Solar fans

[daftlad]

I am building a beer can solar panel

http://www.navitron.org.uk/forum/index.php/topic,6899.0.html

It is to be used in a house that spends alot of the time (the winter) un inhabited.
The house is in France and as some of us know there electrics have a habit of tripping out and if there is no one there, there will be no one to re set it.
SO I was thinking of powering a computer fan with the solar panel, the fan is 3.6 watts. Can I connect a small PV panel directly to a computer fan? and if so what size panel should I use?
I want to heat the house (a bit) and to ventalate it.
Any Ideas?

[PhatBob]

I don't know how much use this is for you but.  My Audi A6 has a solar panel in the sun-roof which when the ignition is off, powers the interior fan.  Which says to me that the fan unit from a car like this would probably be the best bet - they're designed to move a larger quantity of air than a PC fan and can probably work with a 12v solar panel.

For extra points you could keep the heater matrix in the unit and connect it up to solar hot water

Rob

[billi]

for the 3.6 watt fan i reckon a 8-10 watt panel would be needed to supply enough air in not too sunny conditions


Billi

[daftlad]

So what happens to the fan when the sun is blazing? I guess the voltage approaches the open circuit voltage, so the fan would maybe have 16 volts on it?
and at low light conditions it may only have 5 volts, therefore spinning slowly.
Will an 8 to 10 watt panel end up burning the fan out?
Rob
I have checked out some computer fans and the bigger ones move as much air as a standard bathroom fan but use a lot less leccy. I would guess car fans are a lot less efficient??
So does your AUDI fan run when you are not in the car to keep it cooler, Sort of automatic cooling, when the sun is out, the fan runs?
I like the idea of adding hot water to it to act as a heater?
laters

[billi]

 watt and volt      and Ampere

I cannot tell you the 100 % technical details , but as an example most solar powered pond pumps do not perform right cause most sellers underspec the PV (in watt) to keep the costs down in General ) = many people think its not the right performance

The Shop i buy my pondpumps from nearly doubles  the wattage then the manufacturer of the pump -PV kid

The Dc pump installed to circulate the solar hot water from the panels  my folks use uses a 40 Watt panel and i think i saw it advertised with 20 watt panels somewhere else

So my recommendation is to oversize the panel in watt

Volume of air has  not muchg to say , it depends as well on the pressure the fan has to overcome to pump that volume

I like that website to choose http://www.ebmpapst.com/en/products/compact-fans/axial-compact-fans/axial_compact_fans.php

Billi

or  the radial fans cause more pressure

[daftlad]

I was thinking of one of the axial fans out of craplin, the 92 mm one moves 72m3 and uses 3.6 watts, a normal in line 4 inch fan moves 85m3 and uses 20 watts.
The thing is I don't need the fan to work when the sun isn't shining.

Will I knacker the fan if I put more volts on it, and if so could I connect a simple voltage regulation circuit to it?
laters

[billi]

like said its similar to pumps  the volume depends on pressure


i would get the fan first and operate  on a battery to find out if it is sufficient  for your need

[wookey]

You can buy solar-power roof-fans for camper vans (from Reimo). I've had one in my van for several years now and it's still running after what must be thousands of hours. £36 when I bought mine but £50 now. That is a proven-paired set of panel and fan but if you need the panel and fan physically separated then it may not be suitable.

http://reimonew.ms-visucom.de/en/35230-solar_powered_ventilator/

[Iain]

Hi
Just out of interest
Some of the lifeboats use a solar panel and a computer type fan to keep one of the void spaces dry. They use a small voltage regulator from RS (can't find the part number at the moment) between the panel and fan. This allows the fan to start / stop rather than running on a low voltage. Seems to work well. Will try and find the part No. if you are interested.
Other voltage regs will probably work
Iain

[PhatBob]

So what happens to the fan when the sun is blazing? I guess the voltage approaches the open circuit voltage, so the fan would maybe have 16 volts on it?
and at low light conditions it may only have 5 volts, therefore spinning slowly.
Will an 8 to 10 watt panel end up burning the fan out?

You'd want a voltage regulator of some sort, even if it was just a meaty zener diode.

Rob
I have checked out some computer fans and the bigger ones move as much air as a standard bathroom fan but use a lot less leccy. I would guess car fans are a lot less efficient??

Its an assumption that a computer fan will shift more air, but the car fan is a centrifugal fan and I see these in use in HVAC installations so I'm assuming the

So does your AUDI fan run when you are not in the car to keep it cooler, Sort of automatic cooling, when the sun is out, the fan runs?
I like the idea of adding hot water to it to act as a heater?

The fan runs almost every day and keeps the air moving through the car - it doesn't keep it cool but it does keep it fresh.  And the heater element makes it look interesting.

[daftlad]

I have just measured the current going to my car heater fan.
It uses 57 watts on slow speed and 100 watts on fast.
This is too much so back to computer fans.
Some car fans might be more economical but I don't know which and have any of you lot ever taken a heater fan out of a car, not easy!
Can you give me an idea of a simple regulator circuit?
Thanks everyone

[tony.]

daftlad,

what voltages are you talking about?
input?
output?
regards  tony

[daftlad]

The PSU will be for 12volt fan with an input of anything up to 21 volts (the open circuit voltage of a solar panel)
When there is little light I still want there to be a voltage, even if it is only 7 volts.
The Fan wattage is 3.6 watts.
cheers everyone

[billi]

wow it gets intense now    for the intensive care of a computer fan

a 12 volt Pv is normally about 17 volt max  connected to a load  so would be ideal for the fans  i mentioned ...

just a picture of one and they say its a 12 volt fan ( operating at 5-15 volt )  what else do you need ?

or choose a 24 volt version fan with an operating voltage of 12-30 Volt (but then low performance  in overcast conditions)

Donot get the point here  and just say again volume is one thing ,but to pump volume against some pressure is another story  (so watts get more  the higher the head /pressure for the same volume )

surely again it depends on your requirements   , perhaps find some info here http://www.solarventi.dk/internat_pdf/austr/austr_sv_br_gen_08.pdf


Billi

[daftlad]

Thanks Billi
I was not aware that the panels would not go over 17 volts ish
and all the fans i have looked at are only rated up to 13.8 volts
I was hoping i could just connect them together as you suggest, I will either shop around for fans or throw caution to the wind and recycle an old one.
That link covers exactly the sort of thing I am going for....thanks.
As for pressure/ flow, The run to the required spot is only three meters so I would imagine it will be fine, but I guess the thing to do is measure the current flow of the fan when I have it installed
Thanks everyone