Small scale transmission inverter, does it exist


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harrisonpatm

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Jan 5, 2022
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If I set up a solar array I need to place the panels as close to the battery bank as possible to reduce transmission losses. I should also look at wiring in series to up voltage to also reduce transmission losses. Otherwise I have to sink a ton of money into cable cost.

Industry-scale solar farms take their power output up to thousands of volts to transmit electricity over huge distances without much loss. Can something be learned from this for small scale? Is there a transmission inverter available to the public at a smaller scale? I'm imagining someone with a decent amount of land whose house is in the shade and has a nice sunny spot 200ft away. It'd be nice if there was an inverter that can take my 48VDC or similar from my panels and switch it to 100-200VAC to travel a distance to my house. Sure, there would be some inefficiency and loss from said inverter (plus you'd presumably need to rectify it back to DC to charge batteries, more inefficiency). But you could use a lot longer and thinner cable for transmission. In some cases benefits might outweigh cost. Anyone done this before?
 

ajw22

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Standard practice, which happens to be the easiest and cheapest method, is to increase the DC voltage from the panels, by connecting them in series. Then cover as much distance with the high voltage DC line, in order to minimize the battery cable length, as well as the "low voltage" AC line. You'd have to be more specific about your use case, as there are too many device options. And there may be many other factors to take into consideration, such as regulations for high voltage lines/devices. Here are a few examples:

Victron SmartSolar MPPT 250/100
Can take max 250VDC PV input to charge 12/24/48 batteries

MPPSolar LVX6048WP
Hybrid inverter with max 600VDC PV input
 

OffGridInTheCity

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Micro inverter systems take the local panel DC and convert it to higher voltage AC. The benefit is smaller wire and (in the US) easier codes for the AC wiring compared to DC high voltage.

However, the DC -> AC -> DC (battery) -> AC (inverter) could well mitigate any advantages. I believe hi voltage DC from array to Charge Controller is as comparably efficient as AC over the wire.

Finally, wire losses are insignificant (in my experience) with proper sized wire (2%?) compared to *inverter losses* (15%). Me - I'd put money into a really efficient inverter (15% -> 6%) before I would in reducing 2% wire loss to 1%.

Overall I'm running at least 16.6% loss as measured from the Mindnite Classic PV input vs output end of the AIMS inverters.

It's an interesting topic for sure and I don't have much in the way of answers. Will follow this thread with interest.
 

Korishan

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It'd be nice if there was an inverter that can take my 48VDC or similar from my panels and switch it to 100-200VAC to travel a distance to my house.
Yes, they are called Micro-Inverters. They are usually cost prohibitive unless you are installing a lot of panels. They usually over $100USD for each unit.
They convert solar panel voltage into AC current. There are grid-tie MI's and standalone MI's. Obviously the grid-tie ones are more expensive.
But they have a built in MPPT controller to get the max out of the panels.
There's also string level MI's that will take the input of several panels and output in AC.
 

harrisonpatm

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Excellent, thanks for the buzzwords to continue looking. It doesn't even apply to me directly, I have a tiny lot where long wire runs won't exist. Just an intellectual curiosity.
Finally, wire losses are insignificant (in my experience) with proper sized wire (2%?) compared to *inverter losses*
This is somewhat contrary to what I've (briefly) read online. I've read it could be as much as 10-20% loss. Am I mistaken?
 

OffGridInTheCity

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This is somewhat contrary to what I've (briefly) read online. I've read it could be as much as 10-20% loss. Am I mistaken?
In my experience 10-20% is wildly off. Suggest getting to details - for example, I have 150ft runs of up to 100vdc @ 50a on 6AWG from the combiner boxes to the charge controllers - and there is no evidence of anything more than 1-2% loss.

The idea is to size the volts/amps to the wire by arranging panels / buying a compatible charge controller. There's good info on amps per wire size and no reason to accidentally or even 'on purpose' to have 10-20% losses.

For example, here's a SolArk interactive worksheet where I've put in 400ft runs and 8AWG wire to illustrate V loss %1.99 - e.g. 2% (bottom right). It's interactive and you can play with it... https://www.sol-ark.com/wp-content/uploads/2021/09/Solar-Panel-Sizing-Version-2.1.1.html and get a sense of wire you need / losses. In the snap below I clicked "Maxout my Panel!" which raised the voltage to 500v range.

1650475053029.png

T
 
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harrisonpatm

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Joined
Jan 5, 2022
Messages
107
In my experience 10-20% is wildly off. Suggest getting to details - for example, I have 150ft runs of up to 100vdc @ 50a on 6AWG from the combiner boxes to the charge controllers - and there is no evidence of anything more than 1-2% loss.

The idea is to size the volts/amps to the wire by arranging panels / buying a compatible charge controller. There's good info on amps per wire size and no reason to accidentally or even 'on purpose' to have 10-20% losses.

For example, here's a SolArk interactive worksheet where I've put in 400ft runs and 8AWG wire to illustrate V loss %1.99 - e.g. 2% (bottom right). It's interactive and you can play with it... https://www.sol-ark.com/wp-content/uploads/2021/09/Solar-Panel-Sizing-Version-2.1.1.html and get a sense of wire you need / losses. In the snap below I clicked "Maxout my Panel!" which raised the voltage to 500v range.

View attachment 27341
T
Excellent resource, thank you, haven't seen this one yet. That's what I get for simply skimming the internet.
 
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