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Solar with a LOT of Shade and PWM vs MPPT
#11
(02-19-2019, 11:20 AM)runsnbunsn Wrote: water pump(hand pump atm)

This sounds like you are either not using the electric one, or haven't bought one yet. If you haven't gotten an electric pump yet, I would suggest going with a 48VDC pump. They cost close to the same as a standard AC pump (unless the prices have drastically changed over the past couple years) and would allow you to go with a smaller inverter. You could also go with a DC powered coffee machine (unless you are going with those expensive latte, cappuccino, etc type machines) to save there as well. There are DC powered fridges, but also propane ones, too. The coffee machine and fridge can be had from RV's.
The propane fridge actually lasts along time because it doesn't take much heat to keep the system running.
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#12
I'm using a MPP Solar PIP3024MSE and like it. It's not a clone and the build quality is fine, definitely not cheap. Yesterday I got as much as 1.7 kWh from my 3 partly shadowed 200kWp panels wired in parallel, so I would say you will have a good setup. If AC output is on, minimum consumption is about 30-50 W. Therefore you will need to switch the output off when being away at least in winter to not deplete the batteries. It will charge the batteries as long as there is some light on the panels even when switched off.
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#13
Yes the generator would be theoretically the most cost effictive, but I like the luxury of having cold beer when I arrive there and -officially- I dont have a generator there  Wink


About the waterpump, yes I was thinking about DC 24 or 48V but I have around 50-60m cable to the well. Pump near the shed not really possible because of freezing and long suction times. Pump must go into the well and stay there all year long. Would be solveable with really thick cables, or a second small but high discharge battery near the well. Have a 1500W/220V well pump lying around which will go first I think(these things dont work a long time) but I plan on digging in the thickest cables I can get for a reasonable price.

We also have two fridges there, one 12/24V very effective compressor fridge, and a standard 220V low energy one.
The effective one uses about 300Wh/day which is really good, the AC one 370Wh according to manual(+ inverter losses which makes it around 500 - 600Wh I guess)
On the other hand the AC one has almost double the volume of the compressor one.


I think if the solar is big enough to cover the inverter standby usage(on rainy days), its easier to run a few things on 220V, Lights and smaller things excluded.

(02-19-2019, 01:36 PM)stevelectric Wrote: I'm using a MPP Solar PIP3024MSE and like it. It's not a clone and the build quality is fine, definitely not cheap. Yesterday I got as much as 1.7 kWh from my 3 partly shadowed 200kWp panels wired in parallel, so I would say you will have a good setup. If AC output is on, minimum consumption is about 30-50 W. Therefore you will need to switch the output off when being away at least in winter to not deplete the batteries. It will charge the batteries as long as there is some light on the panels even when switched off.

Yeah, that standby usage is a LOT! 1.2kWh/day in worst case.
In reality more like 600Wh I guess because with daylight you almost always get more than 50W with 1.2kWp panels.
In winter AC will be turned off probably, because theres no way of getting that usage in with solar, but thats ok for me.
I wish there would be an option to turn off AC automatically for example from 01:00 to 04:00 at night.
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#14
Looks like you have several bases covered already, great!

One thing you could do about the DC well pump is to either have a soft start installed, or you could use some super caps right at the pump to help with the surge. That would allow you to go down in 1 or 2 sizes on the cable to compensate for voltage drops.
The other thing could be to convert the DC to pulsed DC and transform it up to a higher voltage for that transmission, then drop it back down on the other end. Basically you'd boost the voltage up, then buck it back down. Altho, I don't know what the requirements would be of such a heavy amp usage device.
I'm sure there are other ideas as well.
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#15
(02-19-2019, 01:45 PM)runsnbunsn Wrote: Yes the generator would be theoretically the most cost effictive, but I like the luxury of having cold beer when I arrive there and -officially- I dont have a generator there  Wink

I'm just try to encourage you to think outside of the box a little, as they say on trendy management courses.

A 12v travel fridge would allow you to have a cold beer half way to your destination, and when you get there, and as many as you want on the way home. A split charge system in your automobile, along with a secondary battery would negate the need for your existing DC fridge, and provides the means of charging additional batteries if required.

There's always different ways to get to where you want to be, it's not always wise to base new plans on having to make use of existing appliances and equipment.
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#16
"The new panels need to be all parallel, because I have no other choice." - good option... all in parallel.

If your going 24V pack then just buy a cheap PWM controller and spend the difference on an extra panel as it will be more cost effective (and reliable if it is a good unit) in the longer term. PWM controllers have less components and very few capacitors to fail, so over the years they will last. Given the pack voltage relative to the mpvoltage of the panels and the losses between 32V to 28V (14%), an extra panel would make up the difference...

Cost wise, compare the price of a PWM to MPPT at the low voltage levels with single panels in parallel.... also consider that you can bypass the controller altogether if it fails (hook the panels directly to thre battery) just don't over charge the battery ! The PWM will also drop around 1V for a cheap unit between input and output due to the transistors/diodes.

If your remaining AC equipment is not high wattage, look at some of the 1200VA/600VA 24V based UPS units as these have lower stanby loads, my old APC 1200VA is around 0.8A at 24V (19W). They are cheap and something only valuable as scrap to a thief... I try to avoid moving things of value around by buying less valuable older stuff that does the job... :-)

With the water pump go 48V and run it via a boost converter from 24V. The 1500W units listed for £14-18 will output 20A and maximum 30A input, so limited to around 750W maximum at 24V input. For a smaller well pump this could work ok, reduce your cabling requirement and provide an upgrade route to a 48V battery. Running a 1500W well pump from an inverter will potentially need a much larger than 1500W inverter due to the startup current.
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#17
(02-19-2019, 02:30 PM)Korishan Wrote: One thing you could do about the DC well pump is to either have a soft start installed, or you could use some super caps right at the pump to help with the surge. That would allow you to go down in 1 or 2 sizes on the cable to compensate for voltage drops.
The other thing could be to convert the DC to pulsed DC and transform it up to a higher voltage for that transmission, then drop it back down on the other end. Basically you'd boost the voltage up, then buck it back down.  Altho, I don't know what the requirements would be of such a heavy amp usage device.
I'm sure there are other ideas as well.

I like the supercap idea, cheap and effective for the job.

(02-19-2019, 04:47 PM)Sean Wrote: A 12v travel fridge would allow you to have a cold beer half way to your destination, and when you get there, and as many as you want on the way home. A split charge system in your automobile, along with a secondary battery would negate the need for your existing DC fridge, and provides the means of charging additional batteries if required.
Good solution, I already have a small travel fridge, but with stuff for me, wife and two kids we dont use it much as I would need a bigger one. I also should add ist just 20mins to get there, I go sometimes even by bike, so the visits are more spontaneous. My brother and mother use the place too, so the usage is a bit "unplannable".


(02-19-2019, 08:40 PM)completelycharged Wrote: If your going 24V pack then just buy a cheap PWM controller and spend the difference on an extra panel as it will be more cost effective (and reliable if it is a good unit) in the longer term. PWM controllers have less components and very few capacitors to fail, so over the years they will last. Given the pack voltage relative to the mpvoltage of the panels and the losses between 32V to 28V (14%), an extra panel would make up the difference...

Cost wise, compare the price of a PWM to MPPT at the low voltage levels with single panels in parallel.... also consider that you can bypass the controller altogether if it fails (hook the panels directly to thre battery) just don't over charge the battery ! The PWM will also drop around 1V for a cheap unit between input and output due to the transistors/diodes.

If your remaining AC equipment is not high wattage, look at some of the 1200VA/600VA 24V based UPS units as these have lower stanby loads, my old APC 1200VA is around 0.8A at 24V (19W). They are cheap and something only valuable as scrap to a thief... I try to avoid moving things of value around by buying less valuable older stuff that does the job... :-)

With the water pump go 48V and run it via a boost converter from 24V. The 1500W units listed for £14-18 will output 20A and maximum 30A input, so limited to around 750W maximum at 24V input. For a smaller well pump this could work ok, reduce your cabling requirement and provide an upgrade route to a 48V battery. Running a 1500W well pump from an inverter will potentially need a much larger than 1500W inverter due to the startup current.
The comparison PVM cost saving vs add more panels is interesting, with all the shading its even more difficult calculate because more space -> the space with the least shade isnt that big... I have to measure that, thx!

Inverter is planned 3000W(6000W surge 5 seconds), that should be plenty when the coffee machine isnt running at the same time ;-) As I already have the 1500W pump(its stainless steel, cost about 80 euro), I'll try that first and see how it goes. Handpump will always stay for backup :-)


Thx for all the input guys, a LOT to think about on every "front". I will continue the hunt for panels for now and in the meantime go back to battery work :-)
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#18
If you go the SuperCap route, you will need to limit the charge current back into the caps. Otherwise they will try to draw as many amps as possible to recharge in the shortest time possible. Limiting is needed here for the distance, cable size, and required amps.

Since the visit times are so erratic, and the place is so close, I would recommend either setting up an internet connection and trigger an RPi to turn everything on, or even try LoRa broadcasting that once you get within range, it'll trigger the RPi to turn things on. LoRa can go quite a fair bit of distance (yes, many miles, especially line of sight). I'm going to guess you have trees around the place and maybe even a slightly winding road. LoRa can still make it but it just wouldn't trigger as far. I can't guess/calculate the distance that it would with trees. The modules are fairly inexpensive.
If you want to go the quick route and virtually anywhere access, have internet service to the cabin. This would probably be best as you can remote monitor the system from anywhere.
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#19
Following what @Korishan has to say about IoT based triggering there are some low cost IoT based sim providers that can enable such functions for fairly inexpensive. Hologram.io is one of them but there any many others. Most works in virtually all countries and on hundreds of mobile carriers.
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#20
Have to look at that LoRa thing closer, thx!

Rpi was planned anyway for checking battery and solar. I have 3G/4G reception there too, so that could be easier but LoRa looks interesting...

Oh, and for the solar panels.. I managed ot get an even better deal: 234Wp 49V/40.3V Mono Full Safety glass panels for 100 a piece, took 6 of them  Big Grin
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