[Stoves] Powering a TLUD Fan

[Frans Peeters]

Phil,

3x LiION  =3,7Vx3=11,1V  Charger needs 4,2x3=12,6 maximum or EXPLOSION RISK 
2W motor at 12V-------->0,1666 A 
8h xO,166A =1,8Ah
Laptop cells are 3,6 Ah and more
Sun cell 15,6V---------> 12,6 V +3V for charging  regulator LM317

PC  uP fans exist at 5V x0,2A=1W you could power with 2 cells;
Also a dual fan of 2x 1W 

Regards
Frans

I see Paul Oliver's work to be excellent and appreciate how a variable speed
fan can offer excellent control over TLUD operation. My reservation is that
there are many places where even the small power requirement (Paul says 1-2
watts) just isn't available. Lots of people here in Nicaragua are totally
off-grid and don't have reasonable access to a way to charge a battery. So,
I am been thinking about options. Being, among other things, an electronics
geek, here is what I have been thinking about.


Running the TLUD 8 hours a day at "average" fan speed means 12 watts per
day. At 12 volts that's one ampere hour. I have been thinking about a couple
of approaches. One is "higher tech" but may be a better solution at an
equivalent or lower cost. In both cases I am just thinking of a photovoltaic
panel to charge the battery. The difference is the battery voltage.

Small PV panels are pretty common on the surplus market. For example,
Electronic Gold Mine (http://www.goldmine-elec.com/) offers an assortment.
The specifications vary from 7 to 35 volts open circuit with output power in
the range of 1-3 watts. Prices are from $4.50 to $15. As this is quantity
one retail price information, it is likely the could be found at
significantly lower costs.


As any PV-based system will need some sort of charge controller for the
battery and what PV cells (in particular, what voltage) will be available at
the best price point, I am thinking that using a single-cell Lithium Ion
battery (3.7 volts nominal) would make the most sense. Units with a capacity
of 2.2 ampere hours and more are commonly used in laptop computers. They
offer reasonable life, low cost and the possibility of finding them on the
surplus market. The cells can be paralleled if higher capacity is needed.

A switching "up-converter" would be needed to supply the 12 volts needed for
the fan. The speed control could be incorporated into the up converter which
would reduce the cost and increase the efficiency. 

The alternative would be to use a more or less 12 volt battery (three Li-Ion
cells in series) so that the up-converter could be eliminated. My initial
guess is that the reduced electronics cost would not be as much as the
increased battery cost but it is a viable alternative as long as higher
voltage surplus PV panels are available.

While this sounds like a lot of electronics, this is all very common stuff
that you find in, for example, cellular phones. There is some design work
needed but the actual component costs will be very low. 

Comments? 

-- 
Phil Hughes 
nicafyl at gmail.com