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Comment by algo_trader | Hacker News Reader

What is the cheapest/simplest configuration for an agricultural PV-to-always-on-e-motor (1MW)?

We can serialize the PVs to get 1000v? And then feed that directly to a (suitable) drive without an inverter? Possibly even a DC motor?

This cuts out half the components compared to an EV drive train, since we have much simpler cooling/packaging/response demand?

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What is even the the point of that? An always-on (presumably only on during daytime?) 1 MW motor with enough solar panels to power them and something that actually requires a full megawatt would be pricy enough that the cost of an inverter would not be all that large percentage wise. Especially since you almost certainly would want to have some sort of controller for the motor anyway, which would need the same type of electronics as an inverter would need.

I would assume a huge pump of some kind.

Probably an irrigation pump that needs to move water uphill. Water is heavy.

If your feeding DC from PV to a motor without an inverter, it will be a DC.

If you hook a brushless motor straight to PV panels, the speed the motor runs at vary throughout the day as the volatage output of the panels waxes and wanes. You'll need to make sure that it the motor has sufficient cooling to not damage itself when running at full power on the hottest sunniest day.

Generally, almost every type of PV or DC electric motor setup has a one or more systems that manage volatage, either in the form of a charge controller the outputs a constant(ish) voltage given the varying input voltages provided by the PV, or an ESC that outputs varying voltages to the motor to change it's rate of speed.

To get good efficiency from a solar panel you must continuously track the “Maximum power point” (MPPT). You would never want to run a motor directly off the solar, you want a power converter to maximize efficiency.

Most modern panels seem to be rated for a system voltage of up to 1500V; i.e., you're allows to connect enough in series to get up to but not beyond, as long as your MPPT can cope.

And yeah, 1kV target is practical, you could run a triple half bridge inverter from that into a motor with enough stray inductance to smooth the PWM into pure sine, yeah. It can do the MPPT task at the same time, btw.

The issue is available power is almost never going to be constant enough to directly couple to a load - a cloud passes by and your motor will stall. 1PM on a sunny day, and you’ll be using 1/3 of your power, etc.

What sort of agricultural PV-to-always-on-e-motor object would require 1MW continuously? That's a lot of power for agriculture purposes.

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