connection without battery

abokamel

good afternoon all
how to use a solar panel to run a small van 24 v dc without battery, and what is the suitable panel?

BB.

Find a solar panel with Imp roughly 2-3x (at least) the rated current of the fan (I.e., a 24 volt fan @ 0.8 amps would be a solar panel with, roughly, 1.6 amps or greater Imp rating).

A "typical" "12 volt" solar panel is Vmp~18 volts (voltage maximum power). It will certainly turn most 24 VDC fan, just not at full speed. If the fan runs at an acceptable speed, then you are good to go (+ from panel to + of fan, etc.). With Voc~22 volts or so (voltage open circuit).

The issue is that the next typical standard solar panel is Vmp~30 VDC... A bit high for a 24 VDC fan (Voc~35 volts or so--Voltage open circuit).

You can get a simple "buck" DC to DC voltage converter from Amazon/etc. and they can be set to 24 VDC/whatever you need. It can get a bit "messy" as you are placing a voltage regulator between the solar panel and the fan. In the early morning and later afternoon, the lesser amount of sun can cause some voltage regulators to go a bit nuts at this time (controller may not "restart" during poor sun, etc.).

https://www.amazon.com/s?k=dc+to+dc+buck+converter+adjustable
https://www.amazon.com/s?k=dc+to+dc+buck+converter+24

Depending on the size, there are other electronic options to "control" the voltage at the fan (resistor, multiple diodes, Zener Diode, analog 3-Terminal voltage regulators, etc.). We can talk more if you need the other options.

As to size of solar panel... If you pick 3x the fan current (I.e., running more in the morning and evening times), then size of a (for example Vmp~18 volt panel):

0.8 amps (example fan) * 3 time fan rating * 18 volts = 43 Watt "minimum" suggested "12 volt panel"...

-Bill