V and turn it into 1200W, 100A at 12V (minus a bit of inefficiency.) The "Maximum Power Point Tracking" function is that it constantly adjusts current taken from PV up and down a little, e.g. 11.9A to 12.1A, so see what current (and voltage) delivers the most power.

MPPT just does the best it can with whatever IV curve it sees due to sun intensity and angle.

If you have multiple strings of panels connected in parallel and partial shading hitting some panels of one string, the MPPT algorithm may or may not explore lower voltages to find where both strings contribute current. Some will stop searching when voltage has been pulled down the point where power out of the unshaded string drops off, doesn't find where the partially shaded string starts contributing current. It stops at the first foothill, doesn't reach the mountain.

If you put an SE facing 4000W array on one Growatt and SW facing 4000W array on the second Growatt, one would be limited by its 3000W limit and the other by off-angle sun.
I would put one 2000W SE facing array paralleled with one 2000W SW facing array on each Growatt. (If two MPPT one array to each, but I think it has a single input limited to 18A). That way each one can deliver 3000W for several hours.

6000W is a lot more than the A/C you have (but maybe the amount of A/C you need!) How about an additional A/C chilling an insulated shed full of gravel, bricks, jugs of water, or similar. Then you could blow air through extract the stored cold. Making ice (phase change) is better, but requires more than just a second hand window air conditioner.

@Hedges : Thanks for the quick rundown on MPPT. I suspected as much, but for the time being I was just chalking it up to "magic". But I do experience the functionality of it everyday. Right now, in fact, I've been running the swamp cooler and my MorningStar has been equalizing the batteries from 1200 watts on the roof since 11 am. The swamp cooler only pulls about 170 watts. And yes, I know my 60 amp charge controller can only put out 800 watts, but the 1200 watt overkill was an early mistake. Besides, I do get a bit more out of them in the morning and late afternoon than I might ordinarily.

Shading is not a problem here. There are no trees. I did see a cloud once, but it spontaneously combusted around 8 am. In fact, one of the challenges we have out here is the fact that for six months, there is no cold water from the tap! In fact, it can at times be dangerously scalding. Ice is a necessity.

Curious idea about splitting the array in two directions (SE/SW). I'll have to wrap my head around that. Thanks.

It would be great if I could just have the arrays tracking the sun during the day, but how do you move two 10 foot by 32 foot arrays that each weigh half a ton? I've been toying with the ridiculous concept of a shallow floating barge array like a pond in the back yard. But the water out here is crazy expensive and would evaporate in a matter of hours. Of course, I could create an oil pond, but the stench and potential for combustion would be...problematic. So...Ridiculous, right?

Tracking PV mounts have been around for years. They produce more watt-hours during a day than the same array with fixed orientation.
Back when panels cost $5/watt, a small tracking mount for home use cost as much as just buying extra panels to equal what the tracker would yield.
Today, PV panels can be had for $0.20 to $0.50/watt. Trackers have not decreased in price by a factor of 10 or 20.

That's why I say to just orient multiple strings in different directions and wire them in parallel. "passive tracking"


But if you want tracking, just move your trailer a bit. How about a dolly under the hitch, move it so it pivots about the center of the axle?


PV has become cheap enough that things which didn't make financial sense before, like solar-electric air conditioning, make sense. PV generates power for 25% the cost of retail utility rates (depending on local rates.)

The sun heating your trailer is probably the biggest problem, so a shade structure might help.

Where I am (San Jose), weather is mild. My house is poorly insulated (exposed beam ceiling and shake) so some day I'll put foam boards, maybe an air channel and vent up top. I over-built with PV and have net metering, so I use the credits for electric heat in the winter. If grid goes down I run off PV and battery, and have gas furnace.

(Don't know why the "Strikeout" text sometimes appears?

I agree. I was able to obtain my new panels at a massive fraction of the cost I paid for my hodge-podge of panels over the past eight years.

Just a side thought: I have to wonder if an arched array might provide a constant daytime power feed.

"dolly under the hitch"? Ever seen a travel trailer snap in half? Still, I like you're kind of crazy!

You're absolutely right about a sun shade though. In fact, I was attempting to put up a 30 foot 80% screen shade just yesterday, but the wind picked up and made it impossible and the forecast indicates I may have to wait until next Tuesday before it calms down again. Actually, that's only partially true. I have someone helping me, but they literally only work during the morning and evening golden hours. And most times, the wind doesn't cooperate with that ludicrously tight window.

Better think about moving further north!

45North said:

Better think about moving further north!

Billions of people could live in areas too hot for humans by 2070, study says | CNN

If the planet continues to warm at current levels over the next 50 years, up to 3 billion people could be living in areas that are too hot for humans, a new study has found.

www.cnn.com

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If I'm not already dead by 2070, please kill me.

45North said:

Better think about moving further north!

Billions of people could live in areas too hot for humans by 2070, study says | CNN

If the planet continues to warm at current levels over the next 50 years, up to 3 billion people could be living in areas that are too hot for humans, a new study has found.

www.cnn.com

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"As our planet rapidly heats up due to rising emissions, the temperature experienced by an average person is projected to change more in the coming decades than it has over the past 6,000 years, the study found."

They had to pick their date range carefully, for shock value. "No news is good news."
10,000 years ago, the continental shelf was ocean-front property. Today, it is 400' under water. And they say man-made greenhouse gas emissions could contribute to global warming and raise sea levels an additional 3'.

CO2 levels during human pre-history:


I challenge them to produce the graph using same measurement method for all years. Don't change instruments in the middle of the stream.

And further back:


Don't know if the following statements have any validity, but interesting and at least worth thinking about:

"Atmospheric CO2 concentration is just barely above the life-sustaining levels of 150 ppm. For life to have real buffer against mass extinction, CO2 needs to be closer to 1000 ppm."

"That 400 ppm is actually dangerously low is a fact the alarmists keep avoiding and suppressing. Below 150 ppm, plant-life dies off on a massive scale. The Earth actually came very close to that point many times over the last 2 million years during the ice ages. At the bottom of the last ice age just 20,000 years ago, life on the planet literally teetered on the brink when CO2 fell to a level of just 180 ppm."

Was this study sponsored by your benevolent local petroleum company? Or does it represent legitimate science?

I'm more concerned about habitat destruction and pollution (and by that I don't mean the stuff that promotes plant growth.)
Any reports on the topic of environmental damage which don't say exploding human population is the root of all harm, can't be trusted.

I didn't actually read that article; I just threw it in as an example of how, with global warming, parts of our planet are becoming too hot for humans to live in.
You can argue the fine details all you want but I think there's general consensus that summers are getting brutally hotter and more unlivable.
Smart people will take the hint and make a move sooner, rather than later; the others will be like frogs in water heating up on the stove and not notice anything 'till it's too late!

Yeah, people are fleeing California and the Bay Area (or at least that's what "articles" presumably sponsored by Realtors (R) say.)
I plan to remain here even after I retire, so long as I can afford it. What we get charged for water is criminal. Time will come when my property taxes exceed mortgage payment (as was the case for my mom, a public school teacher, before Prop 13.) Everything that used to be covered by taxes (like admission to parks) now has user fees, because when times were booming and government had money coming out of their ears, they expanded to consume it all. When the Great Recession hit and tax revenue declined to what were previously record high levels, they didn't have enough money to operate.

Even years ago, people moved inland to where homes were more affordable. Riverside (orange growing region) or Sacramento, etc. How does a $700/month electric bill for A/C sound? Now if rooftop solar completely offsets their consumption, it won't be so bad.

OP found himself land he could afford, but like a lizard he's going to have to shelter under a rock during the noontime heat. Maybe excavate a cellar? Or maybe shade structure and PV powered AC will be sufficient.

You hit the nail on the head. Underground. Just a matter of time.

Or, if you're ambitious:



?

I was thinking something more like this...

Well, Mr. Prowse posted his first review of the Growatt 3000LT LVM-ES and while he appeared to have a lot of trouble getting enough power to the unit from his various array configurations, he was able to confirm that the device needs at least 120 volts in-circuit current from the array to work at all and that this system is designed more for off-grid cabins or well pumps. Perfect for my needs.

So, I ordered one. Should arrive this weekend.

He also suggested that while the unit can indeed run without a battery, it would probably be prudent to have at least a small lithium titanate battery to handle brief surges. Also, if you plan to connect these in parallel, the manual says you must have a battery for that. So, I was eyeballing this thing: https://www.ebay.com/itm/Ebike-Batt...thCompV3Ranker&_trksid=p2047675.c101196.m2219

Anyone have any experience with these type of batteries?

Now If I could just get my solar panels delivered...

"Ebike Battery 48v 99.999ah 1000w Pack Charger Lithium Ion High Power Bat E Bike"

I don't believe that is 100 Ah. The larger LiFePO4 cells people buy are 100 Ah to 300 Ah.

Don't know if Growatt could adjust down to a suitable charge rate.

That is what we call an "explody" chemistry. You risk burning your house down unless it is located a safe distance away.

It's current limit (hopefully has fuses) will be lower than what he Growatt wants.